DOT Gas Cylinder Assemblies
Design pressure 25MPa. Generally not used for above-ground storage. DOT does not have the authority to set standards for above-ground applications. Drainage outlets are not allowed. Initial investment is low, but operating and maintenance costs are high. The unit must be disassembled every 3 years for a hydrostatic test on each cylinder. Site area is required to be at least 50 square meters. It has a loose structure, lacks structural integrity, has many containers and joints, posing a risk of leakage, and has small pipeline dimensions with high flow resistance.
ASME Container Units
Design pressure 27.6MPa. Container wall thickness is 39% greater than that of equivalent DOT cylinders. Typically used for above-ground storage. ASME allows drainage outlets on the containers. Initial investment is high, but operating and maintenance costs are low. No further testing is required beyond general external and internal visual inspection. Site requirements are 5-7m², requiring a robust structure that can better withstand impact loads and seismic fluctuations. It has fewer containers, fewer joints, larger pipeline dimensions, and lower flow resistance.
Underground Gas Storage Wells
Design pressure is 25MPa. The depth of gas storage wells is generally 100 meters. It consists of a dozen or so 7-inch casing pipes commonly used in the oil drilling industry, connected by flat trapezoidal threads at the pipe ends. It occupies a small area, which is beneficial for site layout; although the initial investment is relatively large, according to data provided by the Sichuan Petroleum Administration Bureau, this gas storage well can be used for at least 25 years, saving on inspection and maintenance costs, and has good safety and reliability.
