Bendix TR-2-TR-3-TR-4 INVERSION VALVE User Manual

®

Bendix® TR-2™, TR-3™ & TR-4™ Inversion Valves

SD-03-4650

CAP NUT

SUPPLY PORT

INLET & EXHAUST

DELIVERY PORT (2)

CONTROL PORT (3)

PISTON SPRINGS

RETAINER RING

EXHAUST

DIAPHRAGM WASHER

FIGURE 1 - TR-2™ INVERSION VAL VE

DESCRIPTION

GENERAL

The TR-2™ & TR-3™ valves are normally open pilot-operated,
inverting, on-off, two-way valves. The TR-4™ valve is lever
operated. With normal operating pressure at both supply
and control ports, the delivery port will be exhausted to
atmosphere. 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.

TR-2™ INVERSION V AL VE

SEAL RING

VALVE SPRING

BODY

CAP SCREW

MOUNTING NUT

& LOCKWASHER

INLET & EXHAUST

VALVE

PISTON GROMMET

(SMALL)

PISTON

PISTON GROMMET

(LARGE)

COVER PLATE

EXHAUST

DIAPHRAGM

TR-3™ INVERSION V AL VE

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

TR-4™ INVERSION V AL VE

Referring to Figure 4, the TR-4™ valve is a TR-3™ valve with
the internal passage connecting supply and control plus a
manual lever control which permits the valve to be locked in
the open position.

Referring to Figure 1, the TR-2™ valve was used primarily in
early DD-3™ Safety Actuator control systems to apply air
pressure to the emergency diaphragm of the DD-3
actuator’s from a protected reservoir as control pressure is
released from the lock mechanism. The TR-2™ valve is
available in 11/4" bulk head mount only .

OPERATION

TR-2™ & TR-3™ INVERSION V AL VES

™

When sufficient 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 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

1

EXHAUST

DIAPHRAGM

PISTON SPRING

DIAPHRAGM

RETAINER

PISTON

SHIM

1/8” P.T.

CONTROL

INLET &

EXHAUST

VALVE

VALVE STOP

O-RING

1/4” P.T. SUPPLY

FIGURE 2 - TR-3™ INVERSION VAL VE FIGURE 3 - TR-3™ INVERSION VAL VE

predetermined pressure or is vented from the control cavity ,

EXHAUST

NUT

O-RING

O-RING

1/4” P.T.

DELIVERY

VALVE

SPRING

CAP

PIPE

PLUG

INTERNAL

PASSAGE

INTERNAL BLEED CONTROL

PREVENTIVE MAINTENANCE

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.

The TR-3™ valve with the internal control passage functions
the same as above except 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.

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 6 months or 1500
operating hours, whichever comes first, 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.

TR-4™ INVERSION V AL VE

The TR-4™ valve provides the same functions as the internal
passaged TR-3™ valve except the lever override gives the
operator the option of locking the valve in the open or delivery
position.

MOUNTING LOCATION

Care should be given to assure proper mounting location of
the valve with the exhaust pointed downward, 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.

2

OPERA TING AND LEAKAGE TESTS

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 vehicle manual. With air pressure present
in supply and control port, apply a soap solution around the
supply port cap nut. No leakage is permitted. Apply soap
solution to the delivery and exhaust ports. Leakage should
not exceed 100 SCCM or a 1" bubble in not less than 5
seconds. Excessive leakage would indicate a faulty o-ring
or inlet valve. Operate the manual control of the TR-4™ valve
and note that delivery and exhaust occur promptly .