Many, many hot lines in a pertochemical facility are VAPOR lines, thus the Hydro loads will be greater than the operating spring loads. For larger diameter lines the Hydroloads can be 2 to 3+ times greater than the Vapor operating loads. The thermal loads on a spring are LOW (< 25% +/- of installed load)
Usually the springs are capable of safely supporting 2 times the rated load. Special designs/coordination with spring vendor is required above this limit.
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Bob Zimmerman, P.E.
Vice President of The Piping Stress International Association (The PSI)