Diverless weld inspection and repair using ECM/ACFM techniques
Clifton D., Mill F., Esnaola J., Kare R., Dover D.
This paper describes the development and application of an integrated tooling/NDT system which provides the potential to undertake take a weld inspection, carry out removal of the defective zone, and achieve validation of the repair, all within a single ROV deployment operation. Removal of the defect zone is achieved using a novel application of the electrochemical machining process (ECM). This system is integrated with the alternating current field measurement (ACFM) system, for crack detection, location and sizing. The paper describes the development of electrochemical machining process models to cover situations encountered in automated weld sampling operations. From these models, and data collected from experimental trials, it has been determined that the sampling/removal operation can be carried out at tool feed rates of up to 3 mm/min. The model has been extended for determining the change in gap dimensions for the case of zero tool feed. This relationship can be used as a control parameter when determining the degree of overcut required when inclusions are encountered and the tool is required to remain stationary for a certain duration. Tank trials of the system have been carried out, successfully demonstrating effective operation of the integrated strategy in a submersed environment.