The proper hose sizes, therefore, will be: For ordinary buildings where carpet cleaning is important, 1¹⁄₄-in. diameter. For installations with unusually long lines of piping, where carpet cleaning is important, 1-in. diameter.
For all systems where carpet cleaning is of secondary importance, 1¹⁄₂-in. or 1-³⁄₄-in. diameter.
Pipe Lines.
—Pipe lines should always be as large as possible without reducing the velocity in same below 40 ft. per second, as explained in [Chapter VII].
Separators.
—The type of separator to be used is dependent on the type of vacuum producer adopted. Where reciprocating exhausters are used, or other type of exhauster where there is rubbing contact between the moving parts and the dust, the combination of a wet and dry separator is recommended. When rotary or centrifugal exhausters having close clearances are used, total separators with bags are recommended. When exhausters with large clearances are operated, partial separators are satisfactory.
The use of any form of apparatus contemplating the adoption of a satisfactory scrubbing system is not considered advisable, as the author believes that separators for handling water will be improved before scrubbing becomes commercially successful. Changes in the existing separators can be made when satisfactory scrubbing appliances are placed on the market, at no greater expense than would be necessary to bring up to date any of the present systems for handling water.
Vacuum Producers.
—The selection of the vacuum producer is dependent on the degree of vacuum that must be maintained to effectively operate the system selected. For the operation of a system where carpet cleaning is the principal function and 1¹⁄₄-in. hose is used, the vacuum required at the producer will be from 6 in. to 9 in. mercury. Inspection of the efficiency curves of the various types of vacuum producers, given in [Chapter IX], shows that the two-impeller rotary pump has the highest efficiency at this vacuum.
For the operation of systems where carpet cleaning is the most important function and 1-in. hose is found to be the most economical, 14 in. to 15 in. of vacuum at the vacuum producer is necessary, and efficiency curves, given in [Chapter IX], show that the piston pump is the best suited for such service.