The Batelle two-curve method of fracture-arrest prediction for X70 and X80 high toughness steels requires correction factors based on the steel's grade and toughness level. Data illustrate the impossibility of developing influence coefficients to define the effect of changes in rich gas compositions on CVN (Charpy V-notch) toughness required for fracture arrest. The ideal gross gas heating value appears to maintain a rough relationship to arrest fracture toughness, although there is some scatter. Factors not incorporated into the fracture-arrest prediction equation include the effects of backfill. Recent data show the moisture content of soil exhibits a rough correlation with fracture speed, suggesting higher soil moisture contents relate to lower fracture-arrest toughness. This is an area of research requiring further pursuit to improve fracture-arrest predictions. This first part of two articles will present background information and raw data from fracture-arrest tests on X70 pipe, sorting the data by where arrest or propagation occurred and assessing it versus available prediction methodologies. X70 steels are addressed herein, with the X80 steels presented in the concluding article.
Fracture propagation - 1. Fracture-arrest prediction requires correction factors
Oil and Gas Journal ; 106 , 39 ; 52-59
2008
6 Seiten, 6 Bilder, 4 Tabellen, 4 Quellen
Article (Journal)
English
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