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This should be done whenever the safety valve is taken off for adjustment, but the cleaning should not be delayed on that account. Situated where the distributing valve usually is, a great deal of gritty dust enters the safety valve through the small holes and, finding its way in between the periphery of the valve and the valve bush, becomes ground in and causes the valve to stick, or act irregularly.
The final test for pressure adjustment should be made with cap
screwed down tight against the safetyvalve body as, with the cap removed, when the valve lifts from its seat it can rise so high as to close the lower ports from the valve chamber to the atmosphere, as well as the vertical ports through the bush; in which case the only discharge of pressure will be that which can leak around the sides of the valve.
ENGINEER'S BRAKE-VALVES OF THE
NO. 6 E-T EQUIPMENT.
THE H-6 AUTOMATIC BRAKE-VALVE.
Fig. 21 is a photographic view of the H-6 AUTOMATIC BRAKE-VALVE with pipe bracket, complete, and Fig. 22 shows the same valve separated from its pipe bracket; for, like all of the other most important valves of the E-T equipment, the brake-valve proper can be removed for inspection or repair without disturbing any of the pipe joints. Fig. 23 shows two views of the brake-valve, with the addition of a plan, or transparent top view, of the rotary valve; the upper view of the brake-valve is taken from the top, on a section through the rotaryvalve chamber, the rotary valve being removed; the lower one is a vertical section. In these views the pipe connections are indicated. Fig. 24 is a top view of the brake-valve, charting the different positions of the operating handle.
Referring to Fig. 24 and beginning at the left, we have Release Position; use of this position should only be made when the brake-pipe pressure has been reduced below the normal charge, and it is desired to release the train brakes; it has the effect of connecting the main reservoir directly with the brake pipe, and after it is believed that the brake-pipe pressure has been
increased sufficiently to release all car brakes the handle must be moved to the second position, and it should never be left in release position long enough for the brake pipe to charge above the normal pressure
usually 70 pounds. The locomotive brake, however, will not be released by the recharge of the brake pipe.
In the second, or Running, Position the locomotive brake will be released and held so, and this is its normal carrying position; the direct connection from main
reservoir to brake pipe is now cut off, and air is supplied to the brake pipe from the 70-pound, feed-valve pipe.
In the third, or Holding, Position the 70-pound
Fig. 22.—H-6 Automatic Brake-Valve. Removed from its pipe
pressure supply to the brake pipe is continued; it is, in effect, another running position, except that the release ports of distributing-valve and locomotive-brake cylinder pressures are closed. In returning the brake
Fig. 24.-Positions of Automatic Brake-Valve Handle.
valve from release position it is a good plan always to go quickly to holding position, direct; this permits time for the afterthought as to whether it is best to