The brake system is pneumatically controlled and
cab), the service brake relay valves (one for each
can be operated from either cab. The components
axle), park brake relay valve, spring brake control
which make up the brake system include the brake
valve, brake chambers, and service brakes.
valves and park brake valves (one of each for each
THEORY OF OPERATION
Each wheel end has a spring powered brake
will release, applying the brakes.
chamber. This chamber is spring actuated and must
be released by air pressure. The spring brakes
The service brakes are applied by air pressure.
(parking brakes) are released by the parking brake
Depressing the foot brake pedal on the cab floor
push-pull knob in the cabs. Pushing down on the
causes pressurized air to enter the service brake
parking brake causes air pressure to enter the spring
chamber on each wheel, applying the brakes. In the
brake chamber on each wheel and compress the
event of a loss of supply pressure to the service
spring, releasing the brakes.
brakes, the spring brake valve will allow the operator
to release or bleed off the air pressure in the spring
At least 40 psi (275.8 kPa) is required to keep the
brake chamber by depressing the foot brake pedal to
parking brake valve engaged. If supply pressure to
apply the brakes.
the valve drops below 40 psi (275.8 kPa), the valve