PIPING INSPECTION USING MEC™

Within a client’s refinery, they were experiencing small and isolated MIC (Microbiological Induced Corrosion) pipe failures, leading to random losses in their product containment. These pipe defects were occurring internally and mainly within an identified 6“OD x 7.15mm wall thickness, Carbon Steel COSC transit pipeline, with an applied non-electro-conductive painted coating.

Multiple attempts had been made by the client, to locate and plot these small defects, especially with manual Ultrasonics, well in advance of any failures occurring and at their preliminary stages of propagation, but with little to no success.

PROCESS

An inspection campaign was established and completed using a variety of Innospection (a division of Sonomatic)’s  MEC™ topside (permanent magnetic and electro-magnetic) dedicated pipe scanners. These scanners built for different applications, in terms of the available pipework access, outside pipe diameter and wall thicknesses.

MEC™ Eddy Current is a reference  NDT inspection technique; therefore, a calibration is always required of the complete system from a known “like for like” (material and pipe specification) reference test-sample. This sample contains either natural and/or artificial material defects, similar in nature and shape to those defects being sought, and for a reference (impedance signal) response.

Outcome

After intense surface scanning over multiple areas of the pipework, equating to a significant total meterage and nothing being detected, an area of the pipeline was finally located with notable random indications being resolved.

These areas with random isolated indications being discovered, were then subjected to further intense high resolution slower automated ultrasonic scanning, revealing, and confirming internal pitting and their sizes.

Two isolated pits were confirmed and measured out at 5mm x 6mm and at a depth of 25% wall loss, and 3mm x 4.5mm at a depth of 20% wall loss, respectively. Both these areas had been missed previously, by a routine manual Ultrasonic inspection.

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