Integrity Implications of Unintentionally Expanded Line Pipe

Pipeline construction projects underway in the US during the 2005 to 2010 timeframe encountered occurrences of unintended diameter expansion during hydrostatic testing of high-strength line pipe. Causes of expansion were in some cases attributed to inadequate pipe manufacturing and procurement practices or in other cases to high external loads present concurrently during pressure testing. This paper considers the implications to long-term pipeline integrity arising with pipe that underwent unintended diameter change with associated strain accumulation. The paper presents a relationship between test pressure and diameter expansion, estimation of the reserve strain capacity, effects on fracture control, and effects on integrity reassessment intervals. The conclusions are that the integrity issues associated with limited magnitudes of diameter change can be readily managed.