Ensuring Asset Integrity via Non-Destructive Evaluation of Mechanical Properties in Aging Infrastructure

As assets age and operating conditions change assessment for continuous service and life extension necessitate review of equipment integrity and determine their fit for service conditions and set operating limits. One approach is to utilize industry’s best practices as outlined in API RP 579/ASME FFE-1 Fitness-For-Service(1). This approach requires the use of fracture toughness of the material of construction that is not given in typical Material Test Reports (MTRs) or not available at specific operating conditions such as lower temperature Charpy Impact Energy (CVN). To enable effective analysis and reduce the degree of conservatism, Charpy Impact and/or fracture toughness data at the desired operating conditions is needed. Since both properties are typically generated by laboratory tests that require removal of samples from multiple components, traditional destructive testing becomes less practical due to its invasive nature, downtime requirements, and the removal of materials (for machining various mechanical test specimens) from critical components. This approach is deemed impractical especially since multiple tests may be needed to determine the statistical distribution of properties of many piping or vessel segments that could be made from different heats. This led to looking for ways to obtain the required data using non-destructive means. Accurate, nondestructive evaluation of mechanical properties such as yield strength, tensile strength, and fracture toughness is increasingly becoming critical for pipeline and pressure system integrity in upstream, midstream, and downstream oil and gas operations. As an example, an aging production platform was nearing its original design life and the current operator wished to extend its service life, by performing an in-depth engineering review of the facility and submit a life extension to the governing regulatory body for approval. During this detailed engineering review the current operator discovered that the original design for the flaring system which included the structural support of the flare boom and the process calculation for the flaring system were all adequate. However, the original design firm and operator used a unique approach by using the primary flare line for process gases, as well as primary steel support of the flare boom structure. However, no consideration for low temperature effects of rapidly expanding gases [Joule Thomson effect] during a flaring event were ever determined. To complete a comprehensive engineering analysis, the current operator needed to confirm the original materials of construction would be fit for purpose if the full capacity of the flare system was exercised during a flaring event.