pdiculous963,
Thank you for the quick reply and code sections. I tracked down API-ASME 1951 today to educate myself. You are correct and this does explain. I appreciate your time and suggestion.
I have a U-1 form from a vessel constructed in 1954 from A212-B. The form is generally consistent with current U-1 forms, but there is section 17 parts f and g of the form which list hydrostatic stress in longitudinal joints and an "Allowable operating stress" based on this hydrostatic stress...