Rational test-pressure levels for mitigating the pipe-manufacturing-defect integrity threat in natural gas pipelines

摘要

Present guidance documents indicate that a pressure test to 1.25 times the MAOP is adequate to mitigate the integrity threat posed by pipe-manufacturing defects. There is strong evidence that this is sound for pipe operating at the highest stresses but also that a larger test-pressure ratio may be appropriate for pipe operating at lower stresses [1]. A probabilistic analysis has been implemented to enable the specification of a test-pressure ratio tailored to the operating stress level, target time-to-failure, and failure probability, accounting for expected variability in operating conditions, material properties, fatigue-crack-growth rate, and location classes.