Bendix Commercial Vehicle Systems SR-7 User Manual
Bendix® SR-7® Spring Brake Modulating Valve
MOUNTING
STUDS (2)
4-1
PARK CONTROL
(FROM DASH VALVE)
42
CONTROL
PORT
EXHAUST
2
DELIVERY
1
SUPPLY PORT
3
EXHAUST
SD-03-9043
41
BALANCE
PORT
2
DELIVERY
PIPE PLUG
(INCLUDED IN QUICK
RELEASE VALVE
APPLICATIONS)
FIGURE 1 - EXTERIOR VIEW
DESCRIPTION
The Bendix® SR-7® spring brake modulating valve is used
in conjunction with a dual air brake system and spring brake
actuator and performs the following functions:
1. Provides a rapid application of the spring brake actuator
when parking.
2. Modulates the spring brake actuator application using
the dual brake valve should a primary failure occur in
the service brake system.
3. Prevents compounding of service and spring forces.
The valve has one park control, one service control, one
supply, one balance, four delivery NPTF ports, and an
exhaust port protected by an exhaust diaphragm. The
valve incorporates two mounting studs for mounting the
valve to the frame rail or cross member (where applicable).
1
MAIN PISTON
DOUBLE CHECK VALVE
CHECK VALVE
COVER
PARK CONTROL
PORT
IN-LINE SINGLE CHECK
VALVE
SPRING
O-RING
SUPPLY PORT
CHECK VALVE
GUIDE
O-RING
O-RING
CONTROL PISTON
SPRING GUIDE
UPPER BODY
RETAINING RING
O-RING
O-RING
SPACER
MAIN PISTON SPRING
STATIC PISTON
O-RING
O-RING
STATIC PISTON
SPRING
O-RING
O-RING
O-RING
LOWER BODY
BALL CHECK
VALVE
SPRING
FIGURE 2 - SECTIONAL VIEW OF SR-7® SPRING BRAKE MODULATING VALVE USED IN RELAY VALVE APPLICATIONS
O-RING
O-RING
VALVE SEAT
RETAINING RING
DIAPHRAGM
DIAPHRAGM WASHER
EXHAUST
PORT
#10 TORX HEAD SCREW
VALVE RETAINER
SPRING
1/4-20 MACHINE
SCREWS
INLET / EXHAUST
VALVE
LOWER VALVE GUIDE
RETAINING RING
OPERATION
The operation guidelines shown in this manual represent
the relay valve based Bendix® SR-7® (refer to system
schematic shown in fi gure 3). A quick release based valve
functions similarly to the relay valve based version with
the exception that all air delivered to spring brakes passes
through the park control port through the in-line single
®
check valve. The SR-7
quick release style can be easily
identifi ed by the pipe plug in the supply port of the valve.
2
PP-DC
VALV E
®
SYSTEM FOR A 4X2 OR 6X4
STRAIGHT TRUCK WITH
PP-DC PARKING CONTROL
®
R-12® Relay Valve
®
SR-7
valve w/
single check valve
Ref: 5010914
FIGURE 3 - SYSTEM SCHEMATIC WITH PP-DC® PARK CONTROL
®
PP-1
VALV E
SYSTEM FOR A 4X2 OR 6X4
STRAIGHT TRUCK WITH
®
PP-1 PARKING CONTROL
SR-7
R-12
®
Relay Valve
single check valve
®
valve w/ out
FIGURE 4 - SYSTEM SCHEMATIC WITH PP-1
®
DC-4
VALVE
®
PARK CONTROL AND DC-4® DOUBLE CHECK VALVE
3
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