Affect of Black Powder on In-Line Inspection Accuracy

The accuracy of an inline inspection (ILI) tool such as a Magnetic Flux Leakage (MFL) tool is affected by the amount of black powder in the pipeline.  Parameters such as the ILI tool signal strength, speed, girth weld readings, rotation, and inclination are affected resulting in inaccuracy of the ILI tool reports.  The analysis of two subsequent ILI run results may also be affected due to erroneous conclusion that the corrosion depth may be getting worse when in fact the tool is only reporting more accurate readings as the line is cleaned of black powder.  Thus, field verifications of the ILI run becomes very important to determine the accuracy of the readings and the affect of the black powder.  However, field verifications is an expensive exercise especially if all the reported readings must be excavated for inspection.  The bottom line is that the effectiveness of the pipeline validation operation using an ILI tool becomes critical given the affect of the black powder especially if the reported data is misinterpreted.