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Title: Vacuum cleaning systems : A treatise on the principles and practice of mechanical cleaning
Author: Cooley, M. S.
Language: English
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Transcriber’s Notes

Texts printed in italics and bold face in the source document
have been transcribed between _underscores_ and =equal signs=
respectively. Small capitals have been transcribed as ALL CAPITALS.

More Transcriber’s Notes may be found at the end of this text.

Vacuum Cleaning Systems

A Treatise on the Principles and
Practice of Mechanical Cleaning

M. S. COOLEY, M. E.

MECHANICAL ENGINEER IN OFFICE OF THE SUPERVISING
ARCHITECT, TREASURY DEPARTMENT, WASHINGTON, D. C.

FIRST EDITION

New York:
HEATING AND VENTILATING MAGAZINE COMPANY,
1123 Broadway

CONTENTS.

CHAPTER I.

HISTORY OF MECHANICAL CLEANING.

PAGE

Early Attempts 3
Limitations of the Carpet Sweeper 4
Compressed Air Cleaners 5
Compressed Air Supplemented by Vacuum 7
Piston Pump the First Satisfactory Vacuum Producer 9
Systems Using Vacuum Only 11
Renovator with Inrush Slot 13
Steam Aspirators Used as Vacuum Producers 14
Piston Pump Used Without Separators 15
First Portable Vacuum Cleaner 15
First Use of Stationary Multi-Stage Turbine Blowers 16
Separators Emptying to Sewer by Air Pressure 18
Machines Using Root Blowers as Vacuum Producers 18

CHAPTER II.

REQUIREMENTS OF AN IDEAL VACUUM CLEANING SYSTEM.

Necessity and Proper Location of Stationary Parts 24

CHAPTER III.

THE CARPET RENOVATOR.

Four Important Parts of Vacuum Cleaning System 25
The Straight Vacuum Tool 26
Renovator with Auxiliary Slot Open to Atmosphere 27
Renovator with Two Cleaning Slots 30
Renovator with Inrush Slots on Each Side 30
Tests on Dirty Carpets 30
Type A Renovator Most Efficient on Dirty Carpets 36
Tests of Carpets “Artificially” Soiled 36
Effort Necessary to Operate Various Type of Renovators 51
Relative Damage to Carpets with Various Type of Renovators 52

CHAPTER IV.

OTHER RENOVATORS.

Different Form of Renovator Necessary to Clean Walls, Ceilings
and Similar Flat Surfaces 60
Upholstery Renovators Disastrous to Surfaces Cleaned 64
Attempts to Overcome Destructive Tendency of Straight-Slot
Upholstery Renovator 64
Upholstery Renovators Most Serviceable Clothing Cleaners 65
Special Renovators for Cleaning Stairs 66
Renovation of Furs 66
Renovation of Pillows 66

CHAPTER V.

STEMS AND HANDLES.

Use of Drawn Steel Tubing for Stems of Cleaning Tools 70
Drawn Aluminum Tubing for Long Stems 71
Swivel Joints Between Renovator and Stem 72
Wear on Hose Near Stem 74
Methods of Overcoming Wear of Hose 74
Valves to Cut Off Suction 78

CHAPTER VI.

HOSE.

Early Types Made of Canvas-Wound Rubber Tubing 80
Standard Weight Adopted 80
First Type Produced Especially for Use in Vacuum Cleaning Work 81
First Attempt to Produce Light-Weight Hose 81
Other Types 82
Hose Couplings 82
Hose Friction 84
Effect of Hose Friction 88
Most Economical Hose Size for Carpet and Floor Renovators 93
Conditions for Plant of Small Power 97
Limit of Length for Hose 99

CHAPTER VII.

PIPE AND FITTINGS.

Hose Inlets 100
Pipe Friction 107
Determination of Proper Size Pipe 107
Determination of Number of Sweepers to be Operated 113
Determination of Number of Risers to be Installed 115
Size of Risers 115
Illustration of Effect of Long Lines of Piping 120

CHAPTER VIII.

SEPARATORS.

Classification of Separators 127
Primary Separators 127
Secondary Separators 130
Complete Separators 134
Total Wet Separator 138

CHAPTER IX.

VACUUM PRODUCERS.

Types of Vacuum Producers 142
Displacement Type 142
Centrifugal Type 142
Power Required to Produce Vacuum 142
Reciprocating Pumps 143
Rotary Pumps 148
Centrifugal Exhausters 156
Steam Aspirators 162

CHAPTER X.

CONTROL.

First Type of Controller 166
Second Form of Control 168
Appliances for Varying Speed of Motor-Driven Vacuum Pump 171

CHAPTER XI.

SCRUBBING SYSTEMS.

First Real Mechanical Scrubbing Device 176
Combining Scrubbing with Dry Cleaning 177
Ideal Separator for Use with a Combined Cleaning and Scrubbing
System 178

CHAPTER XII.

SELECTION OF CLEANING PLANT.

Renovators 179
Hose 182
Pipe Lines 182
Separators 182
Vacuum Producers 183
Control 183
Selection of Appliances for Four Classes of Work 184

CLASS 1.--Plant for Residence or Small Office or Departmental
Building, to be Not More than One-Sweeper Capacity.

CLASS 2.--Large Office or Departmental Building Where Carpet
Cleaning is Important and Pipe Lines are of Reasonable Length.

CLASS 3.--Large Building or Group of Buildings Where Carpet
Cleaning is Important and Long Lines of Piping are Necessary.

CLASS 4.--Large or Small Plant Where Carpet Cleaning is Not
an Important Function of the Cleaning System.

CHAPTER XIII.

TESTS.

Early Methods of Testing 187
Most Rational System of Testing 189
Use of Vacometer 190
Proper Orifice to be Used with Each Class of Plant 191

CHAPTER XIV.

SPECIFICATIONS.

Award of Contracts on Evaluation Basis 193
Determination Basis of Evaluation 193
Specification for Class 1, Plant for Residence or Small Office
Building of One-Sweeper Capacity 194
Specification for Class 2, Plant for Large Office Building Having
Pipe Lines of Moderate Length 204
Specification for Class 3, Large Installation, with Unusually Long
Pipe Lines 209
Specification for Class 4, Large or Small Plant Where Carpet
Cleaning is of Secondary Importance 215
Specification for Class 5, To Give Widest Competition 218

CHAPTER XV.

PORTABLE VACUUM CLEANERS.

Power Required 228
Weight of Efficient Portable Cleaners 228
Limit of Power Consumption When Attached to Lighting System 229
Disadvantage of Having Dust Bag at Outlet of Fan 230
Portables Equipped with Mechanically-Operated Brushes 231
Portables Exhausting Air Inside of Building 231

TABLES.

PAGE

1. Cleaning Tests of Dirty Carpets 34
2. Cleaning Tests of Carpets Filled with Quicksand 38
3. Cleaning Tests Using 1 oz. of Sand per Square Yard of Carpet 40
4. Comparison of Tests Made by Mr. Reeve and by the Author 48
5. Effort Necessary to Operate Cleaning Tools 51
6. Vacuum Required at Hose Cock to Operate Type A Renovators
Attached to Varying Lengths of Different-Sized Hose 89
7. Air Quantities and Vacuum at Renovator with 1-in. Hose and 10
in. Vacuum at Hose Cock 90
8. Air Quantities and Vacuum at Renovator with 1¹⁄₄-in. Hose and
6 in. Vacuum at Hose Cock 90
9. Vacuum Required at Hose Cock to Operate Type C Renovators with
Various Lengths of Three Sizes of Hose 91
10. Air Quantities Through Floor Brush with Various Sizes and
Lengths of Hose, Operated on Same System with Type A
Renovators 92
11. Horse Power Required at Hose Cock to Operate Bare Floor
Brushes on Same System with Type A Renovators 93
12. Free Air Passing Brush Type of Bare Floor Renovator Operated
on Same System with Type C Carpet Renovators 94
13. Horse Power at Hose Cock with Brush Type of Bare Floor
Renovator Operated on Same System with Type C Carpet
Renovators 94
14. Cubic Feet of Free Air Passing the Felt-Covered Floor
Renovator Operated on Same System with Type A Renovators 96
15. Horse Power Required at Hose Cock to Operate Felt-Covered
Floor Renovators Operated on Same System with Type A
Renovators 96
16. Vacuum at Hose Cock with 2 in. Vacuum at Type A Renovator 97
17. Air Quantities when Bristle Bare Floor Renovators are Used in
Conjunction with Type A Carpet Renovators at 2 in. Mercury 98
18. Pipe Sizes Required, as Determined by Air Passing Renovators 109
19. Friction Loss in Pipe Lines, with Carpet Renovators in Use
Exclusively 109
20. Pressure Losses from Inlet to Separator in System for Cleaning
Railroad Cars 121

ILLUSTRATIONS.

FIG. PAGE.

1. Early Type of Mechanical Cleaning Nozzle Using Compressed Air 6
2. Another Type of Compressed Air Cleaning Nozzle, Supplemented
with Vacuum Pipe 8
3. Separators Used With Combined Compressed Air and Vacuum
Machines 9
4. Piston Type of Vacuum Pump, Mounted Tandem With Air
Compressor 9
5. Mr. Kenney’s First Renovators Vacuum Alone Being Used as
Cleaning Agent 10
6. Air Compressors Arranged for Operation as Vacuum Pumps 11
7. Separators Installed by Mr. Kenney in Frick Building 12
8. Vacuum Renovator With Inrush Slot, Introduced by the
Sanitary Devices Manufacturing Company 13
9. First Portable Vacuum Cleaner, Constructed by Dr. William Noe,
of San Francisco, in 1905 16
10. Late Type of Spencer Vacuum Cleaning Machine, Operated by
Multi-Stage Turbine Blowers 17
11. Type A, the Straight Vacuum Tool 26
12. Type B, with Wide Slot and Wide Bearing Surface 26
13. Type C, with Auxiliary Slot, Open to Atmosphere 28
14. Type D, with Two Cleaning Slots 28
15. Type E, with Inrush Slot on Each Side of Vacuum Slot 31
16. Type F, an Exaggerated Form of Type B 31
17. Tests of Three Renovators on Dirty Carpets 35
18. Cleaning Tests of Carpets Filled with Quicksand 39
19. Cleaning Tests Using 1 oz. of Sand Per Square Yard of Carpet 41
20. Three Series of Tests with Kenney Type A Renovators 45
21. Tests by Mr. Reeve, Using Type C Renovator 46
22. Tests by Mr. Reeve, Using Type D Renovator 47
23. Tests Showing Efficiency of Different Types of Renovators at
Different Degrees of Vacuum 50
24. Early Type of Bare Floor Renovator 55
25. Later Type of Bare Floor Renovator 55
26. Another Type of Bare Floor Renovator 56
27. Bare Floor Renovator with Felt Cleaning Surface 57
28. Bare Floor Renovator with Unusual Form of Slot 58
29. Bare Floor Renovator with Hard Felt or Composition Rubber
Strips 58
30. Bare Floor Renovator with Rounded Wearing Surface 59
30a. The Tuec School Tool 62
31. Round Bristle Brush for Carved or Other Relief Work 62
32. Rubber-Tipped Corner Cleaner for Use on Carved or Other
Relief Work 62
33. Early Type of Upholstery Renovator 63
34. Upholstery Renovator with Narrow Slots to Prevent Damage to
Furniture 64
35. Another Type of Upholstery Renovator with Short Slots 65
36. Hand Brush Type of Renovator 65
37. Form of Swivel Joint Connecting Stem to Renovator 72
38. Swivel Joint Arranged to Prevent Dust Lodging Between the
Wearing Surfaces 73
39. Swivel Joint in Use 74
40. Another Use of Swivel Joint, Showing Possibilities of this
Form 75
41. Operator Cleaning Trim of Door with Swivel Joint 76
42. Swivel Joint, with Screwed Union 76
43. Swivel Joint Having Ball Bearings 76
44. Action of Ball-Bearing Swivel Joint 77
45. Illustration of Defects of Plug Cocks 78
46. Bayonet Type of Hose Coupling, Introduced by the American Air
Cleaning Company 82
47. All Rubber Hose Coupling Used by the Spencer Turbine Cleaner
Company 83
48. Chart for Determining Hose Friction 86
49. Effect of Increase of Velocity on the Friction Loss 88
50. Another Test Showing Friction Loss Due to Velocity 89
51. Inlet Cock to Prevent Air Leakage when Not in Use 101
52. Type of Automatic Self-Closing Inlet Cock 102
53. “Smooth Bore” Pipe Coupling 103
54. Joint Made of Standard Pipe Flanges 104
55. Standard Durham Recessed Drainage Fittings Generally Used in
Vacuum Cleaning Installations 105
56. Friction Loss in Pipe Lines 106
57-60. Diagrams Showing Operation of Brush and Carpet Renovators
Under Different Conditions 110
61. Typical Floor Plan of Office Building Illustrating Number of
Sweepers Required 114
62. Plan of Layout for Office Building Showing Best Location (at
d) for Vacuum Producer 118
63. Vacuum Cleaning Layout for a Passenger Car Storage Yard 122
64. Arrangement of Piping Recommended as Best for Passenger Car
Storage Yard 123
65. Good Location for Dust Separator Where Large Areas Are
Served by One Cleaning System 125
66. Location of Separators at Centers of Groups of Risers for
Large Systems 126
67. Early Type of Primary Separator, Used by Vacuum Cleaner
Company 128
68. Primary Separator Used by the Sanitary Devices
Manufacturing Company 128
69. Primary Separator Used by the General Compressed Air and
Vacuum Cleaning Company 129
70. Primary Separator Made by the Blaisdell Engineering Co. 129
71. Secondary Separator Used by the Vacuum Cleaner Company 131
72. Secondary Separator Used by the General Compressed Air
and Vacuum Cleaning Company 131
73. Secondary Separator Used by the Sanitary Devices
Manufacturing Company 132
74. Type of Dry Separator Used as Secondary Separator 134
75. Form of Complete Separator Used by the Vacuum Cleaner
Company 135
76. Complete Separator Brought Out by the Electric Renovator
Manufacturing Company 136
77. Complete Separator Made by the American Radiator Company 137
77a. Interior Construction of Dunn Vacuum Cleaning Machine 140
78. Power Consumption and Efficiency of Air Compressor Used as a
Vacuum Pump 143
79. Modification of Reciprocating Pump Made by the Sanitary
Devices Manufacturing Company 144
80. Power Consumption and Efficiency of Modified Reciprocating
Pump 145
81 and 82. Indicator Cards for Clayton and Modified Pumps 146
83. One of the Pumps Installed in Connection with the Vacuum
Cleaning System in the New York Post Office, the Largest
Reciprocating Pump Used for this Purpose up to the Present 148
84. Interior Arrangement of the Garden City Rotary Pump 149
85. Power Required to Operate Garden City Type of Rotary Pump 150
86. Arrangement of Double-Impeller Root Type Rotary Pump for
Vacuum Cleaning Work 151
87. Rotary Pump Arranged with Double-Throw Switch for Reversing
Pump 152
88. Power Consumption and Efficiency of Root Type of Pump 153
89. The Rotrex Vacuum Pump, Used by the Vacuum Engineering
Company 153
90. Late Type of Centrifugal Exhauster Made by the Spencer
Turbine Cleaner Company 154
91. Power and Efficiency Curves for the Spencer Machine 155
92. Interior Arrangement of Invincible Machine, Manufactured by
the Electric Renovator Manufacturing Company 156
93. Power Consumption, Vacuum and Efficiency of First Types of
Invincible Machine 157
94. Power Consumption, Vacuum and Efficiency of Invincible
Machine After Valve Was Fitted to Discharge 158
95. Four-Sweeper Invincible Plant Installed in the United States
Post Office at Los Angeles, Cal. 159
96. Centrifugal Pump with Single Impeller, Manufactured by The
United Electric Company 161
96a. Test of Centrifugal Pump with Single Impeller 162
97. Steam Aspirator Used by the American Air Cleaning Company 163
98. Steam Consumption of Steam Aspirator 164
99. First Type of Controller Introduced by the Sanitary Devices
Manufacturing Company, known as the “Unloading Valve” 167
100. Test of Controller Connected to Suction of 8-Sweeper Piston
Pump 168
101. Type of Controller for Use on Pumps Without Valves 169
102. Regulator for Motor-Driven Vacuum Pump, Manufactured by the
Cutler-Hammer Manufacturing Company 170
103. Inspirator Type Vacuum Contactor, Used to Control Pilot Motor
of Cutler-Hammer Controller 171
104. Vacometer for Use in Testing Vacuum Cleaning Systems 190

PREFACE.

The contents of this work are compiled from the observations of the
author through the seven years during which he has been engaged in the
preparation of specifications for, and the testing of, complete plants
installed in the buildings under the control of the Treasury Department.

During this time it has become necessary to alter no less than five
times the stock form of specifications for stationary vacuum cleaning
plants which were adopted by the Government, with the intent of
obtaining the widest competition possible with efficient and economical
operation, in order to keep pace with the variation and improvement
in the apparatus manufactured. As each new type of system has come
on the market a personal investigation at the factory, together
with tests, has been made. An exhaustive test of carpet renovators
was also conducted, using one of the Government plants. In addition
the vacometers recommended for use in capacity tests were carefully
calibrated, using the machine at the Department of Agriculture.

The writer wishes to acknowledge the aid received from the various
manufacturers in furnishing illustrations and data on their machines,
to Messrs. Ewing & Ewing and Prof. Sidney A. Reeve for data on tests
made by Prof. Reeve and used in defending the Kenney basic patent.

In analyzing the results of his tests and observations, the writer has
endeavored to put his own conclusions into concrete form for the use
of the consulting engineer and has not entered into the problems to
be encountered in the design and manufacture of the various forms of
apparatus.

CHAPTER I.

HISTORY OF MECHANICAL CLEANING.

=Early Attempts.=--Whenever machinery has been introduced to assist
or replace manual labor, the earlier attempts have been in imitating
the tools formerly used by man. As the earliest mechanically-propelled
carriages were mechanical walking machines, the earliest steamboats
mechanical rowing machines, and the earliest flying machines mechanical
birds, so were the earliest mechanical cleaners in the form of
mechanical brooms.

These mechanical brooms were introduced about 1880 and took the form
of the well-known street sweeper, with a large circular brush mounted
on a four-wheeled cart and rotated by means of gearing driven from the
wheels, the propelling power being the horses which drew the machine.

This machine at once made itself unpopular with the residents of the
streets cleaned on account of its great activity in stirring up dust,
because the streets were swept dry. This trouble was later overcome to
a considerable extent by sprinkling the streets before sweeping, but
only at a sacrifice in efficiency of cleaning, especially where such
uneven surfaces as cobble or medina stone blocks formed the surface
of the roadway. Various attachments were added to reduce this dust
nuisance, but none has apparently been successful, as we see these
machines in their original form in use today.

Almost simultaneously with the introduction of the street sweeper came
its counterpart, the carpet sweeper, with a similar but smaller brush,
enclosed in a wood and metal case, the brush being driven by friction
from the wheels supporting the box and the power for operation being
derived from the person who pushed the machine along the floor.

This machine has not been modified to any great extent during the
thirty odd years of its existence. It is today in practically its
original form, and is doing no better work than when first introduced.
This form of mechanical cleaner occupied the field of household
cleaning for nearly twenty years without a rival, during which time it
won its way into the hearts and hands of many housekeepers in this and
other countries.

=Limitations of the Carpet Sweeper.=--This device, with its light brush
and equally light pressure on the surface cleaned and its limited
capacity for carrying the material picked up, has never been a thorough
cleaner in any sense of the word, and has been and is now used only
to take up that portion of the usual litter and light dust which is
located directly on the surface, and is, therefore, most annoying to
the housekeeper, owing to its being visible to the eye. Because of its
generous proportions, made necessary to accommodate the material picked
up, and its centrally-pivoted handle, made necessary by its mechanical
construction, it is impossible to operate it under low furniture. Like
the lawn mower, it must be in motion in order to operate its revolving
brush, on which its cleaning action is dependent. It is impossible to
make use of same in corners, along walls, or close to heavy furniture,
its use being limited to a literal slicking up of those portions of the
carpet in the most conspicuous portions of the apartment. In spite of
these serious defects it came into, and is still in, nearly universal
use, even in households equipped with the latest approved types of
mechanical cleaners. Its use on bare floors has never been even a
moderate success and in no case has it superseded the broom and dust
pan of our grandmothers.

=Compressed Air Cleaners.=--Compressed air has been in use for many
years in foundries and machine shops, for cleaning castings and
producing certain finishes on metal. With the introduction of modern
electrical machinery it was rapidly adapted to the cleaning of windings
and other inaccessible parts of this machinery. Its first use in
cleaning buildings was undoubtedly in the form of an open jet for
dislodging dust from carvings and relief work, for which purpose it is
very efficient as a remover of the dust from the parts to be cleaned
and also as a distributor of this same dust over the widest possible
area for subsequent removal by other means. It has a draw-back in that
the expansion of air both cools the same and reduces its ability to
retain moisture, resulting in the deposit of moisture on the surfaces
cleaned.

About 1898, attempts to overcome the objections to the open air jet
and to produce a commercially successful compressed air carpet cleaner
were undertaken almost simultaneously by two companies, the American
Air Cleaning Company, of Milwaukee, operating under the Christensen
patents, and the General Compressed Air Cleaning Company, of St. Louis,
operating under the Thurman patents.

The renovator used by the American Air Cleaning Company consisted of a
heavy metal frame, about 18 in. long and 12 in. wide, having mounted
on its longer axis a wedge-like nozzle extending the entire length of
the frame, with a very narrow slit, ¹⁄₆₄ in. wide, extending the entire
length of its lower edge. This nozzle was pivoted and so connected to
the operating handle, by which the renovator was moved over the floor,
that when the renovator was alternately pushed and pulled over the
surface to be cleaned, the slot was always inclined in the direction
in which the renovator was being moved. The top of the renovator was
closed by a canvas bag, smaller at the neck than in its center, which
was supported by a wire hook.

Air was introduced into the nozzle, at a pressure of from 45 to 55
lbs. per square inch, and issued from the slot in a thin sheet which
impinged on the carpet at an angle. The frame was held close to the
carpet by its weight, preventing the escape of the air under its lower
edge. The air striking the carpet at an angle was deflected up into the
bag, inflating same like a miniature balloon. The dust loosened from
the carpet by the impact of the air was carried up into the bag where
it lodged, the air escaping through the fabric of the canvas into the
apartment.

The renovator used by the General Compressed Air Cleaning Company
differed from the above-described renovator in that it contained two
nozzles, with slots inclined at fixed angles to the carpet. A pair of
hand-operated valves were provided in the handle to introduce air into
the nozzle which was inclined in the direction in which the renovator
was moving; otherwise the renovator was identical with that used by
the Milwaukee company.

These renovators were generally supplied with air from a portable unit,
consisting of an air compressor, driven by a gasoline engine mounted
with the necessary gasoline and air storage tanks on a small truck. One
of these machines was in use in Washington last year, but its use at
that time was very limited and it is not to be seen this year.

These trucks were drawn up in front of the building to be cleaned and
a large-size hose, usually 1¹⁄₄ in. in diameter, was carried into the
house and attached to an auxiliary tank from which ¹⁄₂-in. diameter
hose lines were carried to two or more renovators.

A few buildings were equipped with air compressors and pipe lines, with
outlets throughout the building for use with this type of renovator,
among which was the Hotel Astor in New York City.

These renovators, the construction of which is shown diagrammatically
in Fig. 1, required approximately 35 cu. ft. of free air per minute
at a pressure of from 45 to 55 lbs. per square inch and were usually
driven by a 15 H. P. engine.

[Illustration: FIG. 1. EARLY TYPE OF MECHANICAL CLEANING NOZZLE USING
COMPRESSED AIR.]

The renovators were very heavy to carry about, although their operation
with the air pressure under them was not difficult. However, their
operation was complicated, requiring skilled operators. Owing to their
generous proportions it was impossible to clean around furniture,
making its removal from the apartment necessary, and limiting their use
to the cleaning of carpets at the time of general house cleaning. The
cooling effect of the expansion of the air in the nozzle often caused
condensation of moisture on the carpets when the relative humidity
was high. They were also at a disadvantage in that all the heavy dust
collected in the canvas bag had to be carried from the apartment by
hand. Owing to the constant agitation of the dust in the bag by the
entering air currents, much of the finer particles of dust and all
the disease germs liberated by the renovator were blown through the
bag back into the apartment. They were not, therefore, by any means
sanitary devices.

=Vacuum Produced by Compressed Air.=--The General Compressed Air
Cleaning Company also introduced another form of renovator for use with
their compressed air plants. This was composed of an ejector operated
by compressed air, with a short hose attached to a carpet renovator
of the straight narrow-slot type, such as was used later in vacuum
cleaning systems. The outlet from this ejector was connected by another
short hose to a metal box containing a canvas bag, woven backwards and
forwards over metal frames to give a large surface for the passage of
air. The dust picked up by the suction of the ejector was carried with
the air into the box and there separated from the air, which escaped
through the canvas into the apartment.

This form of renovator overcame some of the objections to the former
type in that there was no condensation of moisture on the carpets, and
it was possible to operate the renovator under and around furniture,
and even on portieres and other hangings. However, the apparatus was
rendered inefficient by the resistance of the bag, causing a back
pressure on the injector which greatly reduced its air-drawing capacity.

=Compressed Air Supplemented by Vacuum.=--Shortly after these two
companies began operation, the Sanitary Devices Manufacturing Company,
of San Francisco, introduced a new system of mechanical cleaning under
the Lotz patents. This system used a renovator having a compressed
air nozzle terminating in a narrow slot, similar to the nozzles of the
American and Thurman systems, but differing from them in that the slot
was fixed vertically, pointing downward. This nozzle was surrounded
by an annular chamber having an opening at the bottom of considerable
width. The whole formed a renovator about 14 in. long and not over 2
in. wide at its base. In addition to the compressed air connection to
its nozzle, a second hose, 1 in. in diameter, was connected to the
annular space surrounding the nozzle and led to a vacuum pump by which
the air liberated through the nozzle, together with the dust which
was liberated from the carpet, was carried from the apartment. The
construction of this renovator is shown diagrammatically in Fig. 2.

[Illustration: FIG. 2. ANOTHER TYPE OF COMPRESSED AIR CLEANING NOZZLE,
SUPPLEMENTED WITH VACUUM PIPE.]

As dust-laden air was not suitable to be carried through the pump used
as a vacuum producer, separators had to be provided to remove the dust
from this air before it reached the pump. The separators used consisted
of two cylindrical tanks. The air was introduced into the first tank in
such a way that a whirling motion was imparted to it, thus separating
the heavier particles of dust by centrifugal force. The second tank
contained water which was brought into intimate contact with the air
by means of an atomizer located in the pipe connection between the
two tanks, thus washing the air in a manner somewhat similar to the
familiar air washers used in connection with mechanical ventilating
systems. The air and spray then entered the second tank, above the
water line, where the entrained water separated on the reduction of
velocity and fell back into the water below, to be recirculated through
the atomizer. The air passed on out of the top of the tank to the pump.
An illustration of these separators is shown in Fig. 3.

[Illustration: FIG. 3. SEPARATORS USED WITH COMBINED COMPRESSED AIR AND
VACUUM MACHINES.]

[Illustration: FIG. 4. PISTON TYPE OF VACUUM PUMP, MOUNTED TANDEM WITH
AIR COMPRESSOR.]

=Piston Pump the First Satisfactory Vacuum Producer.=--Various
types of apparatus were tried as vacuum producers, including an air
ejector, such as was used with the Thurman renovator, and found to
be ineffective due to its inability to overcome the back-pressure
necessary to discharge the air through the hose, which was placed on
its outlet. A rotary pump was next tried, but, owing to the selection
of an inefficient type, this was abandoned and, finally, a piston-type
vacuum pump, with very light poppet valves and mounted tandem with the
air compressor, was adapted and remained in use with this system until
straight vacuum was adopted, when the air compression cylinder was
omitted. This pump is illustrated in Fig. 4.

[Illustration: FIG. 5. MR. KENNEY’S FIRST RENOVATOR, VACUUM ALONE BEING
USED AS CLEANING AGENT.]

In this system we see the first sanitary device to be introduced into
the field of mechanical cleaning, as the dust and germ-laden air
were removed entirely from the apartment and purified before being
discharged into the outside atmosphere. The foulness of the water in
the separators clearly showed the amount of impurities removed from the
air.

These machines were mounted on wagons, similar to their forerunners,
and were also installed in many buildings as stationary plants, among
which were the old Palace Hotel and the branch Mint, in San Francisco,
and the old Fifth Avenue Hotel, in New York City.

=Systems Using Vacuum Only.=--In 1902 David T. Kenney, of New York,
installed the first mechanical cleaning system in which vacuum alone
was used as the cleaning agent. Mr. Kenney used a renovator with a slot
about 12 in. long and ³⁄₁₆ in. wide, attached to a metal tube which
served as a handle, and to a ³⁄₄-in. diameter hose and larger pipe line
leading to separators and vacuum pump. Mr. Kenney’s first renovator is
illustrated in Fig. 5.

[Illustration: FIG. 6. AIR COMPRESSORS ARRANGED FOR OPERATION AS VACUUM
PUMPS.]

Mr. Kenney used as vacuum pumps commercial air compressors, the first
of which was installed in the Frick Building in 1902 and is illustrated
in Fig. 6. Later he adapted the Clayton air compressor, with
mechanically-operated induction and poppet eduction valves on larger
sizes, and single mechanically-operated induction and eduction valves
on the smaller sizes.

The separators used by Mr. Kenney differed from those used by the
Sanitary Devices Manufacturing Company in that they contained several
interior partitions, screens, and baffles, and the air was drawn
directly through the body of water in the wet separator. The relative
merits of these types of separators will be discussed in a later
chapter.

[Illustration: FIG. 7. SEPARATORS INSTALLED BY MR. KENNEY IN FRICK
BUILDING.]

The separators installed by Mr. Kenney in the Frick Building, and
which are practically the same as were used by him as long as he
manufactured vacuum cleaning apparatus, are illustrated in Fig. 7.

After his application had been in the patent office for about six years
he was granted a fundamental patent on a vacuum cleaning system.

=Renovator with Inrush Slot.=--The Sanitary Devices Manufacturing
Company then produced a carpet renovator using vacuum only as a
cleaning agent. This cleaner has a wider cleaning slot than the
cleaners usually furnished by Mr. Kenney, about ⁵⁄₁₆ in. wide, with
a supplemental slot or vacuum breaker opening out of the top of the
renovator and separated from the cleaning slot by a narrow partition
extending nearly to the carpet, as illustrated in Fig. 8. The relative
merits of these types of renovators will be discussed in a later
chapter.

[Illustration: FIG. 8. VACUUM RENOVATOR WITH INRUSH SLOT, INTRODUCED BY
THE SANITARY DEVICES MANUFACTURING CO.]

Shortly after the introduction of vacuum cleaning by Mr. Kenney and
the Sanitary Devices Manufacturing Company, the American Air Cleaning
Company published an interesting little booklet entitled, “Compressed
Air Versus Vacuum,” which set forth in great detail the so-called
advantages of compressed air over vacuum as a medium of mechanical
carpet cleaning, and, apparently, proved that vacuum cleaners were much
less efficient than cleaners operated by compressed air. A year or two
later the American Air Cleaning Company evidently had a change of heart
and began to manufacture these same “inefficient” vacuum cleaners.
Their previous treatise on vacuum cleaning, which apparently was not
copyrighted, was republished by both the Sanitary Devices Manufacturing
Company and by the Vacuum Cleaner Company, which had acquired Mr.
Kenney’s patents, and freely distributed. Thus this little work of the
Milwaukee company, instead of injuring their competitors, was turned
into good advertising for them and required a lot of explanation from
the Milwaukee company.

=Steam Aspirators Used as Vacuum Producers.=--The American Air Cleaning
Company used a steam aspirator as its vacuum producer and, unlike its
predecessor, the air-operated ejector, it made good and has also been
used to a limited extent by the Sanitary Devices Manufacturing Company.
It is now marketed by the Richmond Radiator Company, and its merits
will be discussed in a later chapter. The American Air Cleaner Company
also used as a vacuum producer the single-impeller type of rotary pump,
made by the Garden City Engineering Company, which was also later
adopted, to a limited extent, by the Vacuum Cleaner Company. This will
be discussed further on.

The renovator used by this company was a single-slot type, with ¹⁄₈-in.
by 10-in. cleaning slot. These systems at once became notable on
account of the small size of the vacuum producers used, the low degree
of vacuum carried, and the vigorous campaign of advertising which was
conducted.

Several firms soon began to market vacuum cleaning systems almost
identical with that of Mr. Kenney, among which were the Blaisdell
Machinery Company, The Baldwin Engineering Company, and The General
Compressed Air and Vacuum Machinery Company, the latter being the
original Thurman company.

The Vacuum Cleaner Company then began a series of infringement suits
against nearly every manufacturer of vacuum cleaning systems. In nearly
every case the suit has resulted in the offending company paying
license fees to the Vacuum Cleaner Company, and this concern has now
abandoned the manufacture of vacuum cleaners and has become a licensing
company. At this writing nearly twenty firms are paying license fees
to the Vacuum Cleaner Company and there is one suit now in the courts.

=Piston Pump Used Without Separators.=--A vacuum cleaning system of
somewhat different design was produced by two former employees of the
Vacuum Cleaner Company, Mr. Dunn, the once well-known “Farmer Dunn” of
the weather bureau, afterward salesman for the Vacuum Cleaner Company,
and Mr. Locke, at one time this firm’s engineer. This company was first
known as the Vacuum Cleaning Company, and, shortly afterward, as the
Dunn-Locke Vacuum Cleaning Company. No separators were used with this
system, but the dust-laden air was led from the pipe lines directly
into a chamber on the pump, known as the “saturation chamber,” and
there mingled with a stream of water converting the dust into a thin
mud. The air, water and mud then passed through the pump, the muddy
water was discharged into the sewer, and the air into the atmosphere.
The vacuum producer used was a piston pump without suction valves.
With this system it was possible to handle water in almost unlimited
quantities and with this feature a system of mechanical scrubbing was
attempted for which great claims were made, none of which, however,
were realized in a commercial way.

These gentlemen sold their patents to the E. H. Wheeler Company, which
attempted to market the system in its original form. It was found,
however, that the piston pump was not adapted to the handling of grit
which was picked up by the renovators, and a rotary pump, with single
impeller and a follower was substituted. This system is now marketed by
the Vacuum Engineering Company, of New York, and is known as the Rotrex
system.

Mr. Dunn again entered the field of vacuum cleaning and began marketing
his machine a short time ago with a new form of automatic separator
discharging to sewer.

=First Portable Vacuum Cleaner.=--About 1905, Dr. William Noe, of
San Francisco, constructed the first portable vacuum cleaner. This
machine contained a mechanically-driven rotary brush, similar to the
brushes used in the familiar carpet sweeper, for loosening the dust
from the carpet. This dust was sucked up by a two-stage turbine fan
and discharged into a dust bag, mounted on the handle, similar to the
bags on the compressed air cleaners. The whole machine was mounted on
wheels and provided with a small direct-connected motor. This machine
is illustrated in Fig. 9 and is the original form of the well-known
Invincible renovator manufactured by the Electric Renovator Company, of
Pittsburgh. This company now produces a complete line of stationary and
portable vacuum cleaners, all of which use multi-stage turbines. The
sale of the product of this company, until recently, was controlled by
the United States Radiator Corporation.

[Illustration: FIG. 9. FIRST PORTABLE VACUUM CLEANER, CONSTRUCTED BY
DR. WILLIAM NOE, OF SAN FRANCISCO, IN 1905.]

=First Use of Stationary Multi-Stage Turbine Blowers.=--About 1905
Mr. Ira Spencer, president and engineer of the Organ Power Company,
which manufactured a multi-stage turbine blower for organs, known
as the “Orgoblow,” organized the Spencer Turbine Cleaner Company
and marketed a vacuum cleaning system, using a modification of the
“Orgoblow” as a vacuum producer. These machines were first constructed
with sheet metal casings and had sheet steel fans, with wings riveted
on and mounted on horizontal shafts. The separators were sheet metal
receptacles with screens for catching litter. Light-weight hose, 2 in.
in diameter, was used to connect the renovators to 4-in. sheet metal
pipe lines. A variety of renovators was produced for use with this
system. Carpet renovators having cleaning slots varying from 10 in. by
³⁄₄ in. to 20 in. by ¹⁄₄ in. were used, and a very complete line of
swivel joints for connecting the renovators and the hose to the handles
was developed. This system was operated at 5 in. vacuum, which was much
lower than that used by any other system, 15 in. being standard at that
time, and a much larger volume of air was exhausted under certain
conditions than was possible with any of the then existing systems.
Owing to the large volume of air exhausted and to the large size of
the renovators, hose and pipe lines, larger articles could be picked
up than was possible with any of the existing systems. A great deal of
weight was attached to this condition by the manufacturers, a favorite
stunt being to pick up nails, washers, waste, small pieces of paper and
even pea coal from a floor and finally to pick up a quantity of flour
which had first been carefully arranged for the demonstration.

[Illustration: FIG. 10. LATE TYPE OF SPENCER VACUUM CLEANING MACHINE,
OPERATED BY MULTI-STAGE TURBINE BLOWER.]

This invasion of the vacuum cleaning field was considered by the
established manufacturers as a freak and the apparatus was christened
“the tin machine.” Whenever it was installed in competition with other
forms of cleaning systems, the daily question asked by its competitors
was, “Has the tin machine fallen apart?” However, the tin machine did
not fall apart, but held its own with the other systems, even in its
crude and inefficient state. Finding that the construction he had
adopted was too flimsy and subject to abnormal leakage, Mr. Spencer
developed a new form of machine, using cast-iron casing and welded fan
wheels and adopted standard pipe and fittings. He also brought out a
line of sheet metal tools and on the whole perfected a satisfactory
cleaning system. One of his machines of a later type is illustrated in
Fig. 10.

=Separators Emptying to Sewer by Air Pressure.=--A new form of vacuum
cleaning system was introduced by Mr. Moorhead, of San Francisco, who
used an inrush type of renovator having an inlet for air on each side
of the cleaning slot.

The separator used with this system was a wet separator and contained
a screen cleaned by a rotary brush into which all the dust contained
in the air lodged. The pump used with this system was generally of the
piston type, fitted with a single rotary valve, so connected to the
valve stem that it could be rotated thereon and the machine changed
from a vacuum pump to an air compressor in order that the contents of
the separators might be discharged into the sewer by air pressure when
it was desired to empty same.

This system was marketed by the Sanitary Dust Removal Company, of San
Francisco, and, later, was taken over by the American Rotary Valve
Company, of Chicago, which is now marketing same. It eliminates the
manual handling of the dust at any stage of its removal, a feature
which is made much of by its manufacturers, but one which is likely to
cause some trouble for the sewerage system if care is not exercised.

=Machines Using Root Blowers as Vacuum Producers.=--The use of a Root
type of rotary pump as a vacuum producer was first undertaken by the
Foster and Glidden Engineering Company, of Buffalo, which marketed the
Acme system about 1907, the same company having previously built a
similar system for the removal of grain from steam barges. The other
features of this system did not differ materially from those already on
the market.

Being familiar with the various uses to which this type of vacuum pump
had been adapted, the principal one being the operation of pneumatic
tube systems, the author suggested the use of this type of vacuum
producer about two years previous to its introduction and was advised
by one manufacturer that such a type of pump was not suitable for
vacuum cleaning. The fallacy of this statement will be brought out in
detail in a later chapter.

The type of vacuum producer just described has been adopted in many
makes of vacuum cleaners, including the Hope, Connellsville, Arco, and,
lately, in the American Rotary Valve Company’s smaller systems.

During the past four years a score or more of new stationary vacuum
cleaning systems have been introduced, among which are the Palm, a
modification of the Dunn-Locke system; the Tuec, a turbine cleaner; the
Water Witch, which uses a water-operated turbine as a vacuum producer,
and the Hydraulic, with water-operated ejector. At the same time a
hundred or more portable vacuum cleaners have been marketed. These are
of almost every conceivable type and form and are operated by hand,
electricity, and water power. Among them will be found machines which
are good, bad and indifferent, the efficiency and economy of which will
be discussed in a later chapter.

This nearly universal invasion of the vacuum cleaner field by anybody
and everybody looking for a good selling article, establishes the
fact that the vacuum cleaner is not a fad or fancy, but has become
almost a household necessity and has led large corporations to take
it up as a branch of their business. First, the Sanitary Devices
Manufacturing Company and the Vacuum Cleaner Company, the pioneers in
the field, after a legal battle of years, consolidated with a view
of driving their competitors from the field as infringers of the
patents controlled by the two organizations. The result of this was
the licensing of other companies. In an attempt to control the sale of
their type of apparatus notice was served on all users of other types
of vacuum cleaners that they were liable to prosecution for using
infringing apparatus.

Later, the McCrum-Howell Company, a manufacturer of heating boilers
and radiators, secured control of the products of the American Air
Cleaning Company and the Vacuum Cleaner Company and sold these machines
to the trade for installation by the plumbers and steam fitters. The
McCrum-Howell Company has been succeeded by the Richmond Radiator
Company, which is handling these vacuum cleaning machines.

Shortly afterwards, the United States Radiator Corporation secured
control of the Invincible and the Connellsville systems, and, lastly,
the American Radiator Company secured the Wand system.

Thus we see that vacuum cleaning seems to be virtually in the control
of the manufacturers of heating apparatus, who are also among the
largest corporations in this country and well able to control the
future of this business to their liking.

As to the future of vacuum cleaning the author considers that it is at
present, like the automobile, at the height of its career, and also,
like the automobile, that it is a useful appliance to mankind and that
it has its proper place as a part of the mechanical equipment of our
modern buildings.

As to the type of vacuum cleaner of the future, the author believes
that these appliances will become standardized, just as all other
useful appliances have been, and that the form that it will then take
will be a survival of the fittest. What that form may resemble the
reader may more readily judge when he has completed the reading of this
book.

CHAPTER II.

REQUIREMENTS OF AN IDEAL VACUUM CLEANING SYSTEM.

Before a comparison of the relative merits of any line of appliances,
used for any one purpose, can be intelligently made, one must have
either some form of that apparatus which we consider as a standard for
comparison that we may rate all others as inferior or superior thereto,
or else an ideal of a perfect system must be assumed, and the measures
with which each of the various appliances approaches the requirements
of the ideal will establish their relative merits.

The author has elected to use the latter method in comparing the
various systems of vacuum cleaning, and it is necessary, therefore, to
first determine what are the requirements we shall impose on the ideal
system.

An ideal vacuum cleaning system would be one which, when installed in
any building, will displace all appliances used for dry cleaning in the
semi-annual renovating or house cleaning, the weekly cleaning or Friday
sweeping and the daily supplemental cleaning. If our system be truly
an ideal one, the premises should never become so dirty as to require
any semi-annual cleaning at all, and, if the daily cleaning be anyway
thorough, there need be no weekly cleaning. This latter condition may
be governed by the will of the housekeeper or janitor.

The compressed air cleaners first introduced were intended for use
only at the semi-annual cleaning and they were in reality carpet
renovators, which were assumed as imparting to the carpets all the
beneficial results that could be obtained by taking them up and sending
them to a carpet-cleaning establishment, with the advantage over
this latter method, that the labor of removal and replacement of the
carpets was rendered unnecessary, but with the disadvantage that all
the germ-laden air, used as a means of cleaning the carpets, was blown
back into the apartment, leaving the germs in their former abode.

This disadvantage, however, is partly offset by the fact that while the
majority of the germs in one’s own carpet are blown out at the carpet
cleaners, a mixed company of germs from your neighbors’ and others’
carpets, which may be in the tumbling barrel at the same time with your
own, are returned to you with your carpet.

Neither of these conditions is ideal and we will expect our ideal
cleaner to completely remove from the premises, not only the dust and
dirt, but also the germ-laden air which is used as a means of conveying
this dirt.

For replacing the weekly and the daily cleaning, these earlier
renovators were not suitable, as in order to use same the furniture
must all be removed from the apartment.

To accomplish this daily and weekly cleaning, the ideal vacuum cleaner
must replace the broom and dust pan, and their inseparable companion,
the duster, and must also supersede that time-honored mechanical
cleaner, the carpet sweeper.

The reader will doubtless consider that in making this statement the
author is asking the vacuum cleaner to perform much more than it is
usually called on to do. However, we are now discussing an ideal
system, and the above requirements are not absolutely beyond what can
be accomplished by some of the cleaning systems now on the market.

To accomplish this requirement the ideal cleaner must pick up
everything likely to be found on the floor which cannot be readily
picked up by hand. The character of this material will vary greatly
according to the uses of the apartment cleaned. In residences and
offices, where carpets or rugs are in use, cigar stumps and matches
are usually deposited in cuspidors and small pieces of paper in waste
baskets, consequently there should be nothing but dust to be removed
from a residence and, perhaps, mud and sand from the shoes of the many
visitors, in addition to the dust in an office.

However, there are special conditions likely to be met in many cases;
sewing rooms will be littered with basting threads and scraps of
cloth; department stores, with a great quantity of pins; banking rooms
with bands and large-sized bank pins; all of which increase the
requirements of the ideal system. A cleaner which is perfectly adapted
to one sort of apartment will be entirely unsuited for another, and
the ideal cleaner will be one which can be readily adapted to all
conditions likely to be met in the building in which it is installed.

The ideal cleaner must be able to accomplish the above stated
requirements without the necessity of moving heavy pieces of furniture
out of or about the apartment; that is, it must be capable of being
efficiently operated under beds, tables and chairs, around the legs
of other heavy furniture, behind bookcases, pianos, cabinets, etc.,
over curtains, draperies and hangings, over walls, behind pictures and
over mouldings and carved ornaments, all without injury to any of the
furniture or fittings of the apartment, and with the least expenditure
of energy by the operator.

These conditions should be met with the fewest possible number of
cleaning appliances, none of which should be provided with small
attachments liable to be lost or misplaced, and all parts of the
system, which must necessarily be moved about, either before, after or
during the cleaning operation, should be of minimum weight and bulk,
but of rugged and lasting construction.

The ideal vacuum cleaner should be of such proportions and provided
with ample motive power to clean rapidly and effectively.

For use in an office building the cleaner should be able to thoroughly
clean an average-sized office, including floor, walls, furniture and
fittings in from 10 to 15 minutes, and for residence work, should be
of sufficient capacity to clean an apartment, including floor, walls,
curtains, draperies, pictures and furniture in not exceeding 30 minutes.

The ideal system should be so arranged that any apartment in the
building can be cleaned with the least possible disturbance and without
affecting the use of any other apartment, excepting perhaps, the
corridors or hallways.

In large offices, drafting rooms and similar apartments, it may become
necessary to clean same while they are occupied; therefore, our ideal
system must be practically noiseless in operation and must offer the
least possible obstruction to the proper use of the room by its regular
occupants.

=Necessity and Proper Location of Stationary Parts.=--To be of
sufficient power to do rapid cleaning and in order to remove from
the building all dust and germ-laden air, the cleaning system must
necessarily contain some stationary parts. The motive power can
generally be confined to these stationary parts, and must, in such
cases, be located within the building to be cleaned. Therefore, it
should operate with the minimum of noise and vibration.

Machines located in office or other large buildings, containing
elevators or other complicated apparatus requiring skilled attendance,
which are provided with complicated control and with other attachments,
are not objectionable, and in such cases simplicity should give way to
efficiency, but unnecessary complications should be avoided.

In residences and other small buildings, where the vacuum cleaner is
likely to be the only machinery installed, the system must be one which
requires the minimum attention and must be capable of being started
and stopped by any person of average ability, without the necessity of
going to the point where the machine is located.

The power consumption of the ideal system should be a minimum to
accomplish satisfactory results and should be, as nearly as possible,
directly proportioned to the amount of cleaning being done. This
requirement is most important in hotels, where some cleaning is likely
to be done at all hours, day and night. In other words, vacuum must
be “on tap” and as readily attainable at any point in the building as
your water or electric light. In office buildings, where a schedule of
cleaning hours is fixed, and in residences where cleaning hours are few
and the capacity of the plant is rarely more than could be attended to
by one operator, this requirement is not of as great importance.

Lastly, our ideal system, from the standpoint of the purchaser, must be
of such rugged construction, as will enable it to operate efficiently
for, at least, ten years and its mechanical details such that it will
operate continuously, without expert attention, and that the annual
expense for repairs during the life of the machine will not exceed 5%
of the first cost of the system.

CHAPTER III.

THE CARPET RENOVATOR.

In undertaking the comparison of a number of different makes of any
appliance, in order to determine the good and bad points in each,
where the apparatus is composed of a number of separate and distinct
parts, each having its proper function, which they must perform in
order to make the whole apparatus effective, as in a vacuum cleaning
system, it becomes necessary to isolate temporarily each part and
consider its action, first, as a unit working under the most favorable
conditions, and, second, as a component part of the whole apparatus
in order to determine where the weak points in any system occur and
what modifications are necessary in the various parts of the apparatus
to make some vital part of the whole more effective. It is further
necessary to determine what are the vital parts of the system in order
that the other parts may be accommodated to the effective action of
that part.

=Four Important Parts of Vacuum Cleaning System.=--In analyzing a
vacuum cleaning system it naturally divides itself into four parts,
viz.: the cleaning tool or renovator, the air-conveying system or
hose and pipe lines, the separators or other means of disposal of the
material picked up, and the vacuum producer.

The author considers that the renovator is the most important part of
the system and that the other parts should be made of such proportions
and with such physical characteristics as will produce the proper
conditions at the renovator to permit it to perform its functions in
the most effective manner.

As the vacuum cleaning system must be capable of cleaning surfaces of
a widely variable character many forms of renovators are necessary. Of
the various surfaces cleaned the author considers that carpets and rugs
comprise the most important, as well as the most difficult to clean
effectively, so that the carpet renovator will be considered first.

=The Straight Vacuum Tool.=--Various forms of carpet renovators have
been and are in use by manufacturers of vacuum cleaning systems. The
first type of renovator to be considered is that having a cleaning
slot not over 12 in. long, with its edges parallel throughout its
length, and not over ³⁄₈ in. wide, with a face in contact with the
carpet not over ³⁄₈ in. wide on each side of the slot. This form of
renovator is illustrated in Fig. 11 and is designated by the writer
as Type A. The first of these renovators was introduced by Mr. Kenney
and, as finally adopted by him, was 12¹⁄₂ in. long, with ⁷⁄₈-in. face
and with a cleaning slot 11¹⁄₂ in. long and ⁵⁄₃₂ in. wide. This form
of cleaner was termed the “straight vacuum tool” and is used today by
many manufacturers. Slight modifications in its form and dimensions
were made in some cases, as in the one manufactured by the American
Air Cleaning Company. In the one used in all tests by the writer on
type A renovators, the slot was reduced to 10 in. long and ¹⁄₈ in. wide
and the face of the renovator was slightly rounded at the outer edges,
leaving very little surface in contact with the carpet.

[Illustration: FIG. 11. TYPE A, THE STRAIGHT VACUUM TOOL.]

[Illustration: FIG. 12. TYPE B, WITH WIDE SLOT AND WIDE BEARING
SURFACE.]

A renovator of this type is easily operated over any carpet even when
a considerable degree of vacuum exists within the renovator itself.
It has met with favor when used with the piston type of vacuum pump
without vacuum control, as was the case with the earlier systems.
However, when a very high degree of vacuum occurs within the renovator
it has a tendency to pull the nap from the pile of the carpet.

Soon after the introduction of this form of renovator, some users
of same, particularly in San Francisco, complained that while the
renovator effectively removed the dust from carpets it failed to pick
up matches and other small articles and preliminary or subsequent
cleaning was necessary in order to remove such litter.

To overcome this difficulty Mr. Kenney increased the width of the
cleaning slot to nearly ¹⁄₂ in., with the result that when a high
degree of vacuum existed within the renovator, which often occurred
where no vacuum control was used, it stuck to the carpet, rendering
its operation difficult and, at the same time, doing great damage to
the carpet. Hence, its use with the piston type of vacuum pumps was
abandoned.

Mr. Kenney then modified this wide slot renovator by making the face of
same much wider, thus having more surface in contact with the carpet
on each side of the slot, preventing the renovator from sinking into
the nap of the carpet. This type of renovator is illustrated in Fig.
12 and has been designated as Type B. While not as destructive to the
carpets, when a high degree of vacuum existed under the same, it still
pushed hard and was not as rapid a cleaner as the narrow-lipped Type A
renovator.

=Renovator with Auxiliary Slot Open to Atmosphere.=--The renovator
introduced by the Sanitary Devices Manufacturing Company differed
widely from the former types in that it was provided with an auxiliary
slot, open to the atmosphere through the top of the renovator, which
communicated with the slot open to the vacuum by a space of ¹⁄₃₂-in.
under the partition separating the slots. The cleaning slot was made
⁵⁄₁₆-in. wide and the face of the renovator was made 2-in. wide, which
gave a contact of ¹³⁄₃₂-in. in front of the inrush slot and ²¹⁄₃₂-in.
in the rear of the cleaning slot. This form of renovator is illustrated
in Fig. 13 and is designated as Type C.

The auxiliary slot or vacuum breaker permitted air to enter the
cleaning slot even when the renovator was placed on a surface plate,
and, owing to this feature, a high degree of vacuum never existed
within the renovator. It was always easy to operate and did not damage
the carpet. Owing to the wide slot, articles of considerable size
could be picked up, and there was always an abundance of air passing
through the renovator to produce a velocity in the hose and pipe lines
sufficient to carry any heavy articles picked up.

The vacuum producer, control apparatus and the proportions of the
hose and piping used at that time made the degree of vacuum in the
renovator a function of the quantity of air passing, with wide limits
of variation under existing conditions, and this form of renovator is
practically the only one which will do effective cleaning, including
the picking up of litter, without undue wear on carpets, when used
with a system having the above-stated characteristics. This renovator,
however is not without its faults. Owing to the wide surface in contact
with the carpet, a considerable degree of vacuum is necessary in order
that any air shall enter the renovator under the faces of same and, as
the air entering the inrush slot prevents the formation of such vacuum
within the renovator, very little air enters the renovator between
its face and the carpet. When the renovator is operated on a carpet
having a glue-sized back, no air enters through the carpet, therefore
all air entering the renovator must come through the inrush slot and
under the partition separating same from the cleaning slot. Under these
conditions only one side of the vacuum slot is effective and this
effective side is raised above the surface of the carpet.

[Illustration: FIG. 13. TYPE C, WITH AUXILIARY SLOT, OPEN TO
ATMOSPHERE.]

[Illustration: FIG. 14. TYPE D, WITH TWO CLEANING SLOTS.]

When operated on an ingrain or other loose-fabric carpet, much air
enters through the fabric of the carpet, due to the wide cleaning
and inrush slots, in addition to the quantity of air entering through
the inrush slot, making this renovator, when operating under these
conditions, use an unnecessary amount of air. Apparently, this
renovator has been designed to prevent the formation of any great
degree of vacuum under same and such a design has resulted in a greater
volume of air at a lower vacuum passing through than through renovators
of other types.

This property of the renovator raises the question whether the quantity
of air or the degree of vacuum in the renovator is most essential
for the removal of dirt from carpets. Tests made by Mr. S. A. Reeve,
consulting engineer for the Vacuum Cleaner Company, with this type of
renovator, with the inrush open and repeated with the inrush closed,
disclose the fact that it does more effective cleaning with its inrush
closed, while the volume of air passing is considerably less with
the inrush closed. The degree of vacuum was greater, which tends to
indicate that the vacuum within the renovator is the most important
factor.

An extract from the affidavits of Mr. Reeve in one of the numerous
patent suits will show his explanation of this phenomenon: “If we
examine more closely into the actual process whereby such a sweeper
succeeds in extracting dust from carpets, etc., it will appear that the
actual cleaning is effected at the periphery of the slot in the lower
surface of the sweeper. It is accomplished chiefly by the development
of local changes of air pressure at the lips defining this slot,
incidentally to the movement of the tool over the carpet. These changes
cause the air occupying the interstices between the dust particles
to expand suddenly, thus ‘raising the dust.’ To a lesser degree, the
scouring is effected by highly localized air currents of considerable
velocity, engendered where the tool comes in contact with the carpet.
These air currents pick up the dust which has already been expanded
or raised by pressure change. They will be of higher velocity, and
therefore more effective, the better the contact of the tool with the
carpet. The same is true of the pressure changes.

“All this action depends for its intensity, speed and effectiveness,
not on the vacuum existing at the pump or in the separators, but upon
the vacuum prevailing within the sweeper head itself.”

=Renovator with Two Cleaning Slots.=--Another form of renovator was
introduced by the Blaisdell Machinery Company which contained two
cleaning slots each ³⁄₁₆-in. wide and 12-in. long, separated by a
partition ¹⁄₄-in. wide in contact with the surface of the carpet, as
indicated in Fig. 14 (Type D). While this form of renovator has a
greater area of cleaning slot than Type A, its individual cleaning
slots are no wider; therefore, it cannot pick up anything larger than
can be picked up by Type A. As no air can enter under the partition
it can do no more effective work as a dust remover when operated on a
carpet with a glue-sized back and its only advantage over a cleaner
of Type A is that when operated on a loose-fabric carpet more air can
pass through the fabric into the cleaning slot, thus giving a greater
variation in the quantity of air exhausted when operated on carpets of
different texture, a condition which is undesirable when used with a
system having characteristics previously described.

Tests of this type of renovator, made by Mr. Reeve, are given later in
this chapter.

=Renovator with Inrush Slots on Each Side.=--Another form of renovator,
introduced by Mr. Moorhead, is illustrated in Fig. 15 (Type E). This
is a modification of Type A in that an inrush slot is provided on each
side of the vacuum slot, these inrushes being hinged members which
form the sides of the cleaning slot. This cleaner has the advantage
over Type C renovator in that it can take air from either side, but in
action it takes air from but one side at any time. Its inrush will not
become entirely clogged, but its mechanically-moving parts in contact
with the dust and lint picked up will easily become inoperative and are
as like as not to become caught wide open when the air entering the
cleaner will not come into intimate contact with the carpet. In that
event, its cleaning efficiency will be greatly reduced. The author has
not had an opportunity to make any comparative tests of this form of
renovator.

When Mr. Spencer introduced the centrifugal fan as a vacuum producer,
he also brought out a series of carpet renovators of various forms
and sizes. One had a cleaning slot ³⁄₄-in. wide and 10-in. long,
another a slot 15-in. long, ¹⁄₄-in. wide at its end, increasing to
³⁄₄-in. at the center. Another had a slot 20-in. long and ³⁄₈-in.
wide, and finally he adopted a tool with a cleaning slot 15-in. long
and ¹⁄₂-in. wide throughout its length. This is merely the re-entrance
into the field of the wide-slot tool first used by Mr. Kenney and
its successful operation depends on its use with a vacuum producer
of such characteristics and a hose and pipe line of such proportions
that practically a constant vacuum is maintained within the renovator,
regardless of the quantity of air passing through the tool. The latest
form of this renovator, as used by Mr. Spencer, is illustrated in Fig.
16. At the time that the writer made tests on renovators of this make,
the majority of the tests were made with a renovator having a cleaning
slot 10-in. long and ³⁄₄-in. wide. This renovator is designated as Type
F, while the 15-in. × ¹⁄₄-in. to ³⁄₄-in. slot is designated as Type F¹.

[Illustration: FIG. 15. TYPE E, WITH INRUSH SLOT ON EACH SIDE OF VACUUM
SLOT.]

[Illustration: FIG. 16. TYPE F, AN EXAGGERATED FORM OF TYPE B.]

About seven years ago the Supervising Architect of the United States
Treasury Department gave consideration to the use of a carpet cleaning
test to determine the acceptability of any vacuum cleaning system which
might be installed in any of the buildings under his control. The
author was instructed to make a series of tests of carpet renovators,
with a view of determining: (1) the feasibility of using a carpet
cleaning test to determine the merits of a vacuum cleaning system; (2)
to fix the requirements to be incorporated in a specification where
the acceptance of the system was dependent on a satisfactory carpet
cleaning test, to be made at the building after the completion of the
installation; (3) to determine what requirements, other than a cleaning
test, would be necessary to obtain a first-class cleaning system.

The record of many such tests was shown to the author, shortly before
he began making tests. These purported to have been made by Prof.
Miller at the Massachusetts Institute of Technology, with a pump
furnished by the Sanitary Devices Manufacturing Company, in which the
efficiency of the inrush type of renovator (Type C) and the straight
vacuum renovator (Type A) was compared. The results of these tests, as
given in a brief resumé, which was distributed by the Sanitary Devices
Manufacturing Co., indicated that the Type C renovator was the more
rapid and efficient cleaner.

The author learned that these tests were made by the undergraduate
students as a part of the regular laboratory work, and that later a
series of tests was made as the basis of a thesis by Messrs. Paterson
and Phelps in 1906, using the above-described apparatus. The following
year another series of tests was made by Mr. Stewart R. Miller, as the
basis of an undergraduate thesis, in which the efficiencies of the
piston pump and inrush sweeper of the Sanitary Devices Manufacturing
Co. were compared with those of the steam aspirator and straight vacuum
renovator of the American Air Cleaner Company. A copy of this thesis
was furnished the author by the Sanitary Devices Manufacturing Company
shortly after the completion of the tests made by the author.

The relative efficiency of the two types of renovators reported by
these tests differed widely in each case, an occurrence which is liable
to happen where undergraduate students are engaged in such work. They
were, therefore, considered as of doubtful reliability.

The author could find no record of any tests made by anyone of longer
experience and, indeed, these were the only tests of which he could
find any record.

As the author desired to specify a cleaning test which could be readily
repeated at the building in which the cleaning system was installed,
which building was likely to be located in any part of the United
States, no exhaustive laboratory methods were desired or attempted.
As the building was likely to be located in a city where no other
vacuum cleaning systems were then installed and in a new building in
which no dirty carpets were available, and as it was not desirable
to have the contractor furnish the material for the test, it was
considered necessary to use some material in soiling carpets which
would be readily obtainable anywhere, which could be readily brought
to a standard, and which, when worked into the carpets in a reasonable
length of time, would be as difficult to remove as the dirt found in
the average dirty carpet.

=Tests on Dirty Carpets.=--As no tests of cleaning an actually dirty
carpet were on record, quicksand having been used in the Institute of
Technology tests, it was necessary to first clean some carpets that had
been soiled in actual daily service in order to obtain a standard with
which to compare the results in removing various substances, which it
was intended to try as a substitute for dirt. A carpet which had been
in actual use for a number of years on the floors of the old United
States Mint building, in Philadelphia, and receiving the ordinary
amount of cleaning, was procured. This was a Brussels carpet with a
glue-sized back, containing about 20 sq. yds. It was divided into three
approximately equal parts.

An indicator was attached to the vacuum pump for taking air
measurements, and it was found that there was considerable leakage of
air into the system through the connections to the separators and at
other points, therefore the pump was operated with 22 in. of vacuum in
the separator and a card taken with all outlets closed and the amount
of leakage noted. During the tests this degree of vacuum was always
maintained in the separators and pipe lines and the vacuum in the
renovator was varied throughout the tests by throttling the hose cock.
This manner of making tests gave a practically constant leakage which
was deducted from the quantities shown by the indicator cards taken
with the renovators in operation.

As the writer had already made many tests of the efficiency of various
types of vacuum pumps as air movers under various degrees of vacuum,
and as the capacity of the pump available was far in excess of that
required to operate one renovator, no attempt to obtain the efficiency
of the plant as a unit was made. Instead, the vacuum at the hose cock
was adjusted until the degree obtained was what the writer had found to
be within the limit obtained in practice. The resulting vacuum at the
renovator was then noted.

Each piece of carpet was cleaned during six periods of one minute
each, using a different vacuum at the tool for each piece of carpet.
The carpets were weighed at the beginning of the test and after each
one-minute period. At the conclusion of these tests each carpet was
cleaned until no change of weight occurred after two minutes’ cleaning.
They were then considered as being 100% clean and this standard was
made a basis for computing the percentage of dirt removal. A renovator
of Type C was used in these tests.

Shortly afterward a similar test was made on a dirty carpet of 4.6
sq. yds. area, using a renovator of Type F. This carpet was also a
Brussels, with glue-sized back, which had been in use in the shoe
department of a large department store in Hartford. These carpets
contained approximately 2 oz. of dust per square yard, none of which
was visible on the surface, and they were probably as clean as the
average carpet after being gone over with a carpet sweeper or after a
light application of a broom.

TABLE 1.

CLEANING TESTS OF DIRTY CARPETS.

------------------------------+------------+-----------------+------
Type of Renovator. | A | C | F
------------------------------+------------+-----------------+------
Vacuum in renovator, in. Hg | 2 4¹⁄₂| 1 2¹⁄₂ 4 | 3¹⁄₂
Air exhausted, cu. ft. per min| 16 27 | 24 37 44 | 59
Material removed, per cent. of| | |
total, 1 min. | 50 60 | 37 39 47 | 35
Material removed, per cent. of| | |
total, 2 min. | 72 81 | 52 59 63 | 55
Material removed, per cent. of| | |
total, 3 min. | 85 90 | 59 66 71 | 69
Material removed, per cent. of| | |
total, 4 min. | 90 95 | 61 72 83 | 77
Material removed, per cent. of| | |
total, 5 min. | 93 98 | 66 75 87 | 84
Material removed, per cent. of| | |
total, 6 min. | 95 100 | 67 82 90 | 89
H. P. per ounce dust |0.037 0.147 |0.045 0.116 0.252|0.261
Ounces dust per minute |1.9 2.0 |1.34 1.64 1.8 |1.78
H. P. at renovator |0.07 0.29 |0.06 0.19 0.45 |0.475
------------------------------+------------+-----------------+------

As the sizes of the carpets used in making the tests were not always
the same, allowance has been made for this variation by using, in the
case of Type F renovator, instead of the true time, a calculated time
which allows each renovator the same time for cleaning 1 sq. yd. of
carpet. For instance, in the case of the small carpet cleaned with Type
F renovator, an interval of 60 × 4.6 ÷ 6, or 46 seconds, was taken
as equal to one minute’s cleaning of the carpet with types A and C
renovators. Such interval is stated and plotted as one minute in the
table opposite, which gives the results of cleaning dirty carpets with
the three types of renovators.

=Type A Renovator Most Efficient on Dirty Carpets.=--The results of the
tests of the three types of renovators, each when it was operated with
the highest vacuum under the renovator, are plotted in Fig. 17 in order
that a ready comparison may be made. This curve indicates that Type A
renovator does more effective cleaning in less time than either of the
other two types tested.

[Illustration: FIG. 17. TESTS OF THREE RENOVATORS ON DIRTY CARPETS.]

Referring to the second line of the table, which gives the degree of
vacuum obtained in the renovator during the tests, it will be noted
that the highest vacuum attained with each type of renovator is
practically the same. This degree of vacuum was obtained with the
average vacuum at the hose cock, using 100 ft. of hose in each case,
and corresponds to that obtained in the commercial operation of each
of the renovators with the vacuum producers ordinarily used, which was
15 in. in the case of Type C, 10 in. in case of Type A, and 5 in. in
case of Type F, the hose being the size used by each of the systems as
marketed.

The third line, which shows the cubic feet of free air per minute
passing the renovator, indicates that Type A renovator requires much
less air at the same degree of vacuum than either of the other types to
do better work.

From the readings in these two lines the horse power required at the
renovator, to move the air that passes same is obtained with 100%
efficiency adiabatic compression. The results are tabulated in the
ninth line of the table.

This indicates that Type A renovator does more effective work with
about 50% of the power required by either of the other types of
renovators.

The tenth line gives the rate of cleaning and again shows Type A
renovator to be the most rapid cleaner.

The eleventh line gives the horse power required at the renovator when
in operation, from which it will be seen that effective cleaning cannot
be accomplished with less than ¹⁄₄ H. P. at the renovator.

Attention is called to the great reduction in power in case of Type A
renovator when the vacuum at the tool is reduced from 4¹⁄₂ in. to 2
in. and to the small reduction in the efficiency which results from
this great reduction in power. This is not the case with the Type C
renovator, where there is a considerable reduction in the already low
efficiency with each reduction in the vacuum. This characteristic of
Type A renovator is discussed further on in the chapter on hose.

=Tests of Carpets “Artificially” Soiled.=--Having determined the
efficiency of the various types of renovators when operated on dirty
carpets, the author then attempted to find some substance easily
obtained anywhere which could be used as a substitute for actual dirt,
and which would give approximately equal results with these obtained on
dirty carpets.

A test of this character was made by the author some time previous to
the tests of dirty carpets and was made on a Wilton velvet rug of about
12 sq. yds. area. The material spread on same was ordinary wheat flour,
as used in demonstrations, 3 lbs. of which were placed on the rug and
rubbed in with sticks of wood as well as possible and the rug cleaned
for three minutes, using a Type A renovator attached to the separator
with 50 ft. of 1-in. diameter hose. The results were as follows:

VACUUM AT SEPARATOR, PER CENT. DIRT
INS. MERCURY. REMOVED.
5 95
10 98
15 98

The vacuum at the renovator was not measured at the time of making this
test and its amount is not exactly known, but further tests with this
type of renovator under nearly the same conditions gave the following
results:

VACUUM AT HOSE COCK, VACUUM IN RENOVATOR,
INS. MERCURY. INS. MERCURY.
5 3
10 6¹⁄₂
15 9

and it is probable that the vacuum at the renovator during these tests
was approximately the same.

Comparison of the results of this test, in which 4 sq. yds. of carpet
were cleaned per minute, with those of the tests of dirty carpets, in
which only 1 sq. yd. was cleaned per minute, indicates that wheat flour
is not a suitable substitute for dirt in making a carpet cleaning test.

The author, believing that flour is of sufficient fineness, but not of
sufficient weight, tried Portland cement, which is very heavy and at
the same time exceedingly fine, as a substitute for dirt in soiling
carpets. The same carpet that had been cleaned in Philadelphia was used
and 6¹⁄₂ oz. of cement was worked into the same. It was then cleaned
with a Type C renovator, with a vacuum of 2¹⁄₂ in. hg. at the renovator
and 95% of the cement was removed in two minutes’ cleaning, as against
59% of the dirt in the carpet when received.

Ordinary dirt, taken from some flower pots which had been left dry
for some time, was then tried with the same carpet, using a Type C
renovator and 1 in. hg. With this arrangement, 71¹⁄₂% of the dirt was
removed in two minutes as against 52% of the dirt in the carpet as
received.

This dirt was then mixed with water to a thin mud and spread over the
carpet and the carpet dried before cleaning. Then 11¹⁄₄ oz. of this
material was worked into 6 sq. yds. of carpet and a Type C renovator
removed 100% of this in four minutes’ cleaning, with a vacuum of
2¹⁄₂ in. hg. at the tool as against 72% of the dirt in the carpet as
received.

The author’s ingenuity being about exhausted, he referred to the test
of Mr. Stewart R. Miller in which quicksand which would pass a 50-mesh
to the inch screen was used, a long-napped Brussels carpet being filled
with 5¹⁄₂ oz. per square yard and cleaned with Types A and C renovators.

This test indicated that a nearer approach to the results in cleaning
dirty carpets was possible with this substance than with any which
the author had tried. The author repeated Mr. Miller’s test, using a
Type F renovator, 10-in. × ³⁄₄-in. cleaning slot, and also a Type F¹
renovator, 15-in. × ¹⁄₄-in. to ³⁄₄-in. cleaning slot. In duplicating
these tests the author was associated with Mr. E. L. Wilson, a graduate
of the Institute, who was familiar with the methods used by Mr. Miller.
With his assistance, the conditions of Mr. Miller’s tests were almost
exactly duplicated. The results of Mr. Miller’s and the author’s tests
are given in the table opposite, correction being made in the time of
cleaning proportional to the size of carpets used, to allow the same
time for cleaning 1 sq. yd. of carpet by each renovator.

TABLE 2.

CLEANING TESTS OF CARPETS FILLED WITH 5¹⁄₂ OZ. OF QUICKSAND PER SQUARE
YARD OF CARPET.

--------------------------------------------+----+-----+-----+-----
Type of Renovator. | A | C | F | F¹
--------------------------------------------+----+-----+-----+-----
Vacuum in renovator, in. hg. |4¹⁄₂| 4 |3¹⁄₂ |3¹⁄₂
Air exhausted, cubic feet per minute | 27 | 44 | 59 | 54
Material removed, per cent. of total, 1 min.| 60 | 53 | 66 | 53
Material removed, per cent. of total, 2 min.| 75 | 65 | 83 | 75
Material removed, per cent. of total, 3 min.| 82 | 74 | 94 | 86
Material removed, per cent. of total, 4 min.| 87 | 82 |100 | 94
Material removed, per cent. of total, 5 min.| 92 | 87 | -- |100
Material removed, per cent. of total, 6 min.| 95 | 93 | -- | --
H. P. per ounce sand |0.09|0.138|0.084|0.109
Ounces sand per minute |3.2 |3.1 |5.3 |4.0
--------------------------------------------+----+-----+-----+-----

The results of these tests are shown graphically in Fig. 18. Comparison
of these curves with the curves of cleaning dirty carpets (Fig. 17),
shows a falling off in the efficiency of cleaning by Type A renovator
while there is a gain in the efficiency in cleaning by all of the
other types of renovators, Type C being now nearly as efficient as
Type A, while Types F and F¹ renovators are now more efficient than
Type A. This result must be due either to the increased quantity of
material to be removed, 5¹⁄₂ oz. per square yard in case of the sand
as against 2 oz. per square yard in case of the dirt, or else to the
change in the character of the material removed, the sand having much
sharper surfaces than would be encountered in case of dirt which must
necessarily be ground under the feet before it reaches the carpet, or
to the longer nap of the carpet.

[Illustration: FIG. 18. CLEANING TESTS OF CARPETS FILLED WITH
QUICKSAND.]

In order to determine the effect of the increase in the quantity of
material on the results, the tests were repeated using 1 oz. of sand
per square yard of carpet in each case, omitting the test on Type F¹
renovator.

These tests were made on a glue-sized back, short napped Brussels
carpet, using as much sand as could readily be worked out of sight in
this carpet. The results of tests are given in the following table:

TABLE 3.

CLEANING TESTS USING 1 OUNCE OF SAND PER SQUARE YARD OF CARPET.

----------------------------------+-----------+---------------+-----
Type of Renovator. | A | C | F
----------------------------------+-----------+---------------+-----
Vacuum in renovator, in. hg. | 2 4¹⁄₂ | 1 2¹⁄₂ 4 |3¹⁄₂
Air exhausted, cubic feet per min.| 16 27 |24 37 44 | 59
Material removed, per cent. of | | |
total, 1 min. | 48 54 |45 48 50 | 50
Material removed, per cent. of | | |
total, 2 min. | 70 87 |60 63 65 | 73
Material removed, per cent. of | | |
total, 3 min. | 91 100 |73 75 77 | 87
Material removed, per cent. of | | |
total, 4 min. |100 -- |76 81 88 |100
Material removed, per cent. of | | |
total, 5 min. | -- -- |-- 88 97 | --
Material removed, per cent. of | | |
total, 6 min. | -- -- |-- 92 102 | --
H. P. per ounce sand |0.047 0.143|0.06 0.195 0.44|0.223
Ounces sand per minute |1.5 2.0 | -- 0.92 1.02|2.11
----------------------------------+-----------+---------------+-----

The results of these tests at the higher vacua are shown graphically in
Fig. 19. Comparison of these curves with those obtained when removing
sand from a long napped carpet (Fig. 18), shows:

First, a marked increase in the efficiency of Type A renovator, this
being slightly better than obtained when cleaning a dirty carpet.

Second, practically no change in the efficiency of Type C renovator.

Third, a small decrease in the efficiency of Type F renovator, which
still shows a much higher efficiency than when cleaning dirty carpets.

In order to determine how much, if any, of these changes in the
behavior of the renovators was due to the increase in the quantity of
material to be removed, the horizontal line, representing 1 oz. of sand
remaining in the long-napped carpet, was drawn on Fig. 18 and, using
this as a base line, it will be seen that Type A renovator removes this
remaining material in three minutes, the same time as was required to
remove the same amount from the short-napped carpet. However, the first
4¹⁄₂ oz. of sand have been removed from the long-napped carpet in three
minutes, or at a rate 4¹⁄₂ times as fast as the last 1 oz. was removed.
This indicates that the narrow slot renovator is capable of handling
more material than is likely to be encountered in any dirty carpet and
that the apparent decrease in the efficiency of this renovator is not
due to the increased quantity of material to be removed.

[Illustration: FIG. 19. CLEANING TESTS USING 1 OZ. OF SAND PER SQUARE
YARD OF CARPET.]

It will be noted that the Type C renovator removed the last 1 oz. per
square yard from the long-napped carpet in the same time that was
required by Type A renovator, while it needed nearly twice as long to
remove this amount of material from the short-napped carpet (Fig. 19).
This renovator, however, was slower in removing the first 4¹⁄₂ oz. per
square yard.

Type F renovator removed the last 1 oz. per square yard from the
long-napped carpet in two minutes, while it required twice this time
to remove the same amount from the short-napped carpet. This renovator
also removed the first 4¹⁄₂ oz. per square yard from the long-napped
carpet in two minutes, while it required three minutes for Type A and
3-³⁄₄ minutes for Type C renovators to remove the same quantity. It
is, therefore, evident that sand is removed more rapidly from a long
than from a short-napped carpet when a wide slot renovator is used. The
same time is required to remove small quantities of sand from a long or
short-napped carpet with a narrow slot.

This phenomenon is probably due to the sand being held in the carpets
by the adhesion of its sharp edges to the sides of the nap, this
being more pronounced in the case of the long-napped carpet where
it is easier to work the material out of sight without grinding it
into intimate contact with the pile of the carpet. When the wide-slot
renovator passes over the carpet, the carpet is arched up into the
slot and the upper ends of the nap separated. The longer the nap or
the wider the slot, the greater will be this separation. With the
long-napped carpet this separation will at once release the sand,
while, in case of the short nap, there is less separation and also
more adhesion of the sand to the pile of the carpet, due to the harder
grinding necessary to work the material out of sight. Therefore, the
wider the cleaning slot used, the faster the sand will be removed, as
is evident by comparison of the tests of Types F and F¹ renovators on
the long-napped carpet.

With the narrow slot renovator the arching of the carpet under the
cleaning slot is negligible and no advantage is gained when using this
type of renovator to remove sand from a long-napped carpet. It is also
possible that the nap of the carpet may be longer than the width of the
cleaning slot, in which case the nap will not snap back to a vertical
position when it is under the cleaning slot, but will be pressed down
and will impair the action of the renovator. The author considers that
the width of the slot should always be greater than the length of the
nap of the carpet in order to do effective cleaning.

Shortly after making the above-described tests, the author had occasion
to make somewhat similar tests, using a sand-filled carpet, in an
attempt to try out a proposed carpet cleaning test intended to be used
as a standard for use in specifications for a vacuum cleaning system.
When a Wilton carpet was used, it was found that neither Type A or C
renovator would fulfill the test requirements, which were within the
results obtained in tests already described. Unfortunately a Type F
renovator was not available, but the author is of the opinion that it
would have done better.

The test was then repeated, using a Brussels carpet and the test
requirement was easily met. This discovery led the author to make
further tests of carpets of different makes, filled with sand and
cleaned under the same conditions which yielded far from uniform
or satisfactory results, and the use of a cleaning test, where
artificially-soiled carpets are used, was abandoned.

The author is of the opinion that no substance artificially applied to
a carpet, other than regular sweepings, will give anything like the
same results as will be obtained in actual cleaning. Sand seems to be
the only substance which can be worked into the carpet that is nearly
as difficult to remove as the actual dirt found in carpets, and, in
many cases, this material gives results that are misleading and unfair
to some types of renovators. No test which uses a carpet artificially
soiled with artificially prepared dirt is considered to be of any value
in determining the relative efficiency of various types of carpet
renovators.

A series of tests was made by Mr. Sidney A. Reeve consulting engineer,
of New York City, in October, 1910, at the works of the Vacuum Cleaner
Company, Plainfield, N. J., in which the conditions were such as would
give much more uniform results than were possible in the tests made by
the author.

In making these tests the renovator was held firmly clamped in any
desired position in a wooden carriage rolling upon a straight wooden
track. The portion of the carriage supporting the sweeper is attached
to the remainder of the carriage by hinges, so that the sweeper is
free to seek its own contact with the carpet. The carriage was given a
reciprocating motion by its attachment to a large bell crank, which in
turn received its motion from the factory shafting. The construction of
the bell crank was such that the driving power could be readily thrown
in and out of gear at any time.

The carpet was stretched tightly upon a platen which was fitted for
movement across the line of motion of the sweeper, along straight
guides suitably attached to the floor. The ends of the carpet were
first wedged tightly in clamps and the clamps wedged apart so as to
stretch the carpet.

The tests consisted in first weighing the carpet, then stretching it
upon the platen, then sprinkling thereon a suitable and known weight of
dirt taken from the separators of the company’s machines, from which
the lint and coarse, fibrous material had been sifted and which was
thoroughly trodden into the fibres of the carpet, whereupon the sweeper
was set in motion for a given number of strokes.

In nearly all cases the tests were repeated upon the same piece of
carpet, with the same charge of dirt, by repeatedly placing the carpet
in the frame and giving it a further and more extended cleaning.

All tests were corroborated by repetition before being admitted to
the records. Every effort was made to have the tests approach the
conditions occurring in actual practice, as nearly as possible, and
still keep them definite and measurable.

The carpet used was a Wilton, of the standard width of 27 in. and
something over a yard long, and the sweeper was given a stroke of 34
in. at the rate of 40 strokes per minute. The sweepers were attached to
a 6-ft. tubular handle, ¹⁵⁄₁₆-in. inside diameter, and connected to the
separator by 50 ft. of 1-in. diameter hose.

Before making any tests, the piston pump used in the experiments was
calibrated by pumping through a rotary meter and the amount of air
moved per revolution for each degree of vacuum from open inlet to
closed system was carefully determined. In making the tests of various
renovators, each renovator was allowed to pass the same amount of air
as the others tested in comparison therewith and the vacuum at the
renovator and at the separator was allowed to be what was necessary
to pass this known amount of air through the renovators. This method
is widely different from that used by the author where the degree of
vacuum at the renovator head was determined and used as a limiting
factor, the quantity of air being allowed to vary as necessary to
produce this vacuum.

The results of three series of tests are given in Fig. 20, which shows
those obtained with Kenney Type A renovators, having a face 12¹⁄₂ in.
× ⁷⁄₈ in. and a cleaning slot 11¹⁄₂ in. × ⁵⁄₃₂ in. Curve A was made
with the angle of the handle such as would give as near as possible
a perfect contact of the sweeper with the carpet. Curve B was made
with the sweeper handle canted 5° below the proper angle. Curve C was
made with the sweeper handle raised approximately 15° above the proper
angle. The ordinates represented the amount of dust in the carpet
in 40ths of a pound, also reduced by the author to ounces, and the
abscissae the number of strokes made by the sweeper.

[Illustration: FIG. 20. THREE SERIES OF TESTS WITH KENNEY TYPE A
RENOVATORS.]

Curves B and C show the loss in efficiency which occurs when the
renovator is canted from its proper position on the carpet. This
falling off in efficiency will necessarily be greater the wider the
face of the renovator, as is shown in further tests by Mr. Reeve, using
a Type C renovator, which tests also show that this renovator gives a
slightly higher efficiency when operated with the inrush slot stopped,
as is shown in Fig. 21.

In this curve the ordinates represent the per cent. of normal dirt, _i.
e._, the amount likely to be found in a dirty carpet, remaining in the
carpet at any stage of the cleaning, and the abscissae the number of
strokes that have been made by the sweeper. Heavy solid lines represent
the results with the inrush open and dotted lines the results with the
inrush stopped. The figures on the curve represent the degree to which
the handle has been varied from the position giving the best results in
cleaning.

[Illustration: FIG. 21. TESTS BY MR. REEVE, USING TYPE C RENOVATOR.]

Fig. 22 shows the results of tests by Mr. Reeve using a renovator of
Type D, having a double cleaning slot, and indicate that this type
of cleaner is not as efficient as Type A and is affected more by the
canting of the handle from the best angle for cleaning.

The above mentioned tests are published through the courtesy of Messrs.
Ewing and Ewing, attorneys for the Vacuum Clean Cleaner Company.

Since the method of making these tests is entirely different from that
used by the author, a comparison of the results, with any assurance
that the same conditions existed in both cases, is impossible. It
occurred to the author that a comparison of the results of the tests by
Mr. Reeve, using a carpet artificially filled with actual dirt taken
from carpets, with the tests made by the author on carpets naturally
soiled, would tend to show if equal results could be obtained by a
vacuum cleaner by artificially soiling a carpet with dirt taken from
another carpet, and in cleaning a carpet naturally soiled.

[Illustration: FIG. 22. TESTS BY MR. REEVE, USING TYPE D RENOVATOR.]

The author has reduced these results to the same units of time per
square yard of carpet cleaned as in the test on the Philadelphia carpet
with the small-sized Type A renovator (11-in. × ¹⁄₂-in. face and 10-in.
× ³⁄₁₆-in. cleaning slot). The carpet used by the author contained 6
sq. yds. and was held in cleaning by a weight at each corner, while the
carpet used by Mr. Reeve was ³⁄₄ yd. wide and cleaned for approximately
one yard of its length, the relative size being 1 to 8. The time of
cleaning was 6 min. in the author’s test which would correspond to
³⁄₄-min. cleaning in Mr. Reeve’s test, or 30 strokes of the sweeper.
The total dust in the carpet in Mr. Reeve’s test was ⁵⁄₄₀ lbs., or 2.66
oz. per square yard, and his test is compared with the author’s test
with the carpet containing 2 oz. per square yard. Calculation of the
per cent. of total dirt removed in each 5 strokes of the sweeper in
Mr. Reeve’s test, and a comparison of the per cent. of dirt removed in
each one minute’s test by the author are given below:

TABLE 4.

COMPARISON OF TESTS MADE BY MR. REEVE AND BY THE AUTHOR.

-----------------------------+-----------------------------
MR. REEVE’S TEST. | AUTHOR’S TEST.
-----------------------------+-----------------------------
Material removed, | Material removed,
Strokes. per cent. of total.|Minutes. per cent. of total.
-----------------------------+-----------------------------
5 62 | 1 60
10 80 | 2 81
15 89 | 3 90
20 94 | 4 95
25 97 | 5 98
30 99 | 6 100
-----------------------------+-----------------------------

The above comparison was made using curve A, Fig. 20, with the sweeper
at its best angle with the floor. The close agreement of the two tests
indicates that a carpet artificially soiled with dirt actually removed
from another carpet by a vacuum cleaner is as difficult to remove
as dirt which has been worked into a carpet by ordinary daily use.
This condition does not result when any other substance is used to
artificially soil the carpet, as will readily be seen by reference to
the tests of carpets filled with sand and other substances which have
been described in this chapter.

A comparative test of three different renovators was recently made by
the author. Renovator No. 1 had a cleaning slot 14 in. long by ³⁄₄
in. wide, the edges of the slot being a segment of a circle having a
¹⁄₈-in. radius. This form of cleaning surface allows very small area of
contact with the surface cleaned and permits the admission of large air
volumes, about 56 cu. ft., with 2-in. vacuum. It is practically a Type
F renovator, similar to that used in the tests at Hartford.

Renovator No. 2 had a cleaning slot 9¹⁄₂ in. long and ¹⁄₄ in. wide, the
face of the renovator being approximately ⁷⁄₈ in. wide and practically
a plain surface, a typical Type B renovator.

Renovator No. 3 had a cleaning slot 7¹⁄₄ in. long and ¹⁄₈ in. wide,
the face of the renovator being ³⁄₈ in. wide and the edges slightly
rounded, a typical Type A renovator.

The carpet used was a Colonial velvet rug with ¹⁄₈-in. nap, closely
woven, containing 6 sq. yds. This rug was filled with 12 oz. of dirt
taken from separators of cleaning machines, from which the lint and
litter had been screened. This was rubbed into the carpet until no dirt
was visible on the surface, the surface being then lightly swept with a
brush and weighed.

In cleaning this carpet the renovator was passed once over the entire
surface at the rate of about 70 ft. per minute. This required six
strokes and 50 seconds for No. 1 cleaner, nine strokes and 77 seconds
for No. 2 cleaner, and 12 strokes and 100 seconds for No. 3 cleaner.

The carpet was then weighed, spread down and gone over three times,
weighed, spread down and gone over four times. This operation was
repeated until the carpet came within ¹⁄₂ oz. of its weight when
received.

Each of the three renovators was operated with a vacuum of 2 in. at the
renovator.

The results of these tests are illustrated by curves 1A, 2A and 3A in
Fig. 23. This shows that to remove 95% of the dirt the renovator had to
be passed over the carpet 20 times for No. 1 renovator, 15 times for
No. 2 renovator and 8 times for No. 3 renovator.

Similar tests were then made with each of the renovators, with a
vacuum of 4.5 in. of mercury at the renovator. The results are shown
by curves 1B, 2B and 3B (Fig. 23) These show that to remove 95% of the
dirt the renovator had to be passed over the carpet 11 times with No. 1
renovator, 6¹⁄₂ times with No. 2, and 4¹⁄₂ times with No. 3.

These tests are all on the same carpet, with the same quantity of the
same dirt and with the renovators moved at the same speed in each case.
The comparison of the results should give a fair indication of the
efficiency of the different types of renovators at different degrees of
vacuum within the renovator and, therefore, form the most conclusive
proof of the statements relative to the efficiency of renovators as
given in this chapter.

All cleaning tests that the author has observed indicate that the
higher the vacuum within the renovator the more rapid and effective
the cleaning, and that the efficiency of the renovator is fully as
high with a small as with a large volume of air passing through the
renovator and with the same degree of vacuum within same. Therefore,
the most effective and economical renovator should be that which gives
the highest vacuum with the least air passing.

[Illustration: FIG. 23. TESTS SHOWING EFFICIENCY OF DIFFERENT TYPES OF
RENOVATORS AT DIFFERENT DEGREES OF VACUUM.]

If the degree of vacuum within the renovator be carried to an
abnormally high degree, there will be a tendency for the renovator to
cling so close to the carpet that its operation will be difficult and
the wear on the carpet rapid. The production of this high vacuum, with
a larger quantity of air exhausted, will result in the expenditure of
power at the renovator in excess of the gain in efficiency and speed of
cleaning.

It is evident that the wider the cleaning slot, the greater will be the
tendency of the renovator to stick to the carpet with a high vacuum
within the same. The author has experienced no difficulty in operating
the 10-in. renovator, with ³⁄₁₆-in. cleaning slot, with a vacuum as
high as 9 in. of mercury, but wider-slot renovators always push hard
when any high degree of vacuum exists within them.

=Effort Necessary to Operate Various Types of Renovators.=--The author
made a series of tests to determine the effort necessary to operate the
various types of renovators under different conditions. In making these
tests the renovator was attached to a spring balance and pulled along
the floor, the pull required to move the renovator being observed by
the reading of the balance. Three types of renovators were used in this
test: Type A, having a cleaning slot ⁵⁄₁₆ in. wide and 12 in. long;
Type C, having a cleaning slot ⁵⁄₁₆ in. wide and 12 in. long, with an
auxiliary inrush slot ¹⁄₄ in-wide and 12 in. long; Type F, having a
cleaning slot ³⁄₄ in. wide and 10 in. long. The results were as follows:

TABLE 5.

EFFORT NECESSARY TO OPERATE CLEANING TOOLS.

--------------------+----------+----------+-------+------------
| |Vacuum at | |
| Type of |Renovator,| Pull, |Air, cu. ft.
Kind of Carpet. |Renovator.| In. Hg. |Pounds.| per min.
--------------------+----------+----------+-------+------------
Brussels, short | A | 8 | 20 | 27
Napped, close back | C | 6¹⁄₂ | 17 | 31
| F | 3¹⁄₂ | 11 | 59
Axminster, long nap | F | 3¹⁄₂ | 14 | 59
Velvet, with glue | A | 8¹⁄₂ | 18 | 28
Sized back | C | 6¹⁄₂ | 17 | 31
Velvet, without glue| A | 3¹⁄₂ | 15 | 40
Sized back | C | 1 | 12 | 45
Linoleum | A | 13 | 23 | 12¹⁄₂
| C | 1 | 10 | 40
--------------------+----------+----------+-------+----------

It may be noted that, when operating on the Brussels and the glue-sized
velvet, the pull required to move all types of renovators bears a
direct ratio to the degree of vacuum under the renovator, and that
the quantity of air exhausted is the same for each renovator on either
carpet, but different for each type of renovator. It is evident that,
in this case, very little air enters the renovator by passing up
through the carpet, and hence the action of the inrush slot on Type
C renovator is noticeable only to a slight degree. When operating on
velvet carpet, without glue-sized back, the inrush slot, in conjunction
with the greater quantity of air coming through the carpet, has caused
the passage of a large quantity of air, while the vacuum maintained
at the renovator is greatly reduced over that which was maintained
under Type A renovator when the same quantity of air was passing. In
this case, nearly all of the air entering Type A renovator came from
the under side of the carpet. The effect on the efficiency of cleaning
with Type C renovator under these conditions can readily be imagined,
by reference to former tests, as being greatly reduced over that of
Type A when passing the same quantity of air. With linoleum, the action
of the inrush slot of the Type C renovator has again greatly reduced
the vacuum under the renovator, although the quantity of air is much
in excess of that passing Type A renovator. The difference in the
behavior of the renovators on different makes of carpet is seen to be
due largely to the difference in the quantity of air which passes up
through the carpet into the renovator.

It is evident that, with the same degree of vacuum within the
renovator, all types are equally easy to push and that, if the vacuum
within the renovator becomes higher than is necessary to produce good
cleaning results, unnecessary effort will be required to operate the
renovator.

=Relative Damage to Carpets with Various Types of Renovators.=--A few
tests have been made by the author to determine the relative damage to
carpets with the various types of renovators in use and it is found
that, when the edges of the renovators are made exceedingly sharp,
considerable nap is pulled out. However, if the edges are made slightly
rounding and not too narrow, no undue wear will occur with any of the
types of renovators described, provided the vacuum in the renovator is
not permitted to become greater than 5 in. of mercury.

The author considers that for best results the vacuum should not be
less than 3¹⁄₂ in. of mercury at the renovator and that at least 2 in.
is necessary to do even fair work, while, to permit easy operation and
prevent undue wear on the carpets, it should not be higher than 5 in.

Before deciding which type of renovator will be most economical to use
in any case the character of the cleaning to be done must be considered.

Of the various types of renovators considered in this chapter, Type C
can be dismissed at once, as it is neither as effective a dust remover
as Types A or F nor will it remove litter any more effectively than
Type F. Tests of Type D renovator do not show as good results as a dust
remover as Type A, nor will it remove litter any more effectively. Type
E renovator is a modification of Type C and is not likely to be any
better.

The selection, therefore, lies between Type A and Type F renovators,
the former being by far the best dust remover, while the latter will
pick up a limited amount of small litter, such as matches, cigar and
cigarette stumps, and small bits of paper. Where large quantities of
these articles are likely to be encountered, it is more important
that the renovator should be capable of picking them up, but,
unfortunately, when these articles are met with, there are also likely
to be much larger articles present that cannot be picked up by any but
a specially-designed renovator, and other means must be employed to
remove them.

In residences, private offices and nearly every place where carpets or
rugs are likely to be used, waste baskets and cuspidors are provided
and the articles mentioned are deposited in them rather than on the
floor. Thus, the renovator will be required to remove dust, cigar ashes
and sand or mud only, all of which can be readily removed with a Type A
renovator with less expenditure of power than with a Type F renovator.

Public places, such as ante-rooms, reception rooms and other offices
to which the general public is admitted in great numbers and which are
sometimes carpeted, are likely to contain articles which can be picked
up by Type F renovator and not by Type A. For cleaning such places, a
Type F renovator is necessary, although it requires considerably more
power, but the author sees no reason why this type of renovator should
be used to the exclusion of Type A, even in buildings containing rooms
of this character. If the building also contains several rooms where
litter will not be encountered, the author would recommend that both
types of renovators be used, each in its proper place, and thereby
cause a considerable saving of power in cleaning rooms where no litter
is encountered.

For residence work there is little need of providing carpet renovators
capable of picking up litter and, also, there will be very little bare
floor cleaning to be done, which requires larger volumes of air. A
smaller capacity exhausting plant, therefore, can be installed, if the
Type A renovator is adopted.

In large office buildings where all cleaning is done after office
hours, where the building is provided with its own power plant, and
where speed of cleaning and ability to clean all apartments with the
fewest tools to be carried by the cleaners is desired, it appears to be
better to use only Type F renovators for all carpet work, as the extra
power required will not be of vital importance.

Summing up the matter, the author believes that both Type A and F
renovators have their uses in their proper places but that Type A
has the widest field of usefulness, yet it need not invade the field
of the other. He also believes that this fact will be realized by
manufacturers in the near future, when the two types of renovators will
work together side by side for the general good of the manufacturers
and the users.

CHAPTER IV.

OTHER RENOVATORS.

The renovator which is next in importance to the carpet renovator is
that used for cleaning bare floors. The earliest form of this renovator
was the oscillating floor type introduced by Mr. Kenney. This was a
modification of the narrow-slot carpet renovator introduced by him. The
body of same was curved and supported on two small wheels or rollers,
with the intention of bringing the cleaning slot close to the surface
cleaned without its touching same, as indicated in Fig. 24.

[Illustration: FIG. 24. EARLY TYPE OF BARE FLOOR RENOVATOR.]

[Illustration: FIG. 25. LATER TYPE OF BARE FLOOR RENOVATOR.]

This form of renovator was found to be impracticable for the reason
that any change in the angle with which the stem or tube connecting
the body of the renovator with the handle in relation to the surface
cleaned tended to make its action ineffective. If the angle were
made less the distance between the cleaning slot and the floor was
increased, allowing the air to enter the cleaning slot without coming
in contact with the surface to be cleaned, or, if the angle were made
greater, it would cause the face of the renovator to strike and damage
the surface of the floor.

The wheels or rollers on which this renovator was mounted, being so
small, were subject to rapid wear both on their faces and in their
bearings, and when these wheels were slightly worn the renovator was
practically useless. On account of the above defects this form of
renovator was abandoned shortly after its introduction.

The next form of renovator to be tried was a modification of the
ordinary soft bristle brush, such as had been in general use for
cleaning hard wood floors. The bristles were arranged around the edges
of the cleaning slot, in the body, which was shaped similar to the
slot in the carpet renovator. Rubber or leather curtains or skirting,
extending nearly to the ends of the bristles, was placed inside of
these bristles in order to cause the air in entering the body of the
renovator to come into intimate contact with the surface to be cleaned.
The general form of this type is shown in Fig. 25.

[Illustration: FIG. 26. ANOTHER TYPE OF BARE FLOOR RENOVATOR.]

This form of renovator, while more efficient than the oscillating
floor type, still had its faults in that it had a tendency to push the
dirt along the floor in front of it, much the same as the floor brush
from which it was copied was designed to do. Also, there was too much
tendency for the air to pass into the body of the renovator without
coming into intimate contact with the surface to be cleaned. While this
type of floor renovator or a slight modification thereof is still in
use by several manufacturers today, it never has and never will be an
effective bare floor cleaner.

A modification of this type of bare floor renovator, in which the
bristles have been shortened and made thicker, the skirting or flaps
placed on the outside and the stem provided with a swivel joint, is
shown in Fig. 26. Such an arrangement is an improvement over the former
type as, owing to its wider and shorter mass of bristles, there is less
tendency for the air to pass into the body of the renovator without
coming into intimate contact with the surface cleaned. It is still
prone to push its dirt before it and is far from being a perfect bare
floor cleaner.

[Illustration: FIG. 27. BARE FLOOR RENOVATOR WITH FELT CLEANING
SURFACE.]

The next modification in the bare floor renovator was the abandoning of
the bristle brush in favor of a cleaning surface composed of felt as
shown in Fig. 27. In this form of renovator the air entering the body
of the same must pass either between the felt and the surface cleaned
or through the felt itself, and this air quantity is small. Since this
renovator has a wider cleaning slot than the Type A carpet renovator,
and, as it is used with the same vacuum producer, hose and pipe lines,
a considerable degree of vacuum will be produced under same, especially
when operated on polished floors, where the conditions are nearly the
same as we observed with Type A carpet renovator operated on linoleum.
With the wider slot, the effort to move these renovators becomes too
great for easy operation. This trouble can be overcome by using a
soft grade of felt which permits sufficient air to pass through its
open pores to reduce the vacuum under same and permit easy operation.
Unfortunately, this felt is subject to rapid wear when operated on
surfaces as hard as floors and its use has been abandoned in favor of
a harder felt. Openings are left in the felt to permit the passage of
sufficient air to reduce the vacuum in the renovator to working limits.
These slots have taken many forms. In one form the felt was placed
in alternate X and diamond shapes, glued to the face with small open
spaces between them, as illustrated in Fig. 28. However, as these small
pieces must be held in place by glue, they are easily broken loose and
the efficiency of the renovator impaired.

[Illustration: FIG. 28. BARE FLOOR RENOVATOR WITH UNUSUAL FORM OF SLOT.]

Another method, which has now become standard, is to open the ends
of the renovator sufficiently to permit easy operation. This method
produces high velocities at these end openings which are very effective
in cleaning close to walls and in corners, where large quantities of
dust always lodge and are removed with difficulty without these open
slots.

The wear on these felt faced renovators was found to be so rapid that
hard felt or composition rubber strips, placed so that the wear comes
on the edges of the same, have been substituted. The felt or rubber was
screwed on to the outside of a metal shell and projected sufficiently
below the face of the metal to permit considerable wearing off of
same before the surface of the metal came in contact with the surface
cleaned. When this occurs, the felt strips can readily be replaced with
new ones. The ends are left open about ¹⁄₂ in. to form an inrush for
the entering air. Such a type is shown in Fig. 29.

[Illustration: FIG. 29. BARE FLOOR RENOVATOR WITH HARD FELT OR
COMPOSITION RUBBER STRIPS.]

This renovator, in either of the above-described forms, is a great
improvement over the bristle brush in that the air passing into the
body of the renovator must come into intimate contact with the surfaces
cleaned, but it still has the disadvantage of tending to push the dirt
before it.

A modification of the above-described renovators has been introduced,
in which the wearing surface of the renovator, which is covered with
felt, is rounded as shown in Fig. 30. With this form of bare floor
renovator, the air passing into same is not only brought into intimate
contact with the surface cleaned but the dust is also crowded under the
curved surface of the renovator as the same is pushed over the floor
and thus brought directly into the path of the air current.

[Illustration: FIG. 30. BARE FLOOR RENOVATOR WITH ROUNDED WEARING
SURFACE.]

The last named type is by far the most effective for cleaning either
polished or unpolished floors. It must be provided, however, with
inrush slots in order to prevent its sticking and preventing easy
operation. When operated with hose pipe and a vacuum producer necessary
to produce 2 in. of vacuum in Type A carpet renovators, at least 30
cu. ft. of air must be permitted to pass the renovator. When operated
with systems adapted to produce 4¹⁄₂ in. of vacuum in Type A carpet
renovators, at least 70 cu. ft. of air must pass the renovator in order
to permit easy operation.

This increase in the air quantity without change in the degree of
vacuum in the case of these renovators, is not without increase in
efficiency, as in the case of the carpet renovators, because large
quantities of dust and also small litter are met with much more
frequently on bare floors than on carpets. With the increase in the
volume of air passing, it is possible to pick up much heavier articles
than with the smaller quantity. It is also possible to pull dust out
of deep cracks or from surfaces which are not in contact with the
renovator face, such as the spaces between the slats of floors of
trolley cars. This would not be possible with the small air quantity.
The use of the larger quantity of air prohibits the use of small-sized
hose and pipe and, therefore, larger articles can be conveyed through
them. Where a large amount of bare floor must be rapidly cleaned the
use of the larger air quantity is recommended.

[Illustration: FIG. 30a. THE TUEC SCHOOL TOOL.]

A renovator (Fig. 30a) of unusual interest has recently been developed
by The United Electric Company, known as the Tuec school tool. This
is a bare floor tool open at both ends. It is made telescopic and is
mounted on three wheels fitted with spring-actuated guide rails which
are adjustable to the exact distance between the legs of school desks.
A turbine motor, operated by the air passing through the renovator, is
arranged to drive two of the wheels by means of worm gear and clutch.

In operation the tool is placed opposite the front of a row of desks.
The clutch engaged on the turbine propels the tool through the space
between the desk legs to the rear of the room. When the tool strikes
the wall at the rear of the room, the clutch is disengaged and it is
pulled back by drawing in the hose. The spring-actuated guides cause
the cleaning slot to lengthen when passing between the desk legs
thereby cleaning these spaces. The tool is then sent up the aisle, the
wheels being set so that it hugs the left side of the aisle when going
up and the right side when pulled back. The use of this form of tool
should result in considerable saving of time in cleaning school rooms.
Unfortunately, it cannot be operated where pedestal stools are used.

For use in cleaning walls, ceilings, and other flat surfaces of similar
character, the bristle brush is practically the only form of renovator
used.

Rubber skirting cannot be used on these brushes as it is too harsh
for the easily-marred surfaces encountered by this renovator, and
cotton flannel or a very soft grade of felt takes the place thereof.
This change in the material used for skirting results in a greater
short-circuiting of the air into the cleaner without coming into
intimate contact with the surface cleaned than occurs when used with
rubber or hard felt on bare floors.

As the material to be removed from surfaces of this character is very
light dust, which has simply settled on the surface and is not ground
in, it is very easy to dislodge. When a bristle brush, with a small
volume of air passing through same, is used to remove this material, a
greater portion thereof is pushed off the projections and other points
of lodgment and falls to the floor from whence it must be removed by
a second operation, using a floor renovator. In fact, the use of an
ordinary bristle brush, followed by the use of a floor renovator, will
give almost as good results as the use of a bristle wall brush with a
small quantity of air passing. However, with a large quantity of air
passing into the renovator, this light surface dust will all be picked
up by the rapidly-moving air current and effective cleaning can be
accomplished without the renovator coming into direct contact with the
surface to be cleaned.

The author considers that a different form of renovator is necessary
to effectively clean walls, ceilings and similar flat surfaces, with a
small quantity of air passing and would recommend the use of some form
of renovator having a cleaning face composed of cotton flannel or some
other soft substance which could be moved over the surface cleaned, in
intimate contact therewith and without damage thereto. With the soft,
open fibre of the substance necessary to be used as a working surface,
sufficient air would enter the renovator without resorting to the use
of inrush slots or openings and much better results would be obtained.
No such renovator has been designed for this purpose to date, for what
reason the author does not know, and until some such renovator is
produced a large volume of air will be necessary for cleaning this kind
of surfaces.

[Illustration: FIG. 31. ROUND BRISTLE BRUSH FOR CARVED OR OTHER RELIEF
WORK.]

An illustration of this defect in the wall brush was brought to the
author’s attention recently in watching a gang of laborers cleaning
the walls in the U. S. Treasury Building. They had at their disposal a
portable cleaner of the most efficient type, but in lieu of using the
wall brush provided with same, they were rubbing off the walls with a
cloth mop which had been soaked in oil, then air-dried, known as the
“dustless duster.” This was mounted on the end of a pole. The workmen
frequently cleaned this duster with the vacuum cleaner hose without
any renovator attached thereto. This cleaner, with brush in use,
passed approximately 30 cu. ft. of free air per minute. It is evident
that these laborers had learned by experience that it was practically
useless to try to remove dust from the walls by the direct application
of the wall brush to surfaces and were undoubtedly accomplishing much
better results in the roundabout way they had of necessity adopted.

When carved or other relief work is encountered, the round bristle
brush, with extra long bristles and cotton flannel skirting, is nearly
universally used. This type of renovator is shown in Fig. 31.

Owing to the irregularity of such surfaces, intimate contact therewith
cannot be obtained and practically no results will be had unless
there is a large quantity of air passing through the renovator. When
a large quantity of air is available, nearly as good results in
cleaning this character of surface can be obtained by the use of the
straight rubber-tipped corner cleaner, with a round opening about ³⁄₄
in. in diameter, as illustrated in Fig. 32. A very high velocity will
be obtained through this renovator which will pull the dust out of
inaccessible places. This form of cleaner is also very effective for
cleaning the corners of rooms, where the floor and walls intersect,
veritable dust catchers that they are, the cleaning of which is
fully as important as it is difficult. Pigeon holes and other small
compartments in safes, desks and similar furniture can be easily
cleaned with this little renovator by simply introducing it into the
front of such compartment.

[Illustration: FIG. 32. RUBBER-TIPPED CORNER CLEANER FOR USE ON CARVED
OR OTHER RELIEF WORK.]

[Illustration: FIG. 33. EARLY TYPE OF UPHOLSTERY RENOVATOR.]

To be effective, this renovator must pass approximately 55 cu. ft.
of air per minute and will require a vacuum within the renovator of
approximately 3¹⁄₂ in. of mercury. Where only a small quantity of air
is available, the author considers that it is better to make use of
compressed air to blow the dust out of relief work, pigeon holes, and
other inaccessible places and subsequently pick this dust up with other
forms of renovators after it has found lodgment at more accessible
points.

The cleaner which has met with the most disastrous results to the
surfaces cleaned is the furniture or upholstery renovator. This has
nearly always taken the form of a small carpet renovator. The type
of upholstery renovator used for many years by the Sanitary Devices
Manufacturing Company is illustrated in Fig. 33. This renovator had an
inrush slot in the center, separated from a cleaning slot on each side
by a partition extending to within ¹⁄₃₂ in. of the working face of the
renovator. It had the hose connected into one end which was extended
to form a handle. With this cleaning tool it was considered impossible
to obtain a high vacuum within the renovator, as the inrush slots were
supposed to act as vacuum breakers. However, as the surface of the
upholstery is not firmly attached to the furniture it could be drawn up
into the cleaner, closing the space under the partitions and permitting
a high vacuum to be obtained. This caused the renovator to stick, but,
owing to the narrow slot on each side of the inrush, the fabric was not
caught.

Other manufacturers used a renovator with a single slot, in some cases
as wide as ¹⁄₄ in., and instances are on record where the coverings
of the furniture have been drawn up through the cleaning slot into
the renovator and wedged so tightly that it was necessary to cut the
covering from the furniture in order to release the renovator. To
overcome this difficulty one manufacturer constructed the renovator
in two pieces, secured together with screws, so that, in case the
renovator became caught, it could be taken apart to release the fabric.

Many manufacturers have attempted to overcome this destructive tendency
of the straight-slot upholstery renovator by inserting partitions on
the cleaning face of the renovator, thus dividing the cleaning slot
into a number of small slots the area of each not being sufficiently
large to permit the drawing in of the fabric. These cleaners have
followed two general forms, one having narrow slots running lengthwise
of the cleaner, as illustrated in Fig. 34. This form reduces the
destructive tendency to a great extent, but does not entirely prevent
drawing the fabric into the renovator. If the partitions across the
renovator be continuous, as indicated by the sketch, there will be a
portion of the renovator which will not do any cleaning. Another form
uses short slots, sufficiently inclined for the top of one slot to
overlap the bottom of its neighbor, as shown in Fig. 35. This form of
renovator is effective throughout its entire length and the small area
of each slot makes it practically impossible to draw the fabric into
the cleaning slot. It is considered by the author to be superior to the
former type, especially when cleaning lace curtains or silk hangings or
any other very light fabric.

[Illustration: FIG. 34. UPHOLSTERY RENOVATOR WITH NARROW SLOTS TO
PREVENT DAMAGE TO FURNITURE.]

However, if the exhauster be of such characteristics and the hose and
pipe lines be so proportioned that there is practically a constant
vacuum in the renovator, regardless of the quantity of air passing, and
provided this vacuum is not allowed to exceed 5 or 6 in. of mercury, no
disastrous effects will be experienced in cleaning light-weight fabrics
with a straight-slot renovator having a cleaning slot not over ¹⁄₄ in.
wide. The use of this type, in connection with a system having the
above-described characteristics, is recommended whenever rapid cleaning
is desired.

Upholstery renovators make the most serviceable clothing cleaners,
while a small type of bristle brush, not over 4 in. long and not over
³⁄₄ in. wide, makes the most serviceable hat brush.

[Illustration: FIG. 35. ANOTHER TYPE OF UPHOLSTERY RENOVATOR WITH SHORT
SLOTS.]

An important form of renovator is that used for cleaning between the
sections and behind heating radiators. A piece of tubing, flattened at
its outer end, is by far the most effective device for this purpose.
This renovator, in connection with the hat brush tool, makes the two
best renovators for use in the library, effective cleaning being
possible with not more than 20 cu. ft. of air per minute, but much
faster work can be done with larger quantities.

[Illustration: FIG. 36. HAND BRUSH TYPE OF RENOVATOR.]

Another form of renovator sometimes furnished is the small hand brush.
This is a bristle brush, approximately 8 in. long and 2 in. wide, with
the hose connection made into one end of same, as illustrated in Fig.
36. This renovator is useful for cleaning wooden furniture, shelves,
tables, and other horizontal surfaces at about hand height, but, owing
to the tendency of the air to short circuit in its way to the body of
the renovator, it will not do effective work with small quantities of
air.

Many manufacturers have produced a special renovator for cleaning
stairs. This has nearly always taken the form of a bristle brush,
approximately 4 in. square. When renovators are rigidly attached
to their stems, this form of renovator is convenient and almost a
necessity. However, when swivel joints are provided, the ordinary
carpet or bare floor renovators are fully as convenient, and, being
larger, are more rapid cleaners, and the stair renovator is unnecessary.

In isolated cases, where unusual cleaning is necessary, such as the
removal of cork dust from the floors of a cork factory, picking
up telegraph forms from the floors of stock exchanges, picking up
wrapping papers in watch factories, etc., special forms of renovators,
with large openings and large capacities for air exhaustion, become
necessary. These appliances have generally taken the form similar to
the carpet renovator, but with much wider slots, the forward edges
of which are raised slightly above the surface of the floor when the
renovator is in operation. These renovators, being of no use for any
other purpose than that for which they are specially designed, and
requiring quantities of air in excess of those usually provided for
ordinary types of renovators, may be considered simply as special
appliances and do not form a part of the outfit required to be
furnished with an ordinary cleaning system.

Another class of cleaning which requires a special system and special
appliances is the renovation of furs. Furs must never be brushed, as it
tends to mat the hair and produce an effect opposite to renovation. The
only agent suitable for renovating furs is compressed air and the form
of renovator best suited for this work is a straight nozzle, flattened
at the end with a slot approximately 4 in. long and not over ¹⁄₃₂ in.
wide, from which the air escapes in a thin sheet. When held at such an
angle that the air will impinge on the skin under the hair, a thorough
renovation of the fur is possible.

For the renovation of pillows a hollow needle, with small openings
along its sides, supplied with compressed air, produces the best
results. The needle is thrust through the cover into the mass of
feathers, the air tending to loosen up the matted feathers and to leave
them in practically the same condition as when the pillow was first
filled.

As the arrangement of the air removal system, to permit it being
reversed from exhaustion to compression, complicates the outfit and
adds to its first cost, and as cleaning of this character is required
only at rare intervals, these renovators may also be considered as
special and need not be included in the average equipment.

The author considers that the renovator equipment for a system in which
from 20 to 30 cu. ft. of air per minute is exhausted for each renovator
in operation, and which the author classes as a “small volume” system,
should contain the following renovators in each “set” furnished:

One carpet renovator with cleaning slot ¹⁄₄ in. by 12 in. long.

One bare floor renovator 12 in. long, with curved felt-covered face.

One wall renovator 12 in. long, with cotton flannel and curved face.

One upholstery renovator with slot ¹⁄₄ in. by 4 in.

One corner cleaner.

One radiator cleaner.

In addition, one or more hat brushes should be included with each
installation.

The renovator equipment for a system in which 70 cu. ft. of air per
minute is exhausted for each renovator in operation, which the author
classes as a “large volume” system, should contain the following
renovators in each “set” furnished:

One carpet renovator, with slot ¹⁄₄ in. by 15 in.

One bare floor renovator 15 in. long, with curved felt-covered face.

One wall brush, with skirted bristles 12 in. long and 2 in. wide.

One hand brush, with hose connection at end, 8 in. long and 2 in. wide.

One 4-in. round brush for relief work.

One upholstery renovator.

One corner cleaner.

One radiator tool.

At least one hat brush with each system.

The number of sets of renovators to be furnished should naturally be
at least equal to the number of sweepers which the plant will handle,
and in all buildings, except residences, there should be one set of
renovators for each floor of the building. This will be ample, except
in exceedingly large buildings.

The wearing face of any renovator should never be made of soft metal,
such as brass or aluminum, as the action of the dust passing the face
of the renovator, where the velocity is always the highest in the
system, will roughen these parts and cause undue wear on the surfaces
cleaned. Stamped steel is undoubtedly the best material for wearing
surface and cast-iron ranks next. These are the only materials which
should be permitted.

CHAPTER V.

STEMS AND HANDLES.

Having discussed the various forms of renovators in detail, the next
appliance to be taken up is the connection between the renovator and
the cleaning hose, this being the next portion of the apparatus forming
a conduit for the dust-laden air on its way from the renovator to the
atmosphere on the exhaust side of the vacuum producer.

In order that the renovator may be moved about on the surfaces to be
cleaned, a rigid handle must be provided and, in order that these
various surfaces may be reached while the operator remains in a
standing position, it is necessary that this handle be of considerable,
as well as variable, length. Also, a passage for the dust-laden air
must be provided in connection with this handle. These conditions are
best met by a metal tube, which the author terms the stem.

These stems have been made of various metals, that first used being
drawn brass, probably because it is best suited to be nickel plated. On
the earlier systems they were almost invariably made of No. 16-gauge
tubing, ⁷⁄₈-in. outside diameter, and were bent at their upper end
through an angle of nearly 135° in order that the hose would hang from
the stem vertically downward, when the stem was held at an angle with
the floor of 45°.

The lower ends of these stems were rigidly attached to the renovator
in such a manner as to assume the above-mentioned angle with the floor
when the renovator was in the proper position for cleaning. In order
to bring the curved portion of the stem hand high, the stem was made
approximately 5 ft. long.

When operated with Type A carpet renovators, these curved stems were
apparently satisfactory. However, when they were used in department
stores, and other places where much bare floor cleaning was necessary,
the stems were cut through at the curved portion by the sand blast
action of the dust. The cutting of these stems in bare floor work,
while they were satisfactory in carpet cleaning, indicates that the
velocity in the stem, due to the large volume of air passing the bare
floor renovator, was too great for this soft metal to withstand the
impact of the dust on the curved surface. With the systems in use at
that time no means were provided to control the vacuum at the vacuum
producer and the hose and pipe lines were small, both of which tended
to cause a wide variation in the volume of air exhausted under various
conditions, in the character of surface cleaned, and in the number of
renovators in use. Therefore, the value of this destructive velocity is
not readily obtainable. However, the author considers that, in extreme
cases, the quantity of air passing through these stems may have been as
high as 55 cu. ft. per minute. As the inside diameter of the stems was
³⁄₄ in. the area was 0.44 sq. in., or 0.00328 sq. ft., and the velocity
through the stem was nearly 17,000 ft. per minute. With an average air
passage of 40 cu. ft. per minute the velocity was 12,200 ft. per minute.

Referring to tests of carpet renovators, Chapter III, it will be noted
that the maximum volume of air passing through carpet renovators of
Type A was 33 cu. ft. per minute, which gives a velocity of 10,000 ft.
per minute. Apparently, at this velocity, the cutting action, due to
the impact of the dust on the curved surfaces, was not severe. However,
the author considers that the maximum velocity that should be permitted
through these stems is 9,000 ft. per minute.

As the dirt picked up must be lifted almost vertically, the velocity
in the stem must not become too low or dirt will lodge in the stem.
Experiments made by the author indicate that the minimum velocity
should be at least 4,000 ft. per minute, in order to insure a clean
stem at all times.

Shortly after the introduction of vacuum cleaning, the use of
drawn-steel tubing for the manufacture of stems for cleaning tools was
standard with one manufacturer and, lately, its use has become almost
universal, except in cases where very long stems are necessary, as on
wall brushes when cleaning very high ceilings. For such work, aluminum
stems have been adopted.

This harder metal will better withstand the cutting action of the dust
and can also be made much thinner and lighter in weight than brass
tubing of equal strength. These stems were made from 1 in. outside
diameter, No. 21 gauge tubing, having an internal area of 0.68 sq. in.,
and the author does not know of any cases where these stems have been
cut by the impact of the dust.

Stems of this metal are recommended by the author for use with
all floor renovators and with wall brushes, except in cases where
exceedingly long stems are required, when those of drawn aluminum
tubing are recommended.

For use with Type A renovators, where the minimum air quantity is
approximately 22 cu. ft. per minute, the greatest area permissible is

22
----
4000

= 0.0055 sq. ft., or 0.79 sq. in., equivalent to 1-in. diameter. With a
maximum air quantity, under proper control, of 39 cu. ft. per minute,
the minimum area will be

39
----
9000

= 0.00433 sq. ft. or 0.625 sq. in., equivalent to 0.89 in. diameter,
so that a 1-in. outside diameter stem of No. 21 gauge metal, having an
inside diameter of 0.932 in., is recommended.

For use with a Type F renovator, with a minimum air quantity of 44 cu.
ft. per minute, the maximum area of the stem will be

44
----
4000

= 0.011 sq. ft., or 1.58 sq. in., equivalent to 1.4 in. diameter,
while, with a maximum air quantity of 70 cu. ft. per minute, the
minimum area will be

70
----
9000

= 0.0077 sq. ft., or 1.11 sq. in., equivalent to 1.18 in. diameter,
and a 1¹⁄₄-in. diameter stem of No. 21 gauge metal, having an inside
diameter of 1.18 in. is recommended.

Tests of Mr. S. A. Reeve, which are discussed in Chapter III, indicate
that both edges of the cleaning slot on any renovator must be in
contact with the surface cleaned in order to do effective cleaning. A
renovator which is rigidly connected to its stem can be effectively
operated with the stem at but one angle with the surface cleaned, which
makes the cleaning under furniture, or on wall at various heights above
the floor, impossible. In order to do effective cleaning with any
degree of speed and comfort to the operator, some form of swivel joint
between the renovator and its stem is necessary.

These swivels have been made in many forms, one of which consists of
two hemispheres connected by a bolt on their axis, as shown in Fig.
37. This form of swivel is unsuited for use under these conditions, as
lint, thread and any other small articles picked up will catch on the
bolt which lies directly in the path of the dust-laden air current, and
its use should be prohibited in all cases.

[Illustration: FIG. 37. FORM OF SWIVEL JOINT CONNECTING STEM TO
RENOVATOR.]

Another form of swivel, which is must better than the last mentioned,
is shown in the illustration of the bare floor brush, Fig. 26, Chapter
IV, there being no obstruction in the air passage. However, these
swivels are composed of moving parts which are in contact with the
dust-laden air and great care must be taken in their design so that in
action dust does not lodge between the wearing surfaces and shortly
ruin the swivel. This can be guarded against by making any opening
between the parts of the swivel point away from the dust current,
as indicated in Fig. 38, in which the direction of the air current
is indicated by the arrow. A slightly loose fit between the wearing
surfaces will permit a small leakage of air through the joint which
will tend to remove any dust which may find its way into the joint.
However, it is not considered advisable either to allow very much
leakage through the joint, as it reduces the net efficiency of the
system, or to depend much on the air current through the joint keeping
the wearing surfaces clean. The swivel indicated in the illustration
of the floor brush does not entirely prevent the dust entering same
and it permits the movement of the stem in a vertical plane only. On
the other hand, a swivel consisting of a 45° elbow, rigidly attached
to the stem and turning freely on a horizontal spud, and fastened to
the renovator, as shown in Fig. 38, allows a motion of the stem either
in a vertical plane, which will cause the renovator to rotate, and
enable the operator to pass same around or back of legs of furniture,
or a semi-rotary motion may be imparted to the stem, which will permit
the renovator to move forward in a straight line while the angle which
the stem makes with the floor will constantly decrease. After a little
practice the operator can place a renovator equipped with one of these
swivels in almost any position without inconvenience. Illustrations
of the possibilities of this form of swivel are presented in Figs. 39
and 40, in which an operator is shown cleaning the treads and risers
of a stairway without changing her position, and in Fig. 41, where the
operator is cleaning the trim of a door with apparent ease. The author
considers that this form of swivel is the only satisfactory joint
between the renovator and its stem. It is being rapidly adopted by
nearly every manufacturer of vacuum cleaners.

[Illustration: FIG. 38. SWIVEL JOINT ARRANGED TO PREVENT DUST LODGING
BETWEEN THE WEARING SURFACES.]

In operating any renovator it is nearly always drawn backwards and
forwards in front of the operator, across the surface to be cleaned.
When the hose is rigidly attached to the upper end of the stem, it
becomes necessary to drag at least a portion of the cleaning hose along
with the renovator when it is moved forward, and to crowd the same
back on itself when the renovator is moved backward. This action has a
tendency to kink or snarl the hose about itself and makes the operation
of the renovator very awkward, often causing the operator’s feet to
become entangled in the hose.

[Illustration: FIG. 39. SWIVEL JOINT IN USE.]

This action also brings an undue amount of wear on the hose near
the end which is attached to the stem, as may be readily noted by
inspection of hose used with rigidly-attached stems. This will show
that the end of the hose is entirely worn through, while the remainder
of the hose is still in serviceable condition.

The trouble above stated can be overcome by providing a swivel joint at
the point of connection between the hose and the stem. A few attempts
to use a joint similar to that first described in connection with the
renovator and its stem, as illustrated in Fig. 37, have been made, but
without much success, as the bolt through the air passage catches dirt
and there is not sufficient freedom of movement between the portions
of the swivel. Variations of this form of joint have been made, one of
which is provided with a screwed union to join the two portions, as
shown in Fig. 42. This is a much better form than that first described
and has been successfully used in connection with heavy 1-in. diameter
hose. Care must be exercised that the direction of the flow of air
is always in the direction indicated by the arrows in the sketches,
as a reversal, if only for a short time, will ruin the joint, due to
lodgment of dust in the moving parts.

[Illustration: FIG. 40. ANOTHER USE OF SWIVEL JOINT, SHOWING
POSSIBILITIES OF THIS FORM.]

Still another variation in this form of swivel has the two main parts
made to fit one within the other and a snap ring is placed in a groove
in the male portion of the joint, this groove being deep enough to
take the entire thickness of the ring. The two parts are then fitted
together and the ring snaps out into a corresponding groove in the
female portion of the joint, uniting the two parts. This joint gives
a fairly free movement to the parts thereof, but has the disadvantage
that it cannot be taken apart without breaking one of its parts.

[Illustration: FIG. 41. OPERATOR CLEANING TRIM OF DOOR WITH SWIVEL
JOINT.]

[Illustration: FIG. 42. SWIVEL JOINT, WITH SCREWED UNION.]

[Illustration: FIG. 43. SWIVEL JOINT HAVING BALL BEARINGS.]

A modification of this form of swivel has been made by the
manufacturers of the last-described swivel, in which semi-circular
grooves have been cut, one on the inside of the female portion and one
on the outside of the male portion. Steel balls are forced into this
groove, after the parts are assembled, through an opening provided in
the edges of the parts. This opening is closed, after the balls are in
place, by a small pin, as shown in Fig. 43. The swivel then becomes a
ball-bearing joint, with a freedom of motion characteristic of such
bearings. This joint readily responds to every movement of the stem and
keeps the hose hanging vertically downward and always free from kinks.
Its action is illustrated in Fig. 44, in which it is being used in
connection with a carpet renovator. This joint is considered to be the
most efficient on the market. It is protected by a patent controlled by
a manufacturer of vacuum cleaners.

[Illustration: FIG. 44. ACTION OF BALL-BEARING SWIVEL JOINT.]

Valves are placed at the upper end of the stems by many manufacturers,
to cut off the suction when carrying the renovators from room to room,
and when it is necessary to stop sweeping to move furniture. These
valves have nearly always taken the form of a plug cock with tee or
knurled handle. They are useful on large installations, where vacuum
control is either inherent in the exhauster or where some means of
vacuum control is provided, as a considerable saving of power may be
obtained by closing same, as will be explained in a later chapter, and
to overcome the unpleasant hissing noise caused by the inrush of air
into the renovator when same is held off the floor.

[Illustration: FIG. 45. ILLUSTRATION OF DEFECTS OF PLUG COCKS.]

When the exhauster has a capacity of but one sweeper and when the
cleaning is done at times when the building is unoccupied, there seems
to be little need for this refinement, which has two defects: first,
the operators will not close the valves: second, when they have been
closed they are only partly opened, as indicated in Fig. 45. When this
occurs, the portions of the plug, which are shown stippled, are quickly
cut away by the sand-blast action of the dust, making it necessary to
open the valve a still smaller amount the next time it is operated,
cutting off still more of the plug until a new plug is necessary in
order to make the valve again operative.

A few attempts have been made to overcome these defects by making
the valves self-closing and having them so constructed that when the
operator grasps the handle the valve will be forced wide open, on the
principle of the pistol grip. These valves will, of course, close
whenever the handle is released, and it is impossible to grasp the
handle in any degree of comfort without throwing the valve wide open.
However, since the valve is closed by a spring, considerable pressure
must be applied to the handle in order to keep it open and it acts
similar to the Sandow dumb bell in producing fatigue of the fingers in
a short time; they have not come into general use. The use of valves
in the renovator handle is considered by the author to be an expense
not justified by the gain in economy and they are no longer included in
specifications prepared by him.

CHAPTER VI.

HOSE.

The more important steps in the evolution of the modern vacuum cleaning
system can each be attributed to a change in the design or construction
of some one of its component parts, which, in their former standard
design, have acted as a limiting factor governing the form and size of
other and more important parts of the system.

That part of the early systems which played the most important role
as a limiting factor was one for whose production the builder of the
system had to look to other manufacturers: namely, the flexible hose
connecting the renovator stem to the rigid pipe lines and vacuum
producer.

The early builders of vacuum cleaning systems naturally adopted a
standard article for use as a flexible conduit; that is, the vacuum
hose which had been used as suction lines for pumps of various
characters. For such use it was not necessary that the hose be moved
about to any great extent and, therefore, its weight was not an
important factor and had been sacrificed to strength to withstand
collapse and the rough handling to which suction hose is subject.

This standard hose was built up of many layers of canvas wound around
a rubber tube or lining. A spiral wire was imbedded between the layers
of canvas to prevent collapse and the whole was provided with an outer
covering of rubber. Generally five to seven layers of canvas were used
and the resulting hose was not highly flexible.

When used as a flexible conduit in connection with a vacuum cleaning
system it became necessary to constantly move the hose back and forth
and around the room to be cleaned. It was also necessary to limit the
weight of the hose to that which could be easily handled by one person.
This led to the adoption of small sizes of the then standard hose,
³⁄₄-in. diameter being first used, but soon this was abandoned in favor
of 1-in. diameter hose weighing nearly 1 lb. per foot of length, which
is the maximum weight that can be conveniently handled by one person.
This size hose has become the standard for all systems maintaining a
vacuum at the separators of 10 in. of mercury or more.

Owing to its lack of flexibility this type of hose is easily kinked
and is damaged by the pulling out of such kinks, causing the tubing or
lining to become separated from the canvas and to collapse, rendering
the hose useless. There is also considerable wear at the point of
connection to the stems of renovators, where rigid connections are used.

The outside of this hose, being rubber, is always liberally covered
with soap-stone when it leaves the manufacturer, and when new hose
is dragged about over carpets, it frequently soils same to a greater
degree than they are cleaned by the renovator. When this hose has been
in use about twice as long as is necessary to wear off the soap-stone,
its appearance becomes far from handsome and is not considered to be
in keeping with the nickel-plated appliances which are furnished with
the cleaning tools. To overcome this objection, an outer braid has been
applied generally over the rubber coating, thus adding further to its
already great weight.

What was perhaps the first type of hose to be produced especially for
use with vacuum cleaning systems was that in which the fabric was
woven in layers, instead of being wrapped spirally around the central
tube or lining. Steam was introduced into the lining, vulcanizing the
lining and firmly uniting the whole mass. This hose was made 1 in. in
diameter, without any metal re-inforcement, and was covered with the
usual rubber coating and with braid, when ordered. This hose weighed 12
oz. per lineal foot and 1-in. diameter was still the largest that could
be easily handled.

The first attempt to produce a light-weight hose for use with vacuum
cleaning systems was by covering a spiral steel tape with canvas. The
air leakage through this hose was found to be so high that its use
resulted in loss of efficiency of the cleaning plant and it was found
necessary to line the hose with rubber. This rubber-lined hose is made
in larger sizes than formerly used and 2-in. diameter hose weighs
approximately 14 oz. per lineal foot. It is also much more flexible
than the 1-in. hose formerly used.

The introduction of this type made it possible to use larger hose
in connection with vacuum cleaning systems and permitted the use
of a lower vacuum at the separators, with the same results at the
carpet renovator, and a larger quantity of air when using the brushes
and other renovators. Without this type of hose the low-vacuum,
large-volume systems would be impractical.

Another type of hose has been recently introduced in which a wire is
woven into the fabric of the hose and the rubber lining vulcanized into
place as already described. No outer coating of rubber is used and,
therefore, no braid is necessary. This gives a light-weight hose of
great flexibility and neat appearance and is undoubtedly the best hose
for residence work. It is more costly than the steel tape hose which is
recommended for office building and factory use, where appearance is
not important.

[Illustration: FIG. 46. BAYONET TYPE OF HOSE COUPLING, INTRODUCED BY
THE AMERICAN AIR CLEANING COMPANY.]

=Hose Couplings.=--The earlier systems used couplings having
screw-threaded ground joints, similar to those which were then in
use on hose intended to withstand pressure. These couplings require
considerable time to connect and disconnect and the threads are easily
damaged by dragging the hose about. The exposed metal parts of the
couplings are liable to scratch furniture.

To overcome the time required to connect and disconnect the
screw-coupling, the American Air Cleaning Company introduced the
bayonet type of coupling, as illustrated in Fig. 46. This coupling
is not readily damaged by rough handling, but it has metal surfaces
exposed which will scratch furniture.

Both of these couplings have the disadvantage that the air current
in the hose must always be in the same direction and the same end of
the hose must always be next to the renovator handle. Both of these
features tend to increase the wear on the hose, and the reversal of the
air current to remove stoppages is not possible.

The coupling produced by the Sanitary Devices Manufacturing Company has
a piece of steel tubing fitted into each end of the hose and secured by
means of a brass slip-coupler fitting over the tubing. All ends being
alike, the reversal of the hose is possible with this form of coupling.
However, the metal coupler is liable to mar furniture and sometimes
there is trouble with the couplings pulling apart.

[Illustration: FIG. 47. ALL RUBBER HOSE COUPLING USED BY THE SPENCER
TURBINE CLEANER COMPANY.]

Much of the hose in use today is provided with “pure gum” ends are
vulcanized in place, it is necessary to take the hose of metal
tubing is slipped inside of these ends to make a coupling. With this
arrangement there is no metal exposed to mar furniture and the hose
lengths are reversible. However, there is some trouble from the
couplings pulling apart. Since these ends are vulcanized in place, it
is necessary to take the hose to a rubber repair shop whenever the
hose breaks back of the coupling, which occurs frequently when rigidly
attached to the stem of the renovator. These repair shops are much
more numerous than a few years ago and this drawback is not a serious
one.

Another form of coupling used by the Spencer Turbine Cleaner Company is
the all-rubber male and female end, as illustrated in Fig. 47. This has
the advantage over the metal-slip couplings and the coupling with pure
gum ends in that when it is properly locked it cannot be pulled apart.
It is absolutely air tight, which is true of no other coupling. But it
does not permit the reversal of the hose and is, therefore, recommended
for use only with hose of 1¹⁄₄-in. diameter or larger, where there is
less liability of stoppage, and where the ball-bearing swivel is used
at the connection to the stem, preventing excessive wear at this point.
The pure gum ends, with the internal-slip coupler, is considered to be
the most satisfactory for use in all cases, except as above stated.

=Hose Friction.=--Hose friction plays an important part in the action
of any vacuum cleaning system. In fact, where 1-in. hose is used, it
becomes a limiting factor in the capacity of the system to perform some
kinds of cleaning.

There are several tables of hose friction published by the
manufacturers of vacuum cleaning systems, all of which appear to have
been based on a constant velocity within the hose equal to that which
would be obtained if the air were at atmospheric pressure throughout
the entire length of the hose. But in practice the air is admitted to
the hose from the renovator at a considerably lower absolute pressure
of from 25 in. to 27 in. of mercury, and is, therefore, moving at a
higher velocity. As the pressure is decreased by the friction loss in
the hose, the velocity constantly increases with the expansion of the
air.

The results of many tests made by the author during the past seven
years, with hose ranging from 1-in. to 2-in. diameter and with an
entering vacuum ranging from 0 to 7 in. of mercury and a friction
loss of from 1 in. to 25 in. of mercury, indicate a close agreement
with the formula given in Prof. William Kent’s “Mechanical Engineer’s
Pocketbook,” which is based on the formula:

___
/pd⁵
Q = c \ / ---
√ wL

Q = free air in cubic feet per minute.

c = a constant which was determined by D’Arcy as approximately 60.

p = the loss of pressure in pounds per square inch.

d = the diameter of pipe in inches.

L = the length of pipe in feet.

w = the density of the entering air in pounds per cubic foot.

Reducing the pressure loss to inches of mercury and using in lieu of w,
r which is the ratio of the average absolute pressure in the pipe to
atmospheric pressure, this formula becomes:

___
/pd⁵
Q = 310.3 \ / ---
√ Lr

To permit the rapid calculation of the air quantity which can be
passed through a hose, the author has prepared the diagram shown in
Fig. 48. To use this table, look up the friction loss in the hose in
the right hand margin, pass along the horizontal line to the left
until it intersects the line inclined at an angle of 45° toward the
left, indicating the length of the hose. From this intersection pass
vertically to the line inclined at approximately 30° toward the left,
representing the diameter of the hose. The quantity in the left-hand
margin, opposite the horizontal passing through this intersection,
represents the quantity of air which would pass through this hose in
cubic feet at the average density in the hose. To correct this quantity
to free air, step off the distance on the vertical line from the bottom
of the table, representing the average degree of vacuum in the hose,
to its intersection with the curved line near the bottom of table.
Transfer this distance vertically downward on the left hand margin from
the quantity first read on this margin. The quantity opposite the lower
end of this distance will be the cubic feet of free air per minute
passing through the hose under these conditions.

The line inclined towards the right, which passes through the
intersection of lines representing hose diameter, and the horizontal
line representing the cubic feet of air passing through the hose at
actual density in same, shows the actual velocity in the hose in feet
per second.

For friction loss over 10 in. of mercury, use the figures at the right
hand of the lower margin, instead of those in the right hand margin,
and pass vertically to the hose diameter. Then proceed as before. As
these high frictions are seldom used in practice, this departure has
been made in order to reduce the size of the diagram.

[Illustration: FIG. 48. CHART FOR DETERMINING HOSE FRICTION.]

To illustrate how much the friction tables, based on air at atmospheric
density, vary from actual results, two tests made by the author are
given. In the first test it was desired to pass 68 cu. ft. of free air
per minute through a ⁷⁄₈-in. diameter orifice at the end of 100 ft. of
1-in. diameter hose. Tests on larger hose showed that, to permit this
quantity of air to pass through the orifice, a vacuum at the orifice of
2.6 in. mercury was necessary. The most rational table the writer could
find indicated that the friction loss in the hose should be 18 in.
mercury, and the final vacuum necessary at the hose cock would have to
be 20.6 in. mercury. On test it was found that, with 24.8 in. vacuum at
the hose cock, but 50 cu. ft. of free air per minute was passing, with
a vacuum at the orifice of 1.6 in. mercury, showing a friction loss of
23.2 in. mercury. With the smaller quantity of air passing, the same
friction table indicated a friction loss, with this quantity of air,
of but 9.8 in. mercury, or 39% of that actually observed. Checking the
results of the test with the diagram (Fig. 48) gives 50 cu. ft. of free
air, with a friction loss of 23 in. mercury.

To illustrate more clearly the effect of the increase of velocity on
the friction loss, the actual vacuum in the hose has been computed for
each 10 ft. of its length and curves drawn through these points. The
results are shown in Fig. 49. The straight line indicates the vacuum
which should exist were the velocity in the hose constant throughout
its length, and the curved line shows the vacuum in the hose when
the effect of the increasing velocity, due to the rarefaction of the
air, is considered. The wide variation in the results shows clearly
the error in the former assumption of a constant velocity in the hose
throughout its length.

Another test, in which 44 cu. ft. of free air was passed through 100
ft. of 1-in. diameter hose, is shown graphically in Fig. 50, which
discloses that the assumption of a constant velocity in the hose
produces an error of 35% in the results, indicating a loss of but 7.8
in., when the actual loss is 12 in. mercury.

Naturally, the lower the final vacuum at the hose cock, the less will
be the error due to the assumption of constant velocity in the hose.
Tests with 1¹⁄₂-in. hose gave results which agree substantially with
the result given in tables already published, and it was this condition
that led to the discovery of the error in the assumption stated.

[Illustration: FIG. 49. EFFECT OF INCREASE OF VELOCITY ON THE FRICTION
LOSS.]

=Effect of Hose Friction.=--As any increase in the degree of vacuum
necessary to be maintained at the vacuum producer over that maintained
within the renovator requires a greater expenditure of power, without
any increase in the efficiency or speed of cleaning, it is essential
that the friction loss in the air conduit from the renovator to the
vacuum producer should be made as small as possible. The friction loss
in the hose is the greatest loss in any part of the system, being the
smallest in diameter, and its reduction to the lowest figure possible
is of vital importance.

Take, for example, the use of a Type A renovator with a vacuum
within the renovator of 4¹⁄₂ in. mercury and with 29 cu. ft. of air
passing through same. The friction loss, with varying lengths of
different-sized hose, will be as follows:

TABLE 6.

VACUUM AT HOSE COCK WITH TYPE A RENOVATORS AND WITH VARYING LENGTHS OF
DIFFERENT-SIZED HOSE.

-------------+----------------------------
| Length, in Feet.
Size of Hose,+----------------------------
| 100 75 50 25
In. Diameter.+----------------------------
|Vacuum at hose cock, in. hg.
-------------+----------------------------
1 | 10 8¹⁄₂ 7 5¹⁄₂
1¹⁄₄ | 6 5.7 5.25 4.85
1¹⁄₂ | 5.0 4.85 4.75 4.62
-------------+----------------------------

[Illustration: FIG. 50. ANOTHER TEST SHOWING FRICTION LOSS DUE TO
VELOCITY.]

This indicates, first, that a much lower friction loss will result with
the use of larger hose than is the case with the smaller size. Note,
also, that the difference in the final vacuum at the hose cock is much
more uniform when the larger-sized hose is used in varying lengths.
Since it is desired to maintain a constant vacuum at the renovator at
all times and it is also desirable to be able to vary the length of
hose to suit the conditions of the work, while it is not convenient
to vary the vacuum at the hose cock, much more uniform results will
be possible when larger hose is used. If the smaller hose is used in
varying lengths and a practically uniform vacuum is maintained at
the hose cock, the quantity of air and the vacuum at the renovator
will vary. If 1-in. hose is used and the vacuum at the hose cock be
maintained at 10 in. mercury, the air quantities and vacuum at the
renovator will be approximately:

TABLE 7.

AIR QUANTITIES AND VACUUM AT RENOVATOR WITH 1-IN. HOSE AND 10-IN.
VACUUM AT HOSE COCK.

-----------+----------+-------+----------
|Vacuum at | |
Length of |Renovator,| Air, | H. P. at
Hose, feet.| in. hg. |cu. ft.|Hose Cock.
-----------+----------+-------+----------
100 | 4¹⁄₂ | 29 | 0.80
75 | 5 | 32 | 0.885
50 | 6¹⁄₂ | 34 | 0.94
25 | 7¹⁄₂ | 37 | 1.02
-----------+----------+-------+----------

From this it is evident that the vacuum within the renovator will be
increased above that necessary for economical cleaning. It will require
somewhat more effort to push the cleaner over the carpet and also a
slightly greater expenditure of power at the hose cock to operate the
cleaner with a short than with a long hose. However, the author does
not consider that either the increase of effort to push the renovator
or the increase of power will be sufficient to prohibit the use of
1-in. hose with the Type A renovator.

If we use 1¹⁄₄-in. hose with Type A renovator and maintain a vacuum
of 6 in. of mercury at the hose cock, the resulting vacuum and air
displacement at the renovator will be:

TABLE 8.

AIR QUANTITIES AND VACUUM AT RENOVATOR WITH 1¹⁄₄-IN. HOSE AND 6-IN.
VACUUM AT HOSE COCK.

-----------+----------+-------+----------
|Vacuum at | |
Length of |Renovator,| Air, | H. P. at
Hose, feet.| in. hg. |cu. ft.|Hose Cock.
-----------+----------+-------+----------
100 | 4¹⁄₂ | 29 | 0.43
75 | 4.7 | 30 | 0.445
50 | 5.0 | 33 | 0.448
25 | 5.4 | 35 | 0.518
-----------+----------+-------+----------

This table shows a more uniform degree of vacuum at the renovator with
the varying length of hose, but the greatest difference is in the horse
power required at the hose cock to accomplish the same results at the
renovator.

If we use 1¹⁄₂-in. hose with Type A renovator, the vacuum at the hose
cock can be reduced to 5 in. mercury and a practically constant vacuum
will be obtained at the renovator, with an expenditure of 0.36 H. P. at
the hose cock.

With the Type C renovator where the vacuum within the renovator is
maintained at 4 in. mercury, with 44 cu. ft. of free air per minute
passing through the renovator, the resulting vacuum at the hose cock,
with various lengths of the three sizes of hose, will be as follows:

TABLE 9.

VACUUM AT HOSE COCK, WITH TYPE C RENOVATORS AND VARIOUS LENGTHS OF
THREE SIZES OF HOSE.

-------------+-----------------------------
| Length, in Feet.
Size of Hose,+-----------------------------
In. Diameter.| 100 75 50 25
+-----------------------------
|Vacuum at hose cock, in. hg.
-------------+-----------------------------
1 | 19 14 10 6.7
1¹⁄₄ | 7.5 6.25 5.5 4.7
1¹⁄₂ | 5.1 4.80 4.50 4.25
-------------+-----------------------------

Referring to Fig. 17, Chapter III, it will be noted that Type C
renovator will not accomplish much in the way of cleaning with a
vacuum in the renovator lower than 4 in. mercury. Therefore, if we use
this type of renovator, with 1-in. diameter hose, its length should
be limited to 50 ft., for if we use a vacuum higher than 10 in. at
the hose cock, there will be too much increase in the vacuum at the
renovator when short hose is used to allow easy operation, and if we
use longer hose with 10-in. vacuum at the hose cock, there will be a
reduction in the vacuum at the renovator and effective cleaning cannot
be accomplished. Also, the power required at the hose cock to pass 44
cu. ft. of air, with a vacuum of 19 in. mercury, required to produce a
vacuum of 4 in. at the renovator with 100 ft. of 1-in. hose, will be
3.3 H. P., which is prohibitive when compared with that required with
the use of larger hose, i. e., 0.825 H. P. with 1¹⁄₄-in. hose and 0.59
H. P. with 1¹⁄₂-in. hose.

The Type F renovators tested by the author will show even wider
variations in the vacuum required at the hose cock with the various
lengths and diameters of hose than is given for Type C renovator.
However, the type F renovator, which is now used by the Spencer Turbine
Cleaner Company, having a cleaning slot 15 in. long and ¹⁄₂ in. wide
throughout its length. passes 44 cu. ft. of free air per minute, with
a vacuum under the renovator of 4 in. mercury and the resulting vacuum
at the hose cock will be the same as that given in the case of the Type
C renovator.

When a bare floor renovator of the bristle-brush type is attached to
the hose, the effect is practically the same as when the end of the
hose is left wide open, as the open character of the brush prevents the
formation of any vacuum in the renovator. Therefore, sufficient air
must pass through the renovator to create a friction loss in the hose
equal to the vacuum at the hose cock.

As practically all systems are arranged to maintain a constant vacuum
at the vacuum producer and as the pipe friction is generally less than
the hose friction, the vacuum at the hose cock will be practically the
same when operating a floor brush as with a carpet renovator.

Assuming that 10 in. mercury is maintained at the hose cock with 1-in
hose, 6 in. with 1¹⁄₄-in. hose, and 5 in. with 1¹⁄₂-in. hose, the
quantity of air which will pass through a floor brush with various
sizes and lengths of hose will be:

TABLE 10.

AIR QUANTITIES THROUGH FLOOR BRUSH OPERATED IN CONJUNCTION WITH TYPE A
RENOVATORS.

-------------+----------------------------------
| Hose Length, in Feet.
Size of Hose,+----------------------------------
In. Diameter.| 100 75 50 25
+----------------------------------
|Cubic feet of free air per minute.
-------------+----------------------------------
1 | 42 48 60 86
1¹⁄₄ | 62 72 86 125
1¹⁄₂ | 95 110 135 190
-------------+----------------------------------

The quantities given for the shorter hose lengths are higher than
will be observed in actual practice, due to the increase in the pipe
friction, which will depend on the length of the pipe lines. However,
the results will illustrate the great increase in the quantity of
air which will pass these bare floor brushes when operated on the
same system with carpet renovators. If the same number of bare
floor renovators are to be used at one time as there will be carpet
renovators at some other time, that is, if the sweeper capacity must
be maintained when using bare floor brushes as when using carpet
renovators, a much larger air exhausting plant must be installed than
would be necessary to operate that number of carpet renovators.

If it were possible to so arrange the schedule of cleaning operations
that bare floor brushes were never used at the same time as carpet
renovators, the vacuum at the machine might be reduced when operating
the floor brushes to a point that would reduce the quantity of air
passing to within the capacity of a machine designed to operate the
same number of carpet renovators. Unfortunately, this condition rarely
exists and, therefore, the vacuum must be maintained at the degree
necessary to operate the carpet renovators that may be in use at the
same time with the floor brushes.

It is also evident that if the length of hose used with bare floor
brushes could be limited to the maximum ever used with the carpet
renovators, a reduction in the capacity of the exhauster necessary
could be made. This is another condition which the designer of the
system cannot control.

=Most Economical Hose Size for Carpet and Floor Renovators.=--The horse
power required at the hose cock to operate the bare floor brushes with
each of the different sizes and lengths of hose is:

TABLE 11.

HORSE POWER REQUIRED AT HOSE COCK TO OPERATE BARE FLOOR BRUSHES IN
CONJUNCTION WITH TYPE A RENOVATORS.

-------------+----------------------------
| Length, in Feet.
Size of Hose,+----------------------------
In. Diameter.| 100 75 50 25
+----------------------------
| Horse power at hose cock.
-------------+----------------------------
1 | 1.16 1.32 1.65 2.38
1¹⁄₄ | 0.92 1.06 1.27 1.38
1¹⁄₂ | 1.15 1.32 1.62 2.28
-------------+----------------------------

This shows that where bare floor or wall brushes of the bristle type
are used in conjunction with carpet renovators on any system and with
Type A carpet renovator, 1¹⁄₄-in. diameter hose will give the lowest
power consumption.

When either Type C or F renovator is used in combination with
bristle-type brushes, the use of 1-in. diameter hose must be abandoned
in lengths over 50 ft. and the vacuum at the hose cock must be
maintained at 10 in. mercury. With 1¹⁄₄-in. hose, it will be necessary
to maintain a vacuum at the hose cock of 7 in. mercury, and, with
1¹⁄₂-in. hose, 5 in. will be sufficient, provided we continue to use
100 ft. of hose in the case of the larger sizes. The free air passing a
brush type of bare floor renovator under these conditions will be:

TABLE 12.

FREE AIR PASSING BRUSH TYPE OF BARE FLOOR RENOVATOR OPERATED IN
CONJUNCTION WITH TYPE C RENOVATORS.

-------------+----------------------------------
| Length, in Feet.
Size of Hose,+----------------------------------
In. Diameter.| 100 75 50 25
+----------------------------------
|Cubic feet of free air per minute.
-------------+----------------------------------
1 | 42 48 60 86
1¹⁄₄ | 68 76 92 130
1¹⁄₂ | 95 110 135 190
-------------+----------------------------------

This shows an increase in the volume of air passing the floor brush
with 1¹⁄₄-in. hose, while a higher vacuum is now carried at the hose
cock than was necessary when Type A renovator was used in conjunction
with the bristle-type of floor renovator. The horse power at the hose
cock will now be:

TABLE 13.

HORSE POWER AT HOSE COCK WITH BRUSH TYPE OF BARE FLOOR RENOVATOR
OPERATED IN CONJUNCTION WITH TYPE C RENOVATORS.

-------------+-------------------------
| Length, in Feet.
Size of Hose,+-------------------------
In. Diameter.| 100 75 50 25
+-------------------------
|Horse power at hose cock.
-------------+-------------------------
1 | 1.16 1.32 1.65 2.38
1¹⁄₄ | 1.19 1.36 1.60 2.26
1¹⁄₂ | 1.15 1.32 1.62 2.28
-------------+-------------------------

With this combination of floor and carpet renovators, there is no
difference in the power consumption when any one of the three sizes
of hose is used. However, there is a considerable increase in the
quantity of air passing the larger hose. This leads to the statement
made by some manufacturers that this increase in air volume results in
more efficient cleaning.

Tests given in Chapter III indicate that increase in air volume does
not result in any more rapid or efficient cleaning of carpets. The
results of actual use of the bare floor brush of the bristle type
show no gain when cleaning bare floors. As stated in Chapter IV, the
felt-faced renovator, being more effective while it requires less air.
In other words, it is the degree of vacuum within the cleaner and not
the quantity of air which produces the cleaning in all cases where any
degree of vacuum is possible. When intimate contact between the cleaner
and the surface cleaned cannot be had, the volume of air determines the
efficiency of cleaning. However, the author does not consider that an
exhaustion of more than 60 to 70 cu. ft. of free air through cleaners
of this type will increase the efficiency to such an extent as to
justify the increase of power necessary to adapt a system to larger
volumes.

The author considers that with a system in which brushes of the bristle
type are to be used, the exhauster should have a capacity of 70 cu. ft.
of free air per minute. Such a system is termed by the author a “large
volume system,” as already mentioned in Chapter IV.

When the felt-covered floor renovator is used instead of the brush,
the vacuum within this renovator must not be permitted to rise above 2
in. or the operation of the renovator on the floor will be difficult.
To accomplish this, it is necessary to provide openings in the ends
of the cleaning slot, as has been explained in Chapter IV. If the
vacuum at the hose cock be assumed as 10 in. with 1-in hose, 6 in. with
1¹⁄₄-in. hose, and 5 in. with 1¹⁄₂-in. hose, and the vacuum within the
felt-covered floor renovator be maintained at 2 in. mercury the cubic
feet of free air passing the renovator with the various sizes and
lengths of hose will be:

TABLE 14.

CUBIC FEET OF FREE AIR PASSING THE FELT-COVERED FLOOR RENOVATORS
OPERATED IN CONJUNCTION WITH TYPE A RENOVATORS.

-------------+--------------------------------
| Length, in Feet.
Size of Hose,+--------------------------------
In. Diameter.| 100 75 50 25
+--------------------------------
|Free air, cubic feet per minute.
-------------+--------------------------------
1 | 36 43 54 74
1¹⁄₄ | 49 56 68 94
1¹⁄₂ | 68 78 94 130
-------------+--------------------------------

These figures show a considerable reduction from those obtained with
the brush type of floor renovator, particularly when the larger sizes
of hose are used, and considerable reduction can be made in the
capacity of the exhauster and still obtain the best results when using
carpet renovator and bare floor renovator simultaneously.

The horse power at the hose cock required to operate these felt-faced
floor renovators with different sizes and lengths of hose are:

TABLE 15.

HORSE POWER REQUIRED AT HOSE COCK TO OPERATE FELT-COVERED FLOOR
RENOVATORS IN CONJUNCTION WITH TYPE A RENOVATORS.

-------------+---------------------------
| Length, in Feet.
Size of Hose,+---------------------------
In. Diameter.| 100 75 50 25
+---------------------------
|Horse power at hose cock.
-------------+---------------------------
1 | 1.0 1.19 1.49 2.05
1¹⁄₄ | 0.72 0.83 1.0 1.39
1¹⁄₂ | 0.79 0.93 1.13 1.56
-------------+---------------------------

In this case, the 1¹⁄₄-in. hose is the most economical size to use, as
was the case with the brush renovators. However, the advantage over the
1¹⁄₂-in. hose is not as great as with the brush renovator.

With this type of renovator, the manufacturer has some control over
the length of hose which the operator will use in connection with the
bare floor renovator, as he may open the ends of the renovator just
sufficiently to produce 2 in. of vacuum under same with, say, 50 ft. of
hose. Then, if the operator should attempt to use the renovator with
25 ft. of hose, it will stick and push hard and he will soon learn that
a longer hose is necessary.

=Conditions for Plant of Small Power.=--For locations where it is
desirable to sacrifice efficiency somewhat to reduction in the amount
of power required, as in residences, the Type A carpet renovator may
be used and the vacuum under the same reduced to 2 in. mercury, which
will still do effective cleaning, but at a slower rate, as was shown by
tests in Chapter III. This requires not exceeding 20 cu. ft. of free
air per minute.

With this quantity of air the velocity in the hose must be considered
as, in order to have a clean hose at all times, it is necessary to
maintain a velocity in the hose of not less than 40 ft. per second.
Referring to the diagram, Fig. 48, it will be seen that this velocity
will not be obtained in any hose larger than 1¹⁄₄ in. and this is,
therefore, the largest size which can be used. In all the former
cases the velocity was so much in excess of this minimum that its
consideration was not necessary.

With a vacuum of 2 in. of mercury in the renovator and 20 cu. ft. of
air passing, the vacuum at the hose cock will be:

TABLE 16.

VACUUM AT HOSE COCK, WITH 2-IN. VACUUM AT TYPE A RENOVATOR.

-------------+----------------------------
| Length, in Feet.
Size of Hose,+----------------------------
In. Diameter.| 100 75 50 25
+----------------------------
|Vacuum at hose cock, in. hg.
-------------+----------------------------
1 | 4 3.5 3 2.5
1¹⁄₄ | 2.6 2.45 2.3 2.15
-------------+----------------------------

In this case the increase in vacuum at the renovator would not be
objectionable as, with 4 in. vacuum at the hose cock, the vacuum at
the renovator would never reach the standard used with the former
deductions and the volume of air passing could, therefore, never
reach 29 cu. ft. Any increase, due to the use of shorter hose, would,
therefore, be an advantage in its approach toward the standard set for
the larger plants. Therefore, we will assume that a vacuum of 4 in.
mercury will be maintained at the hose cock with 1-in. hose and a
vacuum of 2¹⁄₂ in. at the hose cock with 1¹⁄₄-in. hose.

The renovators for bare floor work will be the felt-covered type and
will be opened at the ends just sufficiently to limit the vacuum
within the same to 2 in. mercury when operating with 25 ft. of hose.
This will require the passage of 40 cu. ft. of free air per minute
when 1-in. hose is used and 35 cu. ft. when 1¹⁄₄-in. hose is used. The
horse power at the hose cock will be 0.39 H. P. with the 1-in. diameter
hose and 0.17 H. P. with the 1¹⁄₄-in. hose. Here again we see that the
1¹⁄₄-in. hose is the more economical to use.

If bristle brushes are used with this system at the same time that
carpet renovators are in use, the quantity of air which will have to
pass them, in order to maintain the vacuum on the system at the proper
point to do effective cleaning with the carpet renovators, will be:

TABLE 17.

AIR QUANTITIES WHEN BRISTLE BARE FLOOR RENOVATORS ARE USED IN
CONJUNCTION WITH TYPE A CARPET RENOVATORS AT 2 IN. HG.

-------------+-----------------------------
| Length of Hose, in Feet.
Size of Hose,+-----------------------------
In. Diameter.| 100 75 50 25
+-----------------------------
|Free air, cu. ft. per minute.
-------------+-----------------------------
1 | 30 36 42 60
1¹⁄₄ | 41 48 60 80
-------------+-----------------------------

The use of these brushes in plants of more than one-sweeper capacity
would require the use of an exhauster of greater capacity than is
required for either the carpet or the bare floor renovator. Where the
plant is of but one-sweeper capacity, the quantity of air that would
pass these brushes, were the plant of proper capacity to serve the
carpet and floor renovators, would not be sufficient to do effective
work, as was explained in Chapter IV. In such cases, this arrangement
should be prohibited.

A system of the type just described is what has been termed by the
author as a “small volume” plant in Chapter IV.

=Limit of Length for Hose.=--The author has made the deductions in
this chapter, using 100 ft. of hose as the maximum length. This is
considered to be the greatest length that should be used. The adoption
of a shorter length is recommended by many manufacturers, but the
author does not consider that the advantage to be obtained by the
adoption of a shorter length justifies the additional expense of piping
which will result in many cases. This will be governed by the character
of the building and, in many cases, it will be possible to use 50 ft.
as a maximum. It has been the practice of the author to lay out his
installations so that any point on the floor of any room may be reached
in the most direct line with 75 ft. of hose. When this is done 100 ft.
of hose will easily clean any part of the walls or ceilings and give an
ample allowance for running around furniture or other obstructions.

The figures in this chapter will demonstrate to the reader the part
that the cleaning hose plays as a limiting factor in the operation of a
vacuum cleaning system and shows the care that must be exercised in the
selection of the proper hose for each condition.

CHAPTER VII.

PIPE AND FITTINGS.

As we continue to follow the dust-laden air in its passage toward the
vacuum producer we next encounter that portion of the conduit which is
permanently and rigidly fixed in place in the building; namely, the
pipe line, its fittings and other appliances.

=Hose Inlets.=--The first portion of this conduit which we must
consider is the point where the hose is attached to the pipe line;
that is, the inlet, or, as it is often improperly termed, the “outlet”
valves.

As it is necessary to close the inlets air tight when they are not in
actual use, in order to prevent the entrance of air except through the
hose lines in use, some kind of a cut-off valve must be provided, as
well as a receptacle into which the end of the hose may be connected
when desired.

With the earlier systems a high degree of vacuum was carried in the
pipe lines and the vacuum producers were of small displacement. Slight
leakage would greatly reduce the capacity of the system and the best
form of valve was necessary. The valve adopted was the ordinary
ground-seat plug cock, on account of its unobstructed air passage and
air-tight closing. The hose was connected to these cocks either by a
ground-joint, screwed coupling or by a slip coupling similar to those
used to unite the sections of the cleaning hose. An inlet cock of this
type is illustrated in Fig. 51.

These cocks projected about 4¹⁄₂ in. beyond the face of the finished
wall and formed a considerable obstruction, especially when located
in halls or corridors. In order to reduce the projection into the
apartment the manufacturers of the systems using screwed-hose couplings
and substituted a projecting nipple closed by a cap screwed in place.
The whole projected only ³⁄₄ in. beyond the finished wall line.

These outlets were suitable for use only with hose having screwed
connections. When an attempt is made to remove the cap with the vacuum
producer in operation, there is a tendency for the vacuum to cause the
cap to hug the last thread and render its removal difficult. Also, when
the suction is finally broken it is accomplished with considerable
hissing noise.

[Illustration: FIG. 51. INLET COCK TO PREVENT AIR LEAKAGE WHEN NOT IN
USE.]

In order to permit the use of the slip type of hose coupling, a hinged
flap valve was substituted for the screwed cap, a rubber gasket being
placed under the cap. This was held firmly in place by the vacuum in
the pipe line. The interior of the casting inside of the flap was
turned to a slip fit for the end of the hose coupling. With this type
of valve and the slip hose coupling, described in Chapter VI, it is
possible to reverse the hose to equalize wear and remove obstructions.

These inlets have been made with valves that are closed only by gravity
when there is no vacuum on the system and many are so constructed that
when opened wide they will remain open with the vacuum on the piping.
This type of valve will often be opened by the inquisitive person when
no vacuum exists in the system and as there are no immediate results,
they may be left open with the result that there will be a very large
leakage of air on starting the vacuum producer. This makes it necessary
for some one to make a tour of the building in order to close the
valve which is open before the system can be efficiently operated.
If the vacuum producer is designed to operate several renovators
simultaneously, it may not be discovered that there are any valves open
and a considerable amount of power will be wasted.

In order to overcome this difficulty it is necessary to provide a
spring on the hinge of the flap valve that will automatically close the
valve whenever the hose is withdrawn. When the inlets are located in
public places they should be fitted with a lock attachment to prevent
them from being opened by unauthorized persons.

A valve of this type is illustrated in Fig. 52. This valve has a
projection on its inner face which engages with a ridge on the hose
couplings, preventing the removal of the hose without slightly raising
the cap and making it impossible to accidentally pull the hose out of
the inlet.

[Illustration: FIG. 52. TYPE OF AUTOMATIC SELF-CLOSING INLET COCK.]

The particular valve here shown is suitable for use only with the
all-rubber hose connection described in Chapter VI.

We must next consider the material of which the conduit itself is to
be made. The commercial wrought-iron or mild steel, screw-jointed
pipe, such as is used for water and steam lines, is probably the best
suited for this purpose and was the first material used. In earlier
installations the pipe was galvanized, but, owing to the tendency for
the zinc coating to form irregularities within the pipe, its use has
been abandoned in favor of the commercial black iron pipe.

Seamless drawn tubing would undoubtedly make the ideal material
for this purpose. However, the ordinary butt or lap-welded pipe is
satisfactory and is now generally used.

Sheet metal pipe was introduced by one manufacturer but its use was
shortly abandoned in favor of the commercial pipe.

As joints and changes in direction are necessary in the pipe lines,
some sort of fittings must be used. The ideal conduit for passage of
dust-laden air should be of uniform bore and as smooth on the inside
as a gun barrel. Various attempts have been made to accomplish this
result in commercial installations, one of which is illustrated in
Fig. 53. These fittings are made up of three parts for a coupling and
four for a branch or change in direction. One of these is screwed on
to the end of each piece of pipe, the pipe butting against a shoulder
and the end of the pipe made to register with the bore of the fitting
by reaming. This piece is faced true and fitted against the face of
the casting, forming the bend or branch, or fitted against the piece
on the end of the other length of pipe. A thin gasket is placed
between them, a projecting ring on one piece fitting into a groove on
the other, causing the bore of the two halves to register. The two
halves are joined together by the V-grooved clamp, held in place by
a small bolt. This is theoretically an ideal joint, but the clamp is
not of sufficient strength to withstand the strain of settlement of
the building and breakages are frequent. Several instances of this
character, particularly on steamers, have come to the observation of
the author, and there are several buildings which have been roughed in
with this type of fitting, used on concealed piping, which were found
to be useless on the completion of the building, due to breaking of the
joints in inaccessible places.

[Illustration: FIG. 53. “SMOOTH BORE” PIPE COUPLING.]

A modification of this joint which will have ample strength can be
made by using standard pipe flanges, screwing the pipe through the
flange and facing the end off in a lathe. Fittings could be made with
a bore equal to that of the pipe and proper alignment secured by the
use of dowel pins, as illustrated in Fig. 54. The cost of making this
joint would be high and they would occupy too much space to be easily
concealed in partitions, furring or other channels usually provided for
the reception of such piping.

[Illustration: FIG. 54. JOINT MADE OF STANDARD PIPE FLANGES.]

The standard Durham recessed drainage fitting, having the inside cored
to the bore of the pipe and recesses provided for the threads as used
in connection with the modern plumbing system, if left ungalvanized and
having the inside well sand-blasted to remove all rough places, makes a
serviceable fitting. Care should be exercised to cut the threads on the
piping of proper depth to allow the end of the pipe to come as close to
the shoulder of the recess as practicable and to obtain a tight joint.
The end of the pipe should be carefully reamed before assembling.

These fittings have become standard with nearly all manufacturers and
are illustrated in Fig. 55, which shows the right and wrong way to
install same.

Trouble was experienced on some of the earlier systems using high
vacuum with the fittings cutting out on the side subjected to the
impact of the dust-laden air. To overcome this trouble one manufacturer
re-inforced the fittings by increasing the thickness of metal at the
point affected. The trouble was undoubtedly caused by too high a
velocity in the pipe line, as in the case of the small brass stems,
explained in Chapter V. With the introduction of vacuum control and
larger pipes, this trouble disappeared and the special fittings never
came into general use.

[Illustration: RIGHT WAY.

WRONG WAY.

_Use two Y-branches instead of straight or cleanout tees. In case the
latter are used the dirt will shoot by into the other branch._

_Always place Y-branches so they will turn in the direction of the
flow._

_Place the clean-out at right angles to the direction of flow entering
the fitting. Otherwise it serves as a pocket to catch passing dirt._

_Special care must be exercised to see that there is no opportunity for
dirt to collect in the basement drops. Above is shown a common wrong
way and two possible right ways._

FIG. 55. STANDARD DURHAM RECESSED DRAINAGE FITTINGS GENERALLY USED IN
VACUUM CLEANING INSTALLATIONS.]

While the utmost care should be taken to prevent stoppage of the pipe
lines these stoppages are likely to occur in the best-constructed
lines and ample clean-out plugs should be provided for the removal of
such stoppage. Brass plugs are the most serviceable for this purpose,
as they are easily removed when necessary and can usually be replaced
air tight.

The brass clean-outs, while most satisfactory, are costly when
installed in large sizes. Equally satisfactory results can be obtained
at a lower cost by using 2-in. diameter plugs on all lines 2 in. and
over in diameter.

[Illustration: FIG. 56. FRICTION LOSS IN PIPE LINES.]

Matches are perhaps the most frequent cause of stoppage in pipe lines.
Stoppage from this cause can be largely avoided by the use of pipe
of sufficient size to permit the match to turn a complete somersault
within the pipe whenever it catches against a slight obstruction or
rough place in the pipe or fittings. A 2-in. diameter pipe is just
large enough to permit this and smaller sizes of pipe should be avoided
whenever possible.

=Pipe Friction.=--The friction loss in piping follows the same law as
that in hose lines and is easily computed by use of the chart (Fig.
56), which is constructed on the same general principle as the chart
of hose friction (Fig. 48). The directions for use of the hose chart
apply to the pipe chart. In computing this chart the actual inside
diameter of the commercial wrought-iron pipes have been used instead of
the nominal diameters, resulting in an increased capacity for all sizes
except 2¹⁄₂-in. which is less than the nominal diameter.

=Determination of Proper Size Pipe.=--Friction in the pipe lines tends
to increase the vacuum to be maintained and therefore the power to be
expended at the vacuum producer and should be kept as low as possible.
The pipe sizes should be made as large as conditions will permit.
The limit of size is fixed by the velocity in the pipe. When it is
necessary to lift the dirt to any extent, the velocity should not be
allowed to fall below 40 ft. per second at any time. When the pipe is a
vertical drop, the velocity does not matter as gravitation will assist
the air current in removing the dirt. When the line is horizontal a
lower velocity than 40 ft. per second is permissible at times, provided
that this minimum velocity is exceeded at frequent intervals to flush
out any dirt that has lodged in the pipe during periods of low velocity.

If a Type A renovator is used with 1-in. hose and a vacuum of 10 in. of
mercury maintained at the hose cock, the minimum air passing, with 100
ft. of hose in use, will be 29 cu. ft. of free air per minute, which
is equivalent to 44 cu. ft. at 10 in. of vacuum. The entering velocity
in the pipe should be calculated with air at this density. This will
give a velocity of 50 ft. per second in a 1¹⁄₂-in. pipe, but only 30
ft. per second in a 2-in. pipe. Therefore, the 1¹⁄₂-in. pipe is the
largest that should be used where lifts occur on a line serving but
one Type A renovator with 1-in hose. When the renovator is tilted at a
considerable angle or lifted from the carpet, as will frequently occur
in cleaning operations, the quantity of air passing the renovator will
be upwards of 42 cu. ft. of free air, equivalent to 62 cu. ft. at
10-in. vacuum. When this occurs the velocity in a 2-in. pipe will be
44 ft. per second, which will be ample to flush a horizontal line of
piping.

If 1¹⁄₄-in. hose is used with a Type A renovator, the minimum quantity
of air will be 29 cu. ft. and the vacuum entering the pipe will be
6 in. mercury, giving an equivalent volume of 37 cu. ft. This will
produce a velocity of 42 ft. per second in a 1¹⁄₂-in. pipe, which is
the largest that can be used where a lift occurs. However, when the
renovator is lifted free of the carpet, the air quantity will be 62 cu.
ft. of free air, equivalent to 80 cu. ft. at 6 in. of vacuum, and will
produce a velocity of 39 ft. per second in a 2¹⁄₂-in. pipe. This would
be just about sufficient to flush a horizontal line.

If 1¹⁄₂-in. hose were used the air quantity will be 29 cu. ft. and
the vacuum entering the pipe 5 in. mercury, equivalent to 35 cu. ft.
This will give a velocity in a 1¹⁄₂-in. pipe of 40 ft. per second.
When the renovator is raised from the carpet, the air quantity will be
upwards of 90 cu. ft. of free air, equivalent to 110 cu. ft. at the
density of that entering the pipe, and will produce a velocity of 33
ft. per second in a 3-in. pipe. This is too low to thoroughly flush a
horizontal pipe.

The figures given above are repeated from Chapter VI and show that
the use of 1¹⁄₄-in. instead of 1-in. hose, permits the use of a
larger-sized horizontal pipe line for serving one renovator, but that
the use of 1¹⁄₂-in. hose, instead of 1¹⁄₄-in., will not permit of any
enlargement in the pipe size. Since we have seen in Chapter VI that a
1¹⁄₄-in. hose gives the least expenditure of power when used with a
Type A renovator, there will be no gain from a reduction in the pipe
friction due to the adoption of this hose.

The dependence on the raising of the renovator from the floor to flush
out a larger pipe line should not be carried beyond that to be obtained
from a single renovator. That is, when the pipe must serve more than
one renovator at the same time, the quantity of air that two or more
renovators will pass, if they were raised from the floor at the same
time, should not be used in determining the limiting velocity in the
pipe, as such an occurrence is not likely to be obtained often enough
to thoroughly flush the pipe. Furthermore, there will be times when
this pipe will have to serve only one renovator and the pipe will
not be adequately flushed. When the pipe is serving more than one
renovator, the actual air passing the renovators should be used in
determining the maximum size of pipe and it is advisable to use this
maximum size in nearly all cases where the structural conditions will
permit.

These sizes will then be:

TABLE 18.

PIPE SIZES REQUIRED, AS DETERMINED BY AIR PASSING RENOVATORS.

----------+--------+-----------------------
| | Pipe Sizes, In. Diam.
Number of | |----------+--------
Renovators|Cu. Ft. |With 1-in.|With 1¹⁄₄-in.
in Use. |per min.| Hose. | Hose.
----------+--------+----------+------------
1 | 29 | 2 | 2¹⁄₂
2 | 58 | 2¹⁄₂ | 2¹⁄₂
3 | 87 | 3 | 3
4 | 116 | 3¹⁄₂ | 3¹⁄₂
5 | 145 | 3¹⁄₂ | 3¹⁄₂
6 | 174 | 4 | 4
----------+--------+----------+------------

Using these maximum sizes, the friction loss in a pipe line, with
carpet renovators in use exclusively, will be:

TABLE 19.

FRICTION LOSS IN PIPE LINES, WITH CARPET RENOVATORS IN USE EXCLUSIVELY.

---------+-------------------------------------
|Friction Loss per 100 Feet, Inches.
Number of|-------------------------------------
Sweepers.|With 1-in. hose. With 1¹⁄₄-in. hose.
---------+-------------------------------------
1 | 0.20 0.06
2 | 0.30 0.20
3 | 0.24 0.17
4 | 0.19 0.13
5 | 0.30 0.22
6 | 0.24 0.17
---------+-------------------------------------

These friction losses are figured with a density of air in the pipe
equal to 6-in. vacuum in case of the 1¹⁄₄-in. hose and 10-in. vacuum in
case of the 1-in. hose, which will be the density of the air entering
the pipe, while the average density should be used in order to give
correct results. If the pipe line is not over 400 ft. equivalent length
the results will be approximately correct.

These results show, first, that the friction loss in pipe lines is much
lower than that in the hose lines used with the same system; second,
that the higher vacuum in the pipe causes greater loss, an argument in
favor of the use of larger hose.

[Illustration: FIGS. 57-60. DIAGRAMS SHOWING OPERATION OF BRUSH AND
CARPET RENOVATORS UNDER DIFFERENT CONDITIONS.]

These friction losses are obtained only when carpet renovators are used
exclusively and all the renovators are held in the proper position
to perform the most economical cleaning. In actual practice this
condition will not exist except when one renovator is used. Where more
than one renovator is in use simultaneously, some of the renovators
will be raised from the floors at the time others are in position
to do effective cleaning and will admit a greater quantity of air,
increasing the friction. This is not a serious condition as the time
that the renovators will be raised is only a small part of the total
time spent in cleaning and will merely reduce the efficiency of the
other renovators temporarily. However, when brushes or floor renovators
are used at the same time as the carpet renovators, there will be a
continuous flow of air in greater quantities through these brushes,
which will permanently increase the friction loss. The use of a single
brush or floor renovator with the same sized pipe as is necessary to
operate the carpet renovator will not reduce the efficiency of the
brush, as a high degree of vacuum at the brush or floor renovator is
not necessary or even permissible and a further slight reduction will
not affect the operation of these renovators.

When a brush or floor renovator is used on the furthest outlet from
the vacuum producer at the same time that carpet renovators are being
used on outlets nearer the vacuum producer, the larger quantity of
air passing the brush will tend to reduce the vacuum at the hose cock
to which the carpet renovator is attached and thereby impair its
efficiency. For example, if we have a brush renovator connected through
100 ft. of 1-in. hose to an outlet at the end of a pipe line 400 ft.
long, properly designed to serve two carpet renovators, the vacuum at
the separators should be maintained at 10-in., plus 2 × 0.20 plus 2 ×
0.30, or 11 in. of mercury. Suppose that this vacuum is automatically
maintained at this point and a carpet renovator be attached 200 ft.
from end of pipe (Fig. 57). The quantity of air passing through the
2¹⁄₂-in. pipe B-C will be approximately 29 plus 40 or 69 cu. ft., and
the friction loss in this pipe will be 1.1 in. The vacuum maintained
at the outlet B (Fig. 57) will be 9.9 in. or approximately the correct
vacuum to maintain 4¹⁄₂-in. vacuum at the renovator “a.” The friction
loss in the pipe line from B to A will be 0.7 in. and the resulting
vacuum at the hose cock A will be 9.2 in. The quantity of air passing
the brush will be 40 cu. ft. Under these conditions there will be no
loss in efficiency of cleaning due to the brush renovator being used
on the end of the line. If the operator using the brush at the outlet
A should use only 25 ft. of hose instead of 100 ft. (Fig. 58) the air
passing this brush will be 75 cu. ft. and the vacuum at the hose cock A
will be 6.8 in. The vacuum at the hose cock B will be 8.8 in. and the
vacuum at the carpet renovator “a” will be reduced to 3¹⁄₂ in. with 25
cu. ft. of air passing, which will reduce the efficiency of the carpet
renovator “a.”

If the brush renovator be attached to the hose cock B (Fig. 59), using
25 ft. of hose, the vacuum at hose cock B will be 9 in. and the brush
renovator will pass 85 cu. ft. of air, while the vacuum at hose cock A
will now be reduced to 8.6 in. and the vacuum at the renovator will be
reduced to 3 in. mercury and the air passing to 23 cu. ft.

If a brush type of renovator be used at each outlet, with 25 ft. of
hose in each case and the vacuum at the separator be maintained at 11
in. mercury the vacuum at hose cock B will be 7 in. and brush “a” will
pass 76 cu. ft. of air while the vacuum at hose cock “a” will be 5 in.
and brush “b” will pass 63 cu. ft. of air or a total of 144 cu. ft.,
which will be in excess of the 70 cu. ft. per renovator recommended as
the capacity of the plant in Chapter VI. This will not result in any
loss of efficiency if the vacuum producer be designed to handle but 140
cu. ft. as a maximum, for the vacuum at the separator will then fall to
a point where but 140 cu. ft. passes, resulting in a decrease in the
vacuum throughout the system. But as only brushes are now in use there
will be no loss in efficiency, owing to the reduction in the vacuum at
the brushes.

When 1¹⁄₄-in. hose is used with a carpet renovator at the end of the
pipe line connected through 100 ft. of hose and a brush at the hose
cock B connected through 25 ft. of hose (Fig. 60), the worst case of
the three already cited, the vacuum at the separator being maintained
at that necessary to carry 4¹⁄₂ in. when two carpet renovators are in
use, the vacuum at the hose cock B will be 4.5 in. and brush “a” will
pass 116 cu. ft. of air while the vacuum at hose cock A will be 4.4 in.
and the vacuum in renovator “b” will be 3.7 in and will pass 24 cu. ft.
of air.

These are better cleaning conditions than were obtained when 1-in. hose
was used. It will be noted that the total air passing the exhauster is
now 140 cu. ft. and this must not be reduced or there will be a falling
off in the vacuum at the carpet renovator “b.” It is, therefore,
necessary for the exhauster to be capable of handling 140 cu. ft. of
air or 70 cu. ft. of air per renovator in order to do effective carpet
cleaning when carpet renovators and brushes are used in conjunction.

When two floor brushes are used with the above arrangement of pipe and
hose, the vacuum must fall considerably or the air quantity be greatly
increased. However, the reduction in vacuum will not result in serious
loss in efficiency when only brushes are in use.

When a larger number of sweepers are used with a system of piping, it
is necessary to allow 70 cu. ft. of free air per sweeper in figuring
the sizes of pipe to be used, and the total loss of pressure in the
piping between the outlet farthest from the vacuum producer and
that nearest to same must be limited in order to prevent too wide a
difference in the vacuum at the hose cock when all the sweepers for
which the plant is designed are in use. The author considers that this
loss in pressure should not be greater than 2 in. mercury in order to
give satisfactory results.

Before the piping system can be laid out and the sizes of piping
determined it is necessary to ascertain, first, the number of sweepers
to be operated simultaneously and the number of risers necessary to
properly serve these sweepers.

=Number of Sweepers to be Operated.=--This is determined by the
character of the surfaces to be cleaned, the amount of such surface,
and the time allowed for cleaning.

It has been demonstrated in actual practice that one operator can
clean as high as 2,500 sq. ft. of carpet when same is on floors of
comparatively large areas, and not over 1,500 sq. ft. when the carpets
are on small rooms; 2,000 sq. ft. is considered to be a fair average.

Bare floors are cleaned more rapidly. In school house work an ordinary
class room has been cleaned in 10 minutes, or at the rate of 7,200 sq.
ft. per hour, but time is occupied in moving from one room to another
and the writer considers 5,000 sq. ft. per hour as rapid cleaning and
3,500 sq. ft. as a fair average.

The time of cleaning will vary in buildings of different character and
used for different purposes. In office buildings the cleaning force
work throughout the night or about 10 hours, while in school houses the
cleaning is done by the janitor force which has been on duty throughout
the school period and the time is necessarily limited to about two or
three hours after school hours, the corridors and play rooms being
cleaned during the school period and only the class rooms being cleaned
after closing time.

Let us assume, as an example, an office building having eight floors
each 100 ft. × 150 ft., with a floor plan as shown in Fig. 61.

The corridors, stairs and elevator halls will probably be floored with
marble which must be scrubbed in order to remove the stain accumulated
during the day and they will not be considered in connection with a
dry vacuum cleaning system. The area of the floors in the offices on
any floor will be approximately 10,000 sq. ft. and one floor can be
cleaned by one operator in 5 hours, or two floors during the cleaning
period, so the plant must be of sufficient size to serve four sweepers
simultaneously.

[Illustration: FIG. 61. TYPICAL FLOOR PLAN OF OFFICE BUILDING
ILLUSTRATING NUMBER OF SWEEPERS REQUIRED.]

In a school house containing four class rooms, where the janitor
cleans the play rooms and corridors during the school period, as can
be readily done with a vacuum cleaner since there will be no dust
scattered about to fill the air and render it unsanitary, the class
rooms can easily be cleaned in one hour by one operator. The author
considers that one sweeper capacity for each six to eight rooms is
ample for a large school.

Buildings of special construction and used for special purposes must be
considered differently according to the conditions to be met, but the
size of the plant can be readily determined in each case by use of the
rules already given.

=Number of Risers to be Installed.=--Much difference of opinion exists
among the various manufacturers of vacuum cleaning systems as to the
maximum length of hose that should be used with a cleaning system, and
as this maximum length determines the number of risers to be installed,
some fixed standard is necessary. As already stated in Chapter VI, the
author considers that this maximum should be fixed at 75 ft.; that
is, the risers should be so spaced that all parts of the floor of the
building can be reached with 75 ft. of hose. Where 50 ft. is used as
a maximum, as is recommended by many manufacturers, the number of
risers would be increased, incurring a greater cost of installation
and requiring the operator to shift his hose from one inlet to another
more often than would be the case where fewer inlets were used, and
more time would be required in cleaning, with a slight reduction in the
power. The author does not consider that this reduction in power would
be sufficient to offset the additional time required to change the hose
from one inlet to another.

The best and quickest way to determine the number of risers necessary
is to cut a piece of string to the length representing 75 ft. on the
scale of the plans, and by running this around the plan using corridor
doors for access to all rooms, wherever possible, locate the riser so
that every point can be reached with the string. In the case of the
building illustrated in Fig. 61 four risers located as shown will be
necessary.

=Size of Risers.=--Before we can determine the size of risers to be
installed it is necessary to determine the probable number of sweepers
that will be attached to any one riser simultaneously. In the case of
the building (Fig. 61) it is possible that there may be four sweepers
attached to one riser and it is also possible that there may be but
one, and two sweepers to a riser is considered to be a safe assumption.
The author uses the following rule in determining the size of risers to
use:

Where the number of sweepers is double the number of risers, assume
that all sweepers will be on one riser simultaneously.

Where the number of sweepers is equal to the number of risers, assume
that half the sweepers will be on one riser simultaneously.

Where the number of sweepers is half the number of risers, assume that
one-quarter of the sweepers will be on one riser simultaneously.

When no lifts occur a low velocity in the riser is not objectionable
and the size of the riser should be made equal to the size of the
horizontal branch thereto throughout its length, wherever this branch
is not larger than 2¹⁄₂ in. diameter. When larger, reductions in the
riser can be made until 2¹⁄₂ in. is reached when this size should be
maintained throughout the remainder of its length. No riser should be
made less than 2¹⁄₂ in. unless a lift is necessary.

Before finally fixing the size of riser to be used in any case the
size of the branch in the horizontal lines serving the same must be
approximately determined.

These sizes will be dependent on the location in which it is necessary
to install the vacuum producer. In the case of the building (Fig. 61)
the most desirable location for the vacuum producer will be in the
exact center of the building.

With the vacuum producer centrally located the longest run from any
riser will be 55 ft. To this we must add:

5 ft. for each long-turn elbow.
10 ft. for each short-turn elbow.
10 ft. for entrance to each long sweep Y branch.
20 ft. for entrance to a tee branch, except at sweeper inlets on
risers, where 10 ft. is ample.

In calculating the riser friction for risers under 150 ft. in length
the whole capacity of the riser can be assumed as being connected to a
point midway of its length.

In the eight-story building (Fig. 61) the length of the riser from
basement ceiling to eighth floor will be 100 ft. and the length to
be figured, 50 ft. The equivalent length of pipe line for any of the
risers, with the vacuum producer centrally located, will be:

From entrance tee into riser 10 ft.
Length of riser, one-half total length 50 ft.
Turn at base of riser 10 ft.
Run in basement 55 ft.
Y branch or elbow 10 ft.
Elbow at separator 5 ft.
------
Equivalent length 140 ft.

Each riser is to serve two sweepers and must pass 140 cu. ft. of free
air per minute. This will give a friction loss in a 2¹⁄₂-in. pipe of 2
in. mercury, if 10 in. mercury be maintained at the hose cock and 1-in.
hose used; and 1.5 in. mercury if 6 in. mercury be maintained at the
hose cock and 1¹⁄₄-in. hose used. Either of these figures are within
the limits set for the maximum friction loss and 2¹⁄₂-in. pipe will be
the proper size for the risers and their branches in the basement.

The portion of the main in the basement that serves the two risers on
either side of the building (portion “ab,” Fig. 61) must be of such
size as will produce the same loss in vacuum with 280 cu. ft. of air
passing as the 2¹⁄₂-in. pipe gives with 140 cu. ft. of air passing.
This may be determined from any table of equalization of pipes or may
be obtained from the chart, Fig. 48, in the following manner:

Find the intersection of the horizontal line “140” with the diagonal
representing a 2¹⁄₂-in. pipe and pass on the nearest vertical to its
intersection with the horizontal line “280.” The diagonal inclined
toward the left passing nearest this intersection will be the pipe
size required. In this case a 3-in. pipe will give a slightly greater
friction and will be sufficient.

Unfortunately, it is rarely possible to locate the vacuum producer
in as favorable a point as that given in the illustration, but an
effort should always be made to select a location as nearly central to
all risers as possible. The basements of modern office buildings are
generally crowded and the space assigned to the mechanical equipment is
limited and owing to the necessity of ventilation, the vacuum producer
is generally located near the outside of the building.

Probably the best location that could be obtained in this case would be
at “d” (Fig. 62). The length of piping to risers 1 and 2 would now be
the same as that to all risers in case of Fig. 61, but the distance to
risers 3 and 4 will be increased 50 ft. It will be possible to increase
the size of the pipe line “bd” to the maximum size to serve four
sweepers, or 3¹⁄₂ in., the risers and their branches to remain 2¹⁄₂ in.

The total friction loss to risers 1 and 2 will now be:

Entrance to tee in risers, 10 ft. plus 50 ft. 60 ft.
Turn at base of riser, 10 ft., branch from “c” to riser 32 ft. 42 ft.
Entrance to tee in main 20 ft.
-------
Total equivalent length of 2¹⁄₂-in. pipe 122 ft.

When 1-in. hose is used the density of the air entering the 2¹⁄₂-in.
pipe is equivalent to a vacuum of 10 in. mercury and the friction loss
in the 2¹⁄₂-in. pipe will be 1.9 in. mercury. When 1¹⁄₄-in. hose is
used, the density of the air entering the pipe will be equivalent to a
vacuum of 6-in. mercury and the friction loss in the 2¹⁄₂-in. pipe will
be 1.32 in. mercury.

[Illustration: FIG. 62. ELEVATION OF LAYOUT FOR OFFICE BUILDING,
SHOWING BEST LOCATION (AT D) FOR VACUUM PRODUCER.]

The density of the air entering the 3¹⁄₂-in. pipe, “bd,” will be
equivalent to a vacuum of 11.9 in. mercury when 1-in. hose is used,
and to 7.32 in. mercury when 1¹⁄₄-in. hose is used. The friction loss
in the 3¹⁄₂-in. pipe will be 0.31 and 0.23 in. mercury, respectively.
Total friction loss to inlets on risers 1 and 2 will be 2.21 in. with
1-in. hose in use, and 1.55 in. with 1¹⁄₄-in. hose.

To obtain the friction loss to inlets on risers 3 and 4 the friction
loss in the pipe “bc” must be added to the above figures. With 50 ft.
of 3¹⁄₂-in. pipe carrying 280 cu. ft. free air the friction loss is 0.6
in. when the vacuum in the pipe is 12 in. and 0.4 when the vacuum in
the pipe is 8 in.

The total loss of vacuum to inlets on risers 3 and 4 will be 2.91 in.
if 1-in. hose is used and 1.95 in. if 1¹⁄₄-in. hose is used. In this
case, the total loss from inlet to vacuum producer is approximately
equal to the maximum variation of vacuum permitted at sweeper outlets
when 1¹⁄₄-in. hose is used, but is greater than when 1-in. hose is used.

However, it is the variation in vacuum at the hose cock farthest
from and that nearest to the vacuum producer that fixes the maximum
variation allowable. In this case it will be the difference in vacuum
between an inlet on riser 1 or 2 and a similar inlet on riser 3 or
4. The difference in vacuum at the bases of these risers will be the
friction loss in the pipe “bc,” and the total difference in friction in
the risers will occur when one sweeper is attached to the lowest inlet
on one riser, and one sweeper on the eighth and one on the seventh
floor on the other riser. The friction loss in the riser having the two
sweepers attached to its upper inlets will be:

15 ft. of 2¹⁄₂-in. pipe from seventh to eighth floors, 70 cu. ft. of
free air per minute, or 0.051 in. with a density equivalent to 6-in.
vacuum, and 0.075 in. with a density equivalent to 10-in. vacuum.

85 ft. of 2¹⁄₂-in. pipe from first to seventh floors, 140 cu. ft. free
air per minute, or 0.25 in. with a density equivalent to 6-in. vacuum,
and 0.42 in. with a density equivalent to 10-in. vacuum.

The total difference in vacuum at the hose cocks will be:

0.051 + 0.25 + 0.4 = 0.7 in. with 6-in. vacuum at the hose cock.

0.075 + 0.42 + 0.6 = 1.15 in. with 10-in. vacuum at the hose cock.

Either of these values are well within the maximum variation. It is,
therefore, evident that when the vacuum producer cannot be centrally
located that a piping system which will give the most nearly equal
length of pipe to each riser will yield the best results.

A vacuum cleaning system for serving a passenger car storage yard will
best illustrate the effect of long lines of piping. A typical yard
having 8 tracks, each of sufficient length to accommodate 10 cars, is
shown in Fig. 63. The vacuum producer in this case is located at the
side of the yard at one end, which is not an unusual condition.

[Illustration: FIG. 63. VACUUM CLEANING LAYOUT FOR A PASSENGER CAR
STORAGE YARD.]

The capacity of this yard will be 80 cars which must generally be
cleaned between the hours of midnight and 6 A. M., or a period of 6
hours for cleaning.

It will require one operator approximately 20 minutes to thoroughly
clean the floor of one car, on account of the difficulty in getting
under and around the seat legs. In addition to this, it is also
necessary to clean the upholstery of the seats and their backs, which
will require approximately 25 minutes more or 45 minutes for one
operator to thoroughly clean one car. Therefore, one operator can clean
8 cars during the cleaning period and a ten-sweeper plant will be
necessary to serve the yard.

One lateral cleaning pipe must be run between every pair of tracks or
four laterals in all to properly reach all cars without running the
hose across tracks where it might be cut in two by the shifting of
trains.

Outlets should be spaced two car lengths apart in order to bring an
outlet opposite the end of every second car. This will make it possible
to bring the hose in through the end of the car at the door opening and
clean the entire car from one end which can be done by using 100 ft. of
hose. The use of double the number of outlets and 50 ft. of hose would
require two attachments of the hose to clean one car resulting in a
loss of time in cleaning and is not recommended.

In this case, 100 ft. of hose would be the shortest length that would
be likely to be used and 60 cu. ft. of free air would be the maximum to
be allowed for when using 1¹⁄₄-in. hose.

The simplest layout for a piping system to serve this yard would be
that shown in Fig. 63.

When the entire yard is filled with cars and the entire force of ten
operators is started to clean them it would be possible to so divide
them that not over three operators would be working on any one lateral
and this condition will be assumed to exist. The maximum size for the
laterals between the tracks will be that for three sweepers, or 3 in.,
and it will not be safe to use this size beyond the second inlet from
the manifold, from which point to the end of the lateral it must be
made 2¹⁄₂ in., the maximum size for either one or two sweepers. The
total loss of pressure due to friction from the inlet at x (Fig. 63)
to the separator can be readily calculated from the chart (Fig. 56) as
follows:

TABLE 20.

PRESSURE LOSSES FROM INLET TO SEPARATOR IN SYSTEM FOR CLEANING RAILROAD
CARS.

--------+---------+----------+---------+--------+--------+--------
| | | |Average |Friction| Final
|Cubic Ft.|Equivalent| Size of | Vacuum,| Loss, |Vacuum,
Section | Free Air| Length, | Pipe, | Ins. | Ins. | Ins.
of Pipe.| per min.| feet. |In. Diam.|Mercury.|Mercury.|Mercury.
--------+---------+----------+---------+--------+--------+--------
x--5 | 60 | 150 | 2¹⁄₂ | 6 | 0.35 | 6.35
5--4 | 120 | 140 | 2¹⁄₂ | 7 | 1.35 | 7.70
4--2 | 180 | 280 | 2¹⁄₂ | 11 | 7.0 | 14.70
2--w | 180 | 190 | 3 | 16 | 4.0 | 18.70
w--u | 360 | 20 | 5 | 19 | 0.9 | 19.60
u--s | 480 | 20 | 6 | 20 | 0.5 | 20.10
s--sep | 600 | 20 | 6 | 20 | 0.4 | 20.50
--------+---------+----------+---------+--------+--------+--------

This loss will be the maximum that is possible under any condition as
it is computed with three sweepers working on the three most remote
inlets on laterals “xy” and “vw” and with two sweepers on laterals
“tu” and “rs.” The pipes are the largest which will give a velocity
of 40 ft. per second with the full load and at the density which
will actually exist in the pipe lines with the vacuum maintained at
the separator of 20 in. mercury in all cases, except the pipe from
“s” to separator. There the size was maintained at 6 in., as it was
not considered advisable to increase this on account of the reduced
velocity which would occur when less than the total number of sweepers
might be working.

As bare floor brushes will be used for cleaning coaches it is not
considered advisable to reduce the air quantity below that required by
such renovators. However, when carpet renovators are used in Pullman
cars and upholstery renovators are used on the cushions of both coaches
and Pullmans, the air quantity will be reduced. This condition may
exist at any time, also one of these carpet or upholstery renovators
may be in use on one of the inlets most remote from the separator at
the same time that nine floor brushes are in use on the remaining
outlets. In that case a vacuum at the separator of less than 20 in.
would result in a decrease in the vacuum at the inlet to which this
renovator was attached. The vacuum at the separator must, therefore, be
maintained at the point stated.

With such a vacuum there will be variation in the vacuum at the hose
cocks of from 6 in. to 20 in. or seven times the maximum allowable
variation in vacuum at the hose cocks.

If 1-in. hose be used, the maximum air quantities will be 40 cu. ft.
per sweeper. If we start with a vacuum at the inlet “x” of 10-in.
mercury, the vacuum at the separator will again be 20 in. and we now
have a variation of 10 in. between the nearest and most remote inlet
from the separator, or five times the maximum allowed.

Either of these conditions is practically prohibitive, due to:

1. The excessive power consumption at the separator. 50 H. P. in case
1¹⁄₄-in. hose is used, and 33 H. P. in case 1-in. hose is used.

2. The excessive capacity of the exhauster in order to handle the air
at such low density, a displacement of 1,800 cu. ft. being necessary in
case 1¹⁄₄-in. hose is used and 1,200 cu. ft. in case 1-in hose is used.

3. The great variation in the vacuum at the hose cocks which will admit
the passage of so much more air through a brush renovator on an outlet
close to the separator as to render useless the calculations already
made, or the high vacuum at the carpet or upholstery renovators would
render their operation practically impossible.

[Illustration: FIG. 64. ARRANGEMENT OF PIPING RECOMMENDED AS BEST FOR
PASSENGER CAR STORAGE YARD.]

Such a layout must be at once dismissed as impractical, and some other
arrangement must be adapted. The arrangement of piping shown in Fig. 64
is considered by the author to be the best that can be devised for this
case.

With this arrangement the vacuum at the separator must be maintained
at 11.50 in. mercury to insure a vacuum of 6 in. mercury at the outlet
“x” under the most unfavorable conditions, and the maximum variation
in vacuum at the inlets will be 3.45 in. mercury when 1¹⁄₄-in. hose
is used. This will give a maximum vacuum under a carpet renovator of
7¹⁄₂ in. mercury with 37 cu. ft. of air passing and will permit 70 cu.
ft. of free air per minute to pass a brush renovator when operating
with 100 ft. of hose attached to the inlet at which the highest vacuum
is maintained. Both of these conditions will permit satisfactory
operation and the increased air quantities will not seriously affect
the calculations already made. The maximum horse power required at the
separator will now be 20.5 as against over 50 in the case of the piping
arrangement shown in Fig. 63, and will require an exhauster having a
displacement of 950 cu. ft. instead of 1,800 cu. ft. required with the
former layout.

If 1-in. hose is used and 10 in. mercury maintained at the outlet “x”
under the same conditions as before, the vacuum at the separator will
be 14.50 in. and the maximum variation in the vacuum at the inlets will
be 3 in., which will give a maximum vacuum under a carpet renovator
of 6 in. mercury with 32 cu. ft. of air passing and will permit the
passage of 45 cu. ft. of free air through a brush renovator when
operated at the end of 100 ft. of hose attached to the outlet at which
the highest vacuum is maintained. This is a more uniform result, than
was noted when 1¹⁄₄-in. hose was used.

The maximum horse power which will be required at the separator will
now be 18.6 and the maximum displacement in the exhauster will be 740
cu. ft.

It is, therefore, evident that, where very long runs of piping are
necessary and where 100 ft. of hose will always be necessary, the
use of 1-in. hose will require less power and a smaller displacement
exhauster than would be required with 1¹⁄₄-in. hose, without affecting
the efficiency of the cleaning operations, and at the same time
rendering the operation of the renovators on extreme ends of the system
more uniform.

The example cited in Figs. 63 and 64 is not by any means an extreme
case to be met in cleaning systems for car yards, and the larger the
system the greater will be the economy obtained with 1-in. hose.

Such conditions, however, are confined almost entirely to layouts of
this character and will seldom be met in layouts within any single
building. This is fortunate, as the train cleaning is practically the
only place where the use of 100 ft. of hose can be assured at all times.

Very tall buildings offer a similar condition although the laterals are
now vertical and can be kept large enough to sufficiently reduce the
friction without danger of deposit of dirt in them, and the horizontal
branches will be short and also large enough to keep the friction
within reasonable limits without danger of deposit of dust.

Where large areas within one or a group of buildings must be served by
one cleaning system, better results can often be obtained by installing
the dust separator at or near the center of the system of risers
instead of close to the vacuum producer, as indicated in Fig. 65.
When this is done, the pipe leading from the separator to the vacuum
producer carries only clean air and can be made as large as desired and
the friction loss reduced, resulting in a considerable reduction in the
power required to operate the system.

[Illustration: FIG. 65. GOOD LOCATION FOR DUST SEPARATOR WHERE LARGE
AREAS ARE SERVED BY ONE CLEANING SYSTEM.]

Where the system becomes still larger, two or more separators located
at centers of groups of risers can be used and clean air pipes of any
desired size run to the vacuum producer (Fig. 66). When more than
one separator is used care should be exercised in proportioning the
pipe lines from the separators to the vacuum producer so as to have
the friction loss from the vacuum producer to each separator the same
in order to give uniform results at all inlets. This loss should
also be kept as low as possible in order to prevent a high vacuum
in a separator serving a portion of the system on which few sweepers
are in operation. If low friction losses in the clean air pipe will
require larger pipes than it is practical or economical to install,
pressure reducing valves might be located in the clean air pipes near
the separators to so regulate the vacuum at the separators and insure
uniform results. A system of this kind might serve several premises
and the air used by each be metered and the service sold much the same
as heat and electricity. However, the power required to operate the
system would be greater than that needed to operate a similar number
of sweepers by individual plants owing to the higher vacuum required
to overcome the friction in the trunk mains. This would be offset by
the use of larger units and the possibility of operating them at full
load at nearly all times. A system of this kind was contemplated in
Milwaukee some seven years ago, but was never installed.

[Illustration: FIG. 66. LOCATION OF SEPARATORS AT CENTERS OF GROUPS OF
RISERS FOR LARGE SYSTEMS.]

The question of pipe friction in connection with the design of vacuum
cleaning systems requires careful consideration, much more than it ever
received in the early days of the art and a great deal more than it
sometimes receives at the present time.

CHAPTER VIII.

SEPARATORS.

The appliances which remove the dust from the air current which has
carried it through the hose and pipe lines, in order to prevent damage
to the vacuum producer, play an important part in the make-up of a
vacuum cleaning system.

=Classification of Separators.=--Separators may be divided into two
classes according to their use:

1. Partial separators, which must be used in conjunction with another
separator in order to effect a complete removal of the dust from the
air. These separators are again divided into two sub-classes, _i. e._,
primary, or those removing the heavy particles of dust and dirt only,
and secondary, or those removing the finer particles of dirt which have
passed through the primary separator.

2. Complete separators, or those in which the removal of both the heavy
and the finer particles of dust is effected in a single separator.

Separators may also be classified, according to the method employed in
effecting the separation, into dry separators in which all operations
are effected without the use of liquid, and wet separators in which
water is employed in the removal of the dust.

=Primary Separators.=--Primary separators are nearly always operated
as dry separators and depend largely on centrifugal force to effect
the separation. The first type of primary separator used by the
Vacuum Cleaner Company is illustrated in Fig. 67. This consists of a
cylindrical tank, with hopper bottom, containing an inner cylinder
fixed to the top head. The dust-laden air enters the outer cylinder
near the top on a tangent to the cylinder. The centrifugal action set
up by the air striking the curved surface of the outer cylinder tends
to keep the heavy dirt near the outside of same, and as it falls
towards the bottom the velocity is reduced and its ability to carry
the dust is lost. When the air passes below the inner cylinder the
velocity is almost entirely destroyed and all but the very lightest of
the dust particles fall to the bottom, while the air and the light dust
particles find their way out of the separator through the opening in
the center at the top.

[Illustration: FIG. 67. EARLY TYPE OF PRIMARY SEPARATOR USED BY VACUUM
CLEANER COMPANY.]

[Illustration: FIG. 68. PRIMARY SEPARATOR USED BY THE SANITARY DEVICES
MANUFACTURING COMPANY.]

The primary separator used by the Sanitary Devices Manufacturing
Company is illustrated in Fig. 68. The inner centrifugal cylinder
is omitted and the air enters through an elbow in the top of the
separator, near its outer extremity, which is turned at such an angle
that the air is given a whirling motion resulting in the dust being
separated much the same as in the case of the Vacuum Cleaner Company’s
apparatus.

Either of these separators will remove from 95% to 98% of the dirt that
ordinarily comes to them through the pipe lines and are about equally
efficient.

[Illustration: FIG. 69. PRIMARY SEPARATOR USED BY THE GENERAL
COMPRESSED AIR AND VACUUM CLEANING COMPANY.]

[Illustration: FIG. 70. PRIMARY SEPARATOR MADE BY THE BLAISDELL
ENGINEERING COMPANY.]

The separator illustrated in Fig. 69 was used by the General Compressed
Air and Vacuum Cleaning Company. The entering air is led to the center
near the bottom and is then released through two branches curved
to give the air a whirling motion. The clean air is removed from
the center of the separator near the top. This separator is not as
effective in its removal of dirt as either of the former types, owing
to the entering air being introduced near the bottom. This tends to
keep the air and the dust in the bottom of the separator continually
stirred up, also the curved inlets give the air more of a radial than
a tangential motion and there is less separation due to centrifugal
action.

The separator illustrated in Fig. 70 is made by the Blaisdell
Engineering Company. In this separator the inner centrifugal cylinder
of the Vacuum Cleaner Company’s separator is replaced by a spiral
extending nearly to the outlet in the center of the top. This
arrangement tends to prevent the reduction in the air velocity and to
limit its effectiveness in the removal of dust.

Separators similar to the Sanitary separator have been manufactured by
many firms producing vacuum cleaning systems. These all differ somewhat
in details of construction but the principle involved, _i. e._,
centrifugal force and reduction in air velocity, is the same in all
cases.

With vacuum producers in which there are no close clearances or rubbing
contacts, these are the only separators used. The finer particles of
dust passing these separators are carried harmlessly through the vacuum
producer and through the exhaust to the outer atmosphere or to the
chimney or other flue where they are effectively sterilized.

=Secondary Separators.=--With vacuum producers having close clearances
or rubbing parts in contact with each other and the air exhausted,
further separation of the finer dust particles is necessary. To
accomplish this, secondary separators are used.

All of the early systems used a wet separator as a secondary separator.
That used by the Vacuum Cleaner Company is illustrated in Fig. 71.
It consists of a cylindrical tank partially filled with water, with
a diaphragm perforated in the central portion and fixed in place
below the water line, and an inverted frustrum of a cone placed just
above the water line. The air enters the separator below the water
line and passes up through the water in the form of small bubbles
which are broken up into still smaller bubbles on passing through the
perforations in the diaphragm. This action is very essential to the
thorough cleansing of the air, as large bubbles of air may contain
entrapped dust which will pass through the water and out into the
vacuum producer. The inverted frustrum of a cone is intended to prevent
any entrained water passing out of the separator with the air. This
separator has always given satisfactory results when used in connection
with reciprocating pumps.

The separator illustrated in Fig. 72 was manufactured by the General
Compressed Air and Vacuum Cleaning Company. The air enters the
separator through the pipe curved downward and escapes at the center
below the water line. It then rises in the form of bubbles and most of
it strikes the under side of the ribbed aluminum disc “a,” which is
intended to float on the surface of the water, and passes along the
ribbed under surface of this disc, escaping into the upper part of the
separator around the edge.

[Illustration: FIG. 71. SECONDARY SEPARATOR USED BY THE VACUUM CLEANER
COMPANY.]

[Illustration: FIG. 72. SECONDARY SEPARATOR USED BY THE GENERAL
COMPRESSED AIR AND VACUUM CLEANING COMPANY.]

The clean air passes out of the top of the separator to the vacuum
producer. The successful operation of this separator is dependent on
the freedom of motion of the disc “a,” which will always keep it on
the surface of the water, and on all of the air passing up through the
water under the disc.

Should the disc become caught on the supporting pipe the violent
agitation of the water, which occurs when the system is in operation,
will cause the disc to be left high and dry above the water at times,
and submerged at other times. When this disc is above the water line
it will not break up any of the large bubbles. Also, when there is a
large quantity of air passing through the separator, there is great
likelihood that considerable of the air bubbles will pass up through
the water entirely outside of the disc and these bubbles will not be
broken up. This separator has given somewhat unsatisfactory results in
some installations tested by the author.

[Illustration: FIG. 73. SECONDARY SEPARATOR USED BY THE SANITARY
DEVICES MANUFACTURING COMPANY.]

[Illustration: FIG. 74. TYPE OF DRY SEPARATOR USED AS SECONDARY
SEPARATOR.]

The separator used by the Sanitary Devices Manufacturing Company
differs from those already described in that the air and water are
mixed before they enter the separator and the air comes into the
separator above the water line. The air enters the pipe “a” (Fig. 73)
and passes to the aspirator “b,” which is connected to the separator
by the pipe “d” below the water line and the pipe “e” above the water
line. The excess of vacuum in the separator draws the water out of
the aspirator and its pipe connections until the water line in this
pipe is lowered below the top of the horizontal portion of the piping,
when the air bubbles up through the demonstrator glass “c” and passes
into the separator through the pipe “e.” The filling of the vertical
pipe leading to “c” with air causes the static head of the water in
the separator to produce a flow of water through the pipe “d” into
the aspirator “b.” This is formed in the shape of a nozzle and the
water enters in the form of a spray and thoroughly mixes with the air.
The cleansing action of this water spray has been found to be very
effective in removal of all fine dust and this separator has been found
to be the most effective wet separator ever produced.

While the wet separator when properly designed will effectively remove
the finest of dust, greasy soot will not emulsify with the water and
its removal is practically impossible. Fortunately, this form of
material in the finely-divided condition in which it passes the primary
separator is not gritty and does not produce injurious effect on the
vacuum producer.

The wet separator is also at a disadvantage in that there is a loss
of vacuum in passing through same equal to the head of water that is
carried between the inlet and the surface of the water. This generally
amounts to nearly 2 in. mercury.

Means must be provided to observe the height of the water in the wet
separator. For this purpose a glass window in the side of the separator
has been found to be the most effective. The use of an ordinary gauge
glass such as is used on boilers has been tried, but it has been found
that they readily become so clouded by the action of the muddy water
as to render them useless while the constant agitation of the water
against the window when the system is in operation tends to keep the
glass clean.

Dry separators have been used for secondary separators to a limited
extent. All of these contained a bag made of canvas or some other
fabric. The separator illustrated in Fig. 74 contains a bag made of
drilling which is slightly smaller than the inner diameter of the
cylindrical casing of the separator. The air enters the inside of the
bag, inflating it, and passes through the bag and out through the
opening in one side of the casing. A wire guard is placed over this
opening to prevent the bag being drawn against the opening and thus
rendering only a small portion of it effective.

These bags offer very little resistance to the passage of the air when
they are clean but they soon become filled with dust and produce an
increased resistance which, if neglected, may result in so great a
difference in pressure as to hinder the action of the system and result
in the rupture of the bag, letting the dust into the vacuum producer.

Some trouble has been experienced in finding a suitable material
through which the dust will not pass. Hush cloth, such as used on
dining tables, has been found to be the best material for this
purpose. Better results are obtained by passing the air from the
outside of the bag towards the inside than when the air is passed as
indicated in Fig. 74. When this arrangement is adopted, it is necessary
to stretch the bag over a metal screen or frame in order to prevent
collapse.

=Complete Separators.=--Complete separators are of two classes,
_i. e._, dry and wet. The first complete separator that the author
has knowledge of was used by the Vacuum Cleaner Company, in the
form of a cylindrical tank and contained centrifugal cylinder and
also a perforated plate. It was practically a combination of the
separators indicated in Figs. 67 and 71. This separator was installed
in connection with a small rotary pump and mounted on a truck. It
worked very well until it became filled with dirt when, in one case,
the entire contents were ejected into an apartment in which it was
being used. This separator was then rebuilt in the form shown in Fig.
75, the bag being made of hush cloth stretched over a wire screen.
The air enters the cylinder tangentially and much of the separation
is accomplished by centrifugal force, the remainder of the dust
being removed as the air passes through the bag. This separator was
successfully used as long as this company continued to manufacture such
apparatus.

Another form of complete separator quite similar to that above
described has recently been brought out by the Electric Renovator
Manufacturing Company and is shown in section in Fig. 76. The air
enters this separator tangentially below the line of the dust bag,
which is made of muslin folded back and forward over a set of
concentric cylinders thus giving a large area for the passage of the
air. Being entirely above the line of the entering air, none of the
heavy dirt strikes the bag and what dirt is caught on the bag is on the
lower side of same and is shaken off every time the bag is agitated.
This agitation occurs every time there is any change in the volume
of air passing the separator, and when these separators are used in
connection with fan type of exhausters there is a constant surging
whenever the exhauster is operated with a small volume of air passing.
This tends to keep the bag clean automatically.

[Illustration: FIG. 75. FORM OF COMPLETE SEPARATOR USED BY THE VACUUM
CLEANER COMPANY.]

The separator illustrated in Fig. 77 is manufactured by the American
Radiator Company. The air enters this apparatus through the pipe in
the center and passes directly down to the bottom, the velocity being
gradually reduced due to the expansion of the air as it passes down the
cone-shaped inlet, the heavy dirt falling to the bottom. The air then
passes up along the inner surface of the cylindrical shell and thence
through the bag, which is stretched over a screen, to the outlet. In
this separator we see the first case in which centrifugal action is not
utilized in separating the heavy dust, the makers evidently considering
the reduction of air velocity and the action of gravitation to be
ample. This bag is arranged to permit the air passage from the outside
towards the inside and it is tapered to allow the dirt to fall off.
The vacuum gauge is connected to the inner and outer sides of the bag
by means of a three-way cock to permit of measuring the difference in
vacuum between the inside and outside of the bag to determine when the
bag is in need of cleaning, which is accomplished by a reversal of the
air current through the bag. This is quite necessary in order to keep
the separator always in an efficient condition.

[Illustration: FIG. 76. COMPLETE SEPARATOR BROUGHT OUT BY THE ELECTRIC
RENOVATOR MANUFACTURING COMPANY.]

[Illustration: FIG. 77. COMPLETE SEPARATOR MADE BY THE AMERICAN
RADIATOR COMPANY.]

A separator was devised by the Sanitary Devices Manufacturing Company
in which the bag was held extended by a wire ring having a weighted rod
passing out through the top of the separator attached thereto. When
the bag became clogged the difference in pressure on the two sides
would result in a tendency of the bag to collapse and the rod would be
raised up out of the separator, indicating that cleaning was necessary,
which could be easily accomplished by drawing the rod up and down a few
times thus shaking the dust off the bag. This separator never came into
general use, although its arrangement was ingenious and should have
been easy to operate.

The great difficulty with all bags which must be cleaned periodically
is that they are almost universally neglected even when there is a
visual indicator to show the accumulation of dirt, and when it becomes
necessary to manipulate a three-way cock in order to ascertain when
this cleaning must be done it will seldom if ever be attended to. A bag
that will clean itself, such as the Capitol Invincible, is shown in
Fig. 76.

The separator used by one manufacturer consists of a simple cylindrical
tank into which the air is blown tangentially, with a screen near the
top, the whole forming a base for the vacuum producer. This separator
does not remove any but the heaviest dirt and is suitable for use only
with a vacuum producer having very large clearances and in locations
where the discharge of considerable dirt into the atmosphere is not
objectionable.

=Total Wet Separator.=--The only total wet separator which is in
commercial use is manufactured by the American Rotary Valve Company.
This separator is contained in the base of the vacuum producer and is
provided with a screen near the point of entrance of the dust-laden
air, which screen is cleaned by a mechanically-driven bristle brush.
When the water in the separator becomes foul, the contents of the
separator are discharged direct to the sewer by means of compressed
air. If this separator receives proper attention it makes the most
sanitary arrangement that has been introduced in the vacuum cleaning
line to date. However, the separator should be emptied at frequent
intervals or the volume of solid matter contained in the same will
become so great that there will not be enough water present to flush
the sewer and stoppage is likely. These separators are often neglected
until the contents become of the consistency of mortar or molasses
which is not a fit substance to discharge into a sewerage system.

There is still another form of apparatus used in connection with vacuum
cleaning systems which should be called an emulsifier rather than a
separator. That is the type used with the Rotrex and the Palm systems.
The dust is mixed with water when it first enters the pump chamber,
a screen being used to remove the lint and larger particles of dirt
and then the mud produced by the combination of the dust and water is
passed through the pump along with the air. The air and muddy water are
separated on the discharge side of the vacuum producer. In many cases
where the exhaust pipe is long, there is considerable back pressure on
the discharge which is often sufficient to force the seals in traps
on the sewerage system, allowing sewer gas to be discharged into the
building in which the cleaning system is installed. No means are
provided for automatically cleaning the screen used in these appliances
and the author knows of cases where the screen has become so completely
clogged with lint that its removal from the machine was necessary in
order to render the operation of the cleaning tools possible.

When dry separators are used, the manual removal of the dry dirt
accumulated is necessary and is an objectionable as well as unsanitary
operation. The author considers that the ideal arrangement of
separator would be one in which the dirt can all be emulsified with
water and retained in the separator, only the air passing through the
vacuum producer, and in which the contents of the separator would be
discharged automatically to the sewer when the density of this mixture
becomes as heavy as will readily run through the sewer. This discharge
should be of sufficient volume to completely fill an ordinary house
sewer in order to insure a thorough flushing of the drain, and should
be discharged into the sewer under atmospheric pressure in order
to guard against the forcing of water seals in any of the plumbing
fixtures.

[Illustration: FIG. 77a. INTERIOR CONSTRUCTION OF DUNN VACUUM CLEANING
MACHINE.]

A separator of this type has recently been patented by E. D. Dunn,
originator of the Dunn Locke system. It is illustrated in Fig. 77a. The
action of the separator is as follows: After starting the motor and
turning on a small quantity of water, a vacuum is produced in one tank
and through a system of piping to the cleaning implement in use. The
dust and dirt collected by the implement is saturated as it approaches
the plant and in this saturated condition enters the bottom of a body
of water in the tank.

When the accumulating dirt and water reach a certain level a valve
is automatically operated which closes the tank’s communication with
the vacuum pump and allows its contents to flow off to the sewer by
gravity. The mechanism for operating the valve is rather unique and
includes a float which, on rising with the water, makes a positive
electrical contact, as shown in the figure. In this illustration one
tank is about to discharge and the other tank is about to become
operative. The electrical contact causes the core of the magnet at O¹
to rise, making the lever, K, turn over, which action opens one valve
and closes the other. In this way the tanks alternately partly fill and
empty their collections of water and sweepings.

This system has not as yet been in commercial use for a sufficient
length of time to insure its successful operation, and the author does
not consider the passing of dirt and water through ordinary check
valves to be commercially possible without rendering these checks
inoperative.

Check valves have been used where partial wet and dry separators are
operated in tandem to prevent drawing water into the dry separator,
in the event of the plant being shut down with all inlets on the pipe
line closed. In such a case, the leakage through the pump into the wet
separator may raise the pressure in this separator faster than leakage
on the pipe line raises the pressure in the dry separator.

This is accomplished by providing a small connection between the upper
part of the two separators, fitted with a check valve opening towards
the dry separator. When the vacuum producer is in operation, the
vacuum in the wet separator is approximately 2 in. greater than that
in the dry and the check is held closed. When the vacuum producer is
stopped and the vacuum in the wet separator falls faster than in the
dry separator, this check opens and clean air passes from the wet to
the dry separator. When operating under these conditions, the action of
the check valve is satisfactory. However, the author has known of cases
where the check leaked and when this happened the check was immediately
clogged by the dust-laden air from the dry separator.

CHAPTER IX.

VACUUM PRODUCERS.

The next portion of the cleaning system is that which produces the
motion of the air through the system and that to which the motive power
is applied, namely, the vacuum producer.

=Types of Vacuum Producers.=--Vacuum producers can be divided into
general classes: 1. Displacement type, in which a constant volume
of air is displaced during each complete cycle of operations of the
machine, and 2. Centrifugal type, in which the volume of air passing
the producer during each complete cycle of operations varies with the
resistance to the passage of such air through the system.

=Displacement Type.=--Under this head the piston and rotary pumps
are classed, and they are subdivided according to construction into
reciprocating and rotary, valved and valveless, air cooled and water
cooled.

=Centrifugal Type.=--Under this head the fan type of vacuum producers
are classed. They may be divided, according to construction, into
single stage and multi-stage, horizontal and vertical.

=Power Required to Produce Vacuum.=--In order to ascertain the
efficiency of the various types of exhausters to be discussed in this
chapter it is necessary to ascertain the actual power necessary to move
one cubic foot of free air at any degree of vacuum.

As nearly all machines tested by the author were driven by electric
motors and the power was, therefore, indicated in watts, the curve C-D
in Fig. 78 showing the actual power necessary to exhaust one cubic
foot of free air at the vacuum noted in the lower margin, assuming no
clearance and adiabatic compression, is used as a basis for calculation
of efficiency. This shows that to produce a vacuum of 8 in. mercury
there will be required an expenditure of 16 watts for each cubic foot
of free air exhausted, and to produce a vacuum of 12 in. mercury will
require an expenditure of 27 watts. If these quantities be divided
by the efficiency of the machine the actual power required will be
determined.

[Illustration: FIG. 78. POWER CONSUMPTION AND EFFICIENCY OF AIR
COMPRESSOR USED AS A VACUUM PUMP.]

=Reciprocating Pumps.=--The reciprocating pump was used on the majority
of the earlier vacuum cleaning systems. The most common form in early
use was a commercial air compressor which was used as a vacuum pump
without any change in its construction. It was usually fitted with
mechanically-operated induction and poppet type of eduction valves
of heavy pattern, fitted with cushions of the dash pot principle,
the same as are used on air compressors working against terminal
pressures as high as 100 lbs. per square inch. The cylinders were water
jacketed to remove the heat of high compression. The valves in these
compressors were heavy and required considerable pressure to open them
and the friction of the valve gear and other moving parts, which were
made heavy enough to withstand the strains of high compression, was
excessively high for a machine where the compression did not exceed 8
or 9 lbs. per square inch. Their efficiency, therefore, is lower under
actual operating conditions than if they were working against pressures
for which they were designed. A curve of the power consumption of a
14-in. × 8-in. Clayton compressor is shown on Fig. 78, the abscissae
being the vacuum in inches of mercury and the ordinates of curve “AB”
the watts required to exhaust one cubic foot of free air. Curve “cd”
represents the theoretical watts required to do the same work. These
compressors were used in connection with systems operating with 1-in.
hose and the vacuum usually carried was 15 in. mercury. They require
approximately 77 watts per cubic foot of free air at this vacuum and
the efficiency, shown in curve “ce” (Fig. 78) is 46%.

[Illustration: FIG. 79. MODIFICATION OF RECIPROCATING PUMP MADE BY THE
SANITARY DEVICES MANUFACTURING COMPANY.]

Were this compressor used in connection with a system operating through
1¹⁄₄-in. hose and a vacuum of 8 in. mercury maintained, the efficiency
would drop to 31%.

A modification of the reciprocating pump was manufactured by the
Sanitary Devices Manufacturing Company in which light-weight poppet
valves placed in the heads of the cylinder were used, as indicated in
Fig. 79. Curves of the watts per cubic foot and efficiency of this
type of compressor are shown in Fig. 80. It will be noted that this
compressor shows a better efficiency than the air compressor at all
degrees of vacuum and it is the best reciprocating pump that the writer
has ever tested.

This pump was made for several years without water jacket and no
trouble was ever experienced with overheating. However, owing to the
commercial air compressors being jacketed, the makers using same made
this a talking point and this company was obliged to jacket its pumps.

[Illustration: FIG. 80. POWER CONSUMPTION AND EFFICIENCY OF MODIFIED
RECIPROCATING PUMP.]

The Vacuum Cleaner Company used a Clayton pump on its smaller plants
which was fitted with a semi-rotary valve in each end serving as an
induction and eduction valve, while the heavy poppet eduction valve of
the air compressor was dispensed with. The increase in efficiency that
should have resulted from this change was not realized. The reason for
this can be more readily seen by inspection of the indicator cards,
Figs. 81 and 82.

Fig. 81 is a card taken from one of the Clayton compressors fitted
with combined induction and eduction valves, and Fig. 82 a card from a
compressor with light steel induction and eduction valves of the poppet
type.

It will be noted that the compression line, a-d, Fig. 81, extends above
the atmosphere line, the pressure at the time of opening the eduction
valve being 4 lbs. per square inch above the atmosphere. This is due
to the failure of the mechanically-operated valve to open soon enough.
This valve being also the induction valve, it is necessary for the
eduction port to be closed before the induction port can be opened, in
order to prevent a short circuit of air from the atmosphere into the
separators. This fact is responsible for the sudden increase in the
pressure at b, the eduction port having closed before the completion of
the stroke and the air in the clearance space being compressed to 6¹⁄₂
lbs. above atmosphere. The induction port is not opened until after the
beginning of the suction stroke resulting in the high degree of vacuum
at c.

[Illustration: FIGS. 81 AND 82. INDICATOR CARDS FOR CLAYTON AND
MODIFIED PUMPS.]

Compare this with the card, Fig. 82. Here the compression does not
extend above the atmosphere line more than ¹⁄₄ lb. per square inch and
the eduction valve does not close until the end of the stroke so that
the vacuum at the beginning of the suction stroke is no lower than
during the entire stroke.

These pumps were working under the same conditions, _i. e._, 15-in.
vacuum in the separator. The M. E. P. for Fig. 81 is 7.05 while that in
Fig. 82 is 6.7 and is higher than is usually the case with this pump,
due to the fact that the exhaust pipe from this pump was very long and
crooked, a condition which should be avoided whenever possible. Also,
the pump from which this card was taken is one of the older pattern and
the clearance was greater than in the later models. The point at which
the eduction valve opens in Fig. 81 is 53% of the stroke and it closes
at 95% of the stroke and is, therefore, open 42% of the stroke, while
in Fig. 82 the eduction valve opens at 46% of the stroke and remains
open to the end of the stroke, and, therefore, is open for 54% of the
stroke. Thus the pump with the poppet valves will move more air at
the same vacuum with less expenditure of power than the pump with the
mechanically-operated valves.

Another type of reciprocating pump has been introduced in the past two
or three years in which a single valve which rotates continuously in
one direction is used for induction and eduction valve, for both ends
of the cylinder. This valve is a plain cylindrical casting having ports
cored through to alternately connect the cylinder ports with the intake
and exhaust ports.

By rotating this valve 180° on its stem the vacuum pump is changed to
an air compressor. This arrangement is adopted in order to discharge
the contents of the separator into the sewer as was explained in
Chapters I and VIII. In this pump there must be points at which both
the induction and eduction valves are closed at the same time and
results similar to those found with the semi-rotary valves of the
Clayton pump will naturally be in evidence. The author has endeavored
to obtain an indicator card from one of these pumps but has been
unable to do so. The effect of simultaneous closing of both induction
and eduction ports would naturally be more marked in this pump than
in the Clayton, as the motion of the valve in this case is uniform at
all times while the motion of the valve gear of the Clayton pump is so
arranged that the valve moves very fast at the time that both ports are
closed. One of the two pumps of this type which was recently installed
in the New York Post Office is illustrated in Fig. 83. These pumps have
a displacement of 1,200 cu. ft. each and are the largest reciprocating
pumps in use for vacuum cleaning at this writing.

An interesting property of the piston pump which lends itself to the
economical control of the vacuum in the system is illustrated by the
curve at the top of Fig. 78 which shows the total power required to
operate the Clayton type air compressor, the efficiency of which is
indicated by the lower curves on this figure. The compressor was
operated at constant speed and the air volume varied to give various
degrees of vacuum from atmospheric pressure to a closed suction and
the power to operate the compressor read at intervals of two inches.
The current input to the motor in amperes is indicated by ordinates
and the vacuum in the separator by the abscissae. This indicates that
the piston pump requires the maximum power to operate at about 15-in.
vacuum and that the least power is required when the vacuum is at the
highest point possible to obtain. The method employed in utilizing this
characteristic of a piston pump will be discussed in a later chapter.

[Illustration: FIG. 83. ONE OF THE PUMPS INSTALLED IN CONNECTION WITH
THE VACUUM CLEANING SYSTEM IN THE NEW YORK POST OFFICE, THE LARGEST
RECIPROCATING PUMP USED FOR THIS PURPOSE UP TO THE PRESENT.]

=Rotary Pumps.=--The Garden City rotary pump is a good example of the
single-impeller type of pump and is or has been used to some extent
by at least two makers of vacuum cleaning systems. Its interior
arrangement is shown in Fig. 84. A solid cylindrical impeller, A, is
mounted eccentrically in the cylindrical outer casing, the impeller
being fitted with four sliding vanes which are provided with distance
pieces, E, and wearing faces, B. The oil reservoir is provided with
a needle valve which is automatically opened as soon as there is any
vacuum produced and closes automatically when the machine is shut down.
The rate of feed of oil is adjusted by the screw I. This type of pump
offers a large surface in rubbing contact with the case and becomes
very hot when in operation. It requires liberal lubrication in order
to prevent heating and cutting of the surface of the casing. End wear
in these pumps causes leakage, and, as usually constructed, there are
no means provided for taking up this wear. It can be provided for,
however, by using metal shims on the ends of the cylindrical casing.

[Illustration: FIG. 84. INTERIOR ARRANGEMENT OF THE GARDEN CITY ROTARY
PUMP.]

[Illustration: FIG. 85. POWER REQUIRED TO OPERATE GARDEN CITY TYPE OF
ROTARY PUMP.]

The power required to operate this type of pump (Curve a-b, Fig. 85),
is nearly the same as that required to operate a piston pump for vacuum
less than 12 in. mercury, but when the vacuum becomes higher, the power
required becomes much greater than that required by the piston pump.
The efficiency (Curve c-e, Fig. 85), is identical with that obtained
with the light-weight poppet valve pump (Curve c-e, Fig. 80) from 0 to
11 in. vacuum, but for higher vacuum the efficiency of this type of
pump falls off, while the efficiency of the piston pump becomes greater
as the vacuum becomes higher. This difference in the characteristics
of the two types of pumps is due to the presence of valves in one case
and their absence in the other. With the piston pump the atmospheric
pressure reaches the cylinder only while air is being discharged, the
eduction valves being closed at other times and a partial vacuum exists
on both sides of the piston. The higher the vacuum produced, the less
time there is atmospheric pressure on the piston until, when no air is
discharged, the air contained in the clearance space of the cylinder
is compressed and expanded, the compression and expansion lines being
coincident. The indicator card will have no area, and the only power
expended is that required to overcome the friction in the moving
parts. With the rotary pump there are no discharge valves to hold the
atmospheric pressure from the discharge side of the impeller and the
compression of the rarified air is accomplished by the atmospheric
pressure admitting air through the eduction port into the chamber. As
it comes opposite the eduction port there is no difference in the time
during which the impeller is subject to atmospheric pressure, no matter
what the quantity of air being discharged. The higher the vacuum in the
spaces containing rarified air, the greater the difference in pressure
on the opposite sides of the sliding vane and, therefore, the greater
total power required to turn the rotor.

[Illustration: FIG. 86. ARRANGEMENT OF DOUBLE-IMPELLER ROOT TYPE ROTARY
PUMP FOR VACUUM CLEANING WORK.]

Another type of rotary pump which is fast becoming the most popular is
the double-impeller type. This is generally known as the Root blower,
as the firm of this name was the first to manufacture same. They have
been in use for many years as blowers for gas works, and as vacuum
producers for various purposes, mainly the operation of pneumatic tube
systems.

Why this form of vacuum producer was not earlier adopted in vacuum
cleaning systems, instead of the sliding-vane type, is hard to
understand. This pump contains two impellers or cams which are mounted
on shafts geared together and revolve in opposite directions inside of
a case, always being in close proximity to the case and to each other,
but never touching. They are, therefore, frictionless in operation and
the introduction of a small amount of water renders them practically
air tight. There being no metallic contact between the moving parts,
internal lubrication is unnecessary and there is no wear on either the
impellers or the casing and no means of taking up wear are necessary.

The arrangement of the impellers and the method of providing water to
seal the parts is shown in Fig. 86. A reservoir containing water is
provided on the discharge side of the pump and a small pipe leads from
this reservoir to the suction side of the pump. The vacuum lifts water
from the reservoir and discharges same in a spray into the suction
chamber. This water passes through the pump and is separated from the
air in the discharge chamber to be returned to the suction chamber by
the vacuum. This operation will start automatically as soon as any
degree of vacuum is formed and will cease as soon as the pump is shut
down.

[Illustration: FIG. 87. ROTARY PUMP ARRANGED WITH DOUBLE-THROW SWITCH
FOR REVERSING PUMP.]

Any of these rotary pumps having no valves can be changed to an air
compressor by reversing the direction of rotation. This is adapted
by the American Rotary Valve Company in connection with their wet
separators to discharge the contents of the separator into the sewer,
on all of their smaller-sized plants. Fig. 87 shows one of these plants
arranged with double-throw switch for reversing the electric motor used
to operate the pump and also shows the arrangement of the rotary brush
which is used to clean the screen in the wet separator, as has been
explained in Chapter VIII.

[Illustration: FIG. 88. POWER CONSUMPTION AND EFFICIENCY ROOT TYPE OF
PUMP.]

[Illustration: FIG. 89. THE ROTREX VACUUM PUMP, USED BY THE VACUUM
ENGINEERING COMPANY.]

The power consumption and efficiency of this type of pump are shown in
Fig. 88. The watts per cubic foot of free air (Curve a-b) show a much
lower consumption of power at the lower vacuum than any of the pumps
already tested. This is probably due to the fact there is no internal
friction. It will be noted that the power to operate at no vacuum is
but 10 watts per cubic foot of free air, while all the others require
from 24 to 34 cubic feet. This also results in the efficiency curve
(c-e, Fig. 88) reaching its maximum value at a lower vacuum than in the
case of the sliding vane pump (Fig. 85).

[Illustration: FIG. 90. LATE TYPE OF CENTRIFUGAL EXHAUSTER MADE BY THE
SPENCER TURBINE CLEANER COMPANY.]

The efficiency is fairly constant between 6-in. and 10-in. vacuum and
is much higher than is obtained with any of the other types of pumps at
these vacua. When they are operated at higher vacuum the efficiency is
about the same as obtained with the sliding vane pumps and lower than
that obtained with the reciprocating pumps. The best efficiency of this
pump is at the vacuum necessary to operate a cleaning system provided
with 1¹⁄₄-in. hose.

A slight modification of this type of pump is that used by the Vacuum
Engineering Company, known as the Rotrex. This pump has but one
impeller, of nearly the same form as the impellers in the Root blowers
and has a follower driven by crank and connecting rods which is always
in close proximity to the impeller but does not touch same. The
arrangement of this pump is illustrated in Fig. 89 which also shows
the saturation chamber and screens used instead of a separator, as
explained in Chapter VIII.

[Illustration: FIG. 91. POWER AND EFFICIENCY CURVES FOR THE SPENCER
MACHINE.]

The author has never tested the economy of these pumps but would infer
that their economy should be about the same as that of the Root blower.

=Centrifugal Exhausters.=--This type of exhauster has always taken
the form of a fan. The first stationary fan type of exhauster was
manufactured by the Spencer Turbine Cleaner Company. Their latest type
is illustrated in Fig. 90. It consists of a series of centrifugal
fans mounted on a vertical shaft, stationary deflection blades being
provided between the wheels to conduct the air from the periphery of
one wheel to the center of the next.

[Illustration: FIG. 92. INTERIOR ARRANGEMENT OF INVINCIBLE MACHINE,
MANUFACTURED BY THE ELECTRIC RENOVATOR MANUFACTURING COMPANY.]

These centrifugal exhausters do not have a positive displacement, as do
all those already described, and therefore the variation of the vacuum
is not as much as in case of the positive displacement machines. The
vacuum produced when the machine is moving no air is slightly less
than the maximum that the exhauster can produce and there is very
little variation in the vacuum with air quantities which can be moved
without exceeding the capacity of the motor or other means producing
the power. The curves showing the power required to operate and the
efficiency of this type of vacuum producer are, therefore, plotted
with abscissae representing the air moved in cubic feet per minute.
The vacuum produced and the power required to operate are plotted as
ordinates. The curves for the Spencer machine are shown in Fig. 91.
This curve is taken from a four-sweeper machine and the vertical lines
numbered 1 to 4 represent the conditions when that number of sweepers
are in operation; that is, bare floor renovators, with 50 ft. of hose
or 80 cu. ft. of free air per minute. The maximum efficiency is reached
at full load and is approximately 42%. The vacuum at this efficiency is
5¹⁄₂ in. mercury, a drop of ³⁄₄-in. from the maximum which was obtained
at one-fourth load.

[Illustration: FIG. 93. POWER CONSUMPTION. VACUUM AND EFFICIENCY OF
FIRST TYPES OF INVINCIBLE MACHINE.]

These machines have rather large clearances and a preliminary separator
is all that is required. They operate at a speed of about 3,600 R. P.
M. and the peripheral speed of the fans varies from 15,000 to 22,000
ft. per minute. This produces some noise and considerable vibration
and care must be exercised in mounting the machine. In order to insure
quiet running the usual method is to place the machine on a felt pad of
considerable thickness.

[Illustration: FIG. 94. POWER CONSUMPTION, VACUUM AND EFFICIENCY OF
INVINCIBLE MACHINE AFTER VALVE WAS FITTED TO DISCHARGE.]

The machines made by the Electric Renovator Manufacturing Company are
horizontal and have much smaller clearances than the Spencer machines.
They operate at approximately the same rotary and peripheral speed
and are, therefore, as noisy. However, the center of gravity of these
machines is lower and the vibration is not so great. The Spencer
Company is now making a horizontal machine which it furnishes only when
required, the claim for their vertical machine being that the weight
of the moving parts counteracts the thrust of the atmospheric pressure
against the fans and relieves the work of the thrust bearings, at the
expense of greater vibration. With ball bearing thrusts, the author
does not consider this to be of great importance.

A view of the interior arrangement of the Invincible machine, as
manufactured by the Electric Renovator Manufacturing Company, is shown
in Fig. 92.

These machines, when first made, were without valves and the power
consumption, vacuum and efficiency are shown in Fig. 93. It will be
noted that the vacuum produced, when the machine is operated at or
below one-half load, is considerably lower than is obtained at greater
loads. This characteristic produces a disagreeable noise when the
machine is not handling any air, evidently due to air rushing back
through the outlet when the vacuum tends to build up to the maximum
which occurs at intervals of about one-half second.

[Illustration: FIG. 95. FOUR-SWEEPER INVINCIBLE PLANT INSTALLED IN THE
UNITED STATES POST-OFFICE AT LOS ANGELES, CAL.]

In order to overcome this trouble a valve has been fitted to the
discharge, as indicated at 4, Fig. 92. With this valve in place the
power consumption, efficiency and vacuum are as shown in Fig. 94. It
will be noted that the vacuum is as high at no load as at any load up
to full load and is practically constant. The efficiency at light loads
is the same as before but it is slightly lower at full load, being 50%
without the valve and 47% with the valve. This is due to the power
being expended in opening the valve for large quantities of air and to
friction in the valve passage.

A four-sweeper plant of this manufacture is shown in Fig. 95. This
plant is installed in the United States Post Office at Los Angeles,
Cal. The separate centrifugal separator, shown at the left of the cut,
is not used in the regular equipment and was added in this case to
fulfill the specification requirements.

A centrifugal pump with a single impeller is manufactured by The United
Electric Company and is known as the Tuec system. A phantom view of
the pump and separator is shown in Fig. 96. It will be noted that the
shaft is vertical. However, the vacuum is under the impeller in this
case, and the thrust due to the atmospheric pressure is down instead of
up, as in the case of the Spencer machines. This throws the weight of
the parts, plus the thrust due to atmospheric pressure, on the thrust
bearing. These machines do not produce a vacuum greater than 3-in.
mercury, and the additional thrust is not as great as in the case of
the machines producing higher vacuum, the impeller being 24 in. in
diameter, its area 450 sq. in. and the thrust, with a vacuum of 3-in.
mercury, 675 lbs., which is worth considering. This downward thrust
is partially counterbalanced by mounting the armature of the electric
motor used to operate the fan, slightly below the magnetic center,
thereby causing an upward magnetic pull. These machines are intended to
be used with large hose and pipe lines to reduce the friction to a very
low point. When operating carpet renovators the vacuum at the renovator
rises to 1-³⁄₄-in. mercury and the type of renovator used by them
passes approximately 50 cu. ft. of air, while the bare floor renovators
pass approximately 95 cu. ft. They are extensively used where bare
floor work is required, their first cost being low.

The results of tests of two of these machines of four-sweeper capacity,
driven by alternating and direct-current motors, respectively,
are shown in Fig. 96a. These curves indicate a considerably higher
efficiency with the alternating than with the direct-current
motor. This is due to the low efficiency of the special high-speed
direct-current motors used with all centrifugal fan-type exhausters.
The alternating-current motors are not so affected, in fact, the speed
at which these fans are operated is fixed by the requirements of the
alternating-current motors.

[Illustration: FIG. 96. CENTRIFUGAL PUMP WITH SINGLE IMPELLER,
MANUFACTURED BY THE UNITED ELECTRIC COMPANY.]

The efficiency of the other types of centrifugal exhausters (Figs. 91,
93 and 94) is in every case accomplished with direct-current motors.
This machine has an efficiency about the same as the Spencer machine.
It will be noted that the vacuum produced does not fall off as the load
increases, as in the case of the multi-stage fans. This characteristic
is probably due to the fact that there is no wire drawing in the
diversion vanes, as in the case of the multi-stage exhauster.

[Illustration: FIG. 96a. TEST OF CENTRIFUGAL PUMP WITH SINGLE IMPELLER.]

=Steam Aspirators.=--The steam aspirator as a vacuum producer in
connection with vacuum cleaning systems was first used by the American
Air Cleaning Company, and has been used to a limited extent by the
Sanitary Devices Manufacturing Company. The type of apparatus used by
the American Air Cleaning Company is illustrated in Fig. 97. A single
partial separator is used with this system and the lighter dust is
allowed to pass through the aspirator, where it is mixed with the
steam and sterilized. The aspirator is in the form of an ejector, with
a specially designed nozzle, and is always fitted with an automatic
device for cutting off the steam when the vacuum in the separator
reaches the degree desired.

[Illustration: FIG. 97. STEAM ASPIRATOR USED BY THE AMERICAN AIR
CLEANING COMPANY.]

The steam consumption required to exhaust 1 cu. ft. of free air at
various vacua, as determined by actual test of four different nozzles,
is shown in Fig. 98, the steam being the actual weight of dry and
saturated steam at the gauge pressures noted. The American Air Cleaning
Company used to guarantee a steam consumption of 250 lbs. per hour from
and at 212° F., assuming that the feed water temperature was 32° F.,
the vacuum to be maintained at 9 in. mercury at the aspirator.

Taking the results of the test of the three-sweeper nozzle as an
average, 0.066 lbs. of steam will be required to exhaust 1 cu. ft. of
free air at 9 in. vacuum. The total heat in 1 pound of dry steam at 110
lbs. gauge is 1187 B. T. U. and at 212° F. the latent heat is 970 B.
T. U. The factor of evaporation, therefore, is 1.235, and the weight of
steam at 110 lbs. allowed by the guarantee is 202 lbs. This amount of
steam will exhaust 3,060 cu. ft. per hour, or 51 cu. ft. per minute,
which is more than sufficient to operate a carpet renovator, and is a
little less than will pass through a bare floor brush attached to the
end of 50 ft. of 1 in. diameter hose, if the hose is attached directly
to the aspirator. With a line of pipe between the hose cock and the
aspirator, the air quantity will be somewhat less, and this guarantee
will undoubtedly be fulfilled in every case.

[Illustration: FIG. 98. STEAM CONSUMPTION OF STEAM ASPIRATOR.]

The advisability of using an aspirator will depend on the conditions
to be met at the building in each case. Three typical cases are cited
below:

=1. When there is a Generating Plant in the Building, and a Plant Using
1¹⁄₄-in. Hose and 8-in. Vacuum is Desired.=--A Root blower will require
27 watts for each cubic foot of air exhausted (Fig. 88), and the
three-sweeper aspirator, 0.065 lbs. of steam. Then the pounds of steam
required by the aspirator to do the same work as one K. W. hour at the
motor of the Root blower will be

0.065 × 60
---------- = 146.3
0.027

The generating plant will produce a kilowatt hour at the switchboard
with not exceeding 60 lbs. of steam, and if the transmission loss is
10% there will be required by the Root blower not over 66 lbs. of steam
to do the same work that takes 146 lbs. with the aspirator. This case
would require that the Root blower, driven by an electric motor, be
used.

=2. When there is High Pressure Steam Available, but no Generating
Plant.=--Then we may use either the aspirator or a Root blower driven
by a steam engine. This engine should have an economy of 60 lbs. per
indicated horse power, with not over 15% friction loss, which will
require 69 lbs. per brake horse power. This will be equivalent to 69 ×
0.776 = 90¹⁄₂ lbs. per K. W. hour, which is still much better than 146
lbs. required by the aspirator.

=3. When Steam is Generated on the Premises with Coal Costing $3.00
per ton and all Machinery Must be Driven by Electricity Purchased for
5 Cents per K. W. Hour.=--Cost of steam to do the same work in the
aspirator that 1 K. W. hour will do in a motor driving a Root blower is:

146 × 300
--------- = 2.8 cents
7 × 2240

as against 5 cents that would have to be paid for current. In this case
there would be a saving in using the aspirator, which would not require
as much attention as the motor, and at loads less than full load, the
steam used by the aspirator would be in direct proportion to the load,
as the control would shut the steam off entirely during a portion of
the time, while the motor would require some current as long as it was
in operation, even if no air was being exhausted. On the other hand,
the steam which is exhausted from the aspirator is not suitable for use
in heating, as it is mixed with air and fine dirt, and must be thrown
away, a condition that must always be considered where there is an
opportunity to use exhaust steam for heating or other purposes.

CHAPTER X.

CONTROL.

When the displacement type of vacuum producer of more than one-sweeper
capacity is used with a vacuum cleaning system, some means must
be employed to prevent the vacuum rising above that necessary for
efficient operation of the sweepers when there are less renovators in
use than the capacity of the vacuum producer or when carpet renovators
are in use on all outlets.

If the displacement pump be run at constant speed, every change in the
quantity of air exhausted will cause a change in the vacuum produced.
This will result in inefficient operation and may result in undue
effort being necessary to operate the renovator and in excessive wear
on the carpets.

The earlier systems were not provided with any control and the first
attempt to control the vacuum was by placing a spring relief valve on
the pipe line near the separator, which admitted additional air when
the vacuum tended to rise. This resulted in full load being thrown on
the pump at all times when the same was in use, which does not give
economical operation.

The controllers that have been devised for maintaining a constant
vacuum without the introduction of air into the system operate on one
of three principles:

1. Closing the suction of the vacuum producer.

2. Opening the suction of the vacuum producer and holding vacuum in the
system.

3. Varying the speed of the vacuum producer.

[Illustration: FIG. 99. FIRST TYPE OF CONTROLLER INTRODUCED BY THE
SANITARY DEVICES MANUFACTURING COMPANY, KNOWN AS THE “UNLOADING VALVE.”]

The first type of controller was introduced in the vacuum cleaning
field by the Sanitary Devices Manufacturing Company, and was known as
the “unloading valve.” It was similar to the unloader which had been
used for some time in connection with air compressors. The detail of
construction is shown in Fig. 99, and consists of a balanced valve,
which is connected to a weighted piston, operating in a chamber
communicating with the separators by a pilot valve. The pilot valve
is operated by an auxiliary piston which is weighted to overcome the
lifting effort due to the vacuum desired. When the vacuum in the
cylinder becomes great enough to overcome the weights attached to the
auxiliary piston, it rises, allowing vacuum to reach the main piston,
which is drawn up and the suction valve closed. When this valve is
closed the vacuum in the pump at once starts to build up to the maximum
possible for the pump to produce, and if the pump used is of the piston
type the vacuum will run up to nearly 28 in., resulting in the pump’s
taking the least power on which it can be operated. As soon as the
vacuum in the separators falls below that which will sustain the weight
on the auxiliary piston the valve falls open and the pump again draws
air through the system. In actual practice this valve will operate at
more or less frequent intervals. The author timed the action of one of
these valves connected to the suction of an eight-sweeper piston pump,
and its time varied from ²⁄₅ second to 65 seconds. The current taken
by the pump when the suction was open was 100 amperes at 220 volts.
When the valve was closed for but ²⁄₅ second the current dropped to
75 amperes, there not being sufficient elapsed time for the pump to
produce a perfect vacuum. When the valve was closed for 2¹⁄₅ seconds,
the vacuum reached its maximum value and the current fell to 32 amperes.

Fig. 100 is a curve plotted from the results of this test and shows an
increase in the power above that necessary to overcome the friction in
the moving parts of the pump in direct proportion to the percentage of
full load that the pump was serving.

[Illustration: FIG. 100. TEST OF CONTROLLER CONNECTED TO SUCTION OF
8-SWEEPER PISTON PUMP.]

This is as near an ideal condition as one could expect to obtain by any
means other than stopping the pump or otherwise decreasing the friction
load. However, this form of unloader is not suitable for a pump without
valves, as the power will increase with an increase in vacuum, and
other means must be employed to control such a pump.

The second form of control is adapted to this type of pump. The
arrangement of one of these controls is shown in Fig. 101. This
consists of a single-ported valve opened by the vacuum in the cylinder,
M, the action of which is controlled by a pilot or auxiliary control
valve actuated by the vacuum in the separator. This auxiliary valve is
fitted with two pistons, S and O, which are held together by springs,
and when so held the main cylinder is open to the atmosphere through
the small ports in the piston, O. When the vacuum in the separator
becomes great enough to overcome the compressive strength of the
springs, T and P, the pistons, S and O, are drawn apart, closing the
port in the piston, O, and opening the port in piston, S, allowing the
vacuum to enter the main cylinder, M, and open the main valve. This
valve permits the atmospheric pressure to enter the pump suction, the
air being prevented from entering the separators by a check valve, not
shown. The pump then operates without producing any vacuum, and the
power required to operate the pump is reduced. A relief valve of the
common vacuum-breaker type is shown at the left of the cut. This valve
is provided to prevent overload in case the control fails to operate.

[Illustration: FIG. 101. TYPE OF CONTROLLER FOR USE ON PUMPS WITHOUT
VALVES.]

This type of control does not effect as great a reduction in the power
as the first type of control described, since it requires a greater
per cent. of the full load power to operate the pump at no vacuum than
at perfect vacuum. No air is moved in the latter case, and the maximum
volume of air is moved in the former case.

Either of these controls gives fairly economical results when the pump
is serving at least a part of the sweepers at all times. However, when
the system is used in a building where there may be cleaning done at
any time and vacuum must be “on tap” at all times, as in a hotel, there
will be many occasions when no sweepers will be in use, and the pump
might then be stopped entirely, provided that it could be automatically
started when needed.

[Illustration: FIG. 102. REGULATOR FOR MOTOR-DRIVEN VACUUM PUMP,
MANUFACTURED BY THE CUTLER-HAMMER MANUFACTURING CO.]

Where the steam aspirator is used, the control (Fig. 97) is attached to
the steam supply valve. When the valve is closed no steam is consumed
by the aspirator. This is the ideal condition where we must keep vacuum
“on tap,” and is a characteristic of the aspirator system which has led
to its introduction in many instances.

The same economy can be obtained with a steam-driven pump by inserting
a throttle valve, controlled by the vacuum in the separators, which
will start and stop the engine driving the pump and vary its speed in
accordance with the quantity of air required by the system.

Several appliances for varying the speed of a motor-driven vacuum
pump have been placed on the market, the simplest and probably the
best of these appliances being that manufactured by the Cutler Hammer
Manufacturing Company, illustrated in Figs. 102 and 103.

[Illustration: FIG. 103. INSPIRATOR TYPE VACUUM CONTACTOR, USED TO
CONTROL PILOT MOTOR OF CUTLER-HAMMER CONTROLLER.]

The object of the apparatus shown in Fig. 102 is to automatically
start a motor-driven vacuum pump and control the speed of the motor
so that the vacuum is maintained at the desired degree, irrespective
of variation in the number of sweepers in use. This control of the
degree of variation is accomplished in a more efficient manner than if
the pump were to be driven at its maximum speed at all times and the
pressure kept at the desired point by means of a blow-off or by-pass
valve. With this system a motor is used having a control, by shunt
field weakening, of approximately 3:1 in order that the control of the
speed may be as efficient as possible.

Referring to Fig. 103, a small pilot motor is mounted on brackets
at the side of the panel, driving directly, through an insulating
coupling, a screw shaft which carries a traveling cross-head. This
cross-head is shown in the photograph at the extreme right of its
travel, which corresponds to the maximum speed of the motor, the
left-hand end corresponding to zero speed of the motor. In this
position the motor circuit is opened by the clapper type magnetic
switch. Assuming that the cross-head is in the extreme left-hand
position and the knife switch is closed, the pilot motor will be
started in such a direction as to move the cross-head to the right.
A slight movement in this direction completes a connection to the
magnetic switch, which thereupon closes the motor circuit through all
of the resistance, starting the pump motor.

Inasmuch as the pilot continues to move the cross-head toward the
right, the speed of the pump will be gradually increased until, at a
point about midway of its travel, all of the resistance in the armature
circuit of the motor will have been cut out upon the upper segments and
further movement then serves to weaken the field. This is accomplished
by means of the contact buttons shown just below the screw shaft.

As soon as the cross-head has weakened the field to its minimum
value and thus speeded the motor up to its maximum point, a limit
switch stops the pilot motor and thus prevents further motion in that
direction. As soon as the pump working this at its maximum speed has
produced a vacuum in the cleaning system of, say, 12 in. of mercury,
the cross-head will begin to move backward and reduce the speed to a
point corresponding with the air required.

This control of the pilot motor is accomplished by means of what is
termed “inspirator type vacuum contactor.” This apparatus is shown more
in detail in Fig. 103, and consists of a diaphragm closing one side of
a chamber. The diaphragm is pressed outward by an internal spring whose
tension may be adjusted by means of a hexagonal head cap screw, visible
in the photograph of the complete regulator.

The diaphragm is coupled to a pivoted arm carrying insulated
conical-pointed silver screws, so located that they enter holes in
small silver plates mounted on opposite sides, respectively, of the
upper and lower contact posts. These contact posts are hollow and
communicate with the diaphragm chamber, which latter is connected by
piping to the vacuum system.

Normally, the internal spring forces the diaphragm over so that the
lever makes contact with the lower post. This serves to drive the pilot
motor in a direction to move the cross-head to increase the speed of
the pump. When the degree of vacuum for which the apparatus is adjusted
is reached the lever starts to move toward the left hand, and in so
doing stops the pilot motor. This maintains the pump speed at that
particular value. Should the vacuum increase to a sufficient degree the
lever will be drawn further over toward the left and contact will then
be established with the upper post, which will cause the pilot motor to
move the cross-head to the left, and thus decrease the pump motor speed.

Inasmuch as the motion of the diaphragm lever is very gradual,
destructive arcing would take place at the pilot motor contacts were
it not for the small openings in the silver contact plates, which, as
the pointed screw leaves the hole, immediately sucks the arc inward and
extinguishes it.

This method of preventing arcing is exceedingly unique and is subject
to patents now pending.

It is possible to adjust the high and low limits by changing the
setting of the pointed silver screws, the usual adjustments being such
as to maintain the vacuum within 2 in. of mercury. The speed of the
pilot motor may be adjusted by means of the small link shown in the
upper left-hand corner of the panels to correspond with the capacity
of the system, it being found that systems of large capacity require a
slower motion than those in which the amount of piping, etc., is less
for the same size of pump. In practice, the regulator will very quickly
find the position corresponding to the proper speed for the number of
outlets in use, and only moves a slight amount either side of this
particular position.

With this regulator it is possible to employ remote control permitting
the establishment of vacuum in the piping system by the turning of a
pilot switch located at any point in the building. If desired, several
such switches may be placed in parallel, and, under these conditions,
the turning on of any switch will establish the vacuum supply which
will be maintained until all of the pilot switches are turned off. By
this means it is possible to have several janitors working at the same
time on different floors of the building, and each will be independent
of the others in his control of the vacuum; although one man may finish
and turn off the switch on his floor, the pump will not be stopped if
the vacuum is still required by workers on other floors.

When the total size of one installation becomes greater than 25 H. P.,
it is found desirable to provide two pumping units, and, in this case,
the same system is applicable. The cross-head is then arranged to start
first one pump and increase its speed to a maximum. If this does not
supply the necessary amount of air, the cross-head continues to move,
and starts the second pump, which will then be run at a necessary speed
to supply the remaining amount of air.

The first pump always remains in motion at its point of highest
efficiency. It is evident that this duplex arrangement is more
efficient than one large pump when only a very few sweepers are in
operation, since, for this condition, the very large pump would have
to be run at such a slow speed that the armature resistance would be
in circuit, while the single smaller pump would be running at a more
efficient speed and with less proportionate motor losses.

In duplex outfits switches are provided for disconnecting either motor
in case of its being necessary to clean or repair either unit. When
so disconnected the other unit may be operated and maintain the same
degree of vacuum within the limits of its capacity.

While this type of control is more economical in current consumption
than either of the former types described, its cost is much higher, and
it is seldom used unless specifically ordered.

When the centrifugal type of vacuum producers is used no control is
necessary, as the inherent feature of this type of apparatus insures a
practically constant vacuum at all air quantities within the capacity
of the machine.

CHAPTER XI.

SCRUBBING SYSTEMS.

Vacuum cleaning systems in which appliances for scrubbing are provided
in addition to the usual appliances for the removal of the dust
and other materials in a dry state have been introduced by a few
manufacturers, none of which has come into general use.

The usual method employed is to provide an ordinary corn scrubbing
brush which has a connection to the water supply of the building, with
control valves in the tool handle for regulating the flow of water to
the brush. Soap is applied either in the form of soap powder sprinkled
on the floor, in a liquid state fed into the water supply by means of a
sight-feed oil cup or soft soap in a plastic state fed into the water
supply by means of a compression grease cup.

In any case, the water is run onto the floor mixed with the soap and
the floor scrubbed by manipulating the corn brush, in the same manner
that an ordinary corn scrubbing brush without attachments would be used.

After the dirt has been loosened from the floor, the floor may be
rinsed by the application of more water. The water is then drawn up
from the floor by the suction of the cleaning machine, and passes
through the hose and piping system to the separator and vacuum
producer. To effectively remove the water a rubber-faced tool is
usually employed. In one system this rubber face is arranged to permit
the corn brush to be fitted over same when scrubbing is being done, and
the brush must be removed from the tool before the water can be drawn
up from the floor. Other manufacturers provide a double-faced tool
having the brush on the opposite side of the tool from the rubber-faced
slot. By reversing the tool, scrubbing and mopping can be accomplished
without the removal of the corn brush from the tool, which is more
convenient for the operator.

With either of the above forms of scrubbing tools it is necessary or
desirable to cut off the suction to the mopping attachment when using
the corn brush, and it is also necessary to cut off the water supply
to the brush when using the mopping attachment. One system, introduced
several years ago, conducted the water to the brush and away from the
rubber-faced mopping appliance through the same hose. This arrangement
requires the use of a special three-way hose cock, which had to be
manipulated frequently during the scrubbing operation, requiring the
time of another person in addition to the operator, or else greatly
delaying the scrubbing process by requiring the operator to constantly
pass back and forth between the hose cock and the scrubbing tool. This
method of supplying water also requires the use of a removable corn
brush attached over the rubber mopping device.

Other forms of scrubbing appliances are provided with separate hose
for the water supply and suction and with valves in the handles for
controlling the suction and water supply. These valves to be efficient
and quick in action are generally made self-closing, otherwise they
will be short-lived, as explained in Chapter V. When springs are used
to close the valves, the hand and wrist will be quickly fatigued, as
stated in Chapter V.

With either of the above systems all of the scrubbing, that is, the
agitation of the brush, has to be performed by the operator, as in the
case of the ordinary scrubbing brush. However, the combination tool is
much heavier and clumsier than the ordinary scrubbing brush, and the
only advantage obtained by using this heavy and clumsy appliance is
the ability to supply water without carrying it in buckets, also the
removal of the dirty water after scrubbing. These appliances cannot be
termed mechanical scrubbers, nor can they be classed with scrubbing
machines with motor-driven brushes, such as have been recently
introduced.

A real mechanical scrubbing device for use with a vacuum cleaning
system was manufactured by Foster & Glidden, of Buffalo, N. Y., but
was never placed on the market, although at least one is in commercial
operation to-day. This machine is provided with a turbine motor
operated by the air current passing through the machine. This turbine
revolves a pair of scrubbing brushes turning in opposite directions.
Water is fed through a separate hose, and an auxiliary air inlet is
opened when the suction under the brushes is closed, in order to supply
the necessary air to keep the turbine running. Mr. Foster states that
he has experienced no trouble in operating this machine on from 8 in.
to 12 in. of vacuum, being able to scrub and remove the dirt and water
with one operation. The speed with which the work was done depended on
the condition of the floor, the usual rate, as given by Mr. Foster,
being from 10 to 12 yds. per minute.

Mr. Foster also states that he has not pushed the introduction of this
scrubber, as he considers it so far ahead of the times as to require
the education of the public in the use of the hose and ordinary vacuum
cleaning tools before users would be capable of successfully operating
this type of scrubber.

The author considers this condition to be lamentable if true, for until
some such appliance is in commercial use scrubbing attachments to a
vacuum cleaning system can never compete with the mechanical scrubbing
machines now on the market, and are little if any better than the old
method of scrub-brush, mop and pail, and certainly not as rapid in
operation.

When the vacuum cleaning systems combine scrubbing with dry cleaning,
the separator and vacuum producer must provide for the removal of
water as well as air. A few manufacturers have attempted this, among
which are the makers of the Rotrex system, described in Chapter IX, in
which the water is passed through the pump and into the sewer under
sufficient pressure to overcome the friction in the exhaust pipe
through which the expelled air passes after leaving the separator. This
may be sufficient to force the trap seals of the plumbing system, and,
if used, the discharge connection should be made to the sewer outside
the main running trap, close to the fresh air inlet. As large articles
cannot be allowed to pass through the pump, a screen is necessary on
the inlet side of the vacuum producer, but this may give trouble, due
to the clogging with litter.

The Atwood Vacuum Cleaner Company uses a wet tank on the suction side
of the vacuum producer into which the dirt and water are discharged,
the air being separated and passed to the vacuum producer. When this
tank becomes partly filled it is necessary to shut down the plant and
empty the contents of the tank by gravity into the sewer.

This method overcomes the objections to clogged screens and forced
trap seals, and all litter is discharged direct to the sewer, together
with a quantity of water which is presumably sufficient to flush the
litter through the sewer. The last named system is still open to
two objections; first, it is not automatic, and, if neglected, the
tank will fill with water and force same into the vacuum producer.
With the Root type of vacuum pump this will do little harm unless a
large quantity of floating litter should pass into the pump. Second,
the system may be operated with dry renovators exclusively for a
considerable portion of the time, in which case the contents of the
separator may become of such a consistency as will not readily flush
through the sewer, and stoppage of the same may occur.

Another separator of this type has recently been patented by E. B.
Dunn, the originator of the Dunn Locke, in which the mud and the water
are automatically discharged alternately from one of two separators, as
described in Chapter VIII.

Such a separator, in which sufficient water is automatically introduced
to dilute the dirt and which will automatically empty when sufficiently
filled, when so constructed that it will operate continuously,
is considered to be the ideal separator for use with a combined
cleaning and scrubbing system. Until the mechanical scrubber and an
automatically operated separator are commercially introduced the author
does not consider that the use of scrubbing attachments, in connection
with the vacuum cleaning system, is advisable.

CHAPTER XII.

SELECTION OF CLEANING PLANT.

We have considered in detail the various appliances which, taken
together, make a complete vacuum cleaning system, but without
considering their relation to one another. It now becomes necessary to
choose an exact type and form of each of these appliances which will
produce in combination a complete vacuum cleaning system best suited to
the conditions to be met in a given installation.

In selecting a vacuum cleaning system consideration must be given to
the character of the material to be removed, the kind and quality of
the surfaces to be cleaned, the rate at which cleaning must be done,
the extent of the cleaning system, and the cost of labor to operate the
system, all of which must be considered in each step in the selection
of a suitable plant.

In assembling the complete system, the author will take up the various
parts thereof in the order in which they were discussed in the
preceding chapters.

=Renovators.=--The selection of renovators is the most important step
in making up a vacuum cleaning system, as the entire makeup of the
system, whether good or bad, is dependent on the proper selection of
these tools. The carpet renovator is generally considered first in
importance, because the cleaning of carpets has nearly always been
found to be the principal field of usefulness in vacuum cleaning work.
This is due, perhaps, largely to the fact that from the beginning of
the art of vacuum cleaning, this function of the system has been held
before the eyes of the public by the manufacturers of the earlier
systems. Nearly all demonstrations of cleaning systems shown to the
public consist of the removal of ordinary wheat flour from a carpet.
The reason for this is two-fold; first, because it is the most striking
demonstration to the eye of the layman, and, second, it is the easiest
to accomplish with a small air displacement and small power, which was
characteristic of the apparatus made by these manufacturers.

The author was at one time of the opinion that this function of the
cleaning plant was given too much prominence by builders of systems
having small air displacement, and letters were sent to the officials
in charge of sixteen Government buildings in which vacuum cleaning
systems were installed, asking them, among other questions, whether
the cleaning system was used to any extent in cleaning bare floors, of
which there were large areas, both wood and marble, in the buildings
in question. The plants installed were of various makes, some of
which maintained 12 in. mercury at the separator and used 1-in. hose,
while about an equal number of others maintained 6 in. mercury at the
separator and used 1¹⁄₂-in. hose. The answers showed that out of the
sixteen buildings the cleaner was used on bare floors in but two of
the buildings. One writer, who had a plant maintaining 6-in. vacuum,
provided with Type F renovators and 1¹⁄₂-in. hose, stated that he
had tried cleaning bare floors without success, as the renovator and
hose became so clogged with litter as to be inoperative. The majority
stated that the cleaning system displaced brooms on carpets and rugs
and several stated that the cleaning system was used to advantage in
cleaning walls, cases, pigeon holes and relief work.

This indicates that for the average office and departmental building
the cleaning of carpets is the most important function of the vacuum
cleaner. This is also true of residence work. Schools, department
stores and manufacturing buildings contain very little floor space
covered with carpets, and in buildings of this character the cleaning
of bare floors is of the greatest importance. In such cases the
efficiency of the carpet renovator can be sacrificed to a more
efficient and economical operation of bare floor renovators.

In a building where carpet cleaning is an important function of
the cleaning system, the selection of the carpet renovator is most
important. Of all the various types of carpet renovators discussed in
Chapter III, only two need to be considered, Type A and Type F. Of
these, Type A is superior in all respects except the picking up of
large litter, and, unless the character of the material to be removed
contains a large amount of material which can be picked up by Type F
renovator that will not pass Type A, Type A renovator should always be
used. Even when Type F renovators are desirable, the writer considers
that the plant should still contain some Type A renovators for use in
places where this unusual litter will not be encountered.

Among the bare floor renovators, described in Chapter IV, only the one
having a felt face, curved to permit its running over the dirt, is
worthy of serious consideration. This renovator requires an inlet or
vacuum breaker to keep same from sticking to the surface cleaned, the
extent of such opening being dependent on the vacuum maintained in the
carpet renovators, as explained in Chapter VII.

When carpet cleaning is considered as of secondary importance to bare
floor cleaning, the degree of vacuum maintained at the separators
may be reduced to that which will produce a vacuum of 1 in. mercury
at the bare floor renovator, allowing the vacuum maintained at the
carpet renovator to be whatever the conditions of hose and pipe line
will produce. Under such conditions, the area of the inrush or vacuum
breaker in the bare floor renovator may be reduced considerably.

The use of brush renovators is dependent on the capacity of the air
exhauster supplied, as explained in Chapter VI. If it is decided that
brush renovators are necessary, then the “large volume” exhauster must
be installed. The advisability of such installation is dependent on the
time allowed for cleaning and the cost of the operators. In residences
and small buildings where the cleaning operations can be done with one
or even two domestics or laborers, very little, if any, saving in the
wages of operators can be effected by increasing the rate at which the
cleaning can be done. In such buildings a small-volume plant will be
the most economical in first cost and operation. If such a plant is
installed, the brush renovators should be omitted.

In cases where bare floor cleaning is the principal function of the
cleaning system the extra quantity of air at the low vacuum necessary
will not require much larger expenditure of power than that needed
by the small-volume plants when maintaining sufficient vacuum for
effective carpet cleaning and brush renovators should be provided with
systems of this character.

=Hose.=--In Chapter VI it is shown that when carpet renovators are
operated efficiently in combination with bare floor renovators,
1¹⁄₄-in. hose will produce the best results with the lowest expenditure
of power at the hose cock. In Chapter VII it is shown that with pipe
lines of ordinary length 1¹⁄₄-in. hose also gives the best results,
with the least expenditure of power at the separator, but that in cases
of exceedingly long pipe lines, 1-in. hose will be the most economical.
In a system where bare floor cleaning is the principal function,
the vacuum to be maintained at the carpet renovator is no longer
considered, and for such systems the largest hose which can easily
be handled will cause the least hose friction and require the lowest
vacuum at the hose cock. It is, therefore, the most economical to use
on such a system. The author does not recommend the use of a hose
larger than 1-³⁄₄-in. diameter for this type of plant.

The proper hose sizes, therefore, will be: For ordinary buildings where
carpet cleaning is important, 1¹⁄₄-in. diameter. For installations with
unusually long lines of piping, where carpet cleaning is important,
1-in. diameter.

For all systems where carpet cleaning is of secondary importance,
1¹⁄₂-in. or 1-³⁄₄-in. diameter.

=Pipe Lines.=--Pipe lines should always be as large as possible without
reducing the velocity in same below 40 ft. per second, as explained in
Chapter VII.

=Separators.=--The type of separator to be used is dependent on the
type of vacuum producer adopted. Where reciprocating exhausters are
used, or other type of exhauster where there is rubbing contact between
the moving parts and the dust, the combination of a wet and dry
separator is recommended. When rotary or centrifugal exhausters having
close clearances are used, total separators with bags are recommended.
When exhausters with large clearances are operated, partial separators
are satisfactory.

The use of any form of apparatus contemplating the adoption of a
satisfactory scrubbing system is not considered advisable, as the
author believes that separators for handling water will be improved
before scrubbing becomes commercially successful. Changes in the
existing separators can be made when satisfactory scrubbing appliances
are placed on the market, at no greater expense than would be necessary
to bring up to date any of the present systems for handling water.

=Vacuum Producers.=--The selection of the vacuum producer is dependent
on the degree of vacuum that must be maintained to effectively operate
the system selected. For the operation of a system where carpet
cleaning is the principal function and 1¹⁄₄-in. hose is used, the
vacuum required at the producer will be from 6 in. to 9 in. mercury.
Inspection of the efficiency curves of the various types of vacuum
producers, given in Chapter IX, shows that the two-impeller rotary pump
has the highest efficiency at this vacuum.

For the operation of systems where carpet cleaning is the most
important function and 1-in. hose is found to be the most economical,
14 in. to 15 in. of vacuum at the vacuum producer is necessary, and
efficiency curves, given in Chapter IX, show that the piston pump is
the best suited for such service.

For the operation of a system where carpet cleaning is of secondary
importance a vacuum at the producer of from 2 in. to 4 in. of mercury
will be sufficient. For this work, the multi-stage or even single-stage
centrifugal fan is practically as efficient as the two-impeller rotary,
and will be lower in first cost and cost of maintenance. Either of
the above mentioned vacuum producers are satisfactory for operating a
system of this type.

=Control.=--Every system of more than one-sweeper capacity in which a
displacement type of exhauster is used should be provided with some
means of economically controlling the vacuum at the producer. On
one-sweeper plants an automatic starter which will stop the motor when
the vacuum reaches a point 2 in. above that required and start same
when the vacuum drops to 1 in. below that required is convenient, but
not necessary.

For piston pumps and all other displacement pumps fitted with
eduction valves, an unloading device, which closes the suction when
the necessary vacuum is exceeded, is the least expensive to install
and gives very good economy when the demand on the plant is fairly
continuous during the time it is in operation. Where the service is
intermittent and required at nearly all hours, the Cutler Hammer
control, described in Chapter X, is the most economical.

With displacement exhausters having no eduction valves, the by-pass
type of control is satisfactory where the service is continuous, but
is not as economical, as the unloader used with producers having
eduction valves and the Cutler Hammer control is more efficient under
all conditions of service. Centrifugal exhausters need no control, as
vacuum control is an inherent feature of these machines.

Summing up the subject, we can divide the vacuum cleaning systems
into four classes, each of which requires a different selection of
appliances. They are as follows:

=Class 1.=--Plant for residence or small office or departmental
building, to be not more than one-sweeper capacity.

Renovators: See list given for “small volume” plant, Chapter IV.

Hose: 1¹⁄₄-in. diameter.

Separator: Centrifugal, dry, with bag or screen.

Vacuum Producer: Two impeller, rotary, alternate centrifugal fan.
Capacity, 30 cu. ft. of free air per minute, 4 in. vacuum at producer.

Control: Automatic starter, operated by vacuum.

Size of motor: ¹⁄₂ to 1 H. P.

=Class 2.=--Large office or departmental building where carpet cleaning
is important and pipe lines are of reasonable length.

Renovators: See list given for “large volume” plant, Chapter IV.

Hose: 1¹⁄₄-in. diameter.

Separator: Centrifugal, dry, with bag or screen.

Vacuum Producer: Two impeller, rotary. Capacity, 70 cu. ft. of free air
per minute for each sweeper of plant capacity at 7 in. to 9 in. vacuum.

Size of motor: 2¹⁄₂ H. P. per sweeper capacity.

Control: Cutler Hammer.

=Class 3.=--Large building or group of buildings where carpet cleaning
is important and long lines of piping are necessary.

Renovator: See list for “large volume” plants, Chapter IV.

Hose: 1-in. diameter.

Separators: One centrifugal dry and one wet.

Vacuum Producer: Piston type pump. Capacity, 45 cu. ft. of free air per
minute for each sweeper of plant capacity at 14 in. vacuum.

Size of motor: 4 H. P. for each sweeper of plant capacity.

Control: Automatic unloader for continuous service. Cutler Hammer for
intermittent work at all times.

=Class 4.=--Large or small plant where carpet cleaning is not an
important function of the cleaning system.

Renovators: Same as for Class 3.

Hose: 1¹⁄₂ in. or 1-³⁄₄ in.

Separators: One centrifugal, dry, with or without bag, according to
type of exhauster adopted.

Vacuum Producer: Centrifugal fan or two-impeller rotary pump.

Capacity: 70 to 90 cu. ft. of free air per minute for each sweeper of
plant capacity, with a vacuum of from 2 in. to 3 in. mercury.

Size of motor: 1 to 2 H. P. for each sweeper of plant capacity.

Control: With centrifugal fan, none; with pump, Cutler Hammer.

It is interesting to note that to produce the most efficient plant
for all of the four cases named, all of the various types of vacuum
cleaning systems which have come into general use have to be operated
each under its most favorable conditions and the engineer should
select his plant to best fulfill the conditions of the special case
at hand, just as he would select his prime mover for an electric
generating plant according to its size and location. There should be
no more reason why any one of these systems should attempt to fulfill
the requirements of every installation than there would be for a
manufacturer of steam engines to attempt to use the same type of engine
to drive a generator under all conditions. The writer believes that
this condition will soon be realized by all manufacturers of vacuum
cleaning systems and that they will endeavor to install apparatus of
the type best suited to the conditions to be met in each case.

CHAPTER XIII.

TESTS.

Having decided on the type of vacuum cleaning system that is best
suited to the conditions of the particular building in which it is
to be installed, it then becomes necessary to ascertain what are the
tests necessary to determine whether the installation will produce the
desired results.

If the installation is one in which carpet cleaning is important and
the plant is of more than one-sweeper capacity, the exhauster must
be of sufficient capacity to produce a vacuum of not less than 4 in.
mercury at a carpet renovator attached to any inlet on the piping
system, when the plant is operating other renovators of any type
attached to any of the other inlets corresponding to one less than the
total sweeper capacity of the system.

When hose lengths as short as 25 ft. can be used on any or all of the
outlets, it has been demonstrated in Chapter VII that an air removal of
70 cu. ft. of free air per minute for each sweeper of plant capacity is
necessary, no matter what size of hose is used. It was also shown that
where pipe lines are very long and it is possible to always use 100 ft.
of hose, efficient cleaning can be done with less expenditure of power
with an air displacement of 45 cu. ft. of free air for each sweeper of
plant capacity.

Many methods have been recommended for testing a cleaning plant.
Perhaps the earliest was the maintaining of 15 in. of vacuum at the
vacuum producer with carpet renovators each attached to 100 ft. of
hose, equal in number to the sweeper capacity of the plant in operation
on carpets. Another test is to attach 100-ft. lengths of hose to inlets
on the system, with the ends wide open, equal in number to the sweeper
capacity of the plant, and require the pump to maintain a vacuum of 15
in. mercury.

Both of these tests were recommended for use on plants where 1-in.
diameter hose was provided and the results are dependent largely on the
size and length of the piping system. With an average-sized system, the
first test will require an exhaustion of approximately 25 cu. ft. of
free air per renovator per minute if Type A renovators are used. The
second test wall require an exhaustion of approximately 50 cu. ft. of
free air per open hose per minute. Neither of these tests will insure
a plant of sufficient capacity to do effective cleaning where 25-ft.
lengths of 1-in. hose can be used or if larger bore than 1-in. hose be
used.

If these tests are required with bores larger than 1-in. diameter
and the vacuum is maintained the same as before, air exhaustion with
1¹⁄₄-in. open hose will be approximately 70 cu. ft. of free air per
open hose, and with 1¹⁄₂-in. hose, approximately 150 cu. ft. per open
hose, while, if carpet renovators be used, the vacuum at the renovator
would be from 7 to 9 in. of mercury. In either case, the vacuum
required to be maintained at the separators is higher than is necessary
to produce economical cleaning with either 1¹⁄₄-in. or 1¹⁄₂-in. hose.

Tests with carpet renovators attached to 100 ft. hose lines in number
equal to the capacity of the plant, and a vacuum of 4¹⁄₂ in. of mercury
at the renovator will result in an exhaustion below that necessary
to produce efficient cleaning when bare floor renovators and carpet
renovators with shorter hose lines are used, as is likely to occur in
actual practice.

Again, open hose tests require a variable length of hose to be used in
order to obtain the same air quantity with the proper vacuum at the
separator for economical operation.

If 70 cu. ft. of air is desired, as in the case of Class 2 plant
(Chapter XII), the hose lengths should be:

50 ft. 1 in. diameter. 12 in. vacuum at separator.

75 ft. 1¹⁄₄ in. diameter. 9 in. vacuum at separator.

125 ft. 1¹⁄₂ in. diameter. 6 in. vacuum at separator.

Any of these lengths would give satisfactory cleaning with one carpet
renovator in use, together with sufficient bare floor renovators to
equal the capacity of the plant. This is a possible condition in any
plant.

Another method of testing is to measure the actual air passing through
a given length of hose and require sufficient vacuum at the separator
to produce this flow. This method is open to the objection that
variation in the size of the hose will result in considerable variation
in the vacuum at the separator and conditions of hose lengths may be
such that when carpet renovators are attached to the hose, the vacuum
at the renovator will vary according to the resistance offered to the
passage of the air by the friction in the hose. With the small hose,
the friction will be greatest, and the reduction in the quantity of air
passing the renovator from that passing an open hose will result in the
greatest reduction in friction loss through the hose and produce the
highest vacuum at the renovator. This will cause a widely different
vacuum at the renovator with different sizes of hose, each of which
passes the same amount of air with the end of hose open.

What is desired in cleaning operations is a certain degree of vacuum
at the carpet renovator, with the system operated under the same
conditions that will obtain in practical cleaning, and with cleaners of
various types attached to hose ends equal in number to the capacity of
the plant.

The most rational system of testing is one in which the actual
conditions of air quantity and vacuum are measured at the hose ends.
This can be obtained by actually attaching cleaning tools to the hose
ends and measuring the vacuum within the renovator. However, a wide
variation in vacuum will result when the renovator is moved along the
carpet, and this variation will be different with different operators
and different grades of carpet to such an extent as to render it
impossible to actually meet any requirements that may be specified,
unless a considerable variation in vacuum is permitted.

It is also possible for an operator to become so expert in the
manipulation of the renovators as to be able to meet the specification
requirements with a plant which will not give satisfactory results in
actual operation.

The most satisfactory method of testing that has been devised is the
use of an orifice of proper size fixed to the hose end and measure
the vacuum just inside of this orifice. In making such measurements
care must be taken that the tube connecting to the vacuum gauge is not
inserted in such a manner that the air velocity affects the reading
of the vacuum gauge. The shape of orifice must also be carefully
specified, as the rounding of the edges of the opening will greatly
increase the quantity of air passing a given-sized orifice. The
best standard is a sharp-edged orifice in a thin disk which has a
coefficient of ingress of approximately 65%.

[Illustration: FIG. 104. VACOMETER FOR USE IN TESTING VACUUM CLEANING
SYSTEMS.]

A convenient form of testing appliance based on the orifice test is
the vacometer, manufactured by the Spencer Turbine Cleaner Company
and shown in Fig. 104. This device consists of a spherical aluminum
casting, with a 1-in. diameter hole on the equatorial circle, a vacuum
gauge being attached to one polar extremity, the other being attached
to the end of the hose. A ring having a slip fit is placed around the
equatorial circle in which openings varying from ¹⁄₂-in. to ⁷⁄₈-in.
diameter are drilled. By turning this ring any of the orifices may be
made to register with the opening in the sphere. The opening to which
the vacuum gauge is attached is so located that it is not affected by
the entering air current, and its readings are not affected by the
velocity head.

Experiments with this instrument in connection with a Pitot tube show
that a ¹⁄₂-in. diameter orifice is equivalent to a Type A carpet
renovator, a ⁵⁄₈-in. orifice to a Type F renovator and a ⁷⁄₈-in.
orifice to a bare floor renovator.

With instruments of this type equal in number to the capacity of the
plant in sweepers, attached to the ends of the cleaning hose, it is
possible to obtain uniform conditions equal to the average results that
will be obtained in actual practice with renovators attached to the
hose, without the possibility of expert manipulation of the renovators
affecting the results.

The proper orifice to be used in each vacometer during the test will
vary with the character of the service for which the plant is designed,
and the author recommends the following for each of the classes of
plants described in Chapter XII:

Class 1. 2-in. mercury, with ¹⁄₂-in. orifice, maximum length of hose to
be used in actual cleaning.

Class 2. One-half the inlets ¹⁄₂-in. orifice, 4.5 in. mercury at one
orifice attached at end of longest hose desired to use in practice, the
remaining ¹⁄₂-in. outlets on shorter hose lengths. The other half of
inlets to have ⁷⁄₈-in. orifices open at same time, with longest hose on
one-quarter of total inlets and shortest on the balance.

Class 3. All inlets on long hose, one-half with ¹⁄₂-in. orifice,
balance with ⁷⁄₈-in.

Class 4. All inlets to have ⁷⁄₈-in. orifice and 1 in. vacuum at
vacometer, all hose lines maximum length.

CHAPTER XIV.

SPECIFICATIONS.

Before the engineer begins to prepare his specifications for a proposed
vacuum cleaning system, he will naturally consider carefully the
conditions to be met in the particular installation contemplated.
Having considered these conditions, he can readily determine the
type of system that will operate most efficiently and economically
under such conditions. It is, therefore, natural to assume that
the best interests of his clients can be obtained by confining his
specifications to apparatus of the type giving the most efficient
results for the special conditions to be met. However, it is also
necessary to study the apparatus on the market to determine if there is
a sufficient number of manufacturers producing the particular type of
apparatus specified to insure healthy competition and reasonable bids.

It becomes necessary, therefore, to examine the various systems offered
by the manufacturers in order to determine what competition can be
obtained.

Apparatus for Class 1 or Class 2, if confined to the positive
displacement rotary exhausters of the two-impeller type, can be
obtained from at least seven manufacturers. If the centrifugal fan is
included, at least three other manufacturers can be considered and in
either case a healthy competition be had.

If apparatus of Class 3 is desired, it can be obtained from at least
three manufacturers. A few years ago more manufacturers of systems of
this type were in the market. Some of these have dropped out, owing to
the comparatively limited field for this apparatus. However, there are
still enough manufacturers in the field to insure competition.

Apparatus of Class 4 has been especially manufactured by one company.
However, any of the manufacturers of centrifugal fan type of apparatus
can easily meet the specification requirements for apparatus of the
character.

It is, therefore, evident that the specification of apparatus of the
type best suited to any particular installation will not result in lack
of competition, and such a procedure would apparently be justified.

There are installations, such as those for public buildings, where it
may be advisable from an administrative standpoint to allow the widest
competition possible. In such cases the engineer can secure the best
results for his clients by so drawing his specifications as to include
all types of apparatus, fixing carefully the test requirements to be
met and requiring each bidder to state in his proposal the amount of
power required to operate his apparatus under full load, three-quarter
load and half-load conditions, and to base the award of the contract on
an evaluation basis.

To determine what the basis of this evaluation shall be it is first
necessary to ascertain the length of time the plant will be operated
at each of the loads specified and find the annual cost of a unit of
power to operate the plant. Assuming the plant has a life of ten years,
we can charge 10% depreciation, add to this 5% for interest on the
investment and 1% for insurance. We can capitalize the saving in power
at 16% and use this amount as a basis for evaluation.

As an example, assume one bidder guarantees a power consumption of 1
K. W. less at full load, 1.25 K. W. less at three-quarters load and
0.75 K. W. more at half load than a lower bidder. Assume the plant will
operate 500 hrs. per year at full load, 200 hrs. at three-quarters load
and 300 hrs. at half load. The total kilowatt hours saved by the more
economical plant will be:

Full load 500 × 1 = 500
Three-quarter load 200 × 1.25 = 250
---
Total saving 750
One-half load, 300 × 0.75 = 225
---
Net saving (K. W. Hr.) 525

If power costs 5 cents per K. W. Hr. the yearly saving will be $26.25,
which, capitalized at 16%, will equal $164.00. This is the amount which
the owner would be justified in paying for the more economical plant
above the price asked for the cheaper, but less economical, system.

In order to guard against any bidder guaranteeing a lower power
consumption than he can actually show on test, it is necessary to
impose a penalty for failure to meet the guarantee which is in excess
of the increase in price shown to be justified by the evaluation.

The author recommends that this penalty be made not less than 150% of
the increase in price shown by the evaluation.

Actually, the owner will not lose by the less efficient plant any more
than the amount shown by the evaluation if he junks the plant at the
end of ten years. However, it is more than likely that he will either
use it for a longer time or will be able to realize something for
the plant when it is displaced. The increased penalty, therefore, is
justified, and it is absolutely necessary to make this penalty greater
than the increased value to prevent the bidder guaranteeing a power
consumption lower than he can show on test.

The following pages contain sample specifications for apparatus of
each of the four classes of systems described in Chapter XII and a
specification permitting the widest competition, with evaluation and
penalty clauses.

CLASS 1

PLANT FOR RESIDENCE OR SMALL OFFICE BUILDING OF ONE-SWEEPER CAPACITY.

1. _General Description._ The work included in this specification
shall be the installation of a complete vacuum cleaning system for the
removal of dust and dirt from rugs, carpets, floors, stairs, furniture,
shelves, walls and other fixtures and furnishings throughout the
building, and for conveying said dust and dirt to suitable receptacles
located where shown, together with all of the necessary cleaning tools,
hose, piping, separators, exhauster, motor, etc., as hereafter more
fully specified.

2. _Exhauster._ The exhauster in all of its details shall be made of
the best materials suitable for the purpose and shall be of approved
design and construction, and may be either of the positive displacement
(rotary) or of the multi-stage fan type.

3. _Rotary Exhauster._ The rotary displacement exhauster shall be
either of the two-impeller type or of type having single impeller
without sliding vanes revolving without friction contact with case and
with oscillating follower.

4. Exhausters fitted with sliding blade or blades will not be
acceptable.

5. All parts of the exhauster shall be rigid enough to retain their
shape when the machine is working under maximum-load conditions.

6. The impellers must be machined all over and must be of such shape
and size that they will revolve freely and not touch each other, the
follower, or the casing (cylinder) in which they are placed, but
the clearance must be of the least possible amount consistent with
successful operation.

7. The shafts must be of steel with the journals ground to size.

8. The journal boxes must be long and rigidly supported by the
headplates and placed far enough from the headplates to allow the
placing of proper stuffing boxes on the shafts.

9. The shafts of two impeller exhausters must be connected by
wide-faced steel gears, cut from the solid and securely fastened to the
shafts. Follower shaft on single impeller exhauster to be connected
to impeller shaft by crank and connecting rod. The gears shall run in
suitable oil-tight gear boxes that shall be fitted with adequate and
suitable means for lubrication.

10. _Centrifugal Fan Type._ The centrifugal fan exhauster to be so
proportioned and constructed as to handle the volume of air required at
the specified vacuum with the least possible loss. The housing shall
be of cast iron or aluminum, made in sections. The housing must be
air-tight.

11. The fan wheels to be constructed of steel or other metal of high
tensile strength, properly reinforced, and, if cast, must include hub
and arms complete in one piece. If the fan wheels are built up, they
must be strongly riveted to cast-iron, steel or brass hubs or spiders.

12. The fan wheels are to be secured to shaft with a feather and set
screws, or with left-hand screw.

13. The shaft of fan exhauster may be vertical and the wheels so
mounted that their weight will equalize or partly equalize the end
thrust, or the end thrust may be balanced by the magnetic pull of the
armature. Shaft may be horizontal and end thrust taken care of with
ball-bearing thrust rings.

14. The journal boxes for all of the above named types of exhausters
shall be of the design best adapted for the purpose and must be fitted
with first-class approved continuous lubricating devices, either sight
feed, ring oiler, or any other kind best suited for the work or design
of apparatus used.

15. _Cooling._ The rotary type of exhauster must be provided with the
necessary water connections to properly seal and cool the pump. Fan
type of exhauster must be designed to operate continuously without a
rise of temperature over 100° F. above room temperature.

16. _Speed._ Rotary exhausters shall not exceed a peripheral speed of
1,100 ft. per minute at tips of impellers.

17. Centrifugal fans shall not exceed peripheral velocity of 22,000 ft.
per minute when running under specified full-load conditions.

18. _Mounting._ The exhauster, motor and separators shall be mounted
as a unit on suitable cast-iron base plate, either mounted on legs or
resting on the basement floor.

19. _Drive._ The exhauster shall be driven by an electric motor, which
may be direct connected to the exhauster shaft or be operated with an
oak-tanned leather belt, or by cut gearing. Belt and gearing are to be
of ample size and strength for their work and must run without undue
noise or wear. Means shall be provided to take up the slack of the
belt. Furnish and place a suitable metal guard over belt and pulley
wheels that shall prevent oil being splashed outside of the base plate
and prevent clothing being caught.

20. If the exhauster is operated through cut gearing, the gearing must
be inclosed in an oil and dust proof case, which shall be fitted with
means for copious and continuous lubrication of same.

21. _Finish._ The air exhauster and motor and the base plate shall be
finished in a first-class manner, filled, rubbed down and painted at
least one coat at the shop, and after installation shall receive two
more coats, finishing tint to be as directed.

22. _Electric Motor._ Motor to be of such size that when operating
under test conditions it will not be under less than three-fourths nor
more than full-load condition. It is to be of standard make, approved
by the architect.

23. Motor to be wound for .... volts direct current.

24. Armature to be of toothed-core construction, with windings
thoroughly insulated, and securely fastened in place, and must be
balanced both mechanically and electrically.

25. Commutator segments must be of drop-forged or hard-drawn copper
of highest conductivity, well insulated with mica of even thickness
and proper hardness to insure uniform wear, and shall run free from
sparking or flashing at the brushes under all conditions of speed.
It must be free from all defects and have ample bearing surfaces and
radial depth as provision for wear.

26. Brushes to be of carbon, mounted on a common rocker arm for motor,
and to have cross-sectional area of not less than 1 square inch for
each 35 amperes of current.

27. Brush holders to be of a design to prevent chattering, with
individual adjustment in tension for each brush.

28. Bearings to be of an approved self-oiling or ring type.

29. There must be an insulation resistance between motor frame and
field coils, armature windings and brush holders of not less than 1
megohm.

30. Motor must be capable of standing a breakdown test of 1,500 volts
alternating current. Either or both of the foregoing tests to be
applied at the discretion of the architect’s agent at the time of shop
tests.

31. The maximum rise in temperature of the motor at a continuous run
(after installation at building) at full speed and full-rated load for
a period of eight hours must not exceed 50° C. in windings and 55° C.
on commutator above the surrounding atmosphere.

32. Motor to be finished in a first-class manner, filled and rubbed
down and painted two coats at the shop, and after installation to have
two more coats; finishing tints to be as directed by the superintendent
of the building.

33. _Tablet._ Furnish and mount where directed a polished slate tablet
not less than ³⁄₄ in. thick, having mounted thereon one 30-ampere,
250-volt, double-pole knife switch, with enclosed indicating fuses,
and, if displacement exhauster is furnished, one automatic self-starter
having butt contacts, cutting out starting resistance in not less than
two steps, starter to be controlled by the vacuum in separator, and
shall stop motor when vacuum rises 2 in. above that required to meet
test requirements and start motor when vacuum falls to that required
for working.

34. _Electrical Connections._ This contractor shall run feeders from
vacuum cleaner panel in switchboard where shown to the motor panel and
make all electrical connections between panel and motor, etc.

35. All wires are to be run in standard steel conduit, except those
that are so short as to be self-supporting, and these are to be cord
wrapped or otherwise protected. No wire smaller than No. 8 to be used.

36. All material and workmanship to be strictly first class. Electrical
work must show an insulation resistance of at least 1 megohm, and
to be in strict accordance with the latest edition of the “National
Electrical Code.”

37. _Dust Separator._ There shall be one dry separator located where
shown on plans, having a volume not less than 3 cu. ft.

38. The interior arrangement of the separator shall be such that no
part of same will receive the direct impact of the dust. Cloth bags
or metal screens if used in this separator shall be so placed that
nothing but the very lightest of the dust can lodge thereon, and that
same may be easily cleaned without dismantling the separator. It must
be so constructed that it shall intercept not less than 95% of the dust
entering same.

38a. Separator tank shall be constructed with steel shells, with either
cast iron or steel heads, and be fitted with suitable bases or floor
stands for support and proper openings for cleaning same. Separator
shall be fitted with iron-column mercury gauge reading 50% in excess of
operating vacuum.

39. _Pipe Lines._ All pipe lines shall be of the sizes and run as
indicated on drawings.

40. _Pipes._ All pipe conveying air is to be standard black
wrought-iron or mild-steel screw-jointed pipe, and is to be smooth
inside, free from dents, kinks, fins, or burs. Ends of pipe to be
reamed to the full inside diameter and beveled. Bent pipe to be used in
mains where necessary and where shown on plans.

41. Care must be taken in erecting pipe to maintain as nearly as
possible a smooth, uniform bore through all pipe and fittings.

42. _Fittings._ All fittings to be tough gray cast iron, free from
blowholes or other defects; smooth castings in all cases.

43. All fittings on vacuum lines must have inside diameter through body
of same size as pipe bore, and all fins, burs, or rough places must be
removed.

44. Fittings on vacuum lines are to be black or may be galvanized.

45. Where space permits, all tees and elbows must have a radius at
center line of not less than 3 in.

46. Horizontal overhead pipes to be supported with substantial pipe
hangers spaced not more than 10 ft. apart.

47. The hangers must have an approved form of adjustment and the
instructions of the superintendent in regard to securing hangers to
floor construction, etc., above must be carefully followed.

48. Where exposed pipes pass through walls or floors of finished rooms
they must be fitted with cast-iron nickel-plated plates.

49. _Clean-Out Plugs._ Brass screw-jointed clean-out plugs are to be
provided in lines at all turns where indicated on the drawing. The
clean-out plugs to be 2 in. diameter, except in the 1¹⁄₂-in. lines,
where clean-outs are to be same diameter as the lines.

50. _Exhaust Connection._ Exhaust pipe from the exhauster is to be
run up to the basement ceiling and along same into the smoke breeching
beyond damper as directed.

51. _Sweeper Inlets._ The following number of inlets are to be
provided: Subbasement , basement , first story , second
story , attic .

52. The sweeper inlets are to be fitted with hinged covers or caps with
rubber gaskets arranged to be self-closing when hose is removed, and
those in corridors and lobby arranged to be opened with a key.

53. Inlets coming through finished walls or partitions are to be flush
pattern.

54. Inlets on risers run exposed against walls are to be set close up
against bead of fittings.

55. If contractor desires to use other form of connection than above
described which is equally satisfactory, same must be submitted to the
Architect for approval after award of the contract.

56. In this specification the word “renovator” is used to mean that
portion of the tool which is in contact with the surfaces cleaned; the
word “stem,” that portion connecting the renovator and hose; the word
“cleaner” is used to mean a complete cleaning tool.

57. The following cleaning tools are to be furnished:

One carpet renovator, with cleaning slot ¹⁄₄ in. by 12 in. long.

One bare floor renovator, 12 in. long, with curved felt-covered face.

One wall renovator, 12 in. long, with cotton flannel curved face.

One upholstery renovator, with slot ¹⁄₄ in. by 4 in.

One corner cleaner.

One radiator cleaner.

One hat brush.

One long curved stem about 5 ft. long.

One extension tube about 5 ft. long.

58. The renovators for carpets, bare floors and walls to be arranged
with adjustable swivel joint, so that same can be operated at an angle
with stem from 45° for regular use to an angle of about 80° for use
under or back of furniture and other similar places. This movable joint
to be so arranged that lips of cleaning tool will always remain in
contact with surface cleaned, and constructed so that fitted surfaces
are not exposed to dust, and the air currents when deflected to impinge
only upon surfaces which are of heavy metal and where such wear as
occurs will not affect the operation and handling of the tool.

59. All renovators and stems are to be as light as is consistent with
strength and ability to withstand cutting action of dust.

60. The lips of carpet renovators and upholstery cleaner to be of such
proportions and form as will prevent injury to the fabric, and such
widths as will reduce to a minimum the sticking of renovator face to
the material being cleaned.

61. Stems to be not less than 1 in. outside diameter. Air passages in
swivels to be same diameter as inside of stem. Stem for use with floor
renovators shall be curved near upper end to form handle and provided
with swivel to permit hose hanging vertical.

62. Stems to be drawn-steel or brass tubing, not less than No. 21
United States standard gauge thick if steel and not less than No. 16
Brown & Sharpe gauge thick if brass.

63. Carpet renovators to be made preferably of pressed steel, as light
as possible, or may be made of cast iron, brass or aluminum with iron
wearing face.

64. Bare floor renovators shall have renewable elastic wearing face
curved in direction of motion when cleaning.

65. All renovators and brushes must be provided with proper rubber or
other approved buffers to prevent marring the woodwork.

66. Upholstery cleaners are to have inlet slots or openings of such
size and form as to absolutely prevent drawing in loose covering of
furniture.

67. Upholstery and corner cleaners are not to be arranged for use with
stems, but are to have their own handles permanently attached and be
provided with hose couplings.

68. All metal parts of renovators and stems are to be finished, and all
except aluminum parts nickel plated.

69. _Hose._ Furnish 75 ft. cleaning hose in three 25-ft. lengths.

70. The hose to be 1¹⁄₄ in. inside diameter best quality rubber hose,
reinforced in best manner to absolutely prevent collapse at highest
vacuum obtainable with the exhauster furnished and to prevent collapse
if stepped on. Weight of hose to be not over 12 oz. per linear foot.

71. Couplings for hose to be either slip, bayonet-lock or all-rubber
type, with smooth bore of practically same diameter as inside of
hose. The couplings to have least possible projection outside of hose
dimensions and be well rounded, so as not to injure floors, doors,
furniture, etc.

72. Bayonet joints may have packing washer, and slip joints to have
permanent steel pieces on ends of hose and brass slip coupler. All ends
of hose at couplings to have outside ferrules securely fastened in
place, or pure gum ends glued to coupling. Simple conical slip joints
slipped into ends of hose without ferrules will not be acceptable. All
joints must fit together so that they will not be readily pulled apart.

73. _Tests._ All piping to be tested with air pressure equal to 5 in.
mercury before being concealed in walls and other spaces. Mercury must
not fall more than ¹⁄₄ in. in one-half hour.

74. On completion of plant the pump will be operated with all outlets
closed and, under these conditions, there must be an interval of not
less than 10 min. between the stopping and starting of the motor by the
automatic control, if pump system is used. And if fan system be used,
the power required to operate the exhauster must not be more than 65%
that required in capacity test.

75. To test the capacity of the separator, a mixture containing 6 lbs.
of sand, passed through a 50-mesh screen, 3 lbs. of common wheat flour
and 16 lbs. of Portland cement shall be spread over 50 sq. ft. of
floor and picked up with a renovator attached to the end of 50 ft. of
1¹⁄₄-in. hose. The machine shall be stopped and the material removed
from the separator spread on floor and picked up. This procedure shall
be repeated until the material has been handled four times. If the
separator contains a bag, the same must not be disturbed until after
completion of the capacity test, which will be made with the material
in place in separator, after being picked up the fourth time.

After completion of capacity test, the contents of separator shall
be weighed and if same be a partial separator it must contain 95% of
the material picked up. If a displacement machine is used as a vacuum
producer, the separator must prevent the passage of any dust through
separator, which will be determined by holding a dampened cloth over
pump outlet during test of apparatus. Said cloth must not show any dust
lodged thereon at end of test.

76. To test the capacity of the plant a standard vacometer, attached to
the end of 75 ft. of cleaning hose shall show a vacuum of 2 in. mercury
with ¹⁄₂-in. diameter orifice open.

77. _Test of Cleaning Tools._ The plant shall be operated by the
Contractor in the presence of the Architect’s representative, and a
test made of each kind of cleaning tool furnished. The tool shall be
attached to a 50-ft. length of hose attached to an outlet selected by
the Architect’s representative, and under normal working conditions
each tool must satisfactorily perform the work for which it was
designed. Dust and surfaces to be cleaned shall be furnished by the
contractor.

78. _Painting._ After the completion of the specified tests, all
exposed iron work except galvanized iron or tinned work in connection
with this apparatus, not specified to be otherwise finished, shall be
primed with paint suitable for surfaces covered, and then given two
additional coats. Machinery shall be painted as already specified, and
all other work shall be given finishing tints as selected or approved
by the architect. Black iron pipe, etc., shall be given two coats lead
and oil of tint directed.

=Modifications of Specifications when Alternating Current is
Available.=--When alternating current is available, instead of direct,
modify specifications as follows:

23. Motor to be wound for .... volts, .... cycle, .... phase
alternating current.

24. Motor to have rotor of the squirrel cage type.

Omit 25, 26 and 27.

28. To remain as for direct current.

29. There must be an insulation between the starter or primary windings
and the frame of not less than one megohm.

30, 31, and 32. Same as for direct current.

33. _Tablet._ Furnish and mount where directed a polished slate tablet
having mounted thereon a 30 ampere, 250 volt, .... pole knife switch
with enclosed indicating fuses and, if displacement type exhauster is
furnished, an automatic starter of the “across the line” type, operated
by vacuum in the separator which will stop motor when the vacuum in the
separator rises 2 in. above that required to meet test conditions, and
start exhauster when vacuum reaches working range.

CLASS 2

PLANT FOR LARGE OFFICE BUILDING HAVING PIPE LINES OF MODERATE LENGTH.

1. Same as for Class 1.

2. Omit centrifugal fan.

3 to 9. Same as for Class 1.

Omit 10 to 13.

14 and 16. Same as for Class 1.

15. Omit centrifugal fan.

Omit 17 and 18.

18a. _Base Plate, Foundation, etc._ Provide suitable base plate to
rigidly support the exhauster and its motor as a unit, which shall be
large enough to catch all drip of water or oil. Provide a raised margin
and pads for feet of exhauster frame, motor, and anchor bolts, high
enough to prevent any drip from getting into the foundation or on the
floor.

18b. Provide suitable foundation of brick or concrete, to which the
base plate shall be firmly anchored. The foundation shall be built
on top of the cement floor of the basement, which shall be picked to
afford proper bond for the foundation.

18c. Construct the foundation of such a height as to bring the working
parts of the machine at the most convenient level for operating
purposes. Exposed parts of the foundation to be faced with best grade
white enameled brick. If the base plate does not cover the foundation,
the exposed top surface is to be finished with enameled brick, using
bull-nose brick on all edges and corners.

19 to 23. Same as for Class 1.

23a. The guaranteed efficiency of motor shall not be less than 78% at
half load and not less than 84% at full load.

24 to 32. Same as for Class 1.

32a. Motor shall be subject to shop test to determine efficiency,
heating, insulation, etc. Manufacturer’s certified test sheets of motor
giving all readings taken during shop tests, together with calculated
results, must be submitted to the Architect for approval before motor
is shipped from factory.

33. _Rheostat._ Furnish and install where shown, upon a slate panel
hereinafter specified, a starting rheostat of proper size and approved
made, designed for the particular duty it has to perform. It must
have an automatic no-voltage and overload release. All resistance for
rheostat is to be placed on the back of the tablet. Contacts must
project through board to front side. All moving parts must be on front
of board.

33a. _Tablet._ Furnish and place where shown, a slate tablet not less
than ³⁄₄ in. thick, supported by a substantial angle iron frame, so
placed that there will be a space of not less than 4 in. between the
wall and back of resistance. Mount on this tablet one double-pole,
250-volt knife switch, with two 250-volt inclosed fuses and one
starting rheostat, as specified hereinbefore. The connections shall be
on the back of the tablet. The space between the column and the tablet
shall be inclosed with a removable diamond-mesh grill of No. 10 iron
wire in channel frame.

34, 35, 36. Same as for Class 1.

36a. _Automatic Control._ Suitable means shall be provided in
connection with the rotary exhausters that will maintain the vacuum in
the separators within the limit of the machine at point found to be
most desirable, irrespective of the number of sweepers in operation.

36b. Controller shall consist of a suitable means provided in the
exhauster, or as an attachment thereto, which will automatically throw
the exhauster out of action by admitting atmospheric pressure to the
exhauster only, but not to the system whenever the vacuum in the
separators rises above the point considered desirable, and throw the
exhauster into action when the vacuum falls below the established lower
limit.

36c. _Vacuum Breaker._ In addition to the controlling devices above
specified there shall be placed in the suction pipe to the exhauster an
approved positive-acting vacuum breaker having opening equivalent to
the area of 1-in. diameter pipe and set to open at 10 inches vacuum.

(If plant is to be run for long periods without much load, as in a
hotel, omit 36a, b, c, and substitute):

36d. _Automatic Control._ An approved type of controller for
maintaining practically a constant vacuum by varying the speed of the
motor driving exhauster arranged to permit the operation of the motor
continuously at any speed between full speed and stop, so long as there
be no change in vacuum and which will increase speed whenever vacuum
falls and reduce speed whenever vacuum rises, must be provided.

37. _Dust Separator._ There shall be one dry separator located where
shown on plans, having a volume of not less than 3 cu. ft. for each
sweeper of plant capacity.

38. The interior arrangement of the separator shall be such that no
part of same will receive the direct impact of the dust. Cloth bags
or metal screens, if used in this separator, shall be so placed that
nothing but the very lightest of the dust can lodge thereon, and that
same may be easily cleaned without dismantling the separator. It must
be so constructed that it will intercept all of the dust entering same.

38a to 56. Same as for Class 1.

56a. _Tool Cases._ Furnish approved hardwood cabinet-finished cases
for cleaning tools. Each case to be made as light as possible and of
convenient form for carrying by hand and provided with a complete set
of cleaning tools, each securely held in its proper place, and fitted
with lock and key, clamps, and conveniently arranged handles.

57. Each case shall contain the following:

One carpet renovator, with slot ¹⁄₄ in. by 15 in.

One bare floor renovator, 15 in. long, with curved felt-covered face.

One wall brush, with skirted bristles, 12 in. long and ¹⁄₂ in. wide.

One hand brush, with hose connections at end, 8 in. long, 2 in. wide.

One 4-in. round brush for relief work.

One upholstery renovator.

One corner cleaner.

One radiator tool.

One curved stem about 5 ft. long.

One extension tube 5 ft. long.

At least one hat brush with the system.

58 to 64. Same as for Class 1.

64a. All brushes to be of substantial construction, with best quality
bristles set in close rows and as thick as possible, skirted with
rubber, leather, or chamois skin, so that all air entering renovator
will pass over surface being cleaned.

65 to 68. Same as for Class 1.

69. _Hose Racks._ Furnish and properly secure in place, where directed,
.... hose racks in basement, .... each in first and second stories
(.... racks in all). The racks to be constructed of cast iron,
galvanized or enamel finish, and each rack to be suitable for holding
75 ft. of hose of required size.

69a. _Hose._ There must be furnished with each hose rack 75 ft. of
noncollapsible hose in three 25-ft. lengths.

70 to 73. Same as for Class 1.

74. On completion of the plant the pump will be operated with all
outlets closed, and, under this condition, the power consumption must
not be more than 50% of that required under test conditions.

75. _Test of Separators._ At each of ---- points, near ---- outlets
on different risers selected by the architect’s representative, the
contractor shall furnish and spread on the floor, evenly covering an
area of approximately 50 sq. ft. for each outlet, a mixture of 6 lbs.
of dry sharp sand that will pass a 50-mesh screen, 3 lbs. of fine wheat
flour and 6 lbs. of Portland cement.

75b. Fifty feet of hose shall be attached to each of the ---- outlets,
and the surfaces prepared for cleaning shall be cleaned simultaneously
by operators provided by the contractor until all of the sand, flour
and Portland cement has been taken up, when the exhauster shall be
stopped and the dirt removed from the separator and spread on the floor
again, and the operation of cleaning repeated until the mixture has
been handled by the apparatus four times.

The bag contained in the separator must not be disturbed until after
completion of the capacity test, which will be made with material in
place in the separator after being picked up the fourth time. After
completion of the capacity test the contents of separator will be
removed. During test of separators a dampened cloth will be held over
the exhaust from pump. If such cloth indicates dirt passing through the
separator, same will be rejected.

76. To test the capacity of the plant, one hose line 100 ft. long
shall be attached to inlet farthest from the separator with standard
vacometer, with ¹⁄₂-in. opening in end of hose. .... hose lines shall
be attached to other outlets, each with 50 ft. hose and vacometers in
end of hose, .... vacometers having ¹⁄₂-in. opening and .... vacometers
having ⁷⁄₈-in. opening. Under these conditions 4 in. mercury must be
maintained in vacometer at end of 100 ft. of hose.

77 and 78. Same as for Class 1.

=Modifications of Specifications when Alternating Current is
Available.=--When alternating current is available, instead of direct,
modify specifications as follows:

23. Motor to be wound for .... volts, .... cycle, .... phase
alternating current.

23a. Bidders must name efficiency and power factor of motor at one-half
and full load.

24. Motor to have phase-wound rotor with collector rings for insertion
of starting resistance.

Omit 25, 26 and 27.

28. Same as for direct current.

29. There must be an insulation between the starter or primary windings
and the frame of not less than one megohm.

30, 31, 32, 32a. Same as for direct current.

33. _Rheostat._ Furnish and install an approved hand-starting rheostat
for inserting resistance in rotor circuit in starting, of proper size
to insure the starting of motor in not exceeding 15 seconds without
overheating.

33a. Same as for direct current, except that switch must be either
three- or four-pole, according to current available.

Omit 36d with alternating current machine.

CLASS 3

LARGE INSTALLATION WITH UNUSUALLY LONG PIPE LINES.

1. Same as for Class 1.

2. Exhauster shall be of the reciprocating piston type.

3. The piston type of exhauster shall be double acting and so designed
that the cylinder clearance shall be reduced to a minimum, or suitable
device shall be employed to minimize the effect of large clearance.

4. The induction and eduction valves may be either poppet, rotary, or
semi-rotary, and shall operate smoothly and noiselessly.

5. The piston packing shall be of such character as to be practically
air tight under working conditions and constructed so that it will
be set out with its own elasticity without the use of springs of any
sort. If metallic rings are used, they must fill the grooves in which
they are fitted, both in width and depth, and must be concentric; that
is, of the same thickness throughout. The joint in the ring or rings
to be lapped in width but not in thickness, and if more than one ring
is used they are to be placed and doweled in such position in their
respective grooves so that the joints will be at least one-fourth of
the circumference apart.

6. The piston shall have no chamber or space into which air may leak
from either side of the piston. All openings into the body of the
piston must be tightly plugged with cast-iron plugs.

7. The piston rod stuffing box to be of such size and depth that if
soft packing is used it can be kept tight without undue pressure from
the gland. If metallic packing is used, it must be vacuum tight without
undue pressure on the rod. Proper means shall be provided for the
continuous lubrication of the piston rod.

8. The exhauster of the piston type shall be fitted with an approved
cross-head suitably attached to the piston rod; machines having an
extended piston rod for guide purposes will not be acceptable.

Omit 9 to 13.

14. Same as for Class 1.

15. Reciprocating piston exhauster shall be provided with the
necessary devices for the removal of the heat generated by friction
and compression, that shall prevent the temperature of cylinders or
eduction chambers rising more than 100° F. above the surrounding
atmosphere after two hours’ continuous operation under full-load
conditions.

16. _Speed._ Reciprocating exhauster with poppet valves shall operate
at an average piston speed not exceeding 200 ft. per minute, with
rotary valves not exceeding 300 ft. per minute.

Omit 17 and 18.

18b. Provide suitable foundation of brick or concrete, to which base
plate shall be firmly anchored. The foundation shall be built on top
of the cement floor of the basement, which shall be picked to afford
proper bond for the foundation.

19 to 23. Same as for Class 1.

23a. The guaranteed efficiency of motor shall not be less than 80% at
half load and not less than 85% at full load.

24 to 32. Same as for Class 1.

32a. Motor shall be subject to shop test to determine efficiency,
heating, insulation, etc. Manufacturers’ certified test sheets of
motor, giving all readings taken during shop test, together with
calculated results, must be submitted to the Architect for approval
before motor is shipped from factory.

33. _Rheostat._ Furnish and install where shown, upon a slate panel
hereinafter specified, a starting rheostat of proper size and approved
make, designed for the particular duty it has to perform. It must
have an automatic no-voltage and overload release. All resistance for
rheostat is to be placed on the back of the tablet. Contacts must
project through board to front side. All moving parts must be on front
of board.

33a. _Tablet._ Furnish and place where shown, a slate tablet, not less
than ³⁄₄ in. thick, supported by a substantial angle bar frame, so
placed that there will be a space of not less than 4 in. between the
wall and back of resistance. Mount on this tablet one double-pole,
250-volt knife switch, with two 250-volt inclosed fuses and one
starting rheostat, as specified hereinbefore. The connections shall be
on the back of the tablet. The space between the column and the tablet
shall be inclosed with a removable diamond-mesh grill of No. 10 iron
wire in channel frame.

34, 35 and 36. Same as for Class 1.

37. _Dust Separators._ There shall be one dry and one wet separator
located where shown on drawings. Each separator shall have a volume of
3 cu. ft. for each renovator of plant capacity.

38. The separator first receiving the dust shall be a dry separator,
the interior arrangement of which shall be such that no part of same
shall receive the direct impact of the dust. No screens or cloth bags
shall be used in this separator and it must be so constructed that it
will intercept 95% of the dust entering same.

38a. The second separator must be a wet separator which may be
contained in the base of the machine or consist of a separate tank.

38b. Wet separators, whether separate from or integral with the base of
the machine, must be provided with an attachment which will positively
mix the air and water, thoroughly break up all bubbles, separate the
water from the air, and prevent any water entering the exhauster
cylinder.

38c. Suitable means must be provided to automatically equalize the
vacuum between wet and dry separators upon the shutting down of the
exhauster.

38d. The separators must be provided with suitable openings for
access to the interior for inspection and cleaning, and the interior
arrangement of the separators must be such that they may be readily
cleaned without dismantling.

38e. All parts of the wet separator tank not constructed of
non-corrosive metal must be thoroughly tinned or galvanized both inside
and outside. The interior of the wet separator formed in base of
exhauster shall be painted with at least two coats of asphalt varnish
or other paint suitable to prevent the corrosion of same.

38f. Separators must be provided with all necessary valves or other
attachments for successful operation, including a sight glass for the
wet separator, through which the interior of the same may be observed,
and an iron-case mercury column reading 50% in excess of operating
vacuum, attached to the dry separator first receiving the dust.

38g. The wet separator shall be properly connected to water supply
where directed and discharge to sewer where shown on plans.

38h. A running trap with clean-out shall be installed in the waste line.

39 to 41. Same as for Class 1.

41a. Waste and water pipe, in connection with wet separator and jacket,
except waste pipe below basement floor, to be standard galvanized
wrought-iron pipe or steel screw-jointed pipe free from burs. Waste
pipe below the basement floor is to be best grade, “extra heavy”
cast-iron pipe, with lead-calked joints.

42 to 45. Same as for Class 1.

45a. Fittings on water lines to be standard galvanized beaded fittings.

45b. Fittings on waste line above basement floor line to be galvanized
recessed screw-jointed drainage fittings and those below basement floor
to be “extra heavy” cast-iron with hub joints.

46 to 50. Same as for Class 1.

50a. The exhaust pipe is to be fitted with an approved first-class
exhaust muffler not less than 12 in. in diameter and 60 in. high,
closely riveted and constructed of galvanized iron not less than
¹⁄₈ in. thick, and in event an exhauster requiring lubrication is
furnished, this muffler is to be arranged so that it will also be an
efficient oil separator. Drip connection to be arranged at bottom of
muffler.

51 to 56. Same as for Class 1.

56a. _Tool Cases._ Furnish .... approved hardwood cabinet-finished
cases for cleaning tools. Each case to be made as light as possible and
of convenient form for carrying by hand and provided with a complete
set of cleaning tools, each securely held in its proper place, and
fitted with lock and key, clamps and conveniently arranged handles.

57. Each case shall contain the following:

One carpet renovator, with slot ¹⁄₄ in. by 12 in.

One bare floor renovator 12 in. long, with curved, felt-covered face.

One wall brush, with skirted bristles, 12 in. long and ¹⁄₂ in. wide.

One hand brush, with hose connection at end, 8 in. long and 2 in. wide.

One 4-in. round brush for relief work.

One upholstery renovator.

One corner cleaner.

One radiator tool.

One curved stem about 5 ft long.

One straight extension stem 5 ft. long.

At least one hat brush with the system.

58 to 64. Same as for Class 1.

65 to 68. Same as for Class 1.

69. _Hose Racks._ Furnish and properly secure in place where directed,
.... hose racks in basement, .... each in first and second stories
(.... racks in all). The racks to be constructed of cast-iron,
galvanized or enamel finish, and each rack to be suitable for holding
75 ft. of hose of required size.

69a. _Hose._ There must be furnished with each hose rack 75 ft. of
non-collapsible hose in three 25-ft. lengths.

70. Hose to be 1 in. inside diameter of best quality, rubber hose,
reinforced in best manner to absolutely prevent collapse at highest
vacuum obtainable with the exhauster furnished and to prevent collapse
if stepped on. Weight of hose to be not over 12 oz. per linear foot.

71, 72 and 73. Same as for Class 1.

74. On completion of the plant the pump will be operated with all
outlets closed and, under this condition, the power consumption must
not be more than 50% of that required under test conditions.

75. To test the capacity of the plant, .... hose lines each 100 ft.
long will be attached to outlets on the system and each hose fitted
with a standard vacometer. .... vacometers shall have ¹⁄₂-in. opening
and .... vacometers shall have ⁷⁄₈-in. opening. Under these conditions
4 in. vacuum must be maintained at vacometers having ¹⁄₂ in. opening.

75a. _Test of Separators._ At each of ---- points, near ---- outlets
on different risers selected by the architect’s representative, the
contractor shall furnish and spread on the floor, evenly covering an
area of approximately 50 sq. ft. for each outlet, a mixture of 6 lbs.
of dry sharp sand that will pass a 50-mesh screen, 3 lbs. of fine wheat
flour, and 1 lb. of finely pulverized charcoal.

75b. Fifty feet of hose of size required by the system shall be
attached to each of the ---- outlets, and the surface or surfaces
prepared for cleaning shall be cleaned simultaneously by operators
provided by the contractor until all of the sand, flour and charcoal
has been taken up, when the exhauster shall be stopped and the dirt
removed from the dry separator and spread on the floor again, and the
operation of cleaning repeated until the mixture has been handled by
the apparatus four times. If, after thoroughly flushing the system at
completion of above run, any dust or mud is found in the cylinder,
ports, or valve chambers of the displacement exhauster, or if less
than 95% of the dirt removed is found in the dry separator, it shall be
deemed sufficient ground for the rejection of the separators.

76 and 77. Same as for Class 1.

=Modifications of Specifications when Alternating Current is
Available.=--When alternating current is available, instead of direct,
modify specifications as follows:

23. Motor to be wound for .... volts, .... cycle, .... phase
alternating current.

23a. Bidders must name efficiency and power factor of motor at one-half
and full load.

24. Motor to have phase-wound rotor with collector rings for insertion
of starter resistance.

Omit 25, 26 and 27.

29. Same as for Class 1, alternating current.

33a. Same as for direct current, except switch must be either three- or
four-pole, according to current available.

CLASS 4

LARGE OR SMALL PLANT WHERE CARPET CLEANING IS OF SECONDARY IMPORTANCE.

1 to 17. Same as for Class 1.

Omit 18.

19 to 23. Same as for Class 1.

23a. The guaranteed efficiency of motor shall not be less than 78% at
half load and not less than 84% at full load.

24 to 32. Same as for Class 1.

33a. _Tablet._ Furnish and place where shown, a slate tablet not less
than ³⁄₄ in. thick, supported by a substantial angle iron frame, so
placed that there will be a space of not less than 4 in. between the
wall and back of resistance. Mount on this tablet one double-pole,
250-volt knife switch, with two 250-volt inclosed fuses and one
starting rheostat, as specified hereinbefore. The connections shall be
on the back of the tablet. The space between the column and the tablet
shall be enclosed with a removable diamond-mesh grill of No. 10 wire in
channel frame.

34, 35 and 36. Same as for Class 1.

36a. _Automatic Control._ Suitable means shall be provided in
connection with the rotary exhauster that will maintain the vacuum in
the separators within the limit of the machine at point found to be
most desirable, irrespective of the number of sweepers in operation.

36b. Controller shall consist of a suitable means provided in the
exhauster, or as an attachment thereto, which will automatically throw
the exhauster out of action by admitting atmospheric pressure to the
exhauster only, but not to the system; whenever the vacuum in the
separator rises above the point considered desirable, and throw the
exhauster into action when the vacuum falls below the established lower
limit.

36c. In addition to control, a positive vacuum breaker having an
opening equal to 1 in. diameter pipe net for 6 in. of mercury, must be
provided on separator.

36d. If centrifugal fan is used, no control or vacuum breaker will be
required.

37. Furnish one separator having a cubic contents of 4.5 cu. ft. for
each sweeper of plant capacity.

38 to 56. Same as for Class 1.

57. Each case shall contain the following:

One carpet renovator ¹⁄₂ in. by 15 in.

One bare floor renovator, 15 in. long, with curved felt-covered face.

One wall brush, with skirted bristles, 12 in. long and ¹⁄₂ in. wide.

One hand brush, with hose connection at end, 8 in. long and 2 in. wide.

One 4-in. round brush for relief work.

One upholstery renovator.

One corner cleaner.

One radiator tool.

One curved stem about 5 ft. long.

One straight extension stem 5 ft. long.

At least one hat brush with the system.

58 to 68. Same as for Class 1.

69. _Hose Racks._ Furnish and properly secure in place, where
directed, .... hose racks in basement, .... each in first and second
stories (.... racks in all). The racks to be constructed of cast-iron,
galvanized or enamel finish, and each rack to be suitable for holding
75 ft. of hose of required size.

69a. _Hose._ There must be furnished with each hose rack 75 ft. of
non-collapsible hose in three 25-ft. lengths.

70. Hose to be 1¹⁄₂ in. or 1-³⁄₄ in. inside diameter, best quality
rubber hose, reinforced in best manner to absolutely prevent collapse
at highest vacuum obtainable with the exhauster furnished and to
prevent collapse if stepped on. Weight of hose to be not over 12 oz.
per linear foot.

71 to 73. Same as for Class 1.

74. On completion of the plant the pump will be operated with all
outlets closed and, under this condition, the power consumption must
not be more than 50% of that required under test conditions.

75. Same as for Class 1.

76. To test the capacity of the plant, .... hose lines each 75 ft. long
shall be attached to the inlets, each hose to be fitted with standard
vacometer with ⁷⁄₈-in. opening. Under these conditions a vacuum of 1
in. mercury must be maintained in each vacometer.

77 and 78. Same as for Class 1.

CLASS 5

TO GIVE WIDEST COMPETITION.

1. Same as for Class 1.

2. Exhauster to be piston, rotary or centrifugal fan type.

3. The piston type of exhauster shall be double-acting and so designed
that the cylinder clearance shall be reduced to a minimum, or suitable
devices shall be employed to minimize the effect of large clearances.

4. The induction and eduction valves may be either poppet, rotary or
semi-rotary, and shall operate smoothly and noiselessly.

5. The piston packing shall be of such character as to be practically
air tight under working conditions and constructed so that it will be
set out with its own elasticity without the use of springs of any
sort. If metallic rings are used, they must fill the grooves in which
they are fitted, both in width and depth, and must be concentric; that
is, of the same thickness throughout. The joint in the ring or rings
to be lapped in width but not in thickness, and if more than one ring
is used they are to be placed and doweled in such position in their
respective grooves so that the joints will be at least one-fourth of
the circumference apart.

6. The piston shall have no chamber or space into which air may leak
from either side of the piston. All openings into the body of the
piston must be tightly plugged with cast-iron plugs.

7. The piston-rod stuffing box to be of such size and depth that if
soft packing is used it can be kept tight without undue pressure from
the gland. If metallic packing is used, it must be vacuum tight without
undue pressure on the rod. Proper means shall be provided for the
continuous lubrication of the piston rod.

8. The exhauster of the piston type shall be fitted with an approved
cross-head suitably attached to the piston rod; machines having an
extended piston rod for guide purposes will not be acceptable.

Insert paragraphs 3 to 15 from specifications for Class 1.

15a. Reciprocating exhauster shall be provided with the necessary
devices for the removal of the heat generated by friction and
compression, that shall prevent the temperature of cylinders or
eduction chambers rising more than 100° F. above the surrounding
atmosphere after two hours’ continuous operation under full load
conditions.

15b. _Speed._ Reciprocating exhauster with poppet valves shall operate
at an average piston speed not exceeding 200 ft. per minute, with
rotary valves not exceeding 300 ft. per minute.

Insert paragraphs 16 and 17 from specifications for Class 1.

Omit 18.

19 to 23. Same as for Class 1.

23a. The guaranteed efficiency of motor shall not be less than 78% at
half load and not less than 84% at full load.

24 to 32. Same as for Class 1.

32a. Motors shall be subject to shop test to determine efficiency,
heating, insulation, etc. Manufacturers’ certified test sheets of
motor, giving all readings taken during shop test, together with
calculated results, must be submitted to the architect for approval
before motor is shipped from factory.

33. _Rheostat._ Furnish and install where shown, upon a slate panel
hereinafter specified, a starting rheostat of proper size and approved
make, designed for the particular duty it has to perform. It must
have an automatic no-voltage and overload release. All resistance for
rheostats is to be placed on the back of the tablet. Contacts must
project through board to front side. All moving parts must be on front
of board.

33a. _Tablet._ Furnish and place where shown, a slate tablet not less
than ³⁄₄ in. thick, supported by a substantial angle bar frame, so
placed that there will be a space of not less than 4 in. between the
wall and back of resistance. Mount on the tablet one double-pole,
250-volt knife switch, with two 250-volt enclosed fuses and one
starting rheostat, as specified hereinbefore. The connections shall be
on the back of the tablet. The space between the column and the tablet
shall be enclosed with a removable diamond-mesh grill of No. 10 iron
wire in channel frame.

34, 35 and 36. Same as for Class 1.

36a. _Automatic Control._ Suitable means shall be provided in
connection with the reciprocating and rotary exhausters that will
maintain the vacuum in the separators within the limit of the machine
at point found to be most desirable, irrespective of the number of
sweepers in operation.

36b. Controller shall consist of a suitable means provided in the
exhauster, or as an attachment thereto, which will automatically throw
the exhauster out of action by admitting atmospheric pressure to the
exhauster only, but not to the system; or that shall cause suction from
the system to cease whenever the vacuum in the separators rises above
the point considered desirable, and throw the exhauster into action
when the vacuum falls below the established lower limit.

36c. _Vacuum Breaker._ In addition to the controlling devices above
specified, if a reciprocating or rotary exhauster is used, there
shall be placed in the suction pipe to the exhauster an approved
positive-acting vacuum breaker having opening equivalent to the area of
1-in. diameter pipe and set to open at 12 in.

36d. If centrifugal fan is used, no control or vacuum breaker will be
required.

37. _Dust Separators._ There must be provided at least one separator
between the pipe lines and exhauster having a volume of not less than
3 cu. ft. per sweeper of plant capacity. This separator must be so
constructed that no part thereof will receive the direct impact of the
dust. If rotary exhauster is used, this separator must also contain a
bag so placed that only the lightest dust will reach same and must be
arranged to be readily cleaned without dismantling the separator. If a
centrifugal exhauster is used, this apparatus may or may not contain a
bag, and, if piston pump is used, this separator must contain no bags
or screens whatever. If a piston type of exhauster is installed, an
additional separator must be placed between the first separator and the
exhauster. This must be a wet separator and may be contained in the
base of the machine or consist of a separate tank.

Omit 38.

38a. Same as for Class 1.

38c. Suitable means must be provided to automatically equalize the
vacuum between wet and dry separators upon the shutting down of the
exhauster.

38e. All parts of the wet separator tank (if used) not constructed
of non-corrosive metal must be thoroughly tinned or galvanized both
inside and outside. The interior of the wet separator formed in base of
exhauster shall be painted with at least two coats of asphalt varnish
or other paint suitable to prevent the corrosion of same.

38f. Separators must be provided with all necessary valves or other
attachments for successful operation, including a sight glass for the
wet separator (if used), through which the interior of same may be
observed.

38g. The wet separator (if used) shall be properly connected to water
supply where directed and discharge to sewer where shown on plans.

38h. A running trap with clean-out shall be installed in the waste line.

39 to 41. Same as for Class 1.

41a. Waste and water pipe, in connection with wet separator and jacket,
except waste pipe below basement floor, to be standard galvanized
wrought-iron or steel screw-jointed pipe free from burs. Waste pipe
below the basement floor is to be best grade, “extra heavy” cast-iron
pipe, with lead-calked joints.

42 to 45. Same as for Class 1.

45a. Fittings on water lines to be standard galvanized beaded fittings.

45b. Fittings on waste line above basement floor to be galvanized
recessed screw-jointed drainage fittings and those below basement floor
to be “extra heavy” cast-iron with hub joints.

46 to 50. Same as for Class 1.

50a. If reciprocating exhauster is used, the exhaust pipe is to be
fitted with an approved first-class muffler not less than 12 in. in
diameter and 60 in. high, closely riveted and constructed of galvanized
iron not less than ¹⁄₈ in. thick, and in event an exhauster requiring
lubrication is furnished this muffler is to be arranged so that it will
also be an efficient oil separator. Drip connection is to be arranged
at bottom of muffler.

51 to 56. Same as for Class 1.

56a. _Tool Cases._ Furnish ... approved hardwood cabinet-finished cases
for cleaning tools. Each case to be made as light as possible and of
convenient form for carrying by hand and provided with a complete set
of cleaning tools, each securely held in its proper place, and fitted
with lock and key, clamps, and conveniently arranged handles.

57. Each case will contain the following:

One carpet renovator, with slot ¹⁄₄ in. by not less than 12 or more
than 15 in. long.

One bare floor renovator, 15 in. long, with curved felt-covered face.

One wall brush, with skirted bristles, 12 in. long and ¹⁄₂ in. wide.

One hand brush, with hose connection at end, 8 in. long and 2 in. wide.

One 4-in. round brush for relief work.

One upholstery renovator.

One corner cleaner.

One radiator tool.

One curved stem about 5 ft. long.

One straight extension stem 5 ft. long.

At least one hat brush with the system.

58 to 64. Same as for Class 1.

65 to 68. Same as for Class 1.

69. _Hose Racks._ Furnish and properly secure in place, where directed,
.... hose racks in basement, .... each in first and second stories
(.... racks in all). The racks to be constructed of cast-iron,
galvanized or enamel finish, and each rack to be suitable for holding
75 ft. of hose of required size.

69a. _Hose._ There must be furnished with each hose rack, 75 ft. of
non-collapsible hose in three 25-ft. lengths.

70. Hose shall not be less than 1 in. or more than 1-³⁄₄ in. inside
diameter, best quality rubber hose, reinforced in best manner to
absolutely prevent collapse at highest vacuum obtainable with the
exhauster furnished and to prevent collapse if stepped on. Weight of
hose to be not over 12 oz. per linear foot.

71 to 73. Same as for Class 1.

74. On completion of the plant, the pump will be operated with all
outlets closed and under this condition the power consumption must not
be more than 50% of that required under test conditions.

75. To test the capacity of plant, one hose line 100 ft. long shall be
attached to inlet farthest from the separator, with standard vacometer
with ¹⁄₂-in. opening in end of hose. Hose lines shall be attached to
other outlets, each with 50-ft. hose and vacometer in end of hose, ....
vacometers having ¹⁄₂-in. opening and .... vacometers having ⁷⁄₈-in.
opening. Under these conditions 4 in. mercury must be maintained in
vacometer at end of 100 ft. of hose.

75a. _Test of Separators._ At each of ---- points, near ---- outlets on
different risers selected by the .... representative, the contractor
shall furnish and spread on the floor, evenly covering an area of
approximately 50 sq. ft. for each outlet, a mixture of 6 lbs. of dry
sharp sand that will pass a 50-mesh screen, 3 lbs. of fine wheat flour,
and 1 lb. of finely pulverized charcoal, if wet separator be used, and
6 lbs. of Portland cement, if bag be used.

75b. Fifty feet of hose of size required by the system used shall
be attached to each of the ---- outlets, and the surface or surfaces
prepared for cleaning shall be cleaned simultaneously by operators
provided by the contractor until all of the sand, flour and charcoal
has been taken up, when the exhauster shall be stopped and the dirt
removed from the dry separator and spread on the floor again, and the
operation of cleaning repeated until the mixture has been handled by
the apparatus four times. If, after thoroughly flushing the system
at completion of the above run, any dust or mud is found in the
cylinder, ports, or valve chambers of the displacement exhauster, or
if less than 95% of the dirt removed is found in the dry separator
of the centrifugal exhauster, it shall be deemed sufficient ground
for the rejection of the separators. If bag is used, same must not be
disturbed until after capacity test, which will be made with material
in separator after being picked up the fourth time.

76-77. Same as for Class 1.

78. Evaluation of proposal (for 4-sweeper plant): No proposal will be
considered which contemplates furnishing an exhauster requiring more
power to operate under test conditions than:

Full load, 14 K. W.; three-quarter load, 12.25 K. W.; one-half load,
10.5 K. W.

Test Requirement: Paragraph 75 to be considered full load. To reduce
the load to three-quarters, one ⁷⁄₈-in. vacometer opening to be closed;
to produce one-half load, one ¹⁄₂-in. opening to be closed in addition
to the ⁷⁄₈-in. opening.

Bidders are requested to state in proposal the power consumption
required by their apparatus at full, three-quarters and one-half loads,
and in case the guarantees of the various bidders differ, they will be
evaluated as follows for the purpose of comparison:

For each full K. W. of power consumption or fractional part thereof
there will be allowed the following amount or proportionate parts for
fractional parts of a K. W. hour at the various loads:

Per Cent. of Full Load 100 75 50
Amount $156.00 $62.00 $94.00

As an illustration, let it be assumed that proposals have been received
offering equipment in accordance with specification requirements, and
the one offering the most economical apparatus based on guaranteed
power consumption names the highest price for the installation.

To determine if the purchaser will be justified in accepting the
highest proposal, let it be assumed that he has guaranteed a power
consumption of 1 K. W. less at full load, 0.75 K. W. less at
three-quarters load, and 0.25 K. W. more at half-load than the lowest
bidder. Under these conditions the algebraic sum of the saving of the
higher bidder over the lower bidder would be 156 + 46.50 - 23.50 = 179,
which is the additional amount in dollars which the purchaser would be
warranted in paying for the apparatus of higher efficiency.

In making the economy test to determine if the guaranteed power
consumption has been fulfilled, an integrating watt meter, previously
calibrated and found correct, will be placed in circuit and a two-hour
run made at each load and the power consumption based on the meter
readings.

=Penalty.=--It must be distinctly understood to be one of the
conditions under which bids are to be submitted for the work embraced
in this specification that the apparatus shall meet every requirement
of the specification and the guaranty for efficiency under which
conditions the contract price will be paid. In the event the apparatus
tested fails to meet the specified requirements for capacity or
economy, or both, the Architect shall have the right to reject the
apparatus, absolutely, and require the installation of satisfactory
apparatus, which shall comply with the contract requirements; or if
he elects to accept the same, in the event the capacity or efficiency
at any load (irrespective of other loads) is less than that named in
the proposal, then the contract price shall be the amount named in the
contract for a satisfactory plant, less the amount of deficiencies
shown by the test based on the following:

=For Capacity.=--$500.00 for each inch of vacuum and a proportionate
part thereof for each fraction of an inch below the 4 in. required in
vacometer when operating under full load.

=For Economy.=--Deduction for each K. W. or a proportionate part
thereof for each fraction thereof required in excess of guarantee.

Percentage of Full Load 100 75 50
Penalty $229.00 $93.00 $141.00

* * * * *

This evaluation was based on the same time of operation and cost of
current as that used in illustration under tests (Chapter XII).

The maximum power to be allowed for plants of various capacities should
be as follows:

Capacity in 100% 75% 50%
Sweepers of Load of Load of Load
8 24 20 17
6 20 18 15
4 14 12.25 10.5
2 7.5 ..... 6.25

In event that the plant is to be run with vacuum “on tap,” as in a
hotel, a guaranteed power consumption at no load should be required and
evaluated on the number of hours the plant will probably operate under
these conditions. This will be the largest item in the evaluation under
such conditions.

CHAPTER XV.

PORTABLE VACUUM CLEANERS.

While this book is primarily intended to deal only with vacuum cleaning
systems, which would limit the work to such apparatus as is permanently
installed within the building to be cleaned, the author considers that
it would not be complete without some mention of the portable cleaners
which are so popular at the present time.

On first consideration, the portable cleaner would appear to have a
considerable advantage over the stationary type in that the length
of hose is usually limited to not over 15 ft. and there is no pipe
line, which results in the elimination of practically all friction
loss, giving practically the same vacuum at the renovator as at the
exhauster. This should result in a saving of practically 50% of the
power required to operate the exhauster.

Referring to Chapter XII, we find that the power required to operate a
really efficient vacuum cleaning system is approximately 2.5 H. P. per
sweeper. If a portable cleaner, with the same efficiency and capacity,
be built, it would require at least 1¹⁄₂ H. P.

Such a cleaner would not be portable in the sense of the term as
applied to the most popular cleaners today. The same type has been
built on special order by the American Radiator Company, which mounted
its 1¹⁄₂ H. P. Arco Wand machine on a truck. This cleaner weighs
several hundred pounds and could be moved up and down stairs about
as easily as a sewing machine and would not be of any service in a
building not equipped with elevators. The power required to operate
this cleaner is also so great that special power wiring and large
capacity outlet plugs have to be installed throughout the building.
Such equipment has been provided in at least two department stores
where these cleaners are in use. This means that one wires his
building for vacuum cleaning instead of piping it, and there is also
the necessity of moving a heavy machine about to do the same work as a
stationary plant.

It would appear to the author that the cost of wiring would about equal
that of piping and that the additional labor required to move the
machine about would cost as much as the additional power needed by the
stationary exhauster.

This cleaner, as well as all other portable cleaners, discharges the
air from the exhauster directly back into the apartment cleaned, and is
open to the same objection that was raised against the early compressed
air cleaners. While all the dust may be caught by the dust bag, the
microbes are allowed to escape with the air and the cleaner is not a
sanitary device by any manner of means.

There are a few portable machines using rotary exhausters of the Root
type, and piston pumps, all of which are heavy to move about and, in
making them as light as possible, the efficiency of the exhauster has
been sacrificed. These machines will do the same quality of cleaning as
the stationary plants recommended for residence work and they require
about ³⁄₄ H. P., which is no less than is needed for a stationary plant
of the same capacity and efficiency.

The most popular type of portable cleaner is one which can be
attached to a socket or plug connected with the lighting system.
This should limit the power consumption to ¹⁄₈ H. P. However, many
of these cleaners use as much as 400 watts and a fair average for
cleaners retailing at about $125.00 is 250 watts. Such cleaners will
exhaust about 25 cu. ft. of air with a vacuum of 1 in. mercury at the
vacometer, a ⁵⁄₈-in. orifice being used. The theoretical power required
to move the air is approximately 50 watts and the overall efficiency
of these cleaners is, therefore, about 20%, as against 40% to 50% in
a good, one-sweeper stationary plant. The power expended in operating
these portable cleaners in proportion to the work done is no less than
with an efficient stationary plant.

Portable cleaners have been made in many types but practically all the
standard makes use one or two forms of vacuum producers, either the
diaphragm pump or the single or multi-stage fan. The pumps of the
former type are able to produce a vacuum as high as 6 in. to 10 in.
of mercury, when no air is passing, and will displace as high as 30
cu. ft. of free air per minute, when operated with a free inlet. They
produce about 1 in. of mercury at the carpet renovator when operated
on an ordinary carpet. When small-sized upholstery renovators are
used, a much higher vacuum is possible. When operated with bare floor
renovators or brushes, the quantity of air exhausted is not much over
20 cu. ft. per minute and they make very inefficient bare floor and
wall cleaners, but will do thorough carpet and upholstery cleaning
provided a small enough renovator is used.

Machines using a multi-stage fan will produce a maximum vacuum of
approximately 2 in. of mercury when exhausting no air, and will produce
a vacuum of approximately 1 in. of mercury when operated on an ordinary
carpet. With an unrestricted inlet, they will exhaust from 40 to 50 cu.
ft. of air per minute. When operated on a bare floor, they will exhaust
approximately 30 cu. ft. of free air per minute. They are, therefore,
more efficient floor cleaners than the pumps, but cannot do thorough
carpet and upholstery cleaning, no matter how small the renovator.

The smaller-fan type of machines, in which the fan is placed integral
with the carpet renovator and in which hose is not used in cleaning
floors or carpets, are provided with a single-stage fan. They produce
a suction of not exceeding ¹⁄₂ in. of mercury when no air is exhausted
and will exhaust from 5 to 10 cu. ft. of free air per minute when
operated on a carpet. With a free inlet they will exhaust from 15 to 20
cu. ft. of free air per minute. These machines are little if any better
than ordinary carpet sweepers.

Machines of this type are open to another objection in that the dust
bag is placed on the outlet of the fan and the dust in the bag is
continually agitated by the passage of the air, with the result that
all the finer particles of the dust are blown through the bag back into
the apartment. To be effective, the dust bag must always be placed on
the suction side of the exhauster and should be so arranged that the
dust will not quickly cover the entire area of the bag, for, when
this occurs, the suction is quickly reduced to such an extent that no
further cleaning can be done until the bag has been cleaned.

There is another type of mechanical cleaner manufactured by the Hoover
Suction Sweeper Company which is provided with a mechanically-operated
brush for loosening the dirt from the carpet. The dust is then conveyed
through a single-stage fan to a dust bag. The cleaner does not depend
on the vacuum to loosen the dirt and will do quite effective carpet
cleaning with a small expenditure of power. Owing to the small suction
produced, it is of little value for cleaning anything but carpets.

From the experience the author has had with portable vacuum cleaners,
some thirty makes having been tested for the Treasury Department by
him and by the Bureau of Standards, the use of such cleaners is not
considered as either an efficient or sanitary means of mechanical
cleaning.

If a cleaner requiring small power is required, one of the smaller
stationary plants, costing not over $300.00 and operating with ¹⁄₂ or
³⁄₄ H. P., is considered a better investment than $125.00 paid for a
portable cleaner.

If the purchaser feels that he cannot afford to pay more than $125.00
for his vacuum cleaner, a type such as the Water Witch can be
furnished for this price. This cleaner is placed in the basement, with
arrangements for starting same from any floor. The manufacturers state
that this apparatus produces a vacuum of 2 in. mercury in a carpet
renovator, 4 in. mercury in an upholstery renovator and exhausts 25 to
30 cu. ft. of free air per minute with open hose. The machine operates
by water pressure and the manufacturers state that it requires about
6 to 8 gals. of water per minute. All air is exhausted outside of the
building and all dust washed down the sewer with the exhaust water. It
is therefore, a fairly efficient and sanitary cleaning system.

The statements made above apply to parties who own their residences
and occupy offices in modern buildings. There are, besides these, a
great many who live in rented houses and apartments or occupy offices
in buildings where the owners are not sufficiently progressive to
install stationary cleaning plants. To supply the needs of this class
is evidently the field of the portable cleaner, as even the poorest of
these machines is more effective in the removal of dust and dirt than
the broom and carpet sweeper.

The selection of a portable cleaner by one who must necessarily resort
to the use of such a cleaner should be made with care. The motor should
be looked into and only one which has brushes readily removable and
one in which the condition of the brushes can be easily noted should
be selected. Lubrication is important. A good cleaner should be so
constructed that it can be operated for at least 100 hours without
relubrication.

The dust bag should always be on the suction side of the vacuum
producer and of such a design and construction that at least ¹⁄₂ peck
of a mixture of 40% sand, 30% flour, 15% sweepings and 15% Portland
cement can be picked up from the floor and retained in the bag and the
machine still be capable of picking up material from a bare floor.

A good test for capacity of a portable machine is to pick up ¹⁄₂ peck
of such material, then fit a thin disk with ⁷⁄₈-in. diameter opening
over the end of the hose. A machine, to be of any value, should show
a suction of 3 in. water and a first-class machine will show 8 in.
under these conditions. This will do fairly good bare floor work. To
ascertain if the machine will clean carpets, use a similar disk with
⁵⁄₈-in. diameter opening, when a suction of 7 in. water indicates the
lowest value and 16 in. about the best that can be obtained from any
portable cleaner. Cleaners must be readily portable and should not
weigh exceeding 75 lbs.

Transcriber’s Notes

Inconsistent and unusual spelling have been retained. In several
places the text appears to be incomplete or jumbled; this has not
been corrected. In many of the illustrations reference letters are
given in uppercase whereas the text uses lowercase letters; this has
not been standardised.

Inconsistencies and differences in wording and structure between the
Table of Contents and the text have not been rectified.

Page 83, paragraph starting Much of the hose in use today ...: as
printed in the source document; part of the text may be missing or
mixed up.

Changes made:

Illustrations and tables have been moved outside text paragraphs.

In some illustrations reference letters have been enhanced for the
sake of clarity; in Fig. 61 reference #1 has been added.

Obvious minor typographical and punctuation errors have been
corrected silently. In multiplications, the letter x and the
multiplication symbol (×) have been standardised to the latter.

Page 38, Table 2: F´ changed to F¹ cf. text.

Page 141: O´ changed to O¹ cf. Fig. 77a.

Page 149: ... by using metal shins ... changed to ... by using metal
shims ....

Page 170: ... the control (Fig. 107) ... changed to ... the control
(Fig. 97) ....

Page 205, item 33: ... approved made ... changed to ... approved make
....

*** End of this LibraryBlog Digital Book "Vacuum cleaning systems : A treatise on the principles and practice of mechanical cleaning" ***

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