Failure investigations and refurbishment of a 34-in gas pipeline

A 133-km gas/condensate pipeline constructed from API5LX60 linepipe suffered six known failures since its construction in 1972. This paper outlines the work done to re-investigate the causes of the failures and to develop a strategy for refurbishement. It covers the history of the line, the examinations conducted on the line, the laboratory investigations carried out on samples removed from the site, fracture mechanics' evaluation work, the proposed refurbishement strategy, and a survey of intelligent-pig methods capable of detecting critical defects of the types causing the failures. The work started with a detailed examination of all available evidence relating to the failures. Site investigations followed with subsequent laboratory testing of samples from the line. The information obtained was correlated to data acquired from an intelligent-pigging survey conducted in 1992.