Pressure vessel is a kind of equipment which has special process function bears certain pressure in industrial production. The storage transportation vessel, reaction vessel, heat exchanger separation vessel are all pressure vessels. In order to be different general vessels (atmospheric vessels), only vessels meeting the following three conditions at the same time are called pressure vessels:

　　Higher working pressure ≥ 9.8104pa (1kgf / cm2); volume ≥ 25L, the product of working pressure volume ≥ 200l.kgf/cm2 (l.pa); medium is gas, liquefied gas liquid with higher working temperature higher than standard boiling point. Pressure vessels are widely used. It plays an important role in petrochemical industry, energy industry, scientific research, military industry other sectors of the national economy. Stainless steel pressure vessel is generally composed of six parts: cylinder, flange, head, sealing element, opening, connecting pipe support. In addition, it is also equipped with safety devices, meters internals to complete different production processes.

　　Due to the reasons of sealing, pressure bearing medium, pressure vessel is prone to explosion, combustion fire, which endangers the safety of personnel, equipment property pollutes the environment. At present, all countries in the world have listed it as an important supervision inspection product, which is supervised, inspected technically inspected by specialized agencies designated by the state in accordance with the regulations standards prescribed by the state.