| Section of Pipe. | Cubic Ft. Free Air per min. | Equivalent Length, feet. | Size of Pipe, In. Diam. | Average Vacuum, Ins. Mercury. | Friction Loss, Ins. Mercury. | Final Vacuum, Ins. Mercury. | |
|---|---|---|---|---|---|---|---|
| x—5 | 60 | 150 | 2 | ¹⁄₂ | 6 | 0.35 | 6.35 |
| 5—4 | 120 | 140 | 2 | ¹⁄₂ | 7 | 1.35 | 7.70 |
| 4—2 | 180 | 280 | 2 | ¹⁄₂ | 11 | 7.0 | 14.70 |
| 2—w | 180 | 190 | 3 | 16 | 4.0 | 18.70 | |
| w—u | 360 | 20 | 5 | 19 | 0.9 | 19.60 | |
| u—s | 480 | 20 | 6 | 20 | 0.5 | 20.10 | |
| s—sep | 600 | 20 | 6 | 20 | 0.4 | 20.50 | |
This loss will be the maximum that is possible under any condition as it is computed with three sweepers working on the three most remote inlets on laterals “xy” and “vw” and with two sweepers on laterals “tu” and “rs.” The pipes are the largest which will give a velocity of 40 ft. per second with the full load and at the density which will actually exist in the pipe lines with the vacuum maintained at the separator of 20 in. mercury in all cases, except the pipe from “s” to separator. There the size was maintained at 6 in., as it was not considered advisable to increase this on account of the reduced velocity which would occur when less than the total number of sweepers might be working.
As bare floor brushes will be used for cleaning coaches it is not considered advisable to reduce the air quantity below that required by such renovators. However, when carpet renovators are used in Pullman cars and upholstery renovators are used on the cushions of both coaches and Pullmans, the air quantity will be reduced. This condition may exist at any time, also one of these carpet or upholstery renovators may be in use on one of the inlets most remote from the separator at the same time that nine floor brushes are in use on the remaining outlets. In that case a vacuum at the separator of less than 20 in. would result in a decrease in the vacuum at the inlet to which this renovator was attached. The vacuum at the separator must, therefore, be maintained at the point stated.
With such a vacuum there will be variation in the vacuum at the hose cocks of from 6 in. to 20 in. or seven times the maximum allowable variation in vacuum at the hose cocks.
If 1-in. hose be used, the maximum air quantities will be 40 cu. ft. per sweeper. If we start with a vacuum at the inlet “x” of 10-in. mercury, the vacuum at the separator will again be 20 in. and we now have a variation of 10 in. between the nearest and most remote inlet from the separator, or five times the maximum allowed.
Either of these conditions is practically prohibitive, due to:
1. The excessive power consumption at the separator. 50 H. P. in case 1¹⁄₄-in. hose is used, and 33 H. P. in case 1-in. hose is used.
2. The excessive capacity of the exhauster in order to handle the air at such low density, a displacement of 1,800 cu. ft. being necessary in case 1¹⁄₄-in. hose is used and 1,200 cu. ft. in case 1-in hose is used.
3. The great variation in the vacuum at the hose cocks which will admit the passage of so much more air through a brush renovator on an outlet close to the separator as to render useless the calculations already made, or the high vacuum at the carpet or upholstery renovators would render their operation practically impossible.
