Rehab permits desert line to run at original pressures

An extensive inspection and rehabilitation program on a 34-in. desert pipeline in gas-condensate service has restored the line to full operating pressures and ensured the line's active service life for at least 20 years. Since Agip Oil Co. Ltd. built the 133-km pipeline in 1972 using API 5L Grade X-60, it has suffered six known failures. There has been no single cause of the failures. As a consequence of the failures, the line has been progressively down rated from the original operating pressure of 700 psig to 500 psig. So that the line could again be operated between 650 and 700 psig, two options have been considered: extensive study and investigation leading to inspection and replacement of suspect pipe: total replacement of the line. These options were evaluated from economic and safety points of view. A major consideration was that the line will be operating in its current manner for only the next 2 years before changing to dry-gas transportation. The first option was therefore considered viable. The paper discusses the failure mechanisms, the history of hydrogen-induced cracking, the 1989 failure, survey results, calculation of acceptable pressures, and the rehabilitation program.