by Charles H. Panzarella, Ph.D. / Jan 01, 2016

High temperature hydrogen attack (HTHA) is an insidious damage mechanism that typically manifests as methane-filled cavities in the walls of pressure vessels containing hydrogen at elevated temperatures. It can also lead to an increased tendency for cracking. As part of an ongoing Joint Industry Project (JIP) on HTHA, a comprehensive, mechanistic, fully-dynamic model of HTHA has been developed and is being used by our consultants to improve their assessments. New fitness-for-service (FFS) assessment rules for in-service components have also been developed.

One of the key advantages of this new approach is that it properly accounts for the inherent time-dependent nature of HTHA. Analogous to the Nelson curves appearing in API RP 941, new, time-dependent, probabilistic screening curves (the Prager curves) have been developed to demarcate safe regions of operation from those deemed unsafe (depending on the operating time). Probabilistic methods are used to determine the probability of failure as a function of the operating time when uncertainty is high.

This webinar summarizes the background and methodology of the HTHA model, and many practical examples will be given to illustrate the usefulness and robustness of this new approach. An easy-to-use web-based tool that performs the calculations will be demonstrated, and ongoing and future enhancements will also be discussed.

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