ISO 7268 norm defines Nomimal Pressure for pipe components. API 6D compares also ANSI Class with PN.

The pressure rating on this table do not mean design pressure (bar or psi). Factors such as temperature and material should be also considered in order to select a pressure rating.

ANSI Class Rating [#]	Nominal Pressure PN
150	20
300	50
400	64
600	100
900	150
1500	250
2500	420