4-12. INDEPENDENT BRAKE VALVE (cont)
(c) Pressure developed in port 20 will actuate the relay valve to develop pressure in the brake cylinders. As
air pressure develops in port 20, it also develops on the inner face of the diaphragm in the independent
(d) The buildup of pressure on the diaphragm is opposed by spring pressure on the opposite side; and when
the air pressure and spring become balanced, the valve assembly will move to its lap position in which
the supply valve becomes seated to terminate further flow of main reservoir air to port 20.
(3) Pressing the independent brake handle when the handle is in RELEASE position willcause release of any
automatic brake application existing on the locomotive. The valve functions as follows:
(a) Main reservoir air will flow into port 13 which, in turn, is connected to port 10 of the H-5 relay air valve.
(b) When air pressure in port 10 exceeds the strength of the valve return spring, port 11 is connected to 9
(c) Air in application chamber port 2A is exhausted through port 2 at H-5 relay air valve port 9.
(d) Air in the brake cylinder will, in turn, be vented at the 6-NFR distributing valve BC exhaust.
(e) Pressing of the independent brake handle with it somewhere in the application zone will release the
automatic application only to the value corresponding to the position of the handle in the application