TM 3-1040-263-34
CAUTION
4-42. Twelve-Hour Break-In Run
Replacement of the third-stage c3ylindcla.d plunger
During operation, compressor oil pressure
assembly requires a 12-hour break-ill run
must be 20 psi minimum to insure compressor
will not seize cue to lack of oil lubrication.
a. Fill oil sump to the required level with
compressor oil.
c. Perform
compressor
operation
in
accordance with the values in table 4-1.
b. Perform compressor 12-hour operation in
accordance with the values in table 4-3.
d. Check blowby during the last 2 hours of
operation. Blowby must net exceed 0.3 standard cubic
Table 4-2. Four-Hour Break-In Run
feet-per-minute with 1,950 to 2,050 pounds pressure on
the compressor.
Start
Speed
Delivery
Run-in
(hours)
(rpm)
pressure (psi)
(hours)
e. Check oil consumption during the last 4
hours of operation. Oil consumption must not exceed 7
0
1,500
400-600
2
cc per hour.
2
2,500
1,200-1,400
3
3
3,600
1,950-2,050
4
f.
Check oil pressure when performing the oil
consumption check. Oil pressure should be between 55
Table 4-3. Twelve-Hour Break-In Run
to 105 psi.
Start
Speed
Delivery
Run-in
4-41.
Four-Hour Break-In Run
(hours)
(rpm)
pressure (psi)
(hours)
Basic compressor require a 4-hour break-in run Then a
0
1,750
400-600
first-stage piston or cylinder, a second-stage plunger or
6
6
2,500
1,200-1,400
cylinder, a piston pin, a keystone assembly, a crankshaft,
10
or bearings are replaced.
10
3,600
1,950-2,050
a. Fill oil sump to the required level with
12
compressor oil (TM 3-1040-263-12).
4-43.
Periodic Testing
Table 4-1. Twelve-Hour Overhaul Run-In
General support maintenance personnel are responsible
Start
Speed
Delivery
Run-in
for surveillance and testing of AN-M4D compressors in
(hours)
(rpm)
pressure (psi)
(hours)
accordance with TB 742--93--1.
0
1,500-2000
400-600
2
4-44.
Troubleshooting
2
2,500
400-600
4
4
2,500
800-900
6
Table 4 -4 provides information useful in diagnosing and
6
3,600
1,400-1,600
8
correcting unsatisfactory operation or failure of the
8
3,600
1,900-2,050
12
compressor and its components. Malfunctions which
b. Perform compressor 4-hour operation in
may occur are listed.
Each malfunction stated is
accordance with the values in table 4-2.
followed by a list of probable causes of the trouble. The
corrective action recommended is described opposite
the probable cause.
Table 4-4. Troubleshooting
Item
No.
Malfunction
Probable cause
Corrective action
1....
Low airflow-------------
a. Restriction of 1st-stage inlet----
Remove restriction
b. Pinched 1st-stage intake valve
Examine
1st-stage inlet components
c. Leaky l1s-stage head gasket ---- Replace faulty gasket (para 4-27b(4)
d. Leaky 2nd-stage relief valve ------Readjust valves (para 4-10); replace
any defective valve (2, fig. 4-12).
e. Leaky valve plate gasket -------
Replace faulty gasket (para 4-28b(6)).
f. Pinched 2nd- or 3rd-stage stop
Replace gasket; tighten applicable lock-
gasket.
screw (para 4-28b(3) and 4-29b(4)).
g. External air leakage -----------
Check all fittings, screws, connections,
and gaskets for looseness, cracks,
and corrosion.
4-29
