227
Air System
Secondary service line may leak out of the primary service at control
pressures up to 20 psi when the primary signal is not present.
balance
Refer to Figure 6-32. The air pressure delivered by the
open inlet valve is also effective on the bottom area of the
relay piston. When air pressure beneath the piston equals
the service air pressure above, the piston lifts slightly and
the inlet spring returns the inlet valve to its seat. The ex-
haust remains closed as the service line pressure balances
the delivery pressure. As delivered air pressure is changed,
the valve reacts instantly to that change, holding the brake
application at that level.
exhaust or release
See Figure 6-
33. When air pressure is released from the
service port and air pressure in the cavity above the relay
piston is exhausted through the brake valve. At the same
time, air pressure beneath the piston lifts the relay piston
and the exhaust seat moves away from the exhaust valve,
opening the exhaust passage. With the exhaust passage
open, the air pressure in the brake chambers is then per-
mitted to exhaust through the exhaust port, releasing the
brakes.
Figure 6-32, R-12DC Balance Position
Figure 6-33, R-12DC Exhaust Position
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...