Root Causes for Failures in Flattening Test in High Frequency Induction Welded Steel Pipe Mill

The aim of the flattening test in a High Frequency Induction Welded (HFIW) steel pipe mill is to test the weld integrity. Failures in the flattening test may cause rejection of tested pipe and additional costs as result of retesting the other pipes from the same coil, scrapping and cutting the tested material, segregating and transporting of pipes required for flattening retest, and delaying the release of material. This paper presents the root causes for failures in the flattening test due to inadequate process control. The paper also discusses the failures in the flattening test associated with the severity and lack of clarity of the acceptance criteria in some of the pipeline international specifications. The targeted specifications are API 5L and ISO 3183. Specifically, the paper proposes, based on practical experience, changes of the acceptance criteria in the international specifications related to the first step of flattening test which is the test of weld ductility.