BENDIX TP-2 TRACTOR PROTECTION VALVE User manual

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®
SD-03-3651
DESCRIPTION
The Bendix®TP-2™tractor protection valve functions as a
setofremotecontrolledcut-outcocks,protectingthetractor
air supply should a loss of air occur in the trailer side
(delivery)ofthevalve.TheTP-2™valveisa threelinesystem
ascomparedto the TP-3™valve whichisatwo line system.
The valve is normally piped as shown in Figure 2. Lines
deliveringservice and supply (emergency) pressureto the
trailerareroutedthroughthevalve.Athirdcontrol Iinecomes
from the on-off control valve in the cab.
With the control valve in the “normal” (on) position and
reservoir pressure at approximately 50 psi, the valve will
open and service and emergency air is permitted to pass
through the valve. With the control valve in the emergency
position (off) position the vaIve is closed and service and
emergency lines on the trailer (delivery) side of the valve
areopen to atmosphere throughthe vaIve’s exhaust port.
Thevalvewill automatically closeandvent delivery lines to
atmosphereshouldairpressuredropbelowasafeoperating
minimum pressure (approx. 40 psi), thus retaining and
protecting the tractor air brake system against complete
loss of air.
NOTE: With a TP-2™valve system it should be noted that
thepneumaticlogicforthelegallyrequiredautomatic
functionis incorporated intheTP-2™valvewhereas
inthecurrentTP-3™valvesystemthelogic is in the
supplyvalveinthecab.ConsequentlyaTP-2™valve
shouldnever be replacedby a TP-3™valveunless
the on-off control valve in the cab is replaced with
eithera PP-3™or PP-7™trailersupply valve.
OPERATION - NORMAL POSITION
With air pressure at approximately 50 psi at the control
port, the diaphragm and plunger assembly is depressed
and the plunger contacts the service and exhaust valve
surfacesealing theexhaust passage through the center of
theplunger.Continuedtraveloftheplungermovestheservice
valve off its seat, opening the service passage from the
Bendix®TP-2™Tractor Protection Valve
FIGURE1 - TRACTOR PROTECTION SYSTEM
TRAILER
EMERGENCY
PORT
CAP NUT
CONTROL PORT
TRAILER
SERVICE
PORT
EXHAUST PORT
TRACTOR
SERVICE
PORT
TRACTOR
EMERGENCY
PORT
(11) O-RING
(2)COVER
EXHAUST PLUNGER
SPRING(15)
CONTROL CAP (13)
O-RING (9)
VALVESEAT(5)
SERVICEANDEXHAUST
VALVE(6)
O-RING (10)
SPRING(8)
VALVE
RETAINER(7)
O-RING (16)
CAP NUT (12)
EXHAUSTVALVEPLUNGERAND
DIAPHRAGMASS’Y(14)
EMERGENCY
VALVE(3)
EMERGENCYVALVE
SPRING(9)
(1)CAPSCREW

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tractor service port to the trailer service port. The stem of
theserviceandexhaustvalvecontactstheemergencyvalve,
sealingtheexhaustpassage.Continued traveloftheservice
andexhaustvalveplungermovestheemergencyvalveoffits
seat and allows air to flow from the tractor emergency port
tothe traileremergency port.
EMERGENCY POSITION
Ifairpressurein thecontrolport(andontopofthediaphragm
and plunger assembly) drops below approximately 40 psi,
the combined forces of the exhaust plunger spring, the
serviceandexhaust valve spring andtheemergency valve
spring will return the diaphragm and plunger assembly
allowingthe service and exhaustvalveand the emergency
valveto close. Furtherflow of air througheither the service
or emergency ports is stopped. The loss in air pressure
whichwouldprecede such actionwouldbe indicated to the
driver,either visually or audibly by the lowpressure warning
device, before such action would occur.
PREVENTIVE MAINTENANCE
Important: Review the Bendix Warranty Policy before
performinganyintrusivemaintenanceprocedures.Awarranty
maybevoidedifintrusivemaintenance is performed during
thewarrantyperiod.
No two vehicles operate under identical conditions; as a
result, maintenance intervals may vary. Experience is a
valuableguide in determining the best maintenance interval
forairbrake system components.At a minimum, theTP-2™
valveshouldbeinspectedevery6 monthsor1500operating
hours,whichever comes first,for proper operation. Should
the TP-2™valve not meet the elements of the operational
testsnotedinthisdocument,furtherinvestigationandservice
ofthevalvemayberequired.
OPERATING AND LEAKAGE CHECK
NOTE: To make the following operating and leakage
checks,an accurate test gauge installed in spare
hosecouplingis required. The vehicledashgauge
should be checked for accuracy against the test
gauge prior to making these tests.
1. Block and/or hold the vehicle by means other than air
brakesduring these test.
2. Drainvehiclereservoirs. Then close drain cocks.
3. Disconnect vehicle emergency and service hose
couplings and connect assembled hose coupling and
test gauge in tractor emergency hose coupling.
4. Start engine and build up system pressure.
5. As pressure in system builds up there should be no
pressurereadingon test gauge. When system pressure
reaches30 psi on dashgauge, make andhold a foot or
handvalveapplication and observe thatnoair escapes
at the open service hose coupling.
6. Whensystempressurereaches40to60psi,valveshould
open and pressure reading show on test gauge. Allow
system to build up to 100 psi and shut off engine.
7. With soap solution coat exhaust port of the Tractor
Protection Valve. Leakage of a 1" bubble in 3 seconds
ispermissible (175 SCCM).
8. Place the tractor protection control valve in the
“Emergency” position and note that emergency line
pressure drops promptly to zero on test gauge.
Disconnectcoupling and testgauge.
FIGURE2 - TRACTOR PROTECTION SYSTEM
TRAILER
SERVICELINE
TRAILER
EMERGENCY
LINE
TRACTOR
PROTECTION
VALVE
NO.2
RESERVOIR
BRAKE
VALVE
NO.1
RESERVOIR
CHECK
VALVE
COMPRESSOR
CONTROL
VALVE

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9. With soap solution:
A. Coat emergency line coupling. Leakage of a 1"
bubble in 5 seconds is permissible (100 SCCM).
B. Coatservicelinecoupling.Make andholdafullhand
orfootvalveapplication.Leakageofa1"bubblein5
secondsis permissible(100 SCCM).
10. Connect thecoupling andtest gaugeto theemergency
line hose coupling. Place the tractor protection control
valveto“Normal”position.(Ifnecessary,re-startengine
and build system pressure.) With ignition switch “on”
slowlydrain tractor air brakesystem observing that low
pressureindicatoroccursatprescribedpressure(normally
at approximately 60 psi) observe that the emergency
Iinewillbeventedbythetractorprotectionvalvebetween
45 to 33 psi (test gauge will drop to 0 psi.)
IftheTP-2™tractor protection valve does not function as
describedorifleakage is excessive, itisrecommended
thatitbereplacedwithanew or remanufactured unit, or
repairedwithgenuine Bendix parts, availableatBendix
outlets.
REMOVINGAND INSTALLING
REMOVING
1. Block and/or hold vehicle by a means other than air
breaks. Drain air system reservoirs.
2. Identify lines and hoses so that correct lines are
reconnected to proper ports when reinstalling.
3. Remove lines;removevalve.
INSTALLING
1. Mount valve, checking to make certain control cap is
properlypositioned.If it is necessarytore-position cap,
refer to No. 3 of “Assembly Instructions.”
2. Connect lines making certain proper lines are
connected to correct ports.
DISASSEMBLY
Important: Mark position of control port and tractor
emergencyport locationinrelationto bodyinsuchamanner
that mark will not be obliterated during cleaning of parts.
Three(3) springs invalve should be carefullymarked as to
theirproperlocationin valve as valve isdisassembled.
1. Removefour(4)cap screws (1) Figure 1,lockwashers,
and cover (2) from valve.
2. Remove emergency valve (3) and emergency valve
spring (4) from cover.
3. Remove valve seat (5) service and exhaust valve (6),
valve retainer (7), spring (8).
4. Removeo-rings(9),(10),and(11).
5. Removecapnut (12) andcontrolcap. (13).
6. Removeexhaustvalveplungeranddiaphragmassembly
from body. (14).
7. Removeexhaustplungerspring(15)frombody.
8. Inspect bores in valve body to be sure they are not
damaged or out of round. Clean body, control cap and
cover.
CLEANING AND INSPECTION
1. Clean all metal parts in mineral spirits and dry them
completely.
2. Inspect all parts for excessive wear or deterioration.
Inspect valve seats for nicks or burrs. Check the valve
springfor cracks orcorrosion.
3. Inspectthebores of the valve housingfordeep scuffing
orgouges.
Replace all parts that were discarded and any parts not
foundtobeserviceableduringinspection,usingonlygenuine
Bendixreplacementparts.
ASSEMBLY
Before assembling the TP-2™valve, lubricate all o-rings,
o-ringgrooves,bodyboresandrubbingsurfaceswithBendix
siliconelubricant(Pc. No. 291126) or equivalent.
NOTE: When using pipe thread sealant during assembly
and installation, take particular care to prevent the
sealant from entering the valve itself. Apply the
sealantbeginningwiththesecondthreadbackfrom
theend.
1. Place in vise with control cap end up. Install o-ring (16)
in groove in the stem of the exhaust valve plunger and
diaphragmassembly(14).
2. Install exhaust plunger spring (15) in valve body and
installexhaust plunger and diaphragmassembly(14).
IMPORTANT: Both sides of diaphragm and clamping
surfaces of body and control cap must be
free of grease. Plunger should be a neat
sliding fit in bore.
3. Positioncontrolcap(13)andcapnut(12).Positioncontrol
cap to desired port angle (as marked during
disassembly). Install a short (4-6") 1/4" pipe nipple in
controlport of cap. Applypressurefirmlyoncap,holding
in position with pipe nipple and firmly tighten cap nut to
approximately50 ft. lbs.
It is important that the cap not be allowed to turn while
tighteningthecapnut. Remove pipe nipple from control
port.
4. Place valve in vise with control cap down.
5. Installo-ring(10)in valve body (smalleroftwoo-rings).

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6. Preassemblethefollowingpartsbeforeinstallinginvalve:
a. Install valve seat o-ring (11) in small bore of valve
seat making certain it is properly seated in groove.
Install spring (8) (the heavier of the two remaining
springs) over protrusion on small bore end of valve
seat.
b. Installvalveretainer(7)onserviceandexhaustvalve
(6).Install stemofserviceand exhaustvalvethrough
centerof spring and intosmall bore ofvalveseat.
7. Carefullyinstallpreassembledparts in body and holdin
place.
8. Positiono-ring(9) in groove of body.
9. Positionemergencyvalvespring(4)incover(2)andplace
emergencyvalve(3)(metal side of valve incontactwith
spring)on top ofspring.
10. Installcover(2)indesiredportposition(asmarkedduring
disassembly.) Check to be certain o-ring (9) and
emergencyvalve(3)areinposition.
11. Install cap screws and lockwashers and tighten to
approximately100 in. lbs.
TESTING REBUILT TP-2™TRACTOR
PROTECTION VALVE
Performance tests as outlined in “Operating and Leakage
Checks” section.
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 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. 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 certaintodrain theair 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
certainallcomponentsandsystemsarerestoredto
their proper operating condition.
BW1436 © 2004 Bendix Commercial Vehicle Systems LLC. All rights reserved. 3/2004 Printed in U.S.A.