A Comprehensive Approach in Managing the Aftermath of Non-Conformance Seam Welded Linepipes

Abstract

PETRONAS had been notified by its pipe mill that some of the linepipe supplied by the mill were found to be non-compliance with agreed manufacturing process specification (MPS) and inspection & test plan (ITP). The non-conformances happened during longitudinal weld seam repair at the manufacturing stage. The notification has put PETRONAS on high alert as the affected linepipes have already been installed and commissioned as part of gas pipelines i.e. Pipeline 1 and Pipeline 2 supplying to onshore customer. This paper will discuss the investigation strategies implemented by PETRONAS' investigation team which include 1) multidisciplined investigation team, 2) Technical Safety Review, 3) Desktop Review and 4) Repair Simulation and Material Verification Testing. The paper also details out the type of non-conformance and associated hazards with corresponding action plan to address them. Engineering Criticality Assessment (ECA) was one of the critical processes in the investigation where simulated longitudinal weld samples from the linepipe underwent Crack Tip Opening Displacement (CTOD) test. The test provided fracture toughness value of the weld sample and became the main input in the ECA study. The objective of the ECA is to provide defect/ crack acceptance criteria based on methodology specified by BS7910. During ECA, the respective weld sample was analyzed against pipeline operating parameters coupled with fatigue stress mainly contributed by pressure variations. Crack growth was studied and compared against defect/ crack critical dimensions i.e. height, and length. Given all the investigations carried out combined with ECA experts review, the pipelines were proven safe and reliable to operate. The investigation outcomes have saved PETRONAS commercially while maintaining good safety record.