1
®
SD-03-3652
Bendix
®
TP-3
™
Tractor Protection Valve
FIGURE 1
DESCRIPTION
The TP-3
™
(See Figure 1) tractor protection valve is used in
combination with the PP-3
™
trailer supply valve on pre-121
tractors and the PP-7
™
trailer supply valve 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 (3). Figure 3. TP-3
™
valves manufactured prior to
June 1970 required approximately 80 psi on the plunger to
open the inlet valve (4) (See Figure 4) which opens the service
line shut off line. Valves manufactured after June 1970 require
approximately 45 psi to open the inlet valve. (Modification
kit 265066 is available to modify old revision TP-3
™
valves to
the later revision 45 psi opening. Field maintenance kit
280858 contains the parts necessary to service both old
and new).
Whenever the pressure from the trailer supply valve drops
below 45 psi the TP-3
™
valve will close the service line shut-off
valve.
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.
TRACTOR
EMERGENCY
PORT
TRAILER
SERVICE
PORT
TRAILER
EMERGENCY
PORT
TRACTOR
SERVICE
PORT
OLD REVISION TYPE TP-3
™
TRACTOR PROTECTION VALVE
OPENING PRESSURE
APPROXIMATELY 80 PSI
O-RING (7)
RETAINING RING (1)
DIAPHRAGM
SEAT (9)
WASHER (8)
PRELOAD
SPRING (2)
DIAPHRAGM (5)
VALVE SPRING (6)
CAP SCREW (3)
INLET VALVE (4)
O-RING (13)
VALVE (4)
RETAINING
RING (1)
O-RING (7)
SEAT
O-RING (12)
VALVE
RETAINER (10)
PLUNGER (3)
CAP SCREW (3)
WASHER (8)
DIAPHRAGM (5)
DIAPHRAGM
SEAT (9)
SPRING (6)
NEW REVISION TYPE TP-3
™
TRACTOR PROTECTION VALVE
OPENING PRESSURE
APPROXIMATELY 45 PSI
RETAINING
RING (14)
EXTERIOR VIEW
