MIL-HDBK-1022A
10.2.2.2 Refrigerating Effects. At normal atmospheric
pressure, the boiling point of propane is -45 degrees F
(-43 degrees C). Propane in a liquid state and open to the
atmosphere will evaporate (not boil).
a) Provide means to address operational concerns as
described in the following paragraph. When LPG is expanded
through a regulator from its vapor pressure to normal service
pressures, the cooling effect may freeze the regulator if
water is present in the LPG. Freeze-up can also occur on
equipment which accumulates water such as strainers and
control valves. The freezing effect can also result in
exterior ice formations which disrupts the valve operator.
Freeze-ups can be avoided by cleaning and nitrogen-purging the
system.
b) Although it is dehydrated at the refinery,
provide a means to keep LPG dry.
c) In flashing to vapor from the liquid phase, the
refrigerating effect can be severe if an abrupt pressure drop
occurs. Therefore, design a system which provides means to
avoid this problem.
10.2.2.3 Design Standards. Use the following references for
general design and safety standards for all LPG facilities.
(Follow particular sections of standards applicable to types
of facilities. Where conflicts occur, use the more stringent
requirements.) Appropriate standards are as follows:
a) NFPA 54, NFPA 58, and NFPA 59.
b) API Std 2510.
c) Association of American Railroads, Circulars No.
17D and 17E.
d) Federal Specification BB-G-110.
e) Federal Specification RR-C-910, Sections ICC 4BW,
ICC 4E, and ICC 4BA.
f) MIL-HDBK-1027/1.
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