Bendix Commercial Vehicle Systems PP-DC PARK CONTROL VALVE 6/07 - Manual (Page 2)

2
FIGURE 2 - TYPICAL 4 X 2 TRUCK SCHEMATIC WITH BENDIX ® PP-DC ® PARK CONTROL VALVE
Note that Figure 3 shows the primary service reservoir
supplying the Bendix
® PP-DC ® valve. The double check
valve diaphragm has sealed the secondary reservoir supply
port and allows air to pass from the primary reservoir into
the PP-DC valve.
If primary service reservoir pressure drops below secondary
service reservoir pressure, the double check valve reacts
as shown in Figure 4. It seals the primary service reservoir
supply port and supplies the Bendix PP-DC park control
valve with air from the secondary service reservoir. The
push-pull button remains in and the spring brakes remain
released.
PARKING BRAKES APPLIED
Figure 5 shows the PP-DC valve in the parking-brakes-
applied position. This will occur when the driver manually
pulls out the push-pull button, or when the total system
pressure drops to below 20 to 40 psi.
As shown in Figure 6, when the button “pops” out, the
exhaust seal moves to open the exhaust port to the
atmosphere, allowing delivery line pressure to exhaust.
The plunger o-ring moves to seal off supply pressure.
Spring brake hold-off air is exhausted through the spring
brake relay valve.
Air disc & drum brake actuation combined on a single axle are shown for pictorial purposes only.
Front
Axle Reservoir
Rear
Axle Reservoir
Supply
Reservoir
Bendix ®
ADB-22X ™
Disc Brake
Bendix ®
EC-60 ™ Electronic
Controller
Brake Valve
Air Dryer
Air Compressor
Antilock
Modulator
(4 places)
Service
Relay
Valve
Bendix ®
PP-DC ®
Park Control
Valve
Bendix ®
PR-3 ™ / PR-4 ™
Valve
To Accessories
Bendix ®
SR-7 ®
Spring Brake
Modulating
Valve
Quick Release
Valve
ADB-22X ™
Disc Brake
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-DC valve should be inspected every six (6) months or
1500 operating hours, whichever comes fi rst, for proper
operation. Should the PP-DC valve not meet the elements
of the Operational Tests noted in this document, further
investigation and service of the valve may be required.
SERVICE CHECKS
1. Remove any accumulated contaminants. Visually
inspect the valve’s exterior for excessive wear or
physical damage. Repair/replace as nec essary.
2. Inspect all air lines connected to the valve for signs of
wear or physical damage. Repair/replace as necessary.
3. Test air line fi ttings for excessive leakage. Repair or
replace as necessary.