the appropriate number, or else they are identified
The Ship's Service Air System
simply as refrigerants.
The ship's service air system is a low-pressure
Most Navy refrigeration systems use R-12 as the
compressed air system installed on practically all
refrigerant. Because of its low boiling point (-21.7F at
surface ships. This system normally uses a working
atmospheric pressure), R-12 is well suited for use in
pressure of 100 to 150 psi. This system supplies air at
refrigeration systems designed for only moderate
required pressures to operate pneumatic tools and oil
pressures. R-12 is neither flammable nor explosive. It
burning forges and furnaces, to clean equipment, to
is also noncorrosive to iron, steel, copper, brass, and
pressurize electronic equipment wave guides with
Monel. Although the R-12 is practically nontoxic, you
dehydrated air, and many other uses. The ship's service
still have to be careful when using it. When it gets hot,
air system is normally supplied from a low-pressure air
it decomposes and produces products that are toxic, and
can even kill you. Do not let anyone tell you that it is
supplied from the medium- or high-pressure system,
absolutely safe.
through appropriate pressure reducing valves.
In the operating cycle of a refrigerating plant, the
Gas Ejecting Systems
refrigerant gas is compressed and cooled to a liquid. It
is then permitted to expand and become a gas again.
Gas ejecting systems, where required, supply air at
The heat necessary to expand the liquid to a gas is
the required pressure to the breeches of guns for
obtained from the surrounding atmosphere of the space
removing gases and unburned solid matter. The
being cooled. It is this absorption of heat by the
standard working pressure of a gas ejection system is
refrigerant that lowers the temperature of a refrigerated
determined by the type of battery it supplies. Normally
compartment. The amount of heat absorption is
these systems will range from 100 to 200 psi. Air for
controlled by expansion valves and thermostats. The
the gas ejection system is supplied from the medium-
or high-pressure system, through appropriate reducing
controlled expansion in the space to be cooled, and
valves.
return to the compressor.
The principal components of the system are the
Starting and Control System
compressor, the condenser, the receiver, and the cooling
coils (evaporator). Additional equipment required to
is installed on each ship that requires air for diesel
thermometers, various types of control switches and
engine starting and the control of equipment such as
control valves, strainers, relief valves, sight-flow
clutches, engine selector valves, turning gear, and
propeller brakes. Air for this system is provided by a
medium-range compressor at a pressure of 600 psi or
You are not responsible for maintaining and
from the high-pressure system, through appropriate
operating a refrigeration system. However, you may be
reducing valves.
required to assist a Machinist's Mate or an Engineman
in making repairs or alterations to the refrigeration
Combustion Control Air System
piping system.
A compressed air system is installed on some
PIPING SYSTEM MARKINGS
steam-driven ships to provide air for the automatic
To make identification easy, piping systems are
compressed air system consists of an air compressor, air
marked in some conspicuous location (preferably near
receiver, and piping to supply air for pneumatic units of
control valves) and at suitable intervals so that every
line carries at least one marking in each compartment
through which it passes.
REFRIGERATION SYSTEMS
The identification markings include the name of the
service, destination (where feasible), and direction of
According to NAVSEA policy, refrigerants used in
flow. These markings may be painted on by stencil or
the Navy are no longer identified by trade names.
hand lettering, or on adhesive-backed tape that has been
Instead, they are identified by the letter R followed by
previously printed, stenciled, or lettered. These
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