Bendix® SRC-7000™ Trailer Spring Brake Valve
1/4” NPT
CONTROL
1/4” NPT
SUPPLY
1/2” NPT
SPRING BRAKE
RESERVOIR
EXHAUST
3/8” NPT
DELIVERY (4)
SD-03-4656
EXHAUST
FIGURE 1 - BENDIX® SRC-7000™ TRAILER SPRING BRAKE VALVE
DESCRIPTION
The Bendix® SRC-7000™ trailer spring brake valve is
a reservoir-mounted trailer valve that can control up to
six spring brake actuators during parking or emergency
applications. It has the following capabilities:
• Automatically applies trailer spring brakes in the event
PORTS
1 - 1/2" NPT Spring Brake Reservoir Mounting (RES)
1 - 1/4"-18 NPT Trailer Supply (1 SUP)
1 - 1/4"-18 NPT Trailer Service (4 CONT)
4 - 3/8"-18 NPT Delivery (2 DEL)
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.
• Does not allow an automatic trailer spring brake
application with air pressure loss in trailer reservoir(s).
1 - Exhaust (3 EXH)
The SRC-7000
of a composite body, pressure protection valve and
reservoir-mounting nipple.
• Allows the trailer spring brakes to be applied and released
repeatedly with a failed trailer reservoir(s):
• 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.
• Muffl er & snorkel capable.
™
trailer spring brake valve consists
1
TRAILER
SERVICE
SER EMSER EM
TRAILER
SUPPLY
Trailer Schematic
TRAILER
SERVICE
D
D
C
D
D
SER EM
TO
ACCESSORIES
SER EM
S
D
C
D
D
D
SER EM
™
C-5
CUT-OUT
COCK
SRC-7000
VALVE
™
DUMMY
COUPLING
R-12P
RELAY
VALVE
™
PILOT
SRC-7000
VALVE
QUICK
D
S
C
D
™
C
RELEASE
SERVICE
RELAY
SERVICE
BRAKE
CHAMBER
VALVE
TRAILER
SUPPLY
™
C-5
CUT-OUT
COCK
SER EM
Towing Trailer Schematic
FIGURE 2 - TYPICAL SYSTEM SCHEMATICS WITH A BENDIX® SRC-7000™ TRAILER SPRING BRAKE VALVE
2
DUMMY
COUPLING
SERVICE/SPRING
BRAKE RESERVOIR
CONNECTION
SERVICE
RELAY
VALVE
FIGURE 3 - CHARGING BELOW 85 PSI
SPRING
BRAKE
CHAMBER
TRAILER SUPPLY
TRAILER SERVICE
SUPPLY
DELIVERY
EXHAUST
OPERATION
CHARGING BELOW 85 PSI (SEE FIGURE 3)
Air fl ows through the trailer supply line, enters the trailer
supply port of the Bendix® SRC-7000™ trailer spring brake
valve, sealing the anti-compound section. The air passes
through the quick release portion and out of the delivery
port to the spring brakes. The air pressure then releases
the spring brakes.
TRAILER SUPPLY
TRAILER SERVICE
SERVICE/SPRING
BRAKE RESERVOIR
CONNECTION
CHARGING ABOVE 85 PSI (SEE FIGURE 4)
Once the air pressure in the valve builds to 85 psi, the air
pressure fl ows into the trailer service reservoir(s). The
trailer braking system is now in the normal run mode.
Service braking occurs through the trailer service relay
valve.
SUPPLY
SERVICE
RELAY
VALVE
FIGURE 4 - CHARGING ABOVE 85 PSI
DELIVERY
SPRING
BRAKE
CHAMBER
EXHAUST
3
SERVICE/SPRING
BRAKE RESERVOIR
CONNECTION
SERVICE
RELAY
VALVE
FIGURE 5 - P ARKING APPLICATION
TRAILER SERVICE
SPRING
BRAKE
CHAMBER
TRAILER SUPPLY
SUPPLY
DELIVERY
EXHAUST
PARK APPLICATION (SEE FIGURE 5)
To park the trailer, either the trailer air supply valve or the
system park control valve (in the tractor) is actuated. This
vents the trailer supply line. The service reservoir is sealed
off. The quick release section, no longer under supply
pressure, is moved by air pressure from the spring brake
chamber. The exhaust opens, allowing air from the spring
brakes to exhaust through the open passage.
TRAILER SUPPLY
TRAILER SERVICE
SERVICE/SPRING
BRAKE RESERVOIR
CONNECTION
OPERATION WITH A FAILED RESERVOIR (SEE
FIGURE 6)
Should trailer reservoir pressure be lost, trailer service
braking is no longer available. The Bendix® SRC-7000
™
valve's internal spring force will trap approximately 70 psi
supply pressure, thus preventing spring brake parking.
SUPPLY
SERVICE
RELAY
VALVE
SPRING
BRAKE
CHAMBER
FIGURE 6 - OPERATION WITH A FAILED RESERVOIR
4
DELIVERY
EXHAUST
TRAILER SUPPLY
TRAILER SERVICE
SERVICE/SPRING
BRAKE RESERVOIR
CONNECTION
SERVICE
RELAY
VALVE
SPRING
BRAKE
CHAMBER
FIGURE 7 - ANTI-COMPOUNDING APPLICA TION
ANTI-COMPOUNDING (SEE FIGURE 7)
The Bendix® SRC-7000™ trailer spring brake valve has
an anti-compounding feature. (See Figure 7.) A single
check valve in the SRC-7000™ valve cover prevents brake
compounding (simultaneous spring brake and service
brake application), which creates extra load on foundation
brake components.
If a trailer service application is being made and at the
same instant a park application is made, air in the service
line closes the anti-compounding section of the SRC-7000
™
valve. The air then fl ows out of the supply port and
exhausts through the tractor protection control. Future
compounding is prevented by the closed tractor protection
valve. The anti-compounding port should not be used on
towing trailers. See Figure 2.
GENERAL SAFETY GUIDELINES
WARNING! PLEASE READ AND FOLLOW
THESE INSTRUCTIONS TO A VOID PERSONAL
INJURY OR DEATH:
When working on or around a vehicle, the following
general precautions should be observed at all times.
1. Park the vehicle on a level surface, apply the
parking brakes, and always block the wheels.
Always wear safety glasses.
2. Stop the engine and remove ignition key when
working under or around the vehicle. When
SUPPLY
DELIVERY
EXHAUST
working in the engine compartment, the engine
should be shut off and the ignition key should be
removed. Where circumstances require that the
engine be in operation, EXTREME CAUTION should
be used to prevent personal injury resulting from
contact with moving, rotating, leaking, heated or
electrically charged components.
3. Do not attempt to install, remove, disassemble
or assemble a component until you have read
and thoroughly understand the recommended
procedures. Use only the proper tools and observe
all precautions pertaining to use of those tools.
4. If the work is being performed on the vehicle’s
air brake system, or any auxiliary pressurized air
systems, make certain to drain the air pressure
from all reservoirs before beginning ANY work
on the vehicle. If the vehicle is equipped with
a Bendix® AD-IS® air dryer system or a dryer
reservoir module, be sure to drain the purge
reservoir.
5. Following the vehicle manufacturer’s recommended
procedures, deactivate the electrical system in a
manner that safely removes all electrical power
from the vehicle.
6. Never exceed manufacturer’s recommended
pressures.
7. Never connect or disconnect a hose or line
containing pressure; it may whip. Never remove
a component or plug unless you are certain all
system pressure has been depleted.
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8. Use only genuine Bendix® brand replacement parts,
components and kits. Replacement hardware,
tubing, hose, fi ttings, etc. must be of equivalent
size, type and strength as original equipment and
be designed specifi cally for such applications and
systems.
9. Components with stripped threads or damaged
parts should be replaced rather than repaired. Do
not attempt repairs requiring machining or welding
unless specifi cally stated and approved by the
vehicle and component manufacturer.
10.Prior to returning the vehicle to service, make
certain all components and systems are restored
to their proper operating condition.
11. For vehicles with Antilock T raction Control (ATC),
the ATC function must be disabled (ATC indicator
lamp should be ON) prior to performing any vehicle
maintenance where one or more wheels on a drive
axle are lifted off the ground and moving.
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 Bendix® SRC-7000™ trailer spring brake valve should
be inspected every 6 months or 1500 operating hours,
whichever comes fi rst, for proper operation. Should the
SRC-7000™ 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
1. Remove any accumulated contaminants. Visually
inspect the valve’s exterior for excessive corrosion or
physical damage. Replace the valve as necessary.
2. Inspect all air lines connected to the valve for signs
of wear or physical damage. Repair or replace as
necessary.
3. Test air line fi ttings for excessive leakage and tighten
or replace as necessary.
OPERATIONAL AND LEAKAGE TESTS
Check the tractor dash gauge against a gauge known to be
accurate before performing these tests. Connect the tractor
air lines to the trailer on which the SRC-7000™ valve is to
be tested. Block all wheels or hold the vehicles by means
other than the air brakes.
1. Install a gauge in the trailer reservoir(s). Build the
tractor and trailer to full system pressure by placing
the park control valve and the trailer air supply valve
in the charge position. As system pressure reaches
approximately 75-95 psi, the trailer spring brakes
should also build up to approximately 75-95 psi before
the reservoir(s) begin to charge.
2. When full system pressure is reached, and the spring
brakes are fully released, apply a soap solution to
™
the SRC-7000
valve exhaust port and the vent. A 1"
bubble in 5 seconds is permissible.
3. Place the trailer air supply valve in the exhaust position.
The spring brakes should apply. Disconnect the trailer
supply line and apply a soap solution to check for leaks.
A 1" bubble in 5 seconds is permissible.
4. Reconnect the trailer supply hose coupling and
recharge the trailer system. The spring brakes should
release. Shut off the engine and then open the trailer
reservoir drain cock. The tractor air system should bleed
down to approximately 70 psi. The trailer spring brakes
should remain released.
5. If the SRC-7000
™
valve does not function as described;
or if leakage is excessive, repair the valve, or replace
with a genuine Bendix® service replacement valve.
Leakage through the welds is acceptable.
REMOVAL
1. Identify and mark or label all air lines and their
connections on the SRC-7000™ valve. Then disconnect
the air lines.
™
2. Remove the SRC-7000
valve from the reservoir.
INSTALLATION
1. Install the SRC-7000™ valve on the reservoir.
2. Reconnect all air lines to the valve using the identifi cation
made in REMOVAL step 1.
3. Install all fi ttings 2 to 2-1/2 turns past fi nger tight.
4. Perform OPERATIONAL AND LEAKAGE TESTS before
placing the vehicle back in service.
BW2739 © 2010 Bendix Commercial Vehicle Systems LLC. All rights reserved. 08/2010 Printed in U.S.A.
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