b. Adjust pressure regulator to apply an air
4.11.1 REMOVAL. The back pressure valve is installed
pressure of 3000 psig to outlet of check valve.
in the outlet port of the filter and separator assembly(see
Leakage, as indicated by air bubbles escaping from
submerged leakage tube, shall not exceed three cubic
a. Remove check valve.
In accordance with
centimeters per hour.
instructions in paragraph 4.10.1.
c. With check valve connected as in step b,
b. Loosen nut (5-8, 16) and unscrew back pressure
reduce applied air pressure to 5 psig. Leakage shall not
valve from outlet port of filter and separator assembly.
exceed three cubic centimeters per minute.
c. Remove tube fitting gasket (5-8, 14), back-up
d. Reverse test connections to check valve so free
ring (5-8, 15) and nut (5-8, 16) from inlet fitting of back
flow arrow points away from air supply.
pressure valve.
e. Slowly open pressure regulator until air flow
through check valve exceeds three cubic centimeters
4.11.2 DISASSEMBLY (Refer to Figure 5-8.)
per minute. This shall occur when applied pressure is
from 2 to 8 psig.
a. Remove inlet and outlet fittings (3 and 4) and
f. Disconnect check valve from test equipment.
tube fitting gaskets (5) from valve body (13).
b. Unscrew valve cap (6) from top of valve body
4.10.6 INSTALLATION
(13). Remove spring plates (7) and spring (8) from
inside valve body.
a. Install tube fitting gasket (5-7, 10) in groove In
c. Remove piston (9) and piston seat (10) from
outlet fitting of back pressure valve.
inside valve body (13). Remove O-ring packings (11)
b. Screw check valve on outlet fitting of back
and back-up ring (12) from piston and valve seat.
pressure valve so that free flow arrow points away from
back pressure valve (down).
4.11.3 CLEANING AND INSPECTING PARTS. Clean
c. (See Figure 5-3.) Re-install tube fitting gasket
and inspect the parts of the back pressure valve
(36), nipple (35), tee (34), valve (33) and nipple (32) in
assembly as follows: a. Wash all parts in dry-cleaning
outlet port of check valve.
solvent (Federal Specification P-S-661) and dry
thoroughly with filtered, compressed air or clean, lint-
d. (See Figure 5-3. ) Reconnect dryer to the
free cloths. Be sure
connecting tube (31) to nipple (32).
4.11 BACK PRESSURE VALVE ASSEMBLY
Figure 4-5. Set-up for Testing Back Pressure Valve
32
