PR-214-223806-R01 Guidance for Performing Engineering Critical Assessments for Dents on Natural Gas Pipelines

Abstract

This project builds on mechanical damage (MD) assessment and management tools, developed on behalf of Pipeline Research Council International (PRCI), Interstate Natural Gas Association of America (INGAA), Canadian Energy Pipeline Association (CEPA), American Petroleum Institute (API), other research organizations and individual pipeline operators and included in API RP 1183 [1]. These include dent shape, restraint condition and interacting feature characterization; operational maximum and cyclic internal pressure characterization, screening tools defining non-injurious dent shapes based on pipe size and operating condition, failure pressure and fatigue assessment tools for dents with/without interacting features (e.g., corrosion, welds, gouges) in the restrained and unrestrained condition, and direction on available remedial action and repair techniques. The API RP 1183 [1], has not been adopted by the Pipeline and Hazardous Materials Safety Administration (PHMSA) by reference in code of federal regulations (CFR) 192.712 (c). CFR 192.712 (c) allows pipeline operators to follow certain prescriptive requirements for responding to mechanical damage features or perform an engineering critical assessment (ECA). The requirements of CFR 192.712 (c) provide minimum requirements for what would comprise an acceptable ECA. The objective of this research project is to develop a guidance document containing a practical and defensible set of guidelines and processes to address the CFR 192.712 (c) requirements. The work included: - Description of various dent fatigue life screening and assessment approaches detailing data requirements for the different approaches, - Developing a simplified method for dent fatigue life assessment using operational severity when detailed pressure spectrum data is not available, - Development of a Level 0.75 and 0.75+ screening approach that incorporates dent depth available from in-line inspection (ILI) data, - Developing a screening level methodology to carry out fatigue life assessment of dents with potential gouge where metal loss is conservatively assumed to be a planar crack-like feature.