TM 55-4920-231-14
6270 hose. Fabricate replacement tube assemblies
all times and protects the instruments from pres-
identically to the one being replaced. Blow clean
sure overload. When the pump is producing vac-
and dry, compressed air through the hose and
uum, evacuated air from the vacuum section
tube assemblies when they are removed. Apply
passes through the check valve (20) and the
antiseize and sealing thread compound, Military
sump (21) which prevents oil from entering the
instrument lines. The vacuum INCREASE valve
Specification MIL-T5542 or equivalent to the
third and fourth male threads of all fittings be-
(22) controls the amount of vacuum in the sys-
fore installing hose or tube assemblies as identi-
tem and the vacuum DECREASE valve (23)
fied. Refer to figure 11 for proper installation.
opens the line to the ambient air allowing the
Tighten all connections to prevent leakage.
system vacuum to bleed off. Setting the VAC-
UUM selector valve (36) at the desired test posi-
tion completes the circuit to the instrument un-
der test and the master instrument to one of the
VALVES.
three relief valves (24, 25, or 26) which protect
a. Removal.
the instruments from vacuum overloads. The
(1) Disconnect all hose and tube assem-
case leak valves (2, 4, 5, 8, and 11) provide
blies (10 and 11 figure 21) from fittings (15,
isolation for the master instruments on the test
16, and 17) as instructed in paragraph 63.
set to permit case leak tests and/or calibration
(2) Remove four screws (12) and lock-
of the master instruments without removing
washers (13 ) securing PRESSURE selector valve
them from the tester.
(14) to front panel (23).
(3) Remove selector valve from front panel
and remove all fittings (15, 16, and 17) from
valve.
When one of the relief valves (3, 6, 7, 8, 9,
(4) Remove VACUUM selector valve (18)
or 10, figure 20) does not provide relief at a
in a similar manner.
point within the tolerances listed in table 2 in
performing the master instrument tests (para-
b. Cleaning and Inspection.
graph 39) , proceed as follows:
(1) Clean all parts with cleaning solvent,
Federal Specification P-D-680 or equivalent,
and determine the appropriate valve to be ad-
and dry thoroughly.
justed as indicated in figure 20 and on the chas-
(2) Inspect all parts for cracks, breaks, ex-
sis of the tester.
cessive wear, binding, and damaged threads.
b. Loosen the locknut (5) and turn the ad-
(3) Report all defective parts to higher
justing screw (4) to provide a reading on the
authority.
instrument, within the tolerances listed in ta-
c. Installation.
ble 2.
(1) Install fittings (15, 16, and 17, figure
c. Tighten the locknut (5) and close the lower
21) on PRESSURE selector valve (14).
access panel (2).
(2) Place PRESSURE selector valve (14)
in position on f rent panel (23) and secure with
four lockwashers (13) and screws (12).
(3) Connect all hose and tube assemblies
CAUTION
(10 and 11) to the fittings (15, 16, and 17) as
Do not blow compressed air into hoses
instructed in paragraph 63,
or tubes when they are attached to in-
(4) Install VACUUM selector valve (18)
struments as it will damage the instru-
in a similar manner.
ments. Do not allow antiseize and seal-
ing compound to enter the lines as it can
cause leakage and damage the instru-
a. Removal.
ments.
(1) Disconnect hose assembly from fitting
When it is necessary to disconnect the ends of
on rate-of-climb indicator (4, figure 21) as in-
more than one hose or tube assembly at a time,
structed in paragraph 63.
identify and tags the assembly and the fitting
(2) Remove the four nuts (1), lockwashers
for proper installation (figure 11). The parts on
(2), and screws (3) securing rate-of-climb indi-
the selector valves (31 and 36) are numbered
cator (4) to front panel (23). Remove rate-of-
for identification of the hose and tube assem-
climb indicator.
blies. Replace defective hose assemblies with AN
