Advertisement
Reservoir
Trailer Hand
Control Valve
FIGURE 3 - DOUBLE CHECK VALVE: CONTROL OF
SYSTEM FROM EITHER OF TWO CONTROL SOURCES
PP-7
™
Valve
™
PP-1
Valve
Spring Brake Control
Reservoir
Reservoir
FIGURE 4 - DOUBLE CHECK VALVE: SYSTEM WITH TWO
SUPPLY SOURCES
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 DC-4
valve should be inspected every 6 months or 1500 operating
hours, whichever comes first, for proper operation. Should
the DC-4
™
valve not meet the elements of the operational
tests noted in this document, further investigation and service
of the valve may be required.
2
Brake Valve
To Trailer
Brakes
Double
Check
Valve
Trailer Supply
Double Check
Valve
SERVICE CHECKS
OPERATING AND LEAKAGE TEST
A. When the double check valve is used in conjunction with
a trailer control valve, the following operating and leakage
test can be made:
1. Apply and release foot brake valve and note that the
brakes apply and release on both tractor and trailer.
2. Apply and release the trailer control valve and note
that only the trailer brakes apply and release. With
trailer control valve applied check exhaust port of
foot brake valve for leakage with soap solution.
Permissible leakage is a 1" bubble in 5 seconds (100
sccm).
3. Apply and hold a full foot brake valve application.
Check exhaust port of trailer control valve for leakage
with soap solution. Permissible leakage is a 1"
bubble in 5 seconds (100 sccm). (Note: On some
vehicles, an exhaust line is connected to the exhaust
port and piped outside the cab in which case it may
be necessary to disconnect this line to make leakage
check.)
B. If the double check valve is to be bench tested or tested
on the vehicle, two separately controlled air supplies
must be connected to the inlet ports.
1. Install an accurate test gauge in the outlet port or in
a line from outlet port.
2. Apply and release air to one inlet port and note that
gauge registers application and release.
3. Repeat by applying and releasing air to other inlet
port.
4. Leakage check should be performed at inlet ports of
valve in the following manner:
a. Disconnect the line from one inlet port.
b. Apply air to other inlet port and coat opposite
inlet port with soap solution. Permissible leakage
is a 1" bubble in 5 seconds (100 sccm).
c. Repeat Step "b" applying air to other inlet port
while checking opposite inlet port for leakage.
If the double check valve does not function as described or if
leakage is excessive, it is recommended that the valve be
repaired or replaced with genuine Bendix parts. The following
instructions should prove helpful:
DISASSEMBLY
1. Remove the end cap(s) from the valve.
™
2. Remove the grommets (if applicable).
3. Remove the shuttle and/or shuttle guide, disc and/or
disc guide (depending upon type of valve).
Advertisement
