Evacuation and Dehydration. - TM-55-1905-220-14-80869

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Pressure and Leak Test.

TM-55-1905-220-14-8 Landing Craft Utility LCU 1671-1679 NSN 1905-01-009-1056 Manual

Evacuation and Dehydration - continued

TM 55-1905-220-14-8

4-29. AIR CONDITIONING SYSTEM - MAINTENANCE INSTRUCTIONS (Continued).

(g) Test entire system for leaks with an electronic or an halide leak detector. Be sure to test all

fittings and joints. The small amount of refrigerant in the system will act as an indicator. Test tightness of shell

and tube condensers by removing water heads and passing the leak detector probe or exploring tube over the

tube sheets. Repair any leaks.

When heat must be applied to repair a leak, the leaking

section of the system should be opened and the machinery

space ventilated. High concentrations of test gas in the space

will cause a deficiency of oxygen and a health hazard.

(h) Close hand expansion valves and stop valves downstream of thermal expansion valves at

the evaporator. Add dry nitrogen and raise the pressure in the high side of the system to 225 psig (1551 kPa).

Any pressure rise in the low side of the system will indicate a leaky stop valve or hand expansion valve. Repair

such leaks before proceeding. Repeat step (g).

(i) Open condenser purge valve and drop test pressure to 150 psig (1034 kPa), Remove plug

from condenser overboard discharge line and test for a leaky relief valve.

(j) After all leaks have been repaired and system may be considered perfectly tight, open

condenser purge valve and release test pressure. Be sure machinery space is well ventilated while purging.

(k)

Reconnect lines disconnected in step (b). Open all line valves and close condenser

purge valve.

p. Evacuation and Dehydration.

(1) Preparation.

(a) Many serious refrigeration troubles can be traced to faulty system dehydration at the time of

installation or following extensive repairs which require the system to be opened to the atmosphere.

(b) Moisture in the system causes oil sludge and corrosion and it is likely to freeze-up the

expansion valves of a low temperature system. Tests and field experience have shown that most troubles with

seals and internal valves are caused by moisture in the system.

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