Refrigeration and air conditioning

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.

46 CFR §58.20-15

§ 58.20-15 -15 Installation of refrigerating machinery. (a) Where refrigerating machines are installed in which anhydrous ammonia is used as a refrigerant, such machines must be located in a well-ventilated, isolated compartment, preferably on the deck, but in no case is it permissible to install such machines in the engine room space unless the arrangement is such as to eliminate any hazard from gas escaping to the engine room. Absorption machines using a solution of aqua ammonia and machines using carbon dioxide are exempt from this requirement, provided the maximum charges that might be released in the event of breakage do not exceed 300 pounds. (b) Machinery compartments containing equipment for ammonia must be fitted with a sprinkler system providing an effective water spray and hav…

46 CFR §58.20-20

§ 58.20-20 -20 Refrigeration piping. (a) All piping materials must be suitable for handling the primary refrigerant, brine, or fluid used, and must be of such chemical and physical properties as to remain ductile at the lowest operating temperature. (b) Piping systems must be designed in accordance with ASME B31.5 (incorporated by reference; see § 58.03-1). Piping used for cargo reliquefaction systems must also comply with the applicable requirements found in low temperature piping, § 56.50-105 of this subchapter. (c) A relief valve must be fitted on or near the compressor on the gas discharge side between the compressor and the first stop valve with the discharge therefrom led to the suction side. A check valve must be fitted in the atmospheric discharge line if it is led through the s…

46 CFR §58.20-25

§ 58.20-25 -25 Tests. (a) All pressure vessels, compressors, piping, and direct expansion cooling coils must be leak tested after installation to their design pressures, hydrostatically or pneumatically. (b) No pneumatic tests in refrigeration systems aboard ships must be made at pressures exceeding the design pressure of the part of the system being tested. Pneumatic tests may be made with the refrigerant in the system. If the refrigerant has been removed, oil-pumped dry nitrogen or bone-dry carbon dioxide with a detectable amount of the refrigerant added should be used as a testing medium. (Carbon dioxide should not be used to leak test an ammonia system.) In no case should air, oxygen, any flammable gas or any flammable mixture of gases be used for testing.

46 CFR §58.20-5

§ 58.20-5 -5 Design. (a) Refrigeration machinery may be accepted for installation provided the design, material, and fabrication comply with the applicable requirements of the ABS Marine Vessel Rules (incorporated by reference, see § 58.03-1). The minimum pressures for design of all components must be those listed for piping in Table 501.2.4 of ASME B31.5 (incorporated by reference; see § 58.03-1). In no case may pressure components be designed for a pressure less than that for which the safety devices of the system are set. Pressure vessels must be designed in accordance with part 54 of this subchapter. (b) For refrigeration systems other than those for reliquefaction of cargo, only those refrigerants under § 147.90 of this chapter are allowed.

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…