Build up the air system to full pressure and
The leakage check should be performed at the inlet
shut off the engine.
ports of the valve in the following manner.
Apply a soap solution around the cap of the
Disconnect the line from the inlet port.
pressure protection valve. A 1 in. (254 cm) bubble in
three seconds or longer is acceptable.
Apply air to the other inlet port and coat the
opposite inlet port with a soap solution. Permissible
Drain the air pressure from the delivery side
leakage is a 1 in. (254 cm) bubble in five seconds.
of the pressure protection valve and disconnect air
line to it.
Repeat step b. applying air to the other inlet
port while checking the opposite inlet port for
Apply a soap solution to the delivery port. A 1
leakage. If the double check valve does not function
in. (254 cm) bubble in five seconds or more is
as described or if leakage is excessive, it is
recommended that the valve be replaced.
DOUBLE CHECK VALVES
For more detailed information refer to the
The double check valve is used in the air system
applicable SM package.
when a single function or component must be
controlled by either of two sources of pressure. The
double check valve transmits the higher of the two
pressure sources to the outlet port.
The inlet and exhaust valve assembly,
generally referred to as the insert, can be
Chock the wheels.
easily removed and replaced.
remove the snap ring and exhaust cover
Deplete the pressure in both air systems.
assembly, then pull the insert out.
Normally the insert can be removed
Disconnect and tag the air lines from the
without disturbing the valve mounting or
double check valve and remove the valve.
Install the fittings and air lines to the double
Deplete all reservoirs before attempting
check valve as tagged during removal.
to remove the insert.
Chock the wheels.
Deplete all pressure in both air systems.
If the double check valve is to be bench tested or
tested on the vehicle, two separately controlled air
Identify, mark, and disconnect all air lines from
supplies must be connected to the inlet ports.
Install an accurate test gauge in the outlet port
or in a line from the outlet port.
secure the valve and remove the valve.
Apply and release air to one inlet port and note
the gauge registers application and release.
Repeat by applying and releasing air to the
other inlet port.