Oil-Pipe Cracking and Fitness-for-Service Assessment

A new D457 × 7.1 X65ERW oil pipeline leaked twice during the pressure test. The two failed pipes belonged to same batch of products from manufacturer. Failure analysis showed that cracks in 1# and 2# cracking propagated outer surface pipe wall inner along weld fusion line. inclusion phase distributed chains zone is speculated be root cause fitness-for-service this steel was analyzed using failure-assessment chart technique. could used safely under design 10 MPa, re-evaluation period three years recommended for based on fatigue results steel-pipe zone.