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Assessment of Seam integrity of aging hydrocarbon pipelines constructed using Low Frequency Electrical Resistance Welded (LF-ERW) line pipes continues to be an area of concern for pipeline operators. IndianOil Corporation (IOCL) owns and operates a network of nearly 11,000km of cross country hydrocarbon transmission pipelines which also include pipelines constructed using LF-ERW line pipes.
A 738 km long, 12.75” diameter pipeline constructed as per ANSI/ASME B 31.4 with LF-ERW line pipes conforming to API 5L X46, has been in operation since 1966 and is engaged in transportation of refined petroleum products. One of the segments of this pipeline has experienced a few cases of in-service seam failure starting with 1980.
Considering the recurrence of failures attributable to the LF-ERW line pipe in this particular segment, potential hazards associated with in-service failures and also the limitations of currently available non-destructive technology for complete detection / sizing of all seam defects of significance in LF-ERW pipes, a programme of periodic seam integrity assessments using hydrostatic testing to eliminate structurally significant defects of the pipe seam, was implemented as part of IOCL’s Pipeline integrity management programme for this pipeline segment. This paper aims to share the encouraging successful approach and experience of the recent re-assessment of seam integrity of the said aging pipeline segment through hydrostatic testing. Successful completion of seam integrity assessments of this LF-ERW pipeline segment imparts confidence that the pipeline segment may continue to be safely operated at prevailing operating conditions for at least another 12 years.