This paper characterizes pipeline stress-con-osion cracking (SCC) in terms of crack length, depth, and spacing for 17 hydrotest failures and cracking remote to origins. Crack populations with average
circumferential crack spacings greater than - 20 percent of the wall thickness, termed “sparse”, were observed to have similar length and depth and spacing patterns, which differed significantly from those having
closer spacings, which were termed “dense” Sparse populations were found at leaks and breaks and showed active cracking whereas cracks in dense patches, which were only found away from deep cracks and failure
origins, tended to be dormant. Analytical models of SCC nucleation and early growth were used to evaluate possible causes of these tendencies and the apparent role of circumferential crack spacing. This study
indicated that the maximum pressure in the pipeline at the time the cracking environment developed dominated the nucleation process in terms of crack number and relative spacing. The analysis trends, which
were consistent with tapered-tension test data, gave rise to suggestions for performing and interpreting typical accelerated test data
Keywords: gas pipeline, external stress-corrosion cracking, colony, crack, spacing, length, depth, threshold, initiation, propagation, field data, lab data, stress, cracking environment