FAILURE OF A HIGH-STRENGTH LOW-ALLOY STEEL PRESSURE CHAMBER

The premature failure of a high strength low alloy steel (HSLA) pressu re chamber has been analysed using standard metallographic and failure analysis techniques. The chamber used in the upper stage of a satelli te launch vehicle had a premature failure during routine proof pressur e testing. The failure occurred in the welded portion at an internal p ressure of 110 bar against a design proof pressure of 165 bar. Investi gations revealed welding defects as the origin of failure. The welding defect had grown into a semi-elliptical surface crack during the fabr ication process of the pressure chamber, resulting not only in a local ised reduction of the wall thickness of the chamber, but also acting a s a stress raiser, due to which the chamber had failed at a pressure m uch below its design level. (C) 1998 Elsevier Science Ltd. All rights reserved.