dust. As a general rule, the engine space should be enclosed. An engine should not be located in a cellar, on a damp floor, or in badly illuminated and ventilated places.
Gas-Pipes.—The pipes by which fuel is conducted to engines, driven by street-gas, and the gas-bags, etc., are rarely altogether free from leakage. For this reason, the engine-room should be as well ventilated as possible in the interest of safety. Long lines of pipe between the meter and the engine should be avoided, for the sake of economy, since the chances for leakage increase with the length of the pipe. It seldom happens that the leakage of a pipe 30 to 50 feet long, supplying a 30 horse-power engine, is much less than 90 cubic feet per hour. The beneficial effect of short supply pipes between meter and engine on the running of the engine is another point to be kept in mind.
An engine should be supplied with gas as cool as possible, which condition is seldom realized if long pipe lines be employed, extending through workshops, the temperature of which is usually higher than that of underground piping. On the other hand, pipes should not be exposed to the freezing temperature of winter, since the frost formed within the pipe, and particularly the crystalline deposition of naphthaline, reduces the cross section and sometimes clogs the passage. Often it happens that water condenses in the pipes; consequently, the piping should be disposed so as to obviate inclines, in which the water can collect in pockets. An accumulation of water is usually manifested by fluctuations
in the flame of the burner. In places where water can collect, a drain-cock should be inserted. In places exposed to frost, a cock or a plug should be provided, so that a liquid can be introduced to dissolve the naphthaline. To insure the perfect operation of the engine, as well as to avoid fluctuations in nearby lights, pipes having a large diameter should preferably be employed. The cross-section should not be less than that of the discharge-pipe of the meter, selected in accordance with the prescriptions of the following table:
GAS-METERS.
| Capacity. | Normal hourly flow. | Height, inches. | Width, inches. | Depth, inches. | Diameter of pipe, inches. | Power of engine to be fed. |
| burners | cu. ft. | in. | in. | in. | in. | h.-p. |
| 3 | 14.726 | 13 | 11 | 913⁄16 | 0.590 | 1⁄2 |
| 5 | 24.710 | 18 | 133⁄4 | 105⁄8 | 0.787 | 3⁄4 |
| 10 | 49.420 | 211⁄4 | 181⁄2 | 129⁄16 | 0.984 | 1-2 |
| 20 | 98.840 | 233⁄16 | 1911⁄16 | 155⁄16 | 1.181 | 3-4 |
| 30 | 148.260 | 255⁄8 | 2111⁄16 | 183⁄16 | 1.456 | 5-6 |
| 50 | 247.100 | 291⁄2 | 245⁄16 | 207⁄16 | 1.592 | 7-10 |
| 60 | 296.520 | 305⁄16 | 255⁄8 | 255⁄8 | 1.671 | 11-14 |
| 80 | 395.360 | 335⁄16 | 305⁄16 | 271⁄8 | 1.968 | 15-19 |
| 100 | 494.200 | 35 | 337⁄16 | 2915⁄16 | 1.968 | 20-25 |
| 150 | 741.300 | 403⁄16 | 403⁄16 | 3313⁄16 | — | 30-40 |
The records made are exact only when the meters (Fig. 40) are installed and operated under normal conditions. Two chief causes tend to falsify the measurements in wet meters: (1) evaporation of the water, (2) the failure to have the meter level.
Evaporation occurs incessantly, owing to the flowing of the gas through the apparatus, and increases with a rise in the temperature of the atmosphere surrounding the meter. Consequently this temperature must be kept
down, for which reason the meter should be placed as near the ground as possible. The evaporation also increases with the volume of gas delivered. Hence the meter should not supply more than the volume for which it was intended. In order to facilitate the return of the water of condensation to the meter and to prevent its accumulation, the pipes should be inclined as far as possible toward the meter. The lowering of the water-level in the meter benefits the consumer at the expense of the gas company.
