Bendix Commercial Vehicle Systems TP-2 TRACTOR PROTECTION VALVE 3/04 - Manual (Page 2)

2
tractor service port to the trailer service port. The stem of
the service and exhaust valve contacts the emergency valve,
sealing the exhaust passage. Continued travel of the service
and exhaust valve plunger moves the emergency valve off its
seat and allows air to flow from the tractor emergency port
to the trailer emergency port.
EMERGENCY POSITION
If air pressure in the control port (and on top of the diaphragm
and plunger assembly) drops below approximately 40 psi,
the combined forces of the exhaust plunger spring, the
service and exhaust valve spring and the emergency valve
spring will return the diaphragm and plunger assembly
allowing the service and exhaust valve and the emergency
valve to close. Further flow of air through either the service
or emergency ports is stopped. The loss in air pressure
which would precede such action would be indicated to the
driver, either visually or audibly by the low pressure warning
device, before such action would occur.
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 TP-2
™
valve should be inspected every 6 months or 1500 operating
hours, whichever comes first, for proper operation. Should
the TP-2
™ valve not meet the elements of the operational
tests noted in this document, further investigation and service
of the valve may be required.
OPERATING AND LEAKAGE CHECK
NOTE: To make the following operating and leakage
checks, an accurate test gauge installed in spare
hose coupling is required. The vehicle dash gauge
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
brakes during these test.
2. Drain vehicle reservoirs. 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
pressure reading on test gauge. When system pressure
reaches 30 psi on dash gauge, make and hold a foot or
hand valve application and observe that no air escapes
at the open service hose coupling.
6. When system pressure reaches 40 to 60 psi, valve should
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
is permissible (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.
Disconnect coupling and test gauge.
FIGURE 2 - TRACTOR PROTECTION SYSTEM
TRAILER
SERVICE LINE
TRAILER
EMERGENCY
LINE
TRACTOR
PROTECTION
VALVE
NO. 2
RESERVOIR
BRAKE
VALVE
NO. 1
RESERVOIR
CHECK
VALVE
COMPRESSOR
CONTROL
VALVE