TM 5-4310-344-34
2-10.
BACK PRESSURE VALVE.
2-5.
REPAIR.
The back pressure valve is installed downstream of the
a. The
following
paragraphs
describe
check valve to maintain steady pressure within the
procedures for repair of all subassemblies except the
compressor pneumatic system.
electric motor. Refer to Appendix A for motor repair.
2-11.
b. Instructions for removal of wiring, tubing,
fittings, and hardware are not included in this manual.
Refer to the applicable exploded view illustrations in the
a. Remove inlet and outlet fittings (3 and 4),
Illustrated Parts Breakdown section for these items.
and tube fitting gaskets (5) from valve body (13).
2-6.
CONTROL BOX ASSEMBLY. An electric relay
b. Unscrew valve cap (6) from top of valve
in the control box assembly is connected in series with
body (13). Remove spring plates (7) and spring (8) from
the pressure valve at the outlet, the power cable, and
inside valve body.
the electric motor. When excess pressure is sensed at
the back pressure valve an electric signal causes the
c. Remove piston (9) and piston seat (10)
relay to open the circuit to the electric motor.
from inside valve body (13). Remove O-ring packings
(11) and retainer (12) from piston and valve seat.
2-7.
2-12.
CLEANING AND INSPECTION.
a.
Disconnect and tag all electric wires at
a. Wash all parts in dry cleaning solvent,
relay (2).
Federal Specification P-D-680, and dry thoroughly with
filtered, compressed air or clean, lint-free cloths. Be
b. Remove nuts (3), lockwashers (4 and 5),
sure all residue is removed from crevices and packing
screws (6), and the relay.
ring grooves.
c. Remove screws (8 and 10) and connectors
b. Inspect parts for evidence of damage and
(9 and 11).
wear such as stripped screw threads, cracking of valve
2-8.
CLEANING AND INSPECTION.
body, and finished surfaces that are scratched, scored
or pitted.
c. Make sure seat surface of piston is smooth
a. Clean the external surfaces of the relay
and undamaged; mating surface of piston seat must be
with a clean cloth moistened with isopropyl alcohol,
sharp and without nicks or other signs of wear or
Federal Specification TT-I-735A. Allow to air dry.
damage.
b.
Inspect connectors for bent or missing pins.
d.
Check spring for signs of set or out-of-
round.
c.
Check
all
electric
wires
for
frayed
Spring must be cylindrical in shape with ends closed,
insulation.
square and ground. Length of spring with a load of 86
2-9.
REASSEMBLY.
pounds plus or minus 10 pounds should be 0.687 inch.
e. Discard
all
damaged,
worn
and
a. Attach the relay with
screws
(6),
questionable parts.
lockwashers (4 and 5) and nuts (3).
2-13.
REASSEMBLY
b.
Install connectors (9 and 11) with screws (8
and 10).
Note
During reassembly, apply a light film of
c. Connect the electric wires as tagged when
pneumatic system grease, Specification
disconnected.
MIL-G-4343, to all gaskets, packings
and male threads.
2-3
