Impact Toughness Deficiencies in ASME SA-350 LF2 Flanges

Personnel working on a major capital project experienced a significant issue related to the supply of non-conforming ASME SA-350 LF2 low temperature carbon steel (LTCS) weld neck flanges. Flanges were destructively tested and found to have Charpy impact toughness far below minimum values required by the ASME specification. The scope of this issue involved several thousand flanges, and the nature of this non-conformance could have resulted in the unexpected failure while in service. In all cases, mill certificates supplied for the flanges did not indicate any deviation from the ASME specifications. The investigation revealed that industry standards are not adequate to identify and prevent this potential problem, therefore highlighting the need for changes to be made. This paper details the experience and investigation, and includes suggestions for improvement to the ASME specification.