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 TM 55-1905-219-14-8
4-28. AIR CONDITIONING SYSTEM - MAINTENANCE INSTRUCTIONS (Continued).
(i)
Do not wipe down near moving parts.
(j)
In case of electrical fire, open circuit switch and extinguish with CO2 (never use water).
(k)
Be sure power is turned off before working on motors, controllers, solenoid valves and
electrical control switches. Tag circuit breaker to prevent accidental energizing of circuit.
(l)
When isolating any part of the system in which there is liquid refrigerant, close the cut-out
valve on inlet side of the part to be isolated and allow the compressor to remove all liquid refrigerant. This will
be indicated by a sudden chilling of the part being isolated. When the part begins to get warm again it may be
considered devoid of liquid refrigerant. Close valve on outlet side of isolated part before opening bypass
valves, if provided.
(m) Never open any part of the system which is under a vacuum. If this is done, air and moisture
will be drawn into the system and are almost certain to cause trouble at some later date. The section to be
opened should be under 1 - 2 psig (6.9 - 13.8 kPa) pressure to prevent the admission of air and moisture into
the system.
(n) During the shutdown period of any condenser, if there is a possibility of obtaining freezing
temperatures in the machinery room, drain the condenser and connecting piping to prevent a freeze-up and
damage to condenser tubes.
(o) After an inspection or repairs have been made, always be sure to expel all the air from the part
of the system that has been opened by admitting a small amount of refrigerant gas into that part of the system.
(2)
Handling Refrigerant-12.
(a) Refrigerant-12 is practically odorless and non-toxic. It is not necessary to wear a gas mask
when servicing equipment in which it is contained unless the conditions necessary for the decomposition of
R-12 to phosgene gas exist. Refer to item (b) below.
(b) Never use a torch or attempt a repair on a line containing R-12 until it is certain that all gas has
been pumped out of the section of pipe to be repaired, the area is well ventilated and the line has been valued
off. Refrigerant-12 in contact with an open flame of high temperature (about 1,000F (557.8 )) decomposes
C
into phosgene, a highly toxic gas.
(c)
Always wear goggles when handling R-12, or servicing equipment in which it is contained, to
avoid the possibility of liquid refrigerant coming in contact with the eyes.
4-833
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