L51632 Evaluation of the Time Delay for Cold Cracking

Program to determine the potential delay times required to cause cold cracking (hydrogen cracking). Cracking induced in welds deposited into circumferential grooves has been monitored by ultrasonic techniques. Initial use of an array of fixed transducers which were switched electronically was found to be inadequate for the determination of delay times under near threshold cracking conditions. Since delay times are expected to be greatest for such conditions, a change was made to intermit tent monitoring using P-scan equipment. By plotting percentage projected area free from reflections of <-28dB against time from completion of welding, it was found possible to monitor the progress of cracking for near threshold conditions. Single pass welds in 0 .12" (3 mm) grooves and multipass welds 0.24" (6 mm) grooves in 22" (559 mm) diameter, 0.43711 (11 mm) wall thickness, grade X48 pipe, welded with AWS E7010G and E8010G consumables have been used.