Bendix Commercial Vehicle Systems TR-3 User Manual

Bendix® TR-2™ & TR-3™ Inversion Valves

SD-03-4650

SUPPLY PORT

INLET & EXHAUST

VALVE SPRING

DELIVERY PORT (2)

CONTROL PORT (3)

PISTON SPRINGS

RETAINER RING

EXHAUST

FIGURE 1 - BENDIX® TR-2™ INVERSION VALVE

DIAPHRAGM WASHER

DESCRIPTION

GENERAL

The Bendix® TR-2™ & TR-3™ valves are normally open,
pilot-operated, inverting, on-off, two-way valves. As control
pressure is reduced—to the point that the piston return
spring or springs overcomes the force on the control
piston—the valve will deliver full supply pressure at the
delivery port.

BENDIX

Referring to Figure 1, the Bendix TR-2 valve was used
primarily in early Bendix
systems. It applied air pressure to the emergency
diaphragm of the DD-3 actuators from a protected reservoir
as control pressure is released from the lock mechanism.
The TR-2 valve is available in 1-1/4" bulk head-mount only.

®

TR-2™ INVERSION VALVE

®

DD-3™ safety actuator control

CAP NUT

SEAL RING

MOUNTING NUT

& LOCKWASHER

INLET & EXHAUST

VALVE

BODY

CAP SCREW

PISTON GROMMET

(SMALL)

PISTON

PISTON GROMMET

(LARGE)

COVER PLATE

EXHAUST

DIAPHRAGM

BENDIX® TR-3™ INVERSION VALVE

Referring to Figure 2, the Bendix TR-3 valve is similar in
function to the Bendix TR-2 valve, but with a die cast body.
Referring to Figure 3, some TR-3 valves have an internal
passage in the body connecting supply pressure to control.
The external control port is permanently plugged in such
valves.

OPERATION

BENDIX TR-2 & TR-3 INVERSION VALVES

When suffi cient air pressure is present in the control cavity
to overcome the setting of the piston return spring, the
piston is held away from the inlet valve which is, in turn,
held closed by the inlet valve return spring. The delivery
lines are vented to atmosphere through the hollow exhaust
stem of the piston. When air pressure in the control cavity
falls to a predetermined pressure—or is vented from the
control cavity—the piston spring forces the piston against
the inlet valve, closing the exhaust passage in the hollow
piston stem. Further travel of the piston opens the inlet
valve allowing the passage of air past the open inlet valve,
and out the delivery port.

1

CAP

1/4” P.T. SUPPLY

O-RING

INTERNAL

PASSAGE

VALVE

SPRING

1/4” P.T.

DELIVERY

O-RING

SHIM

O-RING

EXHAUST

NUT

DIAPHRAGM

FIGURE 2 - BENDIX® TR-3™ INVERSION VALVE FIGURE 3 - BENDIX® TR-3™ INVERSION

EXHAUST

The Bendix® TR-3™ valve, with the internal control passage
functions the same as described in the previous paragraph.
The only exception is that the control pressure is always
the same as the supply pressure. Consequently, as supply
pressure builds up, when the pressure is great enough to
overcome the piston return spring, the delivery pressure
will be vented out the exhaust. On descending supply/
control pressure, as the piston return spring overcomes
the control pressure the valve will deliver the remaining
supply pressure at the delivery port.

VALVE STOP

INLET &

EXHAUST

VALVE

1/8” P.T.

CONTROL

PISTON

DIAPHRAGM

RETAINER

PISTON SPRING

VALVE INTERNAL BLEED CONTROL

months or 1500 operating hours, whichever comes fi rst,
for proper operation. Should the inversion valves not
meet the elements of the operational tests noted in this
document, further investigation and service of the valve
may be required.

The TR-3 valve is non-serviceable while the Bendix® TR-2™
valve can be serviced with a maintenance kit. For the latest
service parts and kits, refer to the Bendix Quick Reference
Catalog (BW1114) available for order or download at
www.bendix.com

MOUNTING LOCATION

OPERATING AND LEAKAGE TESTS

Care should be given to assure proper mounting location
of the valve with the exhaust pointed downward (toward
the road surface). It should be mounted high on the frame
rail, and away from road spray and debris. Unprotected
or exposed exhaust ports can allow migration of road
contaminants into the valve, which may cause accelerated
wear or unintended operation.

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 inversion valves should be inspected every six(6)

NOTE: The following checks should be made with two

calibrated gauges or two gauges known to be
accurate. Depending upon installation, it may be
easier or necessary to completely remove the
valve to test properly.

Install one test gauge in a common control and supply
line; install the other gauge in the delivery port. Gradually
apply pressure to the common supply and control line. On
ascending pressure, note at what pressure exhaust occurs
and compare with the vehicle manual. With air pressure
present in supply and control ports, apply a soap solution to
the delivery and exhaust ports. Leakage should not exceed
100 SCCM or a 1" bubble in 5 seconds. Excessive leakage
would indicate a faulty o-ring or inlet valve.

Slowly decrease pressure in the control cavity and note
at what pressure delivery is made. Compare this with the
vehicle manual notation.

2