BENDIX R-7 MODULATING VALVE User manual

1
®
Bendix®R-7™Modulating Valve
SD-03-4504
MOUNTING
SURFACE
DELIVERY
PORT (2)
SINGLE
CHECK
VALVE
INLET
EXHAUST
VALVE
CONTROL
PISTON
CONTROL
PORT
EXHAUST
ADJUSTINGSCREW
FIGURE2 - SECTIONAL VIEW
INLET
VALVE
SPRING
OUTER SPRING
INNERSPRING
DOUBLECHECK
VALVE(SUPPLY
PORT&BALANCE
PORT)
BALANCE
PISTON
INLET
VALVE
SEAT
DESCRIPTION
The R-7™modulating valve is used in conjunction with a
dual air brake system and spring brake actuators, and
performsfour functions:
1. Limits hold-off pressure to the spring brake actuators
(adjustable).
2. Providesfor quickreleaseofairpressurefromthe spring
cavity of the spring brake actuator allowing a fast
application of the spring brake actuators.
3. Modulates spring brake actuator application should a
failure occur in the service brake system.
4. Preventscompoundingofserviceand spring forces.
The valve has one 1/4" control, one 3/8" supply, one 1/4"
balance,two3/8" delivery NPTF ports, andanexhaustport
protectedbyanexhaustdiaphragm. Thevalve incorporates
two13/32"holesformounting.
Noteformodelyear2001 andlaterInternationalTrucksonly:
ThereisaninvertedR-7™valve,whichappearsinvertedfrom
the other pictures in this document.Astandard R-7™valve
and an inverted R-7™valve are not interchangeable. See
Figure1 for a pictureofaninverted R-7™valve.
OPERATION - CHARGING SPRING BRAKE
ACTUATORS (FIGURE 3)
Airpressureusedtocontrolthespringbrakeactuatorsenters
thevalve through the supplyport,passingthrough one side
ofthe doublecheckvalve, throughtheopeninletvalve, over
the balance piston, and out the delivery ports to the spring
brake actuators. When air pressure in the spring brake
actuatorcavity has releasedthespringbrake actuators and
when air pressure on top of the balance piston is sufficient
to overcome the force of the balance piston spring, the
balancepistonmovesallowing theinletvalvespringto close
the inlet valve, shutting off further air pressure from the
reservoirsupplying themodulatingvalve.
MOUNTING
HOLE (2)
EXHAUST CONTROL
PORT
DELIVERY(2)
SUPPLY
PORT
BALANCE
PORT
FIGURE 1 - EXTERIOR & INVERTED VIEW
MOUNTING
HOLE (2)
BALANCE
EXHAUST
CONTROL
SUPPLY

2
NOTE: Theforceofthespringbelowthe balance piston is
adjustablebyanexternalscrewon the modulating
valve. This adjustment is normally made so that
theinletvalve willcloseataslightlygreaterpressure
than the hold-off pressure of the spring brake
actuator, but below maximum system pressure.
OPERATION - NORMAL SERVICE APPLICATION
(FIGURE 4)
When a service application is made by actuating the dual
brake valve, air from the primary circuit is delivered to the
lower side of the control piston through the balance port,
and air from the secondary circuit is delivered to the top of
the control piston through the control port. Because air
pressure from the primary and secondary circuits are not
equal,therewillbeaslightmovementofthecontrolpiston.
OPERATION - SERVICEAPPLICATION WITH LOSS OF
AIR IN PRIMARY CIRCUIT (FIGURE 5)
A service application made with a loss of air in the primary
circuitwouldresultin reduced air pressure delivered to the
lower area of the control piston. Air pressure from the
secondary circuit on top of the control piston would force
thepiston down,openingtheexhaust valveandallowing air
pressureinthespringcavityofthespringbrakeactuatorto
release and the spring brake actuator to apply the brakes.
Thepressuredifferentialbetweentheprimaryandsecondary
circuitsregulatestheamountofairpressurereleased from
the spring cavity of the spring brake actuator. This results
in a total brake application on the rear axle which is
proportionatetothe braking on the other axles.
FIGURE4-NORMALSERVICEAPPLICATION
SECONDARY
SERVICE
CIRCUIT CONTROL
PORT
EXHAUST
PORT CONTROL
PISTON DUALBRAKE
VALVE
PRIMARYSERVICE
CIRCUIT
BALANCE
PORT
DOUBLE
CHECKVALVE
SUPPLY
PORT
PARK
CONTROL
VALVE
SINGLE
CHECK
VALVE
BALANCEPISTON
INLET/EXHAUST
VALVE
SPRING
BRAKE
ACTUATOR
+ SPRINGBRAKEHOLD-OFFPRESSURE
- SERVICEAIRPRESSURE
o ATMOSPHEREPRESSURE
#2RES.
#1RES.
PRIMARY -
SECONDARY -
PARK -
FIGURE3- CHARGING
SECONDARY SERVICE CIRCUIT
FIGURE5 - SERVICEAPPLICATIONLOSSOF PRIMARY
CIRCUIT
CONTROL
PORT
EXHAUST
PORT CONTROL
PISTON DUALBRAKE
VALVE
PRIMARY
SERVICE
CIRCUIT
BALANCE
PORT
DOUBLE
CHECKVALVE
SUPPLY
PORT
PARK
CONTROL
VALVE
SINGLE
CHECK
VALVE
BALANCEPISTON
INLET/EXHAUST
VALVE
SPRING
BRAKE
ACTUATOR
PRIMARY -
SECONDARY -
PARK -
+ SPRINGBRAKEHOLD-OFFPRESSURE
- SERVICEAIRPRESSURE
o ATMOSPHEREPRESSURE
#2RES.
#1RES.
SECONDARYSERVICECIRCUIT
CONTROL
PORT
EXHAUST
PORT CONTROL
PISTON DUALBRAKE
VALVE
PRIMARYSERVICE
CIRCUIT
BALANCE
PORT
DOUBLE
CHECK
VALVE
SUPPLY
PORT
PARK
CONTROL
VALVE
SINGLE
CHECK
VALVE
BALANCEPISTON
INLET/EXHAUST
VALVE
SPRING
BRAKE
ACTUATOR
PRIMARY -
SECONDARY -
PARK -
+ SPRINGBRAKEHOLD-OFFPRESSURE
- SERVICEAIRPRESSURE
o ATMOSPHEREPRESSURE
#2RES.
#1RES.
FIGURE6 - SERVICEAPPLICATIONLOSSOF SECONDARY
CIRCUIT
SECONDARY
SERVICE
CIRCUIT CONTROL
PORT
EXHAUST
PORT CONTROL
PISTON DUALBRAKE
VALVE
PRIMARYSERVICE
CIRCUIT
BALANCEPORT
DOUBLE
CHECKVALVE
SUPPLY
PORT
PARK
CONTROL
VALVE
SINGLE
CHECK
VALVE
BALANCEPISTON
INLET/EXHAUST
VALVE
SPRING
BRAKE
ACTUATOR
PRIMARY -
SECONDARY -
PARK -
+ SPRINGBRAKEHOLD-OFFPRESSURE
- SERVICEAIRPRESSURE
o ATMOSPHEREPRESSURE
#2RES.
#1RES.

3
OPERATION - SERVICEAPPLICATION WITH LOSS OF
AIRIN SECONDARY CIRCUIT (FIGURE 6)
Aserviceapplicationmadewithalossofairinthesecondary
circuit would result in less or no air delivered to the top of
thecontrolpiston;however,thepistonwouldnotmoveand
braking on the rear axle(s) is assured because the primary
circuit supplies rear axle service brakes. The spring brake
actuators will not be actuated.
OPERATION - PARKING (FIGURE 7)
Whenthe handleofthe parkingcontrolvalve isplacedin the
“park”(exhaust)position,the modulating valve’s supply air
pressure and the air pressure in the spring brake actuator
cavities is exhausted. The single check valve speeds the
exhaust of air from the actuator cavities by allowing the air
ontopof the balance piston toexhaustbythedouble check
valve through the supply port to atmosphere. When air
pressure drops sufficiently, the balance piston opens the
inletvalvethusopeningthelargerpassageinthe modulating
valveinsuring rapidexhaustof thebalanceof airpressurein
thespring cavity of the spring brake actuator.
SERVICE TESTS
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
enginebe inoperation, 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. Useonly the proper tools andobserve
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,makecertain todrain the airpressure 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
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.
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
notattempt 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.
SECONDARY
SERVICE
CIRCUIT CONTROL
PORT
EXHAUST
PORT CONTROL
PISTON DUALBRAKE
VALVE
PRIMARYSERVICE
CIRCUIT
BALANCE
PORT
DOUBLE
CHECKVALVE
SUPPLY
PORT
PARK
CONTROL
VALVE
SINGLE
CHECK
VALVE
BALANCEPISTON
INLET/EXHAUST
VALVE
SPRING
BRAKE
ACTUATOR
+ SPRINGBRAKEHOLD-OFFPRESSURE
- SERVICEAIRPRESSURE
o ATMOSPHEREPRESSURE
#2RES.
#1RES.
PRIMARY -
SECONDARY -
PARK -
FIGURE 7 - PARKING
PREVENTIVE MAINTENANCE
Important: Review the Bendix Warranty Policy before
performinganyintrusivemaintenanceprocedures.Awarranty
maybe voided if intrusivemaintenanceisperformed during
thewarranty period.
No two vehicles operate under identical conditions, as a
result, maintenance intervals may vary. Experience is a
valuableguide indeterminingthe bestmaintenanceinterval
for air brake system components.At a minimum, the R-7™
valveshouldbeinspectedevery6monthsor1500operating
hours,whichever comes first, for proper operation. Should
the R-7™valve not meet the elements of the operational
testsnotedinthisdocument,furtherinvestigationandservice
ofthe valve mayberequired.

4
OPERATING TEST
Blockvehicle and holdbymeansother than vehiclebrakes.
Chargeairbrakesystem to governor cut-out pressure.
1. Place parking control valve in “park” position. Observe
that spring brake actuators apply promptly. Remove
oneline fromdeliveryport ofvalveand installtestgauge
known to be accurate. Place parking control valve in
“release”position. Observethat spring brake actuators
releasefully.
2. With parking control valve in “release” position, note
gauge pressure reading. (Check vehicle manual for
correct spring brake actuator hold-off pressure.) If
pressurereading is incorrect, modulating valve should
be adjusted. (See section “Adjustment of Modulating
Valve - Spring BrakeActuatorHold-OffPressure”.)
3. Place parking control valve in “park” position - gauge
readingshoulddrop to zero promptly. Alag(morethan
1 second) in drop of pressure would indicate faulty
operationofthesinglecheckvalve(withinthemodulating
valve).
4. Withtheparking control valve in the “park” position fully
applyfootbrakevalveseveraltimes andnote apressure
reading increase on the gauge each time the brake is
applied. If pressure reading does not occur, the
modulatingvalve requires servicing orreplacing.
5. Place parking control valve in “release” position.
Determinethereservoirwhichsuppliesbalanceportand
draincompletely.
Applyfoot brake valveseveraltimesand note thatpressure
reading on gauge decreases each time foot brake valve is
applied. Afterfootbrakevalvehasbeenappliedseveraltimes,
pressureongaugewill dropto thepointwherereleaseofthe
springbrakeactuatorswill no longer occur.
LEAKAGETEST
Placetheparkcontrolvalveinthe “release” position; using
asoapsolution,coatexhaustandventhole(inproximityof
adjustingscrew). Slightbubbleleakage permitted.
If the valve does not function as described, or if leakage is
excessive,it isrecommendedthat it berepairedor replaced
witha genuine Bendixservicereplacement valve.
ADJUSTMENT OF MODULATING VALVE - SPRING
BRAKE ACTUATOR HOLD-OFF PRESSURE
Blockvehicle by means other than vehicle brakes. If ithas
beenascertained that hold-offpressurefor the springbrake
actuators is incorrect (see section “Operating Test”),
adjustmentshouldbemade as follows:
1. Build system pressure to governor cut-out
(approximately 120 psi). It is important that system
leakage for a single vehicle not exceed a 2 psi drop in
one (1) minute with brakes released. Correct system
leakagebeforeproceedingwithadjustment.
2. Placeparkingcontrolvalve in “park” position and install
an accurate test gauge in a delivery port of the
modulatingvalve. Placeparkingcontrolvalvein“release”
positionandobservepressurereadingonthetestgauge.
Refer to vehicle manual for recommended pressure.
Adjust as necessary.
TO RAISE HOLD-OFF PRESSURE
Loosenlocknut.Turnadjustingscrewclockwiseandobserve
readingon gauge. Toraisehold-offpressure,turn adjusting
screwclockwise-tolowerhold-offpressure,turnadjusting
screwcounterclockwise until pressureisbelowthat desired
andthen turn screwclockwiseto desired pressure. Tighten
locknutsecurelyafter completing adjustment.
DISASSEMBLY
1. Remove exhaust cover screw, exhaust cover and
exhaustdiaphragm.
2. Removefour (4)capscrewsandlockwashersandcover.
Removeo-ringfromcover.
3. Removecontrol pistonandremovethree(3)o-ringsfrom
control piston.
4. Removelarge retainingringfrombodyand removeinlet/
exhaustvalveassembly.
5. Removeringfrominlet/exhaustvalveassembly. Remove
o-ring retainer, remove o-ring from o-ring retainer.
Removewasherandspring. Removevalveretainer and
valvefromvalvebody.
6. Remove four (4) cap screws from other cover. (Do not
disturb center cap screw unless spring brake hold off
pressure is to be adjusted). See Section “Adjustment
ofModulating Valve”.
7. Removecoverand inner and outer springs.
8. Remove balance piston. Remove o-ring from balance
piston.
9. Remove retaining ring from supply port and remove
supply adapter and double check valve assembly.
Remove o-ring from supply adapter. Remove double
checkvalvefrom shuttleguide. (NOTE:Toeaseremoval
of supply adapter, a pipe nipple can be screwed in
adapter.)
10. Removeallenheadplugfrom singlecheckvalveservice
port. Remove single check valve assembly. (If single
check valve is difficult to remove, it can be dislodged
insideboreof body of valve).

5
ASSEMBLY
Before assembly, lightly lubricate all o-rings, bores and
mating surfaces with silicone lubricant BW-650-M (Bendix
Pc.No.291126).
1. Installsingle checkvalveassembly andallenhead plug.
Tighten securely.
2. Installo-ringonsupply adapter,installshuttle guideover
supplyadapterand install double check valve in guide.
3. Install adapter and double check valve assembly in
supply port. Install retaining ring, making certain the
retainingringisengaged in groove.
4. Installo-ring onbalancepistonandinstallbalancepiston
in bore of body.
5. Install inner and outer springs and spring seat (note
that cone shaped protrusion on spring seat faces
springs).
6. Install cover with four (4) cap screws, torque to
approximately 45 in. lbs. (Do not disturb center cap
screw unless spring brake hold-off pressure is to be
adjusted. See section “Adjustment of Modulating
Valve”).
7. Installvalveon valve body. Installvalve retainer,spring,
and washer. Install o-ring on o-ring retainer. Install
o-ring retainer, compress retainer and install retaining
ring,makingcertainretainingring is engaged in groove
ofvalvebody.
8. Install inlet/exhaust valve assembly in body. Install
retainingringmakingcertaintheretainingringisengaged
ingroovein bore of body.
9. Install three (3) o-rings on control piston. Install control
pistoninbody. (Larger diameter stem should point up).
10. Install o-ring on cover. Install cover with four (4) cap
screwsandlockwashers. Torquetoapproximately100
in. lbs.
11. Installexhaustdiaphragm and exhaust cover.
TESTING REBUILT R-7™MODULATING VALVE
Performoperating and leakagetestsasoutlined in “Service
Tests” section.

6BW1445 © 2004 Bendix Commercial Vehicle Systems LLC. All rights reserved. 3/2004 Printed in U.S.A.