A hard spot is defined as a localized area with increased hardness compared to the surrounding base metal [1]. The presence of hard spots, especially in combination with other threats such as geometric anomalies, manufacturing features, etc. have a significant impact and relevance on integrity assessment and the subsequent response. Up until recently, the industry has had a fairly rudimentary understanding of hard spots. Assessing this treat brings certain challenges, including but not limited to:
- What types of hard spots exist, and which are actual integrity threats?
- How do we confirm the presence and understand the nature of hard spots?
- How do we assess the integrity of hard spots?
- How do we focus on the right features and get the most of our integrity budget?
- How do we address the threat of hard spots? What are appropriate remediation actions?
Obtaining reliable data
The first step in any decision-making process is reliable data. Based on data published in the period from the 1960s to the early 2000s, pipes manufactured prior to 1970, especially A.O. Smith flash-welded pipes, are known to be particularly susceptible to hard spots. In 2021, there was a significant change to gas regulations, CFR 49 192. A newly created clause, CFR 192.632 – Engineering Critical Assessment for Maximum Allowable Operating Pressure MAOP Reconfirmation, explicitly states, "If a pipeline has segments that might be susceptible to hard spots based on assessment, leak, failure, manufacturing vintage history, or other information, then the ILI program must include a tool that can detect hard spots". Addressing that, ROSEN's RoMat Dual MaGnetization (DMG) service, which is based on standard magnetic flux technology, can serve as the starting point of a coherent holistic integrity management strategy. As hard spots possess different metallurgical properties – magnetic permeability, specifically – compared to the surrounding metal, combining full magnetic saturation with a well-defined lower magnetization enables accurate and precise hard-spot classification and sizing.
Performing an in-line inspection (ILI) is only the tip of the iceberg. Understanding the ILI results and differentiating the types of hardening material features that can exist in the pipeline is vital to ensuring the correct response is implemented.
Delivery of the RoMat DMG service
The use of RoMat DMG can support established integrity management processes and address intended regulatory guidance concerning the existence of hard spots as part of MAOP reconfirmation. The service is based around a framework with RoMat DMG as the cornerstone, as shown in Figure 1 below.