BENDIX SR-5 TRAILER SPRING BRK VALVE User manual

1
®
SD-03-4516
Bendix®SR-5™Trailer Spring Brake Valve
FIGURE 1 SR-5™TRAILER SPRING BRAKE VALVE
*SHOWN WITH OPTIONALANTI-COMPOUNDING COVER
SR-5™VALVE
IDENTIFICATION
HOLE
1/4” NPT TRAILER
SERVICE
1/4” NPT
TRAILER SUPPLY EXHAUST
COVER*
1/4” NPT
SERVICE
RESERVOIR
(2)
3/8” NPT
DELIVERY(4)
1/2” OR 3/4” NPT
SPRINGBRAKE
RESERVOIR
PRESSURE
PROTECTION
VALVE
DESCRIPTION
TheSR-5™valveisareservoir-mountedtrailervalvethatcan
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
breakawayor trailersupply linefailure.
• Allows no automatic trailer spring brake application with
airpressure lossintrailer reservoir(s).
• Allowsthetrailerspringbrakestobeappliedand released
repeatedlywitha failed trailerreservoir(s):
• Optionalanti-compounding-prevents anoverridingservice
brakesignal while thetrailersupply line isat atmospheric
pressure.
• Doesnotallow service systemchargingifa 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 ServiceReservoir(SERV RES)
1 - Exhaust (EXH)
The SR-5™valve appears very similar to the SR-2™valve.
Bothvalvesconsist of adie-castaluminum body andcover,
pressure protection valve, and reservoir-mounting nipple.
However, Figure 1notesthe distinguishing characteristicof
theSR-5™valve–a holedrilledinto the flatsurfacebetween
thepressure protection valveandthe body.

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FIGURE 2 TYPICAL SYSTEM SCHEMATICS WITH SR-5™TRAILER SPRING BRAKE VALVE
TWO-TANK SYSTEM
TRAILERSERVICE
SERVICE/SPRINGBRAKE
RESERVOIR
TRAILER SUPPLY
SERVICE
RELAY
VALVE
SERVICE/SPRING
BRAKE
RESERVOIR
SR-5™
VALVE
ONE-TANK SYSTEM
TRAILERSERVICE
SERVICE/SPRINGBRAKE
RESERVOIR
TRAILER SUPPLY
SERVICE
RELAY
VALVE
SR-5™
VALVE

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FIGURE 3 CHARGING BELOW 70 PSI
TRAILER SUPPLY
SPRING
BRAKE
CHAMBER
TRAILERSERVICERES.
CONTROL PISTON
DELIVERY
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.
Aspiston travel continues,thecontrol inlet valveopens.Air
acting on the control piston also flows through passageA,
unseatingcheck valve B,andflowing past theopen control
inlet valve. This air flows into the spring brake cavities,
releasing the spring brakes.
CHARGING ABOVE 85 PSI (SEE FIGURE 4)
Airpressureactingon 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.
Servicebrakingoccursthroughthetrailerservicerelayvalve.
EXHAUST
PASSAGE A
TRAILERSERVICE
CHECK
VALVE
B
SERVICE/SPRING
BRAKERESERVOIR
CONNECTION
SERVICE
RELAY
VALVE
CHECK
VALVE
D
FIGURE 4 CHARGINGABOVE 85 PSI
CONTROL PISTON
PRESSURE
PROTECTION
VALVE C
SPRING
BRAKE
CHAMBER
TRAILER SERVICE RES.
EXHAUST
PASSAGE A
TRAILER SERVICE
CHECK
VALVE B
SERVICE/SPRING
BRAKE
RESERVOIR
CONNECTION
SERVICE
RELAY
VALVE
DELIVERY
CHECK
VALVE D

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FIGURE 6 PARK RELEASE WITH TRAILER CHARGED
FIGURE5 PARKAPPLICATION
TRAILER SUPPLY
SPRING
BRAKE
CHAMBER
TRAILER SERVICE RES.
CONTROL PISTON
EXHAUST
PASSAGE
TRAILER SERVICE
CHECK
VALVE B
SERVICE/
SPRING
BRAKE
RESERVOIR
CONNECTION
SERVICE
RELAY
VALVE
PRESSURE
PROTECTION
VALVE C
SPRING
BRAKE
CHAMBER
TRAILERSERVICERES.
EXHAUST
PASSAGE A
TRAILERSERVICE
CHECK
VALVE B
SERVICE/SPRING
BRAKERESERVOIR
CONNECTION
SERVICE
RELAY
VALVE
CHECK
VALVE D
CONTROL PISTON
TRAILER SUPPLY
CHECK
VALVE
F
CHECK
VALVE D
PARKAPPLICATION (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 control piston, no longer
under supply pressure, is moved by air pressure on its
delivery side. This allows the control piston to move to the
exhaust position. The control inlet valve closes and the
exhaust valve opens, allowing air from the spring brakes to
exhaustthroughthepassagein the controlpiston andapply
the brakes. Check valves B and D close, preventing trailer
reservoirair pressure loss through passageA.
PARKRELEASE WITH TRAILER CHARGED
(SEE FIGURE 6)
To release a park application with the trailer charged, the
trailersupplyvalve(inthe cab) is actuated.Air flows through
thetrailersupplylineandenterstheSR-5™valvetrailersupply
port. With a minimum of 55 psi on the control piston, the
piston will move, sealing its exhaust passage. As piston
travelcontinues,the inlet valveopens.Reservoirair(approx.
110 psi) then flows through check valve F, past the open
inlet, and out to the spring brake chambers to release the
brakes.

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NotethatpressureprotectionvalveCwillopeniftrailersupply
air is greater than 70 psi. But check valves B and D will not
openunlessreleasepressurefromthetractorexceedstrailer
reservoirpressure.
ANTI-COMPOUNDING (SEE FIGURE 7)
TheSR-5™valvehasanoptionalanti-compoundingfeature.
(SeeFigure 7.)Asingle checkvalveintheSR-5™valvecover
preventsbrakecompounding(simultaneousspringbrakeand
service brake application), which creates extra load on
foundationbrakecomponents.
Ifatrailerserviceapplication is beingmade andat thesame
instant a park application is made, air in the service line
flowsthroughsinglecheckvalveEintheSR-5™valvecover.
Pressure is maintained on the control piston, while air also
flows out the trailer supply line and exhausts through the
tractorprotectioncontrol.Future compounding isprevented
by the closed tractor protection valve.
FIGURE 7 OPTIONALANTI-COMPOUNDING
ANTI-COMPOUNDING
LINE
SPRING BRAKE
CHAMBER
EXHAUST
TRAILER SERVICE
CHECK
VALVE F
SERVICE/SPRING
BRAKE
RESERVOIR
CONNECTION
SERVICE
RELAY
VALVE
TRAILER SUPPLY
CHECK
VALVE E
DELIVERY

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FIGURE 8 FAILED TRAILER RESERVOIR
PRESSURE
PROTECTION
VALVE C
SPRING
BRAKE
CHAMBER
TRAILERSERVICERESERVOIR
EXHAUST
TRAILERSERVICE
CHECK
VALVE B
SERVICE/SPRING
BRAKERESERVOIR
CONNECTION
SERVICE
RELAY
VALVE
TRAILER SUPPLY
FAILED TRAILER RESERVOIR (SEE FIGURE 8)
Shouldtrailerreservoirpressurebelost,trailerservicebraking
isnolongeravailable.Pressure protection valve Cwill close
atapproximately70 psi (minimum),retaining airpressurein
the trailer supply line.
Theairheldbythe pressure protectionvalve willcontinue to
hold the control piston’s inlet valve open, supplying air to
the spring brakes. Thus, no automatic spring brake
application occurs. However, trailer supply line air can be
usedtoapplyandreleasethetrailerspringbrakesrepeatedly.
GENERAL SAFETY GUIDELINES
WARNING! PLEASE READ AND FOLLOW
THESE INSTRUCTIONS TO AVOID
PERSONAL INJURYOR 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
working in the engine compartment, the engine
should be shut off and the ignition key should be
removed. Where circumstances require that the
engine bein operation, EXTREMECAUTIONshould
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. Useonly 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 pressurefrom
all reservoirs before beginning ANY work on the
vehicle. If the vehicle is equipped with an AD-IS®
air dryer system or a dryer reservoir module, be
sure to drain the purge reservoir.
5. Following the vehicle manufacturer’s
recommendedprocedures,deactivatetheelectrical
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®replacement parts,
components and kits. Replacement hardware,
tubing, hose, fittings, etc. must be of equivalent
size, type and strength as original equipment and
be designed specifically 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 specifically 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 Traction 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
performinganyintrusivemaintenanceprocedures.Awarranty
maybevoided if intrusivemaintenanceis performed during
thewarrantyperiod.
No two vehicles operate under identical conditions, as a
result, maintenance intervals may vary. Experience is a
valuableguideindeterminingthe best maintenance interval
forairbrake system components.At a minimum,theSR-5™
valveshouldbeinspected every 6 months or 1500 operating
hours, whichever comes first, for proper operation. Should
the SR-5™valve not meet the elements of the operational
testsnotedinthisdocument,furtherinvestigationandservice
ofthevalve may be required.
SERVICE CHECKS
1. Removeanyaccumulatedcontaminants.Visuallyinspect
the valve’s exterior for excessive corrosion or physical
damage. Repair/replace the valve as necessary.
2. Inspect all air lines connected the valve for signs of
wearorphysicaldamage. Repair/replaceas necessary.
3. Test air linefittingsfor excessiveleakageand tighten or
replace as necessary.
OPERATIONAL AND LEAKAGE TESTS
Checkthe tractor dashgaugeagainst agaugeknown to be
accuratebeforeperforming these tests.Connectthetractor
air lines to the trailer on which the SR-5™valve is to be
tested.Blockallwheels or holdthevehiclesbymeans other
than air brakes.
1. Install a gauge in the trailer reservoir(s). Build tractor
and trailer to full system pressure by placing the park
controlvalveandthetrailerairsupplyvalveinthecharge
position. As system pressure reaches approximately
75-95 psi, the trailer spring brakes should also build up
toapproximately75-95psibefore 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
SR-5™valve exhaust port and the vent.A1" bubble in 5
seconds is permissible.
3. Placethetrailer airsupplyvalvein theexhaustposition.
The spring brakes should apply. Disconnect the trailer
supplylineand applyasoap solution tocheckfor leaks.
A 1" bubble in 5 seconds is permissible.
4. Reconnectthetrailersupplyhosecouplingandrecharge
the trailer system. The spring brakes should release.
Shutofftheengine.Openthetrailerreservoirdraincock.
The tractor air system should bleed down to
approximately 70 psi. The trailer spring brakes should
remainreleased.Afterthe systemis stabilized, leakage
atthe opendrain cock shouldnot exceeda 1"bubble in
5 seconds.
5. If the SR-5™valve does not function as described; or if
leakageis excessive,repair thevalve, or replacewith a
genuineBendixservicereplacementvalve.
REMOVAL
1. Identify and mark or label all air lines and their
connections on the SR-5™valve. Then disconnect the
air lines.
2. RemovetheSR-5™valvefromthereservoir.
INSTALLATION
1. InstalltheSR-5™valveon the reservoir.
2. Reconnectallairlinestothe valveusingtheidentification
made in REMOVALstep 1.
3. PerformOPERATIONALAND LEAKAGETESTSbefore
placing the vehicle back in service.

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PIPE PLUG
VALVEBODY
PIPE PLUG
11
9
12
10
17 18 7
6
8
25
5
4
2
1
3
24
23
16
15
19
20
21
22
18
17
14
13
FIGURE 9 - EXPLODED VIEW

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DISASSEMBLY
The following procedure is for reference only.Always have
the appropriate maintenance kit on hand, and use its
instructions in lieu of those presented here. Refer to Figure
9 throughout the procedure.
1. Removethefourscrews(1)thatsecurespring retainer(2)
tothevalvebody.Notethattheretaineris spring-loaded.
Remove the screws while holding the retainer against
its spring load. Then slowly remove the retainer.
2. Remove spring(3) and piston assembly(4).
3. Remove piston o-ring(5). Do not remove the retaining
ringand stemfrom thepiston. The pistonis servicedas
an assembly.
4. Note and mark the position of control piston cover(7).
Then remove the four screws(6) that secure the cover
to the body.
5. Remove cover(7) and sealing ring(8), control piston(9),
and spring(10).
6. Removeo-rings(11 & 12)from piston assembly.
7. Removereservoirfitting(13)ando-ring(14).
8. Remove spring(15) andinlet/exhaustvalve(16).
9. Remove the pipe plugsthat retain thethree single check
valves. Two check valves are in the body, and one is in
the cover(7).
10. Remove check valve springs(17) and rubber check
valves(18).
11. With a pair of I.D. snap ring pliers, remove the snap
ring(19) in the end of the reservoir fitting check valve
assembly. Remove spring seat(20), spring(21), and
checkvalve(22).
12.Remove screw(23), washer(24), and diaphragm (25)
from the exhaust port.
CLEANING AND INSPECTION
1. Inspect all parts for excessive wear or deterioration.
Inspectvalveseatsfor nicks orburrs. Checkthesprings
for cracks or corrosion.
2. Inspectthe bores ofthevalve housingfordeep scuffing
or gouges.
Replace all non-metallic parts and any part not found to be
serviceable during inspection, using only genuine Bendix
replacementparts.
ASSEMBLY
Before assembling the SR-5™valve, lubricate all o-rings,
o-ring grooves, piston bores, and metal-to-metal moving
surfaces with Bendix silicone lubricant BW-650-M piece
number291126.
NOTE: When using pipe thread sealant during assembly
and installation, take particular care to not allow
the sealant into the valve itself. Apply the sealant
beginningwiththesecondthreadbackfromtheend.
1. Twist the springs(17) on each of the check valves(18).
Drop the assemblies into their respective bores in the
valve body and install the pipe plugs. Torque the plugs
to140-170 inchpounds.
2. Place reservoir fitting(13) upright, pipe threads down.
Drop check valve(22) into place. Install check valve
spring(21), spring seat(20), and snap ring(19). Install
o-ring(14)intofitting.
3. Installinlet/exhaustvalve(16)intovalvebody.NOTE:The
side with four protruding ears rests against the seat in
the body.
4. Place spring (15) in position on the inlet/exhaust valve.
Make sure the spring rests evenly on the four ears of
theinlet/exhaust valve andtherubber protrusion onthe
valve fits into the spring’s inner diameter.
5. Properly align theinlet/exhaustvalvespringboard in the
recess at the end of the reservoir port fitting(13). Install
the fitting into the valve body. Torque to 200-300 inch
pounds.
6. Install o-rings(11 & 12) into their respective grooves in
control piston(9).
7. Drop and position spring(10) into the valve body.
8. Make sure all parts are properly aligned, and install the
control piston(9) into the valve body.
9. Install sealing ring(8) in cover(7), and install cover onto
valve body, using the identification made in
DISASSEMBLY step 4.Torque screws(6) to 40-60 inch
pounds.
10. Install o-ring(5) in its groove in the pressure protection
piston(4).Installthepistonassemblyintothevalvebody.
11. Position the spring(3) and spring retainer(2) on top of
the pressure protection piston assembly, and secure
with the four screws(1). Torque to 20-30 inch pounds.
12. Installdiaphragm(25), washer(24)andscrew(23)intothe
exhaust port. Torque screw to 15-25 inch pounds.
NOTE: BEFORE PLACING THE VEHICLE BACK INTO
SERVICE, PERFORM “OPERATIONAL AND
LEAKAGETESTS,”LISTED IN THISMANUAL.
BW1680 © 2007 Bendix Commercial Vehicle Systems LLC. All rights reserved. 3/2007 Printed in U.S.A.