High pressure vessels include:

1. High pressure and ultra-high pressure vessels;

2. Highly toxic medium with Pw multiplied by V ≥ 200 liters. Low pressure containers with kilogram force/cm2 or medium pressure containers with highly toxic media;

3. A medium pressure reaction vessel with flammable or toxic media and Pw multiplied by V ≥ 50000 liters. kgf/cm2, or a pressure storage and transportation vessel with PW multiplied by V ≥ 5000 liters, kgf/cm2.

The design pressure p of pressure vessels is divided into four pressure levels: low pressure, medium pressure, high pressure, and ultra-high pressure. The pressure ranges of these four levels are as follows:

1. Low pressure code L0.1MPa ≤ p<1.6MPa;

2. Medium pressure code M 1.6MPa ≤ p<10.0MPa;

3. High pressure code H 10.0MPa ≤ p<100.0MPa;

4. Ultra high pressure code U p ≥ 100.0MPa.