What is the nominal pressure class of a valve?

Class：

A designation consisting of a combination of letters and numbers that relates to the mechanical properties and dimensional characteristics of valve materials and indicates the pressure/temperature capabilities of the valve. It consists of the letter “Class” followed by a dimensionless integer. The number following the letter “Class” does not represent a measured value and should not be used in calculations. Unless otherwise specified in the relevant standards, the allowable pressure of piping components depends on the Class value, the material, and the permissible operating temperature. The allowable pressure is specified in the pressure-temperature rating tables of the corresponding standards.