Corrosion Defect Assessment and Maintenance Decision-Making of a Gas Transmission Pipeline

Based on in-line inspection data, a statistical analysis on relationship of defect size feature and girth weld was performed for a gas transmission pipeline. Maintenance judgement criteria were formulated by considering factors including interacting defects, girth weld influence and defects features. Maintenance decisions were made for defects by combining residual strength assessment, remaining life prediction and composite factors analysis, and the time for next inspection was proposed. It was shown that the residual strength assessment results exhibited that the maximum ERF (esmated repair factor) for corroded pipeline was 0.578 and fitted for loading capacity, but 3 defects should be fixed immediately and 18 defects shouled be repaired within one year. The suggestion was given to implement a re-inspection in 2023. Moreover, gas quality should be controlled strictly, pigging frequency and quality should be increased.