There are many ways to classify pressure vessels, from the perspective of use, manufacturing and supervisory inspection, there are the following. (1) Divided into low pressure vessels, medium pressure vessels, high pressure vessels and ultra-high pressure vessels according to the pressure level. (2) According to the containing medium, it is divided into: non-flammable, non-toxic; flammable or toxic; highly toxic. (3) According to the different roles in the process, it can be divided into: ①Reaction vessel: a vessel used to complete the physical and chemical reactions of the medium. ② Heat exchange container: a container used to complete the heat exchange of the medium. ③Separation container: a container used to complete medium quality exchange, gas purification, solid, liquid, and gas separation. ④ Storage and transportation container: a container used to hold liquid or gas materials, storage and transportation media, or to balance and buffer the pressure.