4-13. 6-NFR DISTRIBUTING VALVE (cont)
During an emergency application, the 6-NFR distributing valve functions in the same manner as during a
service application, with the addition of the following:
Main reservoir is connected to port 12 via the brake valve emergency valve.
From port 12, main reservoir air flows
through check valve and choke fitting to passage 2, past
equalizing piston, to the outer face of the application piston via passages 2 and 2b, 24-A double check
valve, and passage 2a.
Main reservoir pressure will increase to the value of the safety valve setting, where it is maintained by
the safety valve control choke and blowdown of the safety valve.
Should the brake valve handle be moved out of EMERGENCY position, control pressure in passage 2
is prevented from escaping from vent pipe No. 12 by a check valve. The pipe 12 choke ensures a
positive brake release when an emergency brake application is bailed off.
During the independent brake application, air pressure from passage 20 of the 26-C brake valve flows
directly to the outer face of the application piston via 24-A double check valve and passage 2a.