BENDIX SD-03-4516 User Manual
Bendix® SR-5™ Trailer Spring Brake Valve
PRESSURE
PROTECTION
VALVE
™
VALVE
SR-5
IDENTIFICATION
HOLE
COVER*
1/4” NPT TRAILER
SUPPLY
1/4” NPT TRAILER
SERVICE
FIGURE 1 - BENDIX
®
SR-5™ TRAILER SPRING BRAKE VALVE (*SHOWN WITH OPTIONAL ANTI-COMPOUNDING COVER)
3/8” NPT
DELIVERY (4)
EXHAUST
SD-03-4516
1/4” NPT
SERVICE
RESERVOIR
(2)
1/2” OR 3/4” NPT
SPRING BRAKE
RESERVOIR
DESCRIPTION
The Bendix® SR-5™ valve is a reservoir-mounted trailer
valve that can control up to four spring brake actuators
during parking or emergency applications. It has the
following capabilities:
• Automatically applies trailer spring brakes in the event
of a breakaway or trailer supply line failure.
• Protects trailer reservoir(s) air pressure in the event of
a breakaway or trailer supply line failure.
• Allows no automatic trailer spring brake application
with air pressure loss in trailer reservoir(s).
• Allows the trailer spring brakes to be applied and released
repeatedly with a failed trailer reservoir(s):
• Optional anti-compounding-prevents an overriding
service brake signal while the trailer supply line is at
atmospheric pressure.
• Does not allow service system charging if a failure occurs
in the parking brake circuit.
PORTS
1 - 1/2" or 3/4" NPT Spring Brake Reservoir Mounting
(SPR BK RES)
1 - 1/4"-18 NPT Trailer Supply (TRL SUP)
1 - 1/4"-18 NPT Trailer Service (TRL SER)
4 - 3/8"-18 NPT Delivery (DEL)
2 - 1/4"-18 Service Reservoir (SERV RES)
1 - Exhaust (EXH)
The SR-5™ valve appears very similar to the Bendix® SR-2™
valve. Both valves consist of a die-cast aluminum body and
cover, pressure protection valve, and reservoir-mounting
nipple. However, Figure 1 notes the distinguishing
characteristic of the SR-5™ valve–a hole drilled into the
fl at surface between the pressure protection valve and
the body.
1
TRAILER SERVICE
SERVICE/SPRING BRAKE
RESERVOIR
TRAILER SUPPLY
SERVICE
RELAY
VALVE
TWO-TANK SYSTEM
SERVICE/
SPRING BRAKE
RESERVOIR
™
SR-5
VALVE
TRAILER SERVICE
™
SERVICE/SPRING BRAKE
RESERVOIR
SR-5
VALVE
SERVICE
RELAY
VALVE
TRAILER SUPPLY
ONE-TANK SYSTEM
FIGURE 2 - TYPICAL SYSTEM SCHEMATICS WITH BENDIX® SR-5™ TRAILER SPRING BRAKE VALVE
2
SERVICE
SPRING BRAKE
RELAY
VALVE
FIGURE 3 - CHARGING BELOW 70 PSI
TRAILER SERVICE RES.
CHECK
VALVE
B
SERVICE/
RESERVOIR
CONNECTION
CHECK
VALVE
D
DELIVERY
SPRING
BRAKE
CHAMBER
TRAILER SERVICE
PASSAGE A
TRAILER SUPPLY
CONTROL PISTON
EXHAUST
OPERATION
CHARGING BELOW 70 PSI (SEE FIGURE 3)
Air fl ows through the trailer supply line, enters the Bendix
SR-5™ valve trailer supply port, and moves the control
piston. The control piston contacts the control inlet/exhaust
valve, sealing off the piston’s exhaust passage.
As piston travel continues, the control inlet valve opens. Air
acting on the control piston also fl ows through passage A,
unseating check valve B, and fl owing past the open control
TRAILER SERVICE RES.
CHECK
VALVE B
SERVICE/
SPRING BRAKE
SERVICE
RELAY
VALVE
RESERVOIR
CONNECTION
®
inlet valve. This air fl ows into the spring brake cavities,
releasing the spring brakes.
CHARGING ABOVE 85 PSI (SEE FIGURE 4)
Air pressure acting on the control piston and fl owing
through passage A also acts on pressure protection valve
C. At approximately 85 psi, valve C opens. This allows
the air to fl ow past check valve D and charge the trailer
reservoir(s). The trailer braking system is now in the normal
run mode. Service braking occurs through the trailer
service relay valve.
TRAILER SERVICE
CHECK
VALVE D
PRESSURE
PROTECTION
VALVE C
PASSAGE A
FIGURE 4 - CHARGING ABOVE 85 PSI
DELIVERY
SPRING
BRAKE
CHAMBER
EXHAUST
CONTROL PISTON
3
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