Development and Implementation of a Dent Engineering Critical Assessment (ECA) in Accordance with PHMSA’s Gas Mega Rule

Abstract In the 2019 US Gas Transmission Rule referred to as the “Mega Rule”, PHMSA introduced a new section within CFR 192.712 [1], allowing operators the opportunity to develop procedures and perform Engineering Critical Assessment (ECA) leveraging industry standards such as API RP 1183, ASME B31.8S [2, 3], or other current research findings to determine if dents and mechanical damage anomalies should be responded or monitored beyond the prescriptive requirements referenced in CFR 192.714 and CFR 192.933. In addition, PHMSA provided guidelines to operators on what an acceptable ECA procedure should consider. If an operator chooses to perform an ECA process, submission of advanced notification with the relevant procedures in accordance with CFR 192.18 would be required. For operators to assess a prevalent pipe integrity threat such as dents, industry standards refer to multiple levels of assessment methods, with increasing orders of complexity and decreasing levels of conservatism. The purpose of this paper is to provide technical suggestions on the development and implementation of an ECA workflow to assess dents and to determine their fitness for service. This paper provides suggestions on how to address plain dents with strain levels potentially exceeding 10% strain limit which typically can account for a significant portion of the dents identified through ILI. The paper also describes the FAD-based method to conduct fracture assessment on cracks/gouges coincident with dents. A workflow was also developed to conduct fatigue crack growth assessment on dents interacting with cracks/gouges in accordance the CFR Mega Rule requirements. Finally, a software tool has been developed to automate the dent ECA process. With this automation, the efficiency in conducting dent ECA could be significantly improved ensuring that a prompt action will be taken on potentially injurious dents. A case study on hypothetical dents was conducted demonstrating the robustness of the workflow performed with the automation tool.