REFRIGERATION SYSTEM DESCRIPTION

TM 9-4120-425-14&P

REFRIGERATION SYSTEM DESCRIPTION

0048-00

Description

WARNING

Unit contains R-22, a chemical substance which harms public health and the

environment by destroying ozone in the upper atmosphere, and that the equipment is

to be serviced by qualified personnel only.

WARNING

Whenever it is necessary to open the refrigeration system for any reason, discharge

the refrigerant carefully. Avoid contact with liquid refrigerant. As a minimum, all

personnel must wear thermal protective gloves, a face shield or goggles and a air

filtering mask when working in any situation to avoid R-22 contact with the skin or

eyes. Severe freezing of body tissues can take place with extreme rapidity. Avoid

excessive inhalation of refrigerant gas and ventilate the area in which it is released.

Refrigerant gas in contact with flame or hot surfaces is converted to phosgene a

highly toxic gas having an odor similar to newly mown grass or hay.

The refrigeration system illustrated by the refrigerant flow diagram is a mechanical, vapor-cycle circuit consisting of

the evaporator thermal expansion valve, compressor, condenser, and the necessary valves and cutout devices for

automatic control during operation and servicing.

The thermal expansion valve releases high-pressure liquid refrigerant into the evaporator at reduced pressure.

The liquid refrigerant begins to vaporize by absorbing heat from the air passing over the outside surface of the

evaporator coil.

The heated vapor is sucked out of the evaporator section by the compressor, and is forced into the condenser section

under high pressure where it is cooled and condensed back into a liquid.

The heat released during condensation is carried off by the condensing airstream.

The liquid refrigerant flows from the condenser to a filter-drier, sight glass and then to the thermal expansion valve

to repeat the cycle.

If the temperature control (evaporator return-air thermostat) becomes satisfied (the evaporator return-air temperature

is lower than the point at which you have set the control) the refrigeration system will go into "Standby

Refrigeration Operating Condition" (no effective cooling but compressor remains operating).

When the temperature control again calls for cooling (the evaporator return air temperature is higher than the point

at which the control is set) the refrigeration system will come out of the "Standby Refrigeration Operation

Condition" to "Full Refrigeration Operating Condition"(full cooling operation). If the system was shut-off (for any

reason) the equalization solenoid valve (15) will open equalizing the system pressure and a time delay of one-

minute will be encountered before compressor will restart.

Refrigeration System Repair

The following paragraphs cover repairs of commonly used hardware, tubing and valves of the refrigeration system.

Re-use or repair of seals and gaskets should not be attempted; new parts should be used at assembly. When heating

refrigeration piping to debraze or unsolder connections (See Work Package WP 0051-00) as well as to solder or

braze them, the piping should be protected with a continuous flow of dry nitrogen to prevent scaling or oxidation of

the inside surface.

0048-00-1