86.  Q. What is the purpose of running position, and when should it be used?

A. This is the proper position for the brake valve when the brakes are charged and not in use, also when it is desired to release the locomotive brake with this valve.  In this position the brake pipe pressure is maintained at a predetermined amount by the feed valve, as all air that now enters the brake pipe must pass through the feed valve.

87.  Q. What is the purpose of holding position?

A. To hold the locomotive brake applied while recharging the brakes.  The charging of the brake pipe and equalizing reservoir is the same in holding as in running position.

88.  Q. What is the purpose of lap position?

A. To hold both the locomotive and train brakes applied after an automatic application.

89.  Q. What is the purpose of service position?

A. This position of the brake valve enables the engineer to make a gradual reduction of brake pipe pressure, thus causing a service application of the brakes.

90.  Q. What is the purpose of emergency position?

A. In this position of the brake valve, the brake pipe is connected directly with the atmosphere through the large ports in the valve, causing a sudden reduction of brake pipe pressure, this in turn causing the distributing valve on the engine and all operating triple valves on cars in the train to move to emergency position, thus insuring a quick and full application of the brake.

91.  Q. How should the brake valve be handled when making an emergency application of the brake?

A. The valve should be placed in full emergency position and left there until the train stops, even though the danger may have disappeared.

DEFECTS OF THE BRAKE VALVE

92.  Q. What will cause a constant blow at the brake pipe exhaust port, and what may be done to overcome it?

A. This indicates that the brake pipe exhaust valve is being held off its seat, due no doubt to dirt; tapping the side of the valve will sometimes stop the blow; if not, close the brake pipe cut-out cock and make a heavy service reduction; next, place the brake valve handle in release position.  This will cause a strong blow at the exhaust port, which will invariably remove the trouble.

93.  Q. If the pipe connecting the brake valve with the equalizing reservoir breaks, can both locomotive and train brakes be operated with the automatic brake valve?

A. Yes; by placing a blind gasket in the pipe connection at the brake valve and plugging the brake pipe exhaust port.  To apply the brake, move the handle carefully toward emergency position, making a gradual reduction of brake pipe pressure through the direct exhaust ports of the brake valve; when the desired reduction is made, the handle should be moved gradually back to lap position.

94.  Q. What would be the effect if the handle were moved to lap quickly?