Bendix SR-5 TRAILER SPRING BRK VALVE User Manual
®
Bendix® SR-5™ Trailer Spring Brake Valve
PRESSURE
PROTECTION
VALVE
SR-5™ VALVE
IDENTIFICATION
HOLE
COVER*
SD-03-4516
1/4” NPT
SERVICE
RESERVOIR
(2)
1/4” NPT
TRAILER SUPPLY
1/4” NPT TRAILER
SERVICE
FIGURE 1 SR-5™ TRAILER SPRING BRAKE V AL VE
*SHOWN WITH OPTIONAL ANTI-COMPOUNDING COVER
DESCRIPTION
The 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.
1/2” OR 3/4” NPT
SPRING BRAKE
RESERVOIR
3/8” NPT
DELIVERY (4)
EXHAUST
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 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 flat 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
SERVICE
RELAY
VALVE
TRAILER SUPPLY
ONE-TANK SYSTEM
FIGURE 2 TYPICAL SYSTEM SCHEMA TICS WITH SR-5™ TRAILER SPRING BRAKE VA L VE
SR-5
VALVE
™
2
TRAILER SERVICE RES.
CHECK
VALVE
B
TRAILER SERVICE
CHECK
VALVE
D
PASSAGE A
SERVICE
RELAY
VALVE
FIGURE 3 CHARGING BELOW 70 PSI
SERVICE/SPRING
BRAKE RESERVOIR
CONNECTION
OPERATION
CHARGING BELOW 70 PSI (SEE FIGURE 3)
Air flows through the trailer supply line, enters the 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 flows through passage A,
unseating check valve B, and flowing past the open control
TRAILER SUPPLY
CONTROL PISTON
DELIVERY
SPRING
BRAKE
CHAMBER
EXHAUST
inlet valve. This air flows into the spring brake cavities,
releasing the spring brakes.
™
CHARGING ABOVE 85 PSI (SEE FIGURE 4)
Air pressure acting on the control piston and flowing through
passage A also acts on pressure protection valve C. At
approximately 85 psi, valve C opens. This allows the air to
flow 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.
SERVICE
RELAY
VALVE
FIGURE 4 CHARGING ABOVE 85 PSI
TRAILER SERVICE RES.
CHECK
VALVE B
SERVICE/SPRING
BRAKE
RESERVOIR
CONNECTION
CHECK
VALVE D
DELIVERY
SPRING
BRAKE
CHAMBER
TRAILER SERVICE
PRESSURE
PROTECTION
VALVE C
PASSAGE A
CONTROL PISTON
EXHAUST
3
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