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46 U.S.C. 3703, 9101; Department of Homeland Security Delegation No. 0170.1.
CGD 74-289, 44 FR 26009, May 3, 1979, unless otherwise noted.
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Subscribe to: 46 CFR Part 154 Subpart C - Cargo Pressure and Temperature Control
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Nomenclature changes to part 154 appear part 154 appear by CGD-95-072, 60 FR 50466, Sept. 29, 1995, CGD-96-041, 61 FR 50732, Sept. 27, 1996, USCG-2009-0702, 74 FR 49235, Sept. 25, 2009, and USCG-2012-0832, 77 FR 59785, Oct. 1, 2012.
Except as allowed under § 154.703, cargo tanks must:
(a) Have their safety relief valves set at a pressure equal to or greater than the vapor pressure of the cargo at 45 °C (113 °F) but not greater than the MARVS under § 154.405; or
(b) Be refrigerated by a system meeting § 154.702, and each refrigerated incompatible cargo refrigerated by a separate system.
(a) Each refrigeration system must:
(1) Have enough capacity to maintain the cargo vapor pressure in each cargo tank served by the system below the set pressure of the relief valves under ambient temperatures of 45 °C (113 °F) still air and 32 °C (89.6 °F) still water with the largest unit in the system inoperative; or
(2) Have a standby unit with a capacity at least equal to the capacity of the largest refrigeration unit in the system.
(b) For the purpose of this section, a “refrigeration unit” includes a compressor and its motors and controls.
(c) Each refrigeration system must:
(1) Have a heat exchanger with an excess capacity of 25 percent of the required capacity; or
(2) A standby heat exchanger.
(d) Where cooling water is used in a refrigeration system:
(1) The cooling water pump or pumps must be used exclusively for the system;
(2) Each pump must have suction lines from sea chests on the port and starboard sides of the vessel; and
(3) There must be a standby pump, that may be used for:
(i) Non-essential purposes on the vessel; or
(ii) Essential purposes on the vessel, if the pump is sized to simultaneously provide for the capacity requirements for the essential purposes and the refrigeration cooling water.
(e) Each refrigeration system must use refrigerants that are compatible with the cargo and, for cascade units, with each other.
(f) The pressure of the heat transfer fluid in each cooling coil in a tank must be greater than the pressure of the cargo.
Unless a cargo tank carrying methane (LNG) can withstand the pressure build up due to boil-off for 21 days, the pressure in the cargo tank must be maintained below the set pressure of the safety relief valve for at least 21 days by:
(a) A refrigeration system that meets § 154.702;
(b) A waste heat or catalytic furnace that burns boil-off gas, and:
(1) Maintains the stack exhaust temperature below 535 °C (995 °F);
(2) Exhibits no visible flame; and
(3) Is specially approved by the Commandant (CG-OES);
(c) Boilers, inert gas generators, and combustion engines in the main propelling machinery space that use boil-off gas as fuel; or
(d) Equipment for services, other than those under paragraph (c) of this section, that use boil-off gas as fuel and that are located:
(1) In the main propelling machinery space; or
(2) a space specially approved by the Commandant (CG-OES).
[CGD 74-289, 44 FR 26009, May 3, 1979, as amended by CGD 82-063b, 48 FR 4782, Feb. 3, 1983]
(a) Each cargo boil-off fuel system under § 154.703(c) must meet §§ 154.706 through 154.709.
(b) The piping in the cargo boil-off fuel system must have a connection for introducing inert gas and for gas freeing the piping in the machinery space.
(c) A gas fired main propulsion boiler or combustion engine must have a fuel oil fired pilot that maintains fuel flow as required under § 154.1854 if the gas fuel supply is cut-off.
(a) Gas fuel lines must not pass through accommodation, service, or control spaces. Each gas fuel line passing through other spaces must have a master gas fuel valve and meet one of the following:
(1) The fuel line must be a double-walled piping system with the annular space containing an inert gas at a pressure greater than the fuel pressure. Visual and audible alarms must be installed at the machinery control station to indicate loss of inert gas pressure.
(2) The fuel line must be installed in a mechanically exhaust-ventilated pipe or duct, having a rate of air change of at least 30 changes per hour. The pressure in the space between the inner pipe and outer pipe or duct must be maintained at less than atmospheric pressure. Continuous gas detection must be installed to detect leaks in the ventilated space. The ventilation system must meet § 154.1205.
(b) Each double wall pipe or vent duct must terminate in the ventilation hood or casing under § 154.707(a). Continuous gas detection must be installed to indicate leaks in the hood or casing.
(a) A ventilation hood or casing must be installed in areas occupied by flanges, valves, and piping at the fuel burner to cause air to sweep across them and be exhausted at the top of the hood or casing.
(b) The hood or casing must be mechanically exhaust-ventilated and meet § 154.1205.
(c) The ventilated hood or casing must have an airflow rate specially approved by the Commandant.
(a) Gas fuel lines to the gas consuming equipment must have two fail-closed automatic valves in series. A third valve, designed to fail-open, must vent that portion of pipe between the two series valves to the open atmosphere.
(b) The valves under paragraph (a) of this section must be arranged so that loss of boiler forced draft, flame failure, or abnormal gas fuel supply pressure automatically causes the two series valves to close and the vent valve to open. The function of one of the series valves and the vent valve may be performed by a single three-way valve.
(c) A master gas fuel valve must be located outside the machinery space, but be operable from inside the machinery space and at the valve. The valve must automatically close when there is:
(1) A gas leak detected under § 154.706(a)(2) or § 154.706(b);
(2) Loss of the ventilation under § 154.706(a)(2) or § 154.707(c); or
(3) Loss of inert gas pressure within the double-walled piping system under § 154.706(a)(1).
(a) The continuous gas detection system required under § 154.706(a)(2) and (b) must:
(1) Meet § 154.1350(c), (d), and (j) through (s); and
(2) Have a device that:
(i) Activates an audible and visual alarm at the machinery control station and in the wheelhouse if the methane concentration reaches 1.5 percent by volume; and
(ii) Closes the master gas fuel valve required under § 154.708(c) before the methane concentration reaches 3 percent by volume.
(b) The number and arrangement of gas sampling points must be specially approved by the Commandant (CG-OES).
[CGD 74-289, 44 FR 26009, May 3, 1979, as amended by CGD 82-063b, 48 FR 4782, Feb. 3, 1983]