Remove diaphragm spring cap or diaphragm
protector, spring and shim from upper body. Be
sure to retain shim which is used to adjust the
pressure regulation of the valve.
CLEAN AND INSPECTION
Clean all parts in good cleaning solvent. Make
sure vent hole in upper valve body is not
Inspect diaphragm, especially at lower contact
Replace any parts that show wear or spring if
Inspect the diaphragm seat for pitting or nicks.
The seat should be smooth, if not, it may be
dressed with emery cloth. Replace complete
valve assembly if excessive pitting is found.
REASSEMBLY (Refer to Fig. 5)
Position the shim if used in the upper body. The
same number of shims should be used to obtain
proper pressure adjustment.
Position spring, spring cap and diaphragm on
Place lower body over the assembly and force
the two body halves together.
Turn assembly over and install screws.
Test repaired valve assembly.
TEST REPAIRED VALVE
Prior to installing the repaired valve assembly the valve
should be tested for leakage and proper adjustment.
Assemble air gauge and shut-off valve at inlet and outlet
of pressure protection valve then connect to shop air
source. Open shut-off valve at outlet of pressure
protection valve and slowly open shut-off valve at air
source until air pressure reaches 379 kPa (55 psi).
Check for air leakage with soap solution at outlet.
Leakage must not exceed 90 cc per minute (I in. soap
bubble in 6 seconds).
Close the shut-off valve at outlet and increase air
pressure at inlet side of pressure protection valve. No air
pressure at outlet air gauge should be available until
pressure re-reaches 448-517 kPa (65-75 psi) at inlet.
Then both gauges should equalize.
If pressure protection valve opens prior to 448 kPa (65
psi) add shim to valve and if valve remains closed after
517 kPa (75 psi) is obtained remove shim.
After valve has been tested and meets requirements, it is
ready to be installed on vehicle.
PRESSURE REDUCING (LIMITING) VALVE
The pressure reducing (limiting) valve is used to reduce
air pressure and maintain it at a constant specified pre-
set pressure below that of the supply pressure (Fig. 6 ).
The pressure reducing valve has a delivery port on the
side and a supply port on the bottom. Two mounting
holes are cast into the body. A lockwire and seal are
optional for a tamper proof setting.
Fig. 6 Pressure Limiting Valve
OPERATION (Refer to Fig. 7)
The pressure setting of the pressure limiting valve is
determined by the setting of the adjusting cap, which
exerts a force on the spring on top of the piston.
Compressed air enters the supply port and passes out
the delivery port. When the air pressure on the bottom of
the piston overcomes the force of the spring on top of
the piston, the piston moves upward and the inlet valve
spring forces the inlet valve on its seat, closing off the
supply of air. As the pressure in the delivery line drops,
the force of the spring above the piston becomes greater
than the air pressure below the piston, allowing the
piston to move downward, moving the inlet valve off its
seat and allowing air to pass out the delivery port.
CTS-4079 - CHAPTER III
PRINTED IN UNITED STATES OF AMERICA