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.="">