February 2022, Vol. 249, No. 2


Managing the Threat of Hard Spots

By Khanh Tran, Pipeline Integrity Engineer, and Simon Slater, Principal Engineer, Rosen Group   A hard spot is a localized area with increased hardness compared to the surrounding base metal. API 5L defines a hard spot as being larger than 2 inches in any direction with a hardness greater than 327 HBW1.    Figure 1: Schematic of a time-temperature transformation diagram Hard spots are believed to result from application of a local thermal cycle, such as localized quenching of the surface, to produce a microstructure that is different from (and harder than) the surrounding parent material. Hard spots have typically been observed in old

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