What Class Means
ASME B16.5 "class" is a rating that combines material allowable stress with design temperature — not a single pressure number. The class derates as temperature rises.
Picking the Right Class
Map your design pressure-temperature point to the relevant material table — pick the lowest class that envelopes the operating point with margin.
Gasket & Bolting Implications
Higher classes demand greater bolt pre-load, switching from spiral-wound to ring-type joints (RTJ) at 900# and above — plan groove machining accordingly.
