Know Your Enemy – Improvements in Managing the Threat of Hard Spots

Abstract

Operators of gas and liquid pipelines are expected to manage the threats associated with hard spots as part of their Integrity Management Plan (IMP). Over the past two years, a considerable amount of work has been completed to assess hard spots and characterize exactly what these features are, and how they can be managed. There is a significant body of data from ILI and metallurgical verification to develop a more complete understanding of the threat from hard spots. A hard spot is a localized increase in hardness compared to the surrounding base metal, which is defined in API 5L as an area larger than two inches in any direction and a hardness greater than 327 HBW [1]. Hard spots have been observed on EFW and DSAW pipes of various grades. The data collected confirms that there are different types of hard spots, which vary depending on the specific thermal cycles that create them. In the majority of cases, hard spots are introduced during the plate or pipe manufacturing process, and therefore can be related to specific pipe types, batches or manufacturers. It follows that understanding the types of pipes present within a pipeline system can help with susceptibility analysis and threat management. This fits with updated regulatory requirements driving the industry to verify material properties and attributes to support integrity management, when they are not evidenced by traceable, verifiable and complete (TVC) records. This paper discusses the processes used to assess, characterize and size hard spots, providing the information needed to make informed integrity decisions. Examples of different types of hard spots will be presented and discussed in relation to the various pipe types that can be differentiated using ILI-based material property verification. The paper will demonstrate how a close collaborative approach between operators and vendors can yield significant improvements in technology, processes and the integrity management plan.