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.