Bendix Commercial Vehicle Systems SR-1 SPRING BRAKE VALVE - Manual (Page 6)

6
OPERATION - PARKING
If both systems #1 and #2 are intact and the park control
valve is placed in the “park” or exhaust position, the Bendix
®
SR-1 ™ valve supply of air pressure and the air pressure in
the spring brake actuator cavities is exhausted. The single
check valve in the SR-1 valve assists this exhaust of air
pressure by allowing the air below piston B to fl ow back
out the open exhaust of the park control valve. When air
pressure below piston B has dropped suffi ciently, piston
B moves down, opening the inlet of valve B and providing
an additional exhaust passage for air exhausting through
the SR-1 valve from the spring brakes.
PREVENTIVE MAINTENANCE
Important: Review the Bendix Warranty Policy before
performing any intrusive maintenance procedures. A
warranty may be voided if intrusive maintenance is
performed during the warranty period.
No two vehicles operate under identical conditions, as
a result, maintenance intervals may vary. Experience is
a valuable guide in determining the best maintenance
interval for air brake system components. At a minimum,
the SR-1 valve should be inspected every 6 months or
1500 operating hours, whichever comes fi rst, for proper
operation. Should the SR-1 valve not meet the elements
of the operational tests noted in this document, further
investigation and service of the valve may be required.
SERVICE CHECKS
OPERATING CHECKS
Block all wheels and hold by means other than vehicle
brakes. Charge air brake system to governor cut-out
pressure.
1. Place parking control valve in the “park” position.
Observe that the spring brake actuators apply promptly.
In the delivery port of the valve install a test gauge
known to be accurate. Place the parking control valve
in the “release” position. Observe that the spring brake
actuators release fully.
2. With the parking control valve in the “release” position,
note the gauge pressure reading. (Check the vehicle
manual for the correct spring brake actuator hold-off
pressure.) If the pressure reading is incorrect, the valve
must be repaired or replaced.
3. Place the parking control valve in the “park” position,
the gauge reading should drop to zero promptly. A slow
release of pressure may indicate faulty operation of the
single check valve (within the modulating valve.)
4. Place the parking control valve in the “release” position.
Locate the number one service reservoir and drain it
completely.
Apply the foot brake valve several times and note that
the pressure reading on the gauge decreases each
time the foot brake valve is applied. After several
applications, pressure on the gauge will drop to the
point where release of the spring brake actuators will
no longer occur.
FIGURE 10 - PARK APPLICATION
#2 SERVICE
RESERVOIR
#1 SERVICE
RESERVOIR DOUBLE
CHECK
VALVE
PISTON B
CHECK VALVE
INLET &
EXHAUST A
PISTON A
INLET
&
EXHAUST
B
EXHAUST
SPRING
BRAKE
R-14 ®
RELAY
VALVE
PARK
CONTROL
VALVE