Bendix Commercial Vehicle Systems QR-N User Manual

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Bendix® QR-N™ Quick Release Valve

SD-03-905

MOUNTING HOLE (2)

DELIVERY PORT

SEALING RING

LOCKWASHER

CAP SCREW

SPRING FOLLOWER

DIFFERENTIAL SPRING

FIGURE 1

DESCRIPTION

The function of the Bendix® QR-N™ quick release valve is to
“speed up” the exhaust of air from the actuators it serves. It
is generally mounted on the vehicle axle midway between
the two actuators connected to it.

In the standard (Refer to Figure 1) QR-N™ valve a flat circular
diaphragm is installed between the nonmetallic upper body
and stamped steel lower body . An o-ring seals the two body
halves which are held together using four 1/4" machine
screws and flange nuts.

In its standard configuration the QR-N™ valve is supplied
with a 1 psi (6.9 kPa) maximum differential. For example
with supply pressure at 10 psi (68.9 kPa) delivery pressure
is 9 psi (61.8 kPa). Higher differential pressures are available
for special applications and are obtained by the addition of a
spring and diaphragm follower to the standard QR-N™ valve
(Refer to Insert A). The QR-N™ valve also comes in sustained
(black body) and non-sustained (gray body) differential
versions.

V arious pipe thread sizes are available for the single supply
port and two delivery ports of the QR-N™ valve. Some versions
of the QR-N™ valve have a threaded exhaust port. (Refer to
Insert B). QR-N™ valve mounting is accomplished via two
1 1/32" diameter holes on 1-1/2" centers.

SUPPLY PORT

EXHAUST PORT

UPPER BODY

DIAPHRAGM

DELIVERY PORT

LOWER

BODY

THREADED EXHAUST PORT

INSERT BINSERT A

OPERATION

With no air pressure applied to the QR-N™ valve (Refer to
Figure 1), the diaphragm is slightly flexed by the upper and
lower body. In this condition the center portion of the
diaphragm rests on the exhaust port in the lower body while
the outer edge and opposite side of the diaphragm rests
against the sealing lip of the upper body .

APPLY

Air entering the supply port of the QR-N™ valve causes the
center portion of the diaphragm to seal the exhaust port.
Simultaneously , the outer edge of the diaphragm moves away
from the sealing lip of the upper body allowing air to flow
from the supply port out the delivery ports.

BALANCE

When air pressure on both sides of the diaphragm is
approximately equal (1 psi differential), the natural resiliency
of the diaphragm material causes the outer edge of the
diaphragm to move into contact with the upper body sealing
lip. The QR-N™ valve exhaust remains sealed because air
pressure bears against the center portion of the diaphragm
from one side only .

1

RELEASE

When air pressure is reduced or removed from the QR-N
valve supply port, the air pressure on the delivery side of the
diaphragm is greater than that on the supply side. The higher

delivery side pressure holds the outer edge of the diaphragm
against the upper body sealing lip while simultaneously
moving the center portion away from the exhaust port. Air
from the delivery ports flows out the exhaust. When air
pressure on the delivery side of the diaphragm equals the
pressure on the supply side, the center portion of the
diaphragm moves into contact with the exhaust port.

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 QR-N
valve should be inspected every 12 months or 3600 operating
hours, whichever comes first, for proper operation. Should

the QR-N™ valve not meet the elements of the operational
tests noted in this document, further investigation and service
of the valve may be required.

WARNING! PLEASE READ AND FOLLOW
THESE INSTRUCTIONS TO AVOID
PERSONAL INJURY OR DEATH:

When working on or around a vehicle, the following
general precautions should be observed at all times.

1. Park the vehicle on a level surface, apply the
parking brakes, and always block the wheels.
Always wear safety glasses.

2. Stop the engine and remove ignition key when
working under or around the vehicle. When
working in the engine compartment, the engine
should be shut off and the ignition key should be
removed. Where circumstances require that the
engine be in operation, EXTREME CAUTION should
be used to prevent personal injury resulting from
contact with moving, rotating, leaking, heated or
electrically charged components.

3. Do not attempt to install, remove, disassemble or
assemble a component until you have read and
thoroughly understand the recommended
procedures. Use only the proper tools and observe
all precautions pertaining to use of those tools.

4. If the work is being performed on the vehicle’s air
brake system, or any auxiliary pressurized air
systems, make certain to drain the air pressure from
all reservoirs before beginning ANY work on the
vehicle. If the vehicle is equipped with an AD-IS
air dryer system or a dryer reservoir module, be
sure to drain the purge reservoir.

5. Following the vehicle manufacturer’s

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recommended procedures, deactivate the electrical
system in a manner that safely removes all
electrical power from the vehicle.

6. Never exceed manufacturer’s recommended
pressures.

7. Never connect or disconnect a hose or line
containing pressure; it may whip. Never remove a
component or plug unless you are certain all
system pressure has been depleted.

8. Use only genuine Bendix® replacement parts,
components and kits. Replacement hardware,
tubing, hose, fittings, etc. must be of equivalent
size, type and strength as original equipment and
be designed specifically for such applications and
systems.

9. Components with stripped threads or damaged
parts should be replaced rather than repaired. Do
not attempt repairs requiring machining or welding
unless specifically stated and approved by the
vehicle and component manufacturer.

10. Prior to returning the vehicle to service, make

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certain all components and systems are restored
to their proper operating condition.

OPERATING AND LEAKAGE TESTS

1. Apply 100 psi (689 kPa) air pressure to the supply port

of the QR-N™ valve and note that the device connected
to the QR-N™ valve responds promptly .

2. With 100 psi (689 kPa) air pressure applied to the

QR-N™ valve SUPPL Y port apply a soap solution to the
exhaust port and around the junction of the upper and
lower body halves.

A.No leakage is permitted between the body halves.
B.Leakage of greater than a 1" (25.4 mm) bubble in 3

seconds at the exhaust port is unacceptable.

3. Release the air pressure at the supply port and note

that the device connected to the QR-N™ valve responds
promptly and returns to a zero air pressure condition.

4. If the QR-N™ valve does not function as described or if

leakage is excessive, it is recommended that it be
replaced with a new or remanufactured unit or repaired
using a genuine Bendix maintenance kit.

5. Use only genuine Bendix replacement parts and

components.
A. Only components, devices, mounting and attaching

hardware specifically designed should be used.

B. Replacement hardware, tubing, hose, fittings, etc.

should be of equivalent size, type, length, and
strength as the original equipment.

C. Make certain that when replacing tubing or hose, all

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supports, clamps or suspending devices that were
originally installed by the vehicle manufacturer are
reinstalled.

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