TEMA Class R vs C
vs B, Explained

TEMA Class R, C and B are not “good / better / best” quality tiers. They are service classes with different mechanical design margins and construction expectations for shell-and-tube exchangers — including the tube sheets.

Class R — severe / petroleum

Highest mechanical design expectations among the three common classes. Typical for refinery and severe process service where consequence of failure is high. Expect tighter attention to thickness, joints and inspection. Pair with API 660 where the project requires it.

Class C — general commercial

Balanced requirements for general process and commercial exchangers. Still a real TEMA design basis — not an excuse to skip ligament checks or documentation.

Class B — chemical process

Aimed at chemical process plant practice. Do not assume it is “between” R and C on every clause — read the specified edition for the paragraphs that affect tube sheet thickness and testing.

How class shows up on a tube sheet RFQ

• Design margin and mechanical formulas used with ASME VIII
• Inspection / hydro expectations
• Documentation depth EPCs expect at handover

Deep dive: standards pillar · tolerance reference: TEMA tolerances · pitch checks: pitch calculator.

Continue reading