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.
| Size of Hose, In. Diameter. | Length, in Feet. | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| 100 | 75 | 50 | 25 | ||||||
| Vacuum at hose cock, in. hg. | |||||||||
| 1 | 19 | 14 | 10 | 6 | .7 | ||||
| 1 | ¹⁄₄ | 7 | .5 | 6 | .25 | 5 | .5 | 4 | .7 |
| 1 | ¹⁄₂ | 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.