Prediction of Dent Size Using Tri-axial Magnetic Flux Leakage Intelligent Pigs
Scott Miller · 2007
Abstract According to statistics compiled by the U.S. Office of Pipeline Safety, external mechanical damage is one of the primary failure mechanisms for transmission pipelines. Mechanical damage can be described as a pipeline deformation with or without secondary features such as gouging or cracking. These types of features are a major concern of pipeline integrity engineers. This is why inline inspection tools specifically designed to detect geometry deformation have been used in the industry for many years. A pipeline dent of sufficient depth can reduce the burst pressure of the pipeline. Some of the most severe pipeline conditions possible occur when a dent is in coincidence with another defect such as a gouge or a crack. Since the development of Tri-axial Magnetic Flux Leakage (MFL) inspection tools, a number of pipelines have been inspected with both caliper and MFL inspection tools. A large database of features was created that contained detailed information from both the caliper inspection tool as well as signal information from the MFL tool for dent like features. An empirical study of the relationship between the MFL signal of a dent and the recorded mechanical deflection of a dent from a calliper tool was conducted and the results from this study indicated it is possible to accurately predict the size (Depth, Length, and Width) of a dent from tri-axial MFL inspection tool data. The methodology of sizing dents and the accuracy of dent size predictions will be demonstrated in this paper.