BENDIX SD-03-3652 User Manual

Bendix® TP-3® Tractor Protection Valve

TRACTOR
EMERGENCY
PORT

TRACTOR
SERVICE
PORT

TRAILER
EMERGENCY
PORT

TRAILER
SERVICE
PORT

VALVE SPRING(6)

DIAPHRAGM

SEAT(9)

DIAPHRAGM(5)

SD-03-3652

O-RING(13)

PLUNGER(11)

INLET VALVE(4)

VALVE RETAINER(10)

RETAINING RING(2)

O-RING(12)

SEAT
O-RING(7)

EXTERIOR VIEW

FIGURE 1 - BENDIX® TP-3® TRACTOR PROTECTION VALVE

DESCRIPTION

The Bendix® TP-3® Tractor Protection Valve is used in
combination with the Bendix® PP-3™ Trailer Supply Valve
on pre-121 tractors, and the Bendix
V alve, or the Bendix

®

MV-3® V alve, on post-121 tractors. It
contains a passage for trailer supply air and a service line
shut off valve. It is normally mounted behind the cab, with
the delivery line from the trailer supply valve connected
into the tractor emergency port and a delivery line from the
brake valve connected to the tractor service port. The trailer
supply and service hoses are mounted in their respective
ports in the TP-3 valve. See Figure 2.

OPERATION

Air from the trailer supply valve passes through the
emergency ports of the TP-3 valve to supply the trailer air
system and simultaneously exerts pressure on the end of
the plunger(1 1). The TP-3 valve requires approximately 45
psi to open the inlet valve. Whenever the pressure from
the trailer supply valve drops below 45 psi, the TP-3 valve
will close the service line shut-off valve.

®

PP-7™ Trailer Supply

WASHER(8)

CAP SCREW(3)

CROSS SECTION

RETAINING RING(1)

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 TP-3 valve should be inspected every 6 months
or 1500 operating hours, whichever comes fi rst, for proper
operation. Should the TP-3 valve not meet the elements
of the operational tests noted in this document, further
investigation and service of the valve may be required.

1

DOUBLE

CHECK

VALVE

BRAKE

VALVE

BENDIX® MV-3®

CONTROL VALVE

BENDIX® TP-3®

TRACTOR

PROTECTION

VALVE

TRAILER

EMERGENCY LINE

TRAILER

SERVICE LINE

AIR

DRYER

COMPRESSOR

FIGURE 2 - SYSTEM SCHEMATIC

FRONT

RESERVOIR

OPERATING AND LEAKAGE CHECKS

1. Block and/or hold the vehicle by a means other than the
air brakes during these tests. Place the trailer supply
valve in the emergency position and disconnect the
trailer supply and service couplings.

2. With the tractor reservoirs charged to at least 100 psi,
make and hold a full service brake application. Leakage
at either tractor hose coupling should not exceed a 1
inch bubble in fi ve seconds (100 SCCM).

3. Connect the trailer supply, or emergency line, hose
coupling and place the trailer supply valve in the “run”
position. Leakage at the “service” coupling should not
exceed a 1 inch bubble in fi ve seconds (100 SCCM).

4. Connect the service coupling and make and hold a full
service brake applicat ion: Leakage at the diaphragm
end of the Bendi x® TP-3® Valve shall not exceed a
1 inch bubble in three seconds (175 SCCM).

NOTE: If the TP-3 V alve does not function as described,
or if leakage is excessive, it is recommended that it be
replaced or repaired using genuine Bendix service
replacement parts.

REAR

RESERVOIR

REMOVING

Remove the trailer hose assemblies from the TP-3 valve.
Disconnect tractor service and supply lines and remove
the TP-3 valve.

INSTALLING

When installing the TP-3 valve, refer to Figure 2, and the
following explanation, for proper connections.

1. The delivery line from the Bendix® MV-3® Dash Control
V alve is connected to the tractor emergency port of the
TP-3 valve.

2. The delivery line from the brake valve (or double check
valve) is connected to the tractor service port of the
TP-3 valve.

3. Trailer hose assemblies are installed in the trailer
emergency and trailer service ports of the TP-3 valve.

2