PSA 3.5 — Restrained vs Unrestrained, and the Hot-Sustained (Lift-Off) Check
A 12″ hot line on a rack. The report says sustained = 18 % of Sh, green, signed. During the first hot walkdown you can slide a feeler gauge — then a finger — under three consecutive shoes. The pipe has risen off them. Nobody is alarmed: the line looks fine, and weight has not changed.
Commit before reading on: is the 18 % still true?
It is not. The belief behind the shrug is:
"Weight is weight. The pipe weighs the same hot or cold, so the sustained case cannot change with temperature."
The weight is indeed identical. The…
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