An Operator’s Experience of Managing the Hard Spot Threat

Abstract Hard Spots are a recognized pipe manufacturing threat classified under ASME B31.8S for managing system integrity of Natural Gas (NG) transmission pipelines. Hard spots with sufficiently high hardness properties may be susceptible to hydrogen embrittlement and hydrogen stress cracking (HSC). Enbridge experience of managing Hard Spot threat through a Hard Spot ILI program is discussed in this paper. Enbridge has run roughly 2500 miles of Hard Spot tool in its US and Canadian transmission pipelines. Overall tool performance is discussed for both baseline from the perspective of initial Hard Spot callouts and subsequent in-the ditch validation of Hard Spot features. ILI reported Hard Spot features, feature confirmation in the ditch, and subsequent metallurgical laboratory assessment, has been discussed for Enbridge’s gas transmission system. Tool performance has been discussed leveraging Enbridge’s vast mileage of Hard Spot data using API 1163 unity plot methodology comparing tool called features and in-the-ditch and laboratory validation data. Finally, Enbridge’s Bellhole inspection and repair protocol has been discussed specific to related digs for managing the Hard Spot threat.