PR276-223814-R02 Pragmatic Application of MegaRule RIN 1-192.712 Toughness Values L2 and L3 Procedures

This project addresses pragmatic application of the new DOT/PHMSA MegaRule RIN 1 – 192.712 for recommended toughness values for determining if an ILI detected axial flaw needs repair or can instead be observed for any future growth. The MegaRule toughness is expressed as the Charpy energy value, which came from Charpy test data at 50°F. However, the fracture toughness of a surface-cracked pipe is quite different than Charpy impact toughness values, especially if the Charpy data is in the brittle-to-ductile transition region. The surface-cracked pipe burst-pressure transition temperature can be greatly lower than the Charpy impact specimen transition temperature due to loading rates and constraint effects (bending versus tension loading). In cases with axial surface cracks in vintage base-metal pipe tests, the surface-cracked pipe burst pressure transition temperature was >200°F lower than the Charpy transition temperature. The procedures were extended to welds, and in the Level 1 report, databases from member companies were examined to establish what Charpy energy values should be used to reflect the toughness of a surface crack in the pipe at the operating temperatures, and still be consistent with the MegaRule Charpy information and safety desires.