Air conditioning, ventilation, and compressed air

46 CFR §58.20-1

§ 58.20-1 -1 Scope. (a) The regulations in this subpart apply to fixed refrigeration systems for air conditioning, refrigerated spaces, cargo spaces, and reliquefaction of low temperature cargo installed on vessels. (b) The regulations in this subpart do not apply to small self-contained units.

NAVEDTRA 14075 §6-1

The vapor-compression refrigeration cycle Refrigeration moves heat from a cold space to a warmer one, against its natural direction, by repeatedly evaporating and condensing a refrigerant in a closed cycle. It works because a liquid absorbs a large amount of heat (its latent heat) when it boils, and gives that heat up again when it condenses; by controlling the pressure, the refrigerant can be made to boil at a low temperature in the space being cooled and to condense at a higher temperature where the heat is rejected. The vapor-compression cycle has four essential components connected in a loop: the compressor, the condenser, the metering (expansion) device, and the evaporator. Following the refrigerant around the loop: low-pressure liquid refrigerant boils in the evaporator (the cooling…

NAVEDTRA 14075 §6-7

Air conditioning systems and controls Shipboard air conditioning uses the same vapor-compression refrigeration cycle to cool and dehumidify air for crew comfort and for equipment spaces. In a typical central plant, refrigerant chills either the air directly (a direct-expansion coil in an air handler) or a supply of chilled water that is then pumped to cooling coils throughout the ship (a chilled-water system, favored on larger vessels because it distributes cooling with water piping rather than long refrigerant lines). Air handlers draw in a mixture of recirculated and fresh outside air, pass it across the cooling coil where it is cooled and dehumidified, and distribute it through ducts to the spaces; the moisture condensed out of the air on the coil is collected and drained. Heating coil…

NAVEDTRA 14075 §7-1

Compressed-air systems and air compressors Compressed air is a vital shipboard utility used to start large diesels, to operate pneumatic controls and automation, to run air tools, to sound the ship's whistle, and to blow through and clear lines. It is produced by air compressors that take in atmospheric air and raise it to the pressure required — high pressure (several hundred psi) for diesel starting air, lower pressures for control and service air. Most are positive-displacement reciprocating compressors: a piston draws air in through a suction valve and forces it out through a discharge valve into a receiver. High-pressure air is compressed in two or more stages because compressing to high pressure in one step generates excessive heat; an intercooler between stages removes the heat of …

NAVEDTRA 14075 Ch. 6 — Compressors

Many different types and sizes of compressors are used in refrigeration and air conditioning systems. They vary from the small hermetic units used in drinking fountains and refrigerators, to the large centrifugal units used for air conditioning. One of the most commonly encountered compressors on today’s modern ships is a high speed, continuous running unit with a variable capacity. This compressor is of the multicylinder, reciprocating design, with a positive unloaded system built into the compressor to control the compressor’s capacity.

NAVEDTRA 14075 Ch. 6 — Correcting Troubles

Faulty operation of the refrigerating and air conditioning plants is indicated by various definite symptoms. Information in figures 6-12 and 6-13 indicates some possible troubles that may be encountered, the possible causes of these troubles, and the corrective action which may be taken. But remember always consult the manufacturer’s technical manual before attempting any repair or adjustment on your equipment. Trouble Possible Cause Corrective Measure High condensing pressure. Air or non-condensable gas in system. Purge air from condenser. Inlet water warm. Increase quantity of condensing water. Insufficient water flowing through condenser. Increase quantity of water. Condenser tubes clogged or scaled. Clean condenser water tubes. Too much liquid in receiver, condenser tubes submerged in…