CHAPTER XIII.
Tests.
Having decided on the type of vacuum cleaning system that is best suited to the conditions of the particular building in which it is to be installed, it then becomes necessary to ascertain what are the tests necessary to determine whether the installation will produce the desired results.
If the installation is one in which carpet cleaning is important and the plant is of more than one-sweeper capacity, the exhauster must be of sufficient capacity to produce a vacuum of not less than 4 in. mercury at a carpet renovator attached to any inlet on the piping system, when the plant is operating other renovators of any type attached to any of the other inlets corresponding to one less than the total sweeper capacity of the system.
When hose lengths as short as 25 ft. can be used on any or all of the outlets, it has been demonstrated in [Chapter VII] that an air removal of 70 cu. ft. of free air per minute for each sweeper of plant capacity is necessary, no matter what size of hose is used. It was also shown that where pipe lines are very long and it is possible to always use 100 ft. of hose, efficient cleaning can be done with less expenditure of power with an air displacement of 45 cu. ft. of free air for each sweeper of plant capacity.
Many methods have been recommended for testing a cleaning plant. Perhaps the earliest was the maintaining of 15 in. of vacuum at the vacuum producer with carpet renovators each attached to 100 ft. of hose, equal in number to the sweeper capacity of the plant in operation on carpets. Another test is to attach 100-ft. lengths of hose to inlets on the system, with the ends wide open, equal in number to the sweeper capacity of the plant, and require the pump to maintain a vacuum of 15 in. mercury.
Both of these tests were recommended for use on plants where 1-in. diameter hose was provided and the results are dependent largely on the size and length of the piping system. With an average-sized system, the first test will require an exhaustion of approximately 25 cu. ft. of free air per renovator per minute if Type A renovators are used. The second test wall require an exhaustion of approximately 50 cu. ft. of free air per open hose per minute. Neither of these tests will insure a plant of sufficient capacity to do effective cleaning where 25-ft. lengths of 1-in. hose can be used or if larger bore than 1-in. hose be used.
If these tests are required with bores larger than 1-in. diameter and the vacuum is maintained the same as before, air exhaustion with 1¹⁄₄-in. open hose will be approximately 70 cu. ft. of free air per open hose, and with 1¹⁄₂-in. hose, approximately 150 cu. ft. per open hose, while, if carpet renovators be used, the vacuum at the renovator would be from 7 to 9 in. of mercury. In either case, the vacuum required to be maintained at the separators is higher than is necessary to produce economical cleaning with either 1¹⁄₄-in. or 1¹⁄₂-in. hose.
Tests with carpet renovators attached to 100 ft. hose lines in number equal to the capacity of the plant, and a vacuum of 4¹⁄₂ in. of mercury at the renovator will result in an exhaustion below that necessary to produce efficient cleaning when bare floor renovators and carpet renovators with shorter hose lines are used, as is likely to occur in actual practice.
Again, open hose tests require a variable length of hose to be used in order to obtain the same air quantity with the proper vacuum at the separator for economical operation.
If 70 cu. ft. of air is desired, as in the case of Class 2 plant ([Chapter XII]), the hose lengths should be: