46 CFR § 38.05-2 - Design and construction of cargo tanks - general - TB/ALL.

§ 38.05-2 Design and construction of cargo tanks - general - TB/ALL.

(a) The maximum allowable temperature of the cargo is defined as the boiling temperature of the liquid at a pressure equal to the setting of the relief valve.

(b) The service temperature is the minimum temperature at which cargo is loaded and/or transported in the cargo tank. However, the service temperature shall in no case be taken higher than given by the following formula:

ts = tw−0.25(tw−tb) (1)
where:
ts = Service temperature.
tw = Boiling temperature of gas at normal working pressure of tank but not higher than + 32 °F.
tb = Boiling temperature of gas at atmospheric pressure.

(c) Heat transmission studies, where required, shall assume the minimum ambient temperatures of 0 °F. still air and 32 °F. still water, and maximum ambient temperatures of 115 °F. still air and 90 °F. still water.

(d) Cargo tanks in vessels in ocean; Great Lakes; lakes, bays, and sounds; or coastwise service shall be designed to withstand, simultaneously, the following dynamic loadings:

(1) Rolling 30° each side (120°) in 10 seconds.

(2) Pitching 6° half amplitude (24°) in 7 seconds.

(3) Heaving L/80′ half amplitude (L/20′) in 8 seconds.

(e) Cargo tanks on barges shall be designed in accordance with § 32.63-25 of this subchapter.

(f) Each liquefied flammable gas tank shall be provided with not less than a 15-inch by 23-inch or an 18-inch nominal diameter manhole fitted with a cover located above the maximum liquid level and as close to the top of the tank as possible. Where access trunks are fitted to the tanks, the nominal diameter of the trunks shall be not less than 30 inches.

(g) Cargo tanks vented above 10 pounds per square inch gage shall be of the pressure vessel type.

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