(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.

(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.

(a) Each pressure vessel containing refrigerants, which may be isolated, must be protected by a relief valve set to relieve at a pressure not exceeding the maximum allowable working pressure of the vessel. When a pressure vessel forms an integral part of a system having a relief valve, such vessel need not have an individual relief valve.

(b) Relief valves fitted on the high-pressure side may discharge to the low-pressure side before relieving to atmosphere. When relieving to atmosphere, a relief valve must be fitted in the atmospheric discharge connection from the receivers and condensers. The relief valve from the receivers may relieve to the condenser, which in turn may relieve either to the low side or to atmosphere. It must be set to relieve at a pressure not greater than the maximum allowable working pressure. A rupture disk may be fitted in series with the relief valve, provided the bursting pressure of the rupture disk is not in excess of the relief valve set pressure. Where a rupture disk is fitted on the downstream side of the relief valve, the relief valve must be of the type not affected by back pressure.

(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 having a remote-control device located outside the compartment.

(c) All refrigeration compressor spaces must be effectively ventilated and drained and must be separated from the insulated spaces by a watertight bulkhead, unless otherwise approved.

(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 side of the vessel below the freeboard deck, or a shutoff valve may be employed if it is locked in the open position.

(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.