02101 Brittle Fracture of an Underground Gas （02101 脆性断裂的一个地下气体）.PDF

Brittle Fracture of an Underground Gas Gathering Pipeline at ERW Weld Groove Defects under Hydrogen Charging Conditions and Wet COz/HzS Corrosion David E. Hendrix The Hendrix Group Inc. Steve OToole Dynegy Midstream Services Richard A. Mueller Dynegy Midstream Services Dr. Ronald E. Frishmuth Consulting Engineer Abstract This paper discusses the laboratory failure analysis investigation of a 10 underground gas gathering pipeline that ruptured while attempting to remove a hydrate blockage. Failure occurred as a macroscopically brittle fracture along longitudinal groove defects associated with an ERW weld. Laboratory investigation of the failure included ERW defect length and depth measurements, charpy impact toughness testing, wall thickness profiles along the fracture, metallographic examinations at ERW groove defects, microhardness measurements and mechanical property testing. Remaining strength and critical flaw size analyses were conducted using several fracture mechanics programs and the results compared with one another. Fracture mechanics analysis results supported the role of absorbed hydrogen due to corrosion in causing failure at internal pressures below that predicted based on overload. Keywords: API 5L pipe, corrosion, brittle fracture, hydrogen charging, API 579, ASME B31G, ASME B31.8, wet CO2 corrosion. 1