Bendix Commercial Vehicle Systems PP-DC PARK CONTROL VALVE 6/07 - Manual

1
®
SD-03-3619
Bendix ® PP-DC ® Park Control Valve
FIGURE 1 - BENDIX ® PP-DC ® PARK CONTROL VALVE
SUPPLY
12
BUTTON
EXHAUST
3 SUPPLY
12
BUTTON
COVER
EXHAUST
3
EXHAUST
3
SUPPLY
12
SUPPLY
11
DELIVERY
21
DESCRIPTION
The Bendix ® PP-DC ® park control valve is a push-pull,
manually operable on/off valve. It is dash board-mounted
and provides in-cab control of truck or bus parking brakes.
The valve is pressure sensitive—it automatically
moves from the applied to the exhaust position when
total system pressure drops below 20 to 40 psi. (Note
that this is a Bendix
® product specification and not a
mandated requirement. Refer to Bendix Technical
Bulletin TCH-003-051). Also, manually pulling the
button will apply the parking brakes.
The PP-DC valve body is made of non-metallic, non-
corrosive material, and the cover is available in several
variations (see Figure 1). The valve is designed to accept
pipe thread fi ttings or push-to-connect fi ttings that use SAE
J844 non-metallic air brake tubing.
Ports:
Port Embossed I.D.
Primary Reservoir Supply SUP 11
Secondary Reservoir Supply SUP 12
Delivery DEL 21
Exhaust EXH 3
OPERATION
GENERAL
The PP-DC valve receives its supply of air from the primary
service reservoir or the secondary service reservoir,
whichever is at the higher pressure. When the button
is pushed in, the valve delivers air to the spring brake
chambers (usually through a spring brake valve such as
the Bendix
® SR-7 ® valve and a relay, or quick release,
valve). The air releases the spring brakes for normal vehicle
operation.
To apply the parking brakes, the button is pulled out, which
exhausts the PP-DC valve delivery and releases air from
the spring brake chambers.
When total system pressure drops below 20 to 40 psi,
the valve will automatically “pop out,” which removes the
hold-off air in the chambers and applies the spring brakes.
PARKING BRAKES RELEASED
To release the parking brakes, the push-pull button is
pushed in. The PP-DC valve plunger moves, closing the
exhaust port with the exhaust seal and allowing the plunger
o-ring to move past the guide spool. Supply air then travels
out the delivery port to release the brakes.