BENDIX SR-1 SPRING BRAKE VALVE User manual

1
SD-03-4508
Bendix®SR-1™Spring Brake Valve
1/4 P.T.
RES. #1
1/4 P.T.
DELIVERY
1/4 P.T.
SUPPLY
PISTON SPRING
(14) O-RING
(LARGE)
(18)
PISTON
SPRINGS (14)
FIGURE 1 - EXTERIOR VIEW
COVER(13)
1/4 P.T.
CONTROL
FIGURE 2 - SECTIONAL VIEW
DESCRIPTION:
The SR-1™spring brake valve is used in dual or “split” air
brake systems equipped with spring brake actuators. The
function of the SR-1™valve is to supply a specific, limited
hold-off pressure to the spring brakes, and in the event of
loss of No. 1 service air pressure, to modulate the spring
brakesthrough theuse ofthe servicebrake valve.
The valve has four identified 1/4" N.P.T.F. ports and a
diaphragmprotectedexhaustport.Two5/16"diameter holes
are provided in the integral mounting bracket of the valve
body. The SR-1™valve must be mounted with the exhaust
portdown towardthe roadsurface.
OPERATION - INITIAL AIR SYSTEM CHARGE
Uponinitialcharge, airfrom#1 &#2service reservoirsflows
through the park control valve and enters the SR-1™valve
supplyport.Airentering the supplyport flows pastinlet and
exhaust valve B to the underside of piston B and out the
delivery port of the SR-1™valve to the emergency air
connectionatthespringbrakeactuator.Notethatthesprings
above piston B force it into contact with inlet and exhaust
valveB. Intheposition shownthe exhaustisclosed andthe
inlet is open.
Airflowing fromtheNo. 1reservoir onlyenters thereservoir
port of the SR-1™valve. This air remains under pistonAas
systempressurebuilds.WithNo. 1reservoirpressurebelow
approximately 55 P.S.I. the spring above piston A forces it
into contact with inlet and exhaust valve A causing the
exhaust to seal and the inlet to open.
With air system pressure above approximately 55 P.S.I. in
No. 1 & 2 service reservoirs, piston A has moved against
the force of the spring above it, allowing the inlet of valve A
to close and opening the hollow exhaust passage through
piston A.
OPERATION - AIR BRAKE SYSTEM FULLY
CHARGED
When air pressure beneath piston B is approximately 95*
P.S.I.,piston Brisesslightly, againstthe forceof thesprings
above it, allowing the inlet of valve B to close. The exhaust
through valve B remains closed. The closing of the inlet
portion of valve B retains approximately 95* P.S.I. in the
hold- off cavity of the spring brake actuators while allowing
full air system pressure to build elsewhere.
*Note: Otherspring brakehold-off pressuresare supplied
according to the vehicle manufacturer’s
specifications. 95 P.S.I. was chosen only for the
purposeof explanation.
PISTON (15)
PISTON O-RINGS
(16)
VALVE(12)
VALVESPRING(11)
VALVESTOP(10)
O-RING (9)
CAP NUT
(8)
PISTON (17)
O-RING
(SMALL)(19)
BODY
CHECK
VALVESPRING(2)
PIPE PLUG
(1)
CHECK
VALVE(4)
EXHAUST
COVER(5)
DIAPHRAGM
(6)
INLET &
EXHAUST
VALVE(7)

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FIGURE3-PIPINGDIAGRAM
FIGURE 4 - CHARGING - BELOW 55 P.S.I.
PP-7™
CONTROL
VALVE TP-3™TRACTOR PROTECTION VALVE
DS-1
PARK
CONTROL
MODULATOR
SUPPLY
RESERVOIR #1SERVICE
RESERVOIR
#2SERVICE
RESERVOIR
DOUBLE
CHECK
VALVE
LQ-4™VALVE
LP-3™INDICATOR
R-8™
VALVE R-8™
VALVE
SB-3 SB-3
SB-3 SB-3
#1SERVICE
RESERVOIR
#2SERVICE
RESERVOIR
DOUBLE
CHECK
VALVE PARK
CONTROL SB-3
PISTON B
CHECK VALVE
INLET &
EXHAUSTA
PISTON A
INLET
&
EXHAUST
BEXHAUST

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FIGURE6 - NORMALSERVICEAPPLICATION
FIGURE5 - SYSTEM FULLYCHARGED
#1SERVICE
RESERVOIR
#2SERVICE
RESERVOIR
DOUBLE
CHECK
VALVE PARK
CONTROL SB-3
PISTON B
CHECK VALVE
INLET &
EXHAUSTA
PISTON A
INLET &
EXHAUST
BEXHAUST
#1SERVICE
RESERVOIR
#2SERVICE
RESERVOIR
DOUBLE
CHECK
VALVE PARK CONTROL
SB-3
PISTON B
CHECK VALVE
INLET &
EXHAUSTA
PISTON A
INLET
&
EXHAUST
BEXHAUST
OPERATION - NORMAL SERVICE
RESERVOIRS 1 & 2 CHARGED
When a service application is made by actuating the dual
brake valve, air from the No. 2 delivery circuit is delivered
from the brake valve to the control port, and is stopped at
the closed inlet of valve A. No movement of the internal
components of the SR-1™valve takes place. Air from the
No. 1 delivery circuit of the dual brake valve actuates the
service section of the spring brake actuators.
OPERATION - SERVICE APPLICATION WITH
LOSS OF NO. 2 RESERVOIR PRESSURE
Intheevent airpressureislost intheNo. 2reservoir, theNo.
1reservoirandthe parkingcontrolvalvewillbe protectedvia
the double and single check valves in the air system. A
service application of the foot brake valve in this situation
resultsinlittleornoairbeingdeliveredfromtheNo.2delivery
circuit to the control port of the SR-1™valve. No movement
oftheSR-1™valveinternalcomponentstakes place.Braking
is assured because the No. 1 service reservoir is protected
by a check valve and the No. 1 delivery circuit of the dual

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FIGURE 8 - SERVICEAPPLICATION - LOSS OF #1 RESERVOIR
FIGURE 7 - SERVICEAPPLICATION - LOSS OF #2 RESERVOIR
#1SERVICE
RESERVOIR
#2SERVICE
RESERVOIR
DOUBLE
CHECK
VALVE PARK
CONTROL SB-3
PISTON B
CHECK VALVE
INLET &
EXHAUSTA
PISTON A
INLET &
EXHAUST
BEXHAUST
#1SERVICE
RESERVOIR
#2SERVICE
RESERVOIR
DOUBLE
CHECK
VALVE PARK
CONTROL SB-3
PISTON B
CHECK VALVE
INLET &
EXHAUSTA
PISTON A
EXHAUST
brakevalvewill applytheservice sectionofthe springbrake
actuators.
OPERATION - SERVICE APPLICATION WITH
LOSS OF NO. 1 RESERVOIR PRESSURE
If air pressure in the No. 1 service reservoir falls below
approximately 55 P.S.I., the pressure beneath piston A is
insufficient to resist the spring force above and piston A
movesintocontactwithvalveA.Initialcontactbetweenpiston
A and valve A closes the hollow exhaust passage of piston
A. Continued movement of the piston opens the inlet of
valveA.
The No. 2 service reservoir and the park control valve are
protected from pressure loss by the action of the double
checkvalve.
Whena serviceapplicationof thedual brakevalve ismade,
air delivered from the No. 2 delivery circuit of the dual
brakevalveenters theSR-1™valve controlport.Air entering
the control port moves past the inlet of valve A and is
conducted through a passage in the body to the underside
of piston B. The air pressure moves piston B up, opening
theexhaust ofvalveB. Whenthe exhaustof valveB opens,
airpressure trappedin theemergency sectionof thespring
brake actuator is allowed to escape, resulting in an
emergencybrakeapplication.Theairpressurereleasedfrom
thespringbrake isproportional totheair pressuredelivered
tothecontrol portofthe SR-1™valvebythe No.2delivery of
thedualbrake valve.
INLET &
EXHAUST
B

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OPERATION - PARKING
If both systems #1 and #2 are intact and the park control
valve is placed in the “park” or exhaust position, the SR-1™
valvesupplyofairpressureand theair pressureinthespring
brakeactuatorcavitiesis exhausted.Thesinglecheck valve
in the SR-1™valve assists this exhaust of air pressure by
allowing the air below piston B to flow back out the open
exhaust of the park control valve. When air pressure below
piston B has dropped sufficiently, piston B moves down,
opening the inlet of valve B and providing an additional
exhaustpassageforair exhaustingthroughtheSR-1™valve
from the spring brakes.
PREVENTIVE MAINTENANCE
Important: Review the Bendix Warranty Policy before
performinganyintrusivemaintenanceprocedures.Awarranty
maybe voidedif intrusivemaintenanceis performedduring
thewarranty period.
No two vehicles operate under identical conditions, as a
result, maintenance intervals may vary. Experience is a
valuableguidein determiningthebest maintenanceinterval
forair brakesystem components.Ata minimum,the SR-1™
valveshouldbeinspectedevery 6monthsor1500operating
hours, whichever comes first, for proper operation. Should
the SR-1™valve not meet the elements of the operational
testsnotedinthisdocument,furtherinvestigationandservice
ofthe valvemaybe required.
SERVICE CHECKS
OPERATING CHECKS
Blockallwheelsandholdbymeansotherthanvehiclebrakes.
Chargeair brake system togovernor cut-out pressure.
1. Placeparkingcontrolvalveinthe“park”position.Observe
that the spring brake actuators apply promptly. In the
deliveryportof thevalveinstalla testgaugeknown tobe
accurate.Placetheparking controlvalveinthe “release”
position.Observethatthespringbrakeactuators release
fully.
2. With the parking control valve in the “release” position,
note the gauge pressure reading. (Check the vehicle
manual for the correct spring brake actuator hold-off
pressure.)If thepressure readingis incorrect,the valve
mustbe repaired or replaced.
3. Placethe parkingcontrolvalve inthe“park” position, the
gauge reading should drop to zero promptly. A slow
release of pressure may indicate faulty operation of the
singlecheck valve(withinthe modulatingvalve.)
4. Placethe parkingcontrol valvein the“release”position.
Locate the number one service reservoir and drain it
completely.
Apply the foot brake valve several times and note that
the pressure reading on the gauge decreases each
time the foot brake valve is applied. After several
applications,pressureon the gaugewilldrop tothepoint
where release of the spring brake actuators will no
longer occur.
LEAKAGE CHECK
With the air system fully charged and the parking control
valve in the “release” position, coat the exhaust port and
aroundthevalve cornerwith asoapsolution. Slightleakage
is permitted.
IftheSR-1™springbrakevalvedoesnotfunctionasdescribed
above,or leakageisexcessive, itisrecommended thatit be
repaired or replaced with a genuine Bendix service
replacementvalve.
FIGURE 9 - PARKAPPLICATION
#1SERVICE
RESERVOIR
#2SERVICE
RESERVOIR
DOUBLE
CHECK
VALVE PARK
CONTROL SB-3
PISTON B
CHECK VALVE
INLET &
EXHAUSTA
PISTON A
EXHAUST
INLET &
EXHAUST
B

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Note: Amaintenancekit forthe SR-1™springbrake valveis
availablefrom any authorizedBendix outlet.Allparts
necessaryfor minorrepair are included.
REMOVAL
1. Prior to removing the SR-1™valve apply the parking
brakes and drain allthe vehicle reservoirs.
2. Identify all air lines before disconnecting.
3. Remove the two mounting bolts from the SR-1™valve
andremovethevalve.
DISASSEMBLY (REFER TO FIGURE 2)
1. Remove the socket head pipe plug (1).
2. Remove thecheck valvespring (2)and thecheck valve
(4).
3. Remove the two phillips head screws and remove the
exhaust cover (5).
4. Separate the exhaust diaphragm (6) from the cover.
5. Remove theinlet andexhaustvalve assembly(7).
6. Remove the inlet and exhaust valve cap nut (8) and
separate the cap nut o-ring (9).
7. Remove the valve stop (10) valve spring (11) and inlet
andexhaust valve(12).
8. Remove thefour phillipshead screws andlockwashers
that secure the cover to the body. Caution: the cover is
undera springload, andshould beheld whileremoving
the screws.
9. Remove the cover (13) and the three piston springs
(14).Note: SomeSR-1™valve piecenumbershave one
large piston spring.
10.Remove the small piston (15) and the small and large
o-rings (16).
11. Remove the large piston (17). Remove piston o-rings
(18) & (19).
CLEANING & INSPECTION
Inspect all parts for excessive wear or deterioration.
Inspect the valve seats for nicks or burrs.
Check the springs for cracks or corrosion.
Replace all rubber parts and any part not found to be
serviceable during inspection. Use only genuine Bendix
replacementparts.
ASSEMBLY (REFER TO FIGURE 2)
Priorto assemblyofthe SR-1™springbrake valve,lubricate
all o-rings, o-ring grooves, and piston bores with Bendix
silicone lubricant BW-650-M piece number 291126.
Note: All torques specified in this manual are assembly
torques and can be expected to fall off, after
assembly is accomplished. Do not retorque after
initial assembly torques fall.
1. Assemble the check valve (4), and valve spring (2) and
install in body.
2. Apply pipe sealant to the socket head pipe plug (1) and
install in the body. Tighten to 130-170 inch pounds
torque.
3. Installinletandexhaustvalveassembly(7)invalve body.
4. Secure the exhaust cover (5) with two 10-24 phillips
screws and lockwashers. Tighten to 20-30 inch pounds
torque.
5. Install exhaust diaphragm (6) into the exhaust cover.
6. Place inlet exhaust valve (12) in the body. Install the
valvespring(11) andvalvestop(10).
7. Install o-ring (9) on cap nut and install cap nut (8) in
body. Tighten to 100-125 inch pounds torque.
8. Install the small and large o-rings (16) on the small
diameter piston (15) and install piston in the body.
9. Installlarge o-ring(18)and smallo-ring(19)on thelarge
diameter piston and install piston in the body.
10. Install thepiston springs(14)in theirrespective pistons.
11. Securethe cover tobodyusingfour 1/4"-20phillipshead
screwsand lockwashers.Tighten to50-80 inch pounds
torque.
TESTING THE REBUILT SR-1™SPRING BRAKE
VALVE
Test therebuilt SR-1™springbrake valve byperforming the
operationand leakagetest outlinedinthe “ServiceChecks”
section of this manual.
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, EXTREME CAUTION should
be used to prevent personal injury resulting from
contact with moving, rotating, leaking, heated or
electrically charged components.

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3. Do not attempt to install, remove, disassemble or
assemble a component until you have read and
thoroughly understand the recommended
procedures. Useonly the propertools 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,makecertainto drain the air pressure from
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, 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.
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.

8BW1589 © 2004 Bendix Commercial Vehicle Systems LLC. All rights reserved. 3/2004 Printed in U.S.A.