ILI Tool Tolerance and Repeatability Effect on Corrosion Growth Rates

The knowledge of the rate at which corrosion grows in a given pipeline could be used to determine the time between inspections, find hot spots of high corrosion growth, and possibly prevent catastrophic failure of the pipeline. For these reasons many pipeline companies employ some method to calculate the growth between inspections years apart. This calculation may be on two sets of inspection data from different vendors using different technologies. This paper discusses normalization of data which is necessary for a fair data comparison. Growth rates are calculated for the normalized data for the complete population of anomalies, as well as individual anomalies. Analysis of tool tolerance and repeatability is then used to put the results into perspective.