Strength of Line Pipe With Dent and Crack Defect

Pipeline industry and various research organizations have been undertaking studies to understand how the pressure strength of line pipes reduces as the defects in the line pipes grow. Defect in pipe lines can be in the form of corrosion, dent, wrinkle, gouge, crack, and combinations of these. A large number of studies have been completed in developing methods for determining the pressure strength of line pipes with dent and gouge defects and also in the form of combined dent-gouge defect. Some of these studies were undertaken with the intention of determining the pressure strength of line pipes when a combined dent and crack (dent-crack) defect has formed. However, in these studies no cracks were simulated in the test pipe specimens; instead, a gouge (machined cut or notch) was produced and considered as a crack. Therefore, it is not realistic to call this defect a dent-crack defect; rather, it should be called dent-gouge defect. Hence, the current project is being undertaken at the University of Windsor to study how the dent-crack defect influences the pressure strength of line pipes. In this study, a crack in true sense was introduced in the pipe wall. Two different techniques were used to simulate the crack in the pipe wall. This paper discusses the procedures used in this study to simulate crack and dent. In addition, the test procedure and test data obtained from denting and pressure tests are discussed.