Three cases of failure in two 30-40 year old pipelines are analyzed. The first case arose as a consequence of an unsafe working practice on the line. A pressure burst was generated, leading to a through axial crack corresponding to a pre-existing manufacturing defect. The second accident occurred during normal operation, but was a consequence of the first accident, which weakened the pipe, causing the subcritical growth of pre-existing defects related to the high carbon equivalent content of the pipe steel. The third accident occurred in another pipeline: external corrosion, related to incomplete tar lining of the pipe near a welding seam, caused oil leakage. To clarify the fracture conditions for the first two accidents, the collapse pressure has been evaluated employing the R6 Structural Integrity Assessment Method. The results verify quantitatively previously reported explanations, obtained by flow dynamics analysis and macroscopic and microscopic fracture observations.
Structural collapse calculations of old pipelines
International Journal of Fatigue ; 20 , 2 ; 161-168
1998
8 Seiten, 19 Quellen
Article (Journal)
English
Fehleranalyse , Fehler , Riss , Unfall , Materialermüdung , Pipeline , Materialbruch , Stahlkorrosion
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