Effect of Dent Depth on the Burst Pressure of NPS30 X70 Pipes With Dent-Crack Defect

Pipeline is the common mode for transporting oil, gas, and various petroleum products. Buried linepipe can be exposed to various external interferences and corrosive environment and as a result, damage in the form of dent or corrosion or crack or gouge or combination of any of these damages can form in the pipe wall. Such damage or combined damages can reduce the pressure capacity of the pipeline. A defect combining dent and crack, often known as dent-crack defect, can develop in the wall of a buried oil and gas linepipe. This combined defect may lead to a leak or a rupture in the pipe wall and hence, the pipeline operator becomes concerned about the performance and safety of the pipeline when a dent-crack defect is detected in the field pipeline. A long-term research program is currently underway at the Centre for Engineering Research in Pipelines, University of Windsor to study the influence of various parameters such as dent depth and operating line pressure on the pressure capacity or burst strength of 30 inch diameter and X70 grade pipes with D/t of about 90. From the study completed so far, it has been found that the dent depth of 8% with crack depth of 4 mm or more can reduce the pressure capacity by 32%. This paper discusses the test specimens, test setup, test procedure, test results, and data obtained from finite element analyses.