226
Air System
Figure 6-31, R-12DC Operation
Relay Valve (Bendix R-2DC)
The brake relay valve (Figure 6-30) receives air from the brake treadle valve and sends air (at the same
pressure and higher volume) to the rear service brake chambers. This speeds up the application and
release of the brakes.
Figure 6-30, R-12DC Brake Relay Valve
Operation
Application
Refer to Figure 6-31. Under normal conditions, the internal biased double check valve ensures that the
primary service signal controls the valve. Air pressure delivered to the primary service port enters the
small cavity above the piston and moves it down. The exhaust seat moves down with the piston and
seats on the inner or exhaust portion of the inlet/exhaust valve, sealing off the exhaust passage. At the
same time, the outer or inlet portion of the inlet/exhaust valve moves off its seat, permitting supply air
to flow from the res
-
ervoir, past the open
inlet valve, and into the
service brake cham-
bers. In the event of
a loss of air pressure
in the primary service
line, the double check
valve mechanism in the
cover of the R-12DC
will move, shutting
off the primary service
line, and instead allow
the secondary service
line to apply the air
pressure needed to
operate the valve.
Summary of Contents for LOW FLOOR
Page 18: ...Specifications 18...
Page 58: ...Preventive Maintenance 58...
Page 110: ...Engine 110...
Page 138: ...Transmission Driveline Rear Axle 138...
Page 182: ...Suspension 182...
Page 260: ...Air System 260...
Page 420: ...Electrical System 420 Deutsch DT Series Connectors...
Page 421: ...Electrical System 421...
Page 422: ...Electrical System 422 Deutsch HD 10 Series Connectors...
Page 423: ...Electrical System 423...
Page 424: ...Electrical System 424 Deutsch HD 30 Series Connectors...
Page 425: ...Electrical System 425...
Page 442: ...Heating Air Conditioning 442...
Page 492: ...Body and Interior 492 Figure 11 33 USSC Seat Assembly...
Page 493: ...Body and Interior 493 Figure 11 34 USSC Seat Suspension Assembly...
Page 495: ...Body and Interior 495 Figure 11 37 Seat Air Connections...