Pressure Class

The ASME B16.5 rating designation — Class 150 to Class 2500 — whose allowable pressure falls as temperature rises.

A Class 150 flange is not a 150 psi flange. The class is an index into a pressure-temperature table that varies by material group: a Class 150 A105 flange is good for about 285 psi at ambient and roughly 100 psi at 400 °C. Mixing material groups on the same joint, or quoting a class without its design temperature, is the usual source of an under-rated flange arriving on site.

Related terms

Flange Facing
Schedule

Where this applies

flanges

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