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 TM 55-1905-220-14-8
4-29. AIR CONDITIONING SYSTEM - MAINTENANCE INSTRUCTIONS (Continued).
(e) After the compressed gas passes the discharge valve and enters the condenser, heat flows from the
hot gas into the condenser coolant, thus cooling the compressed gas and changing the state of the refrigerant
from a gas to a liquid. This liquid then drains into the receiver from which the liquid refrigerant (under pressure)
is forced through the liquid line to the expansion valve for a repetition of the cycle.
c. Characteristics of Refrigerant-12.
(1) The chemical formula for refrigerant-12 (R-12) is CCl2F2, dichlorodifluoromethane. R-12 resembles
carbon tetrachloride (the fire extinguishing fluid) in odor, and at ordinary temperatures it is a liquid when under
pressure of about 75 psig (517.1 kPa). R-12 is shipped in a liquid state and under pressure in steel cylinders.
For safety precautions in handling refrigerant-12, refer to paragraph 4-29d(2).
(2) Liquid R-12 is colorless (like water) and free from cloudiness. It is odorless in concentrations of less
than 20% by volume of air. Its vapor or vapor air mixture higher than 20% is mildly ethereal. In general it may
be stated that R-12 is:
(a) A non-combustible, non-toxic, non-irritating, nonexplosive, non-inflammable refrigerant under normal
conditions, where volume of air is sufficient and no open flame is present. (This may not be the case in a ship's
hold where refrigeration machinery may be installed in a confined space with poor ventilation.)
(b) A stable compound capable of undergoing, without decomposition, the physical changes to which it is
commonly subjected in refrigeration service.
(c) Non-corrosive to iron, steel, copper, brass, monel metal, etc., in the absence of moisture.
(3) For pressure temperature relationship of refrigerant-12 refer to table on page 4-856 thru 4-858.
NOTE
If R-12 should come into contact with an open flame of high temperature (about
1,000 (537.8 ) it may be decomposed into phosgene, a highly toxic gas.
F
C
However, in such a case the pungent and irritating fumes would be noticed long
before a concentration dangerous to health could be reached.
4-861
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