On the Calibration of Design Collapse Strengths for Quenched and Tempered Pip

The joint API/ISO Work Group 2b under Steering Committee 5 (SC5) for tubular goods is currently rewriting API Bull. 5C3/ISO 10400 for casing and tubing performance property equations. This paper describes the proposed newtreatment for collapse of quenched and tempered (Q&T) pipe. The work is still in progress, and the final text has yet to be agreed upon, but the present results are considered reasonably mature and have been circulated as a committee draft for international comment. Committee work has shown that the current (sixth edition) rating equations give highly variable risk over the DJt range for downhole well tubulars, whereas the proposed new equations give nearly uniform risk. Different ratings are proposed for cold- and hot-straightened pipe. Overall, they result in minor cost savings with respect to the sixth edition of API Bull. 5C3 collapse strengths.