Tanks and Tube Trailers

A cargo tank is defined as any tank permanently attached to or forming a part of any motor vehicle or any bulk liquid or compressed gas packaging not permanently attached to any motor vehicle, which by reason of its size, construction, or attachment to a motor vehicle, is loaded or unloaded without being removed from the motor vehicle. 

Cargo tanks complying with Specifications MC-330 or 331 must be of ASME Pressure Vessel Code construction, and must have a design pressure of not less than 100 psig (689 kPa) nor more than 500 psig (3447 kPa). [3] Tanks of either specification may be insulated to meet product requirements. Refer to the individual gas monographs in Part III of this Handbook for further product information. 

Each cargo tank must be provided with one or more pressure relief devices which, unless otherwise specified for a particular product, must be pressure relief valves of the spring-loaded type. Refer to Chapter 7 for detailed information on pressure relief devices. 

Specifications 3AX, 3AAX, and 3T are commonly used in new production for containers approximately 22 inches (55.88 cm) in diameter instead of the older 9 -inch (24.45-cm) diameter tubes which were made to Specifications 3A and 3AA. Specifications 3AX, 3AAX, and 3T cylinders have a minimum size of 1000 lb (454 kg) water capacity under the TC and DOT regulations. Tube trailers in the United States have been built to carry as much as 180 (XX) standard ft (5097 m ) of helium. In some Canadian provinces, capacities up to 200 000 ft (5663 m ) of hydrogen are possible. 

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