BENDIX SD-03-3617 User Manual
Bendix® PP-7™ Trailer Supply Valve
NUT & THREAD
1/8 P.T.
SUPPLY
EXHAUST
SD-03-3617
FUNCTION AND DESCRIPTION
The PP-7™ trailer supply valve provides in cab control for the
tractor protection system and functions in conjunction with
the park control valve. It is responsible for synchronizing
the tractor and trailer parking and emergency brakes.
It is essentially a combination of two non-modulating, on-off
control valves in a single, compact package.
Each of the four pipe tapped ports of the PP-7™ valve are
identifi ed with cast in, raised letters. The supply and control
ports have 1/8 inch N.P .T.F . dry seal pipe threads while the
delivery and exhaust ports have 1/4 inch N.P.T .F. dry seal
pipe threads.
LOCK
WASHER
CAP SCREW
FIGURE 1 - EXTERIOR
(17) PLUNGER
(18) PLUNGER
RETURN
SPRING
HEX LOCK NUT (15)
(12) O-RING
(13) INLET
& EXHAUST
VALVE
1/4 P.T. DELIVERY
(9) O-RING
1/8 P.T. CONTROL
LOCK
WASHER
CAP SCREW
BUTTON (2)
SPIROL
PIN (1)
THIN NUT
O-RING (19)
BODY
INLET & EXHAUST
(16) VALVE
RETAINING RING (10)
SEALING RING (3)
O-RING RETAINER (11)
INLET & EXHAUST (14)
VALVE SPRING
SPRING (7)
LOWER BODY
PISTON (6)
O-RING (8)
O-RING (5)
FIGURE 2 - SECTIONAL
END PLATE (4)
1
PP-7
Control
Valve
™
DS-1™ Double Check
& Stoplight Switch
TRACTOR DUAL AIR BRAKE SYSTEM
TP-3® Tractor Protection Valve
Park
Control
Valve
LQ-3™ Valve
Modulator
FIGURE 3 - PIPING DIAGRAM
Double Check
Supply
Reservoir
™
E-7
Dual
Brake Valve
Valve
#1 Service
Reservoir
SR-1
Brake Valve
LP-3™ Low Pressure
Indicator
#2 Service
Reservoir
™
Spring
Spring Brake
™
R-8
Relay
Valve
Spring Brake Spring Brake
Spring Brake
PP-7™ VALVE LESS THAN 50 PSI
SYSTEM PRESSURE
To
Parking
Brakes
Double
Check
Valve
™
FIGURE 4 - PP-7
TRAILER SUPPLY VALVE LESS THAN 50 PSI SYSTEM PRESSURE
Park
Control
Valve
#1 Service
Reservoir
#2 Service
Reservoir
Inlet & Exhaust
Exhaust Vent
To Tractor
Protection
Control Port
Supply
Port
Plunger
Control Inlet
and Exhaust
Exhaust
Port
Control
Piston
2
PP-7™ VALVE SYSTEM FULLY CHARGED
Park
Control
Valve
To
Parking
Brakes
#1 Service
Reservoir
Double
Check
Valve
FIGURE 5 - PP-7™ TRAILER SUPPLY VALVE SYSTEM FULLY CHARGED
#2 Service
Reservoir
Plunger
Inlet & Exhaust
Exhaust Vent
To Tractor
Protection
Control Port
Supply
Port
Control Inlet
and Exhaust
Exhaust
Port
Control
Piston
GENERAL OPERATION
The PP-7™ trailer supply valve is a dash panel mounted,
push-pull operated control valve. The button of the PP-7™
valve must be manually depressed, but will automatically
pop out and exhaust if supply air is below 40 p.s.i. Fifty p.s.i.
or greater supply air pressure is required for the button to
remain in after it is depressed, and it will remain in until
supply air pressure falls below 40 P.S.I. or until the valve
is manually actuated.
OPERATION - LESS THAN 50 P.S.I. SYSTEM
PRESSURE
With less than 50 P.S.I. system air pressure, the button of
the PP-7™ valve will remain out, and the park control valve
will not deliver air to the control port of the PP-7™ valve.
In this condition supply air cannot fl ow past the closed
plunger inlet, and the plunger exhaust valve is off its seat.
With no air pressure on the control port, the control inlet
is seated, and the exhaust passage through the control
piston is open.
OPERATION - ABOVE 50 P.S.I. SYSTEM AIR
PRESSURE
When system air pressure is greater than 50 P.S.I., the
button of the PP-7™ valve can be depressed and will stay
in. If the vehicle is in the running condition, the park control
valve will be delivering system air pressure to the control
port of the PP-7™ valve. (See Note.)
With the button of the PP-7™ valve depressed, the plunger
inlet will be open and the exhaust valve will be seated,
sealing the exhaust vent. Supply air is permitted to fl ow
through the body to the control inlet and exhaust valve. With
the park control valve delivering full system pressure to the
control port of the PP-7™ valve, the control piston moves
into contact with the control valve, closing the exhaust
passage through the piston and opening the inlet. Opening
the control inlet permits supply air to fl ow out the delivery
port of the PP-7™ valve. (See Note.)
NOTE: If the vehicle is parked and system air pressure is
above 50 P.S.I., the park control valve will not be
delivering air to the PP-7™ valve control port and
the control inlet valve will be closed. In this case
no air will be fl owing from the delivery port of the
™
valve.
PP-7
OPERATION - MANUAL OR AUTOMATIC
EMERGENCY
MANUAL
In order to disconnect the tractor and trailer, the button of
the PP-7™ valve is pulled by the operator. Pulling the button
closes the plunger inlet and unseats the exhaust valve. Air
that was fl owing out the delivery port returns to the PP-7™
valve and is exhausted from the vent in the midsection of
the PP-7™ valve.
NOTE: If the parking brakes were applied prior to pulling
the PP-7™ valve button, no delivery air would be
present to exhaust. Delivery air would have been
exhausted when the parking brakes were applied.
See “Operation Park Application.”
3
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