Phased Array Technique for Inspection of Contact Point Corrosion

Inspection for wall loss at pipe and vessel supports is complicated due to limited access. Indirect techniques are required which position sensors away from the area of interest. Corrosion morphology and pipe geometry can produce very complex transmission paths and attenuation at different angles. Conventional ultrasonic techniques rely on data from only a single angle and may require highly skilled data analysis.

The PA-CAT^TM phased array technique developed by Holloway NDT & Engineering Inc. is an attenuation-based modelling algorithm used to evaluate the minimum remaining wall thickness at pipe or vessel supports. The Veo3 instrument is fully capable “in the box” to easily generate phased array pitch-catch focal laws for two separate transducers at the touch of a button. On board the instrument the multi-skip data can be quickly output and analysed online via www.pa-cat.ca to calculate the “river bottom” plot along the scan length. The PA-CAT^TM modelling algorithm has been developed through extensive testing of realistic corrosion based on laser scans of actual touch point corrosion.