Necessity and suitability of in-line inspection for corrosion resistant alloy (CRA) clad pipelines

This paper outlines the necessity and suitability of in-line inspection (ILI) using intelligent pigging for Corrosion Resistant Alloy (CRA) subsea clad pipelines through an incident that occurred during a baseline survey performed on a 20-inch y CRA clad pipeline of 2.7 km long. In this incident, an ultrasonic (UT) intelligent pigging tool was impacted and resulted in damage to the pipeline's clad layer. This damage was due to the collosion of the sealing pigs with the rear of the UT intelligent pigging tool, resulting in the UT intelligent pigging tool to get stuck and stop at the end of the pipeline. Pressure surges were used to dislodge the UT intelligent pigging tool, but caused the UT pig to be crashed into the pig receiver, resulting in severe damage to the UT pigging tool. The analysis of the metal swarf recovered from the pig receiver revealed that the damage was limited to the pipeline's clad layer. It was also revealed that a bypass has occurred to the sealing pigs causing damage to the sensor carriers of the intelligent pigging tool.