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.