RELIEF VALVE ADJUSTMENT.

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-

64. PRESSURE AND VACUUM SELECTOR

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

62. RELIEF VALVE ADJUSTMENT.

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,

a. Open the lower access panel (2, figure 20)

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).

63. HOSE AND TUBE ASSEMBLIES.

(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

65. RATE-OF-CLIMB INDICATOR.

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