Full matrix capture ultrasonic inspection of girth welds in CS pipe and CRA clad pipe
Status: Completed
Date Announced: May, 2016
Project reference: 25678
The accurate sizing, positioning and characterisation of flaws in carbon steel (CS) and corrosion resistant alloy (CRA) clad pipeline girth welds is a key aspect of laying and maintaining pipelines of high structural integrity in the oil and gas industry.
Automated ultrasonic testing (AUT) using zonal discrimination technique (ZDT), is commonly used to determine the structural integrity of such welds in both J-bevel CS pipe and CRA clad pipe. Coherent noise contributions, caused by differences in acoustic impedance at the interface between parent, clad and weld materials, as well as coarse grained materials typically used, create challenges for effective ultrasonic inspection. Furthermore, accurate flaw sizing and characterisation of near vertical flaws in J-bevel CS girth welds (i.e. lack of side wall fusion (LoSF)) relies heavily on accurate calibration using flat bottomed holes orientated along the weld bevel. This calibration relies on a complex, time consuming and operator dependent set up process and the resulting technique is still dependent on the orientation of the defect during inspection. Even slight mis-orientation can significantly affect probability of detection and sizing accuracy. The project promotes a novel approach, combining full matrix capture (FMC) data acquisition with the total focusing method (TFM) image reconstruction algorithm in order to overcome a number of short comings associated with existing pipeline girth weld inspection techniques and procedures.
The project has included a number of work phases including (i) development of an optimised ultrasonic FMC+TFM inspection setup and procedure (ii) FMC+TFM ultrasonic inspection of girth weld pipe samples (iii) validation of inspection performance, (iv) development of a best practice guide for FMC+TFM inspection of girth welds.