Handle Positions release the locomotive brake at once, or to hold it on and so keep the head end from surging ahead until the rear brakes of the train have had ample tine to fully release; the latter results will be attained by keeping the brake-valve in the holding position for a few moments, and meanwhile the brake pipe, the car auxiliary reservoirs, and the pressure chamber of the locomotive distributing-valve are receiving the normal pressurerecharge. When it is desired, the brake-valve handle can be moved back to running position and the locomotive brake will release. In the fourth, or Lap, Position all separable connections in the brake-valve are blanked; this is a negative position, and is to be taken after a graduated, or service, reduction of brake-pipe pressure has been made, to hold the brake conditions in a fixed state; pressure is no longer being supplied to the brake pipe, and there is no further reduction of the latter, except from leakage. Service Application is the fifth position; feed of air to the brake pipe is still cut off, and the brake-pipe pressure is being reduced through the equalizing-discharge valve of the brake-valve, but so gradually that the sensitive quick-action triple valves on the cars, and the distributing valve on the locomotive, will apply their respective brakes with a degree of force commensurate with the amount of reduction, yet not permit emergency action. When the desired reduction has been made as indicated by the black hand of the large duplex gauge-the handle is to be returned to the lap position. If the quickest and most powerful action of the brakes is desired, the brake-valve handle should be turned to Emergency Application, which is the sixth and last position to the right on the brake-valve; there is no supply of air to the brake pipe, and the pressure of the latter is discharged through a very large port in the brake-valve, causing such a quick and heavy reduction as to throw all triple valves and the distributing valve into emergency action; the brakes of a train of any length will apply at emergency much quicker than the slack can be run in solid from the rear end. In the E-T equipment the brake-valve has been simplified in its functions over the brake-valve of the common, automatic system in which the feed valve was an integral part. In the H-6 brake-valve there are but two operative parts to study: the rotary valve that is operated by the brake-valve handle, the duty of which is to distribute the pressures that flow through the brakevalve; and the equalizing-discharge valve that automatically measures the discharge of brake-pipe pressure during a service application. An understanding of the operation of these two parts will give the air-brake student the knowledge that is necessary in regard to Westinghouse brake-valves of all types-if we add an Details of H-6 Brake-Valve explanation of the brake-pipe feed-valve, which will follow later. Referring to Fig. 23, lower view: in this vertical, sectional cut, main-reservoir pressure is shown entering the lower piece of the brake-valve body termed the PIPE BRACKET, 5; the pipe connection referred to can be made from either the side or the bottom, the unused opening plugged; the supporting stud (No. 25, upper view) is in this lower piece, making it a permanent attachment to the boiler or other rigid base; and as the other three parts that form the body of the brake-valve are bolted together independently of the pipe bracket, the brake-valve proper may be removed without the disconnection of pipe joints, as the latter are all made to the pipe bracket direct. This necessitates a number of ports through the sections of the brake-valve body, and the intermediate gaskets; thus the main-reservoir pressure is shown passing up through each and filling the TOP CASE, 4, in which the pressure covers the ROTARY VALVE, 6, In this plate the brake-valve is represented with the rotary valve in running position, in which the mainreservoir pressure goes no further than the top and sides of the rotary valve, except through a small port in the rotary valve and seat to the pipe connection, as shown in the upper view, leading to the excess-pressure governor top. |