Bendix Commercial Vehicle Systems PP-3 User Manual

®

Bendix® PP-3™ Trailer Supply Valve

SD-03-3613

DESCRIPTION

FIGURE 1 - PP-3

BUTTON

MOUNTING

NUT

SUPPLY

PORT

DELIVERY

PORT

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TRAILER SUPPLY V AL VE EXTERIOR

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PP-3

CONTROL

VALVE

TC-2

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VALVE

The PP-3™ trailer supply valve, installed in the cab, operates
in conjunction with a TP-3

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tractor protection valve to supply
air under pressure to the trailer and protect the tractor air
supply in case of a break-away or an air leak on the trailer
which would reduce the pressure in the trailer supply line
below the design trip point of the PP-3™ valve.

With reference to Figure 2 the supply port of the PP-3
valve is supplied from the towing vehicle reservoir. Its
delivery goes directly to the supply port on the TP-3™ tractor
protection valve.

OPERATION

The PP-3™ control valve is a push-pull operated valve. The
button must be pushed in to open the valve. The button will
not stay in unless there is 50 psi or more in the supply line.
Once the pressure is enough that the button will remain in,
air flows through the tractor protection valve to the trailer.

DOUBLE

CHECK

VALVE

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TP-3

TRACTOR

PROTECTION

VALVE

TRAILER

EMERGENCY LINE

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FIGURE 2

COMPRESSOR

NO. 1

RESERVOIR

TRAILER SERVICE

LINE

BRAKE

VALVE

NO. 2

RESERVOIR

1

If, in the case of an emergency or for some other reason the
driver wishes an application of the trailer brakes, he pulls

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the PP-3
will exhaust out the PP-3

valve control button out. Emergency line pressure

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valve exhaust port causing an

application of the trailer brakes. Also, the TP-3™ inlet valve

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seats and closes the service line. The PP-3

valve button is
pulled out and left out during bob-tailed operation of the tractor .
In normal use the button is pulled out before uncoupling
from the trailer and pushed in after coupling to the trailer.

Should a condition occur resulting in air loss from the tractor
or trailer system through leakage and the driver fails to
manually pull out the PP-3™ valve button, the PP-3™ valve
will automatically close at approximately 40 psi and seal
the tractor air lines. The driver cannot, in this condition,
overcome the emergency application of the trailer brakes by
holding the PP-3

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valve button in. If the driver should hold
the button in as emergency line pressure bleeds down from
the 40 psi range to approximately 30 psi, the tripper piston
will move and open the tripper exhaust in the PP-3™ valve.
Emergency line air will exhaust through the tripper exhaust
and hold the trailer brakes applied.

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 PP-3
valve should be inspected every 12 months or 3600 operating
hours, whichever comes first, for proper operation. Should
the PP-3™ 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 CHECKS

To make the following operating and leakage checks, an
accurate test gauge installed in a 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 a means other than air

brakes during these tests.

2. Drain vehicle reservoir supply , then close drain cocks.

3. Connect assembled hose coupling and test gauge in

tractor emergency hose coupling. Start engine and build
up system pressure.

4. As reservoir pressure builds up there should be no

pressure reading on test gauge. When system pressure
reaches the 30 to 40 psi range on dash gauge make
and hold a foot or hand valve application and observe

2

that no air escapes at the open trailer service hose
coupling.

5. When system pressure reaches approximately 60 psi,
the PP-3™ valve button should be pushed in. System
pressure should show at once on the test gauge
connected in the emergency line and the button of the
PP-3™ valve should remain in without being held.

6. Build system pressure up to approximately 100 psi, then
stop engine. With engine stopped, wait momentarily,
then notice that dash gauge and test gauge pressure
reading equal. While still in this position, make a foot or
hand valve application and observe that air is delivered
out the open trailer service coupling.

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7. With PP-3
PP-3

valve button still in, check for leakage at

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valve exhaust and tripper exhaust ports. Leakage
should not exceed a 1" bubble in 5 seconds at either
point.

8. With PP-3™ valve button still in, check for leakage at the
TP-3™ valve exhaust and open service coupling. Leakage
should not be more than a 1" bubble in 5 seconds at
either point.

9. Pull the PP-3™ valve button out: pressure on the test
gauge connected in the emergency line should drop to
zero. Make and hold a hand valve application and observe
that air delivered at the open service coupling does not
exceed a 1" bubble in 5 seconds. Release foot or hand
valve application.

NOTE: If the PP-3™ valve does not function as described
or if leakage is excessive, it is recommended that it be

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returned to the nearest Bendix authorized distributor for
a factory rebuilt valve. If this is not possible, the valve
should be repaired using genuine Bendix parts, in which
case the following should prove helpful.

REMOVING AND INSTALLING

REMOVING

1. Block and/or hold the vehicle by a means other than air
brakes. Drain air brake system.

2. Disconnect supply and delivery lines from PP-3™ valve.

3. Drive out PP-3™ valve button roll pin and remove button.
Remove PP-3™ valve mounting nut, then PP-3™ valve.

INSTALLING

When installing the PP-3™ valve, refer to Figure 2 for proper
connections along with following explanations:

1. Supply line from tractor reservoir is connected to supply
port of PP-3™ valve.

2. Delivery line from PP-3™ valve delivery port is connected
to tractor emergency port of TP-3™ valve.

3. PP-3™ valve exhaust port and tripper exhaust must be
open.

4. Two (2) ports marked “Del” on upper PP-3™ control valve
body are plugged and must remain plugged.