A pressure vessel is a closed vessel that can withstand pressure. The use of pressure vessels is extremely wide, and it has an important position and role in many sectors such as industry, civilian use, military industry, and many fields of scientific research. Among them, the most used in the chemical industry and the petrochemical industry, the pressure vessels used in the petrochemical industry alone account for about 50% of the total number of pressure vessels. In the chemical and petrochemical industry, pressure vessels are mainly used for heat transfer, mass transfer, reaction and other processes, as well as storage and transportation of pressurized gas or liquefied gas; it is also widely used in other industrial and civil fields, such as air compressor. All kinds of special compressors and auxiliary equipment of refrigeration compressors (coolers, buffers, oil-water separators, gas storage tanks, evaporators, liquid refrigerant storage tanks, etc.) are all pressure vessels.