Non-Destructive testing of welds
In the framework of a GROWTH Programme project, the Non-Destructive Testing (NDT) technique of Alternating Current Field Measurement (ACFM) was employed to inspect welds. ACFM works by passing an alternating current near the surface of the weld. Small coils then perceive minute disturbances in the resulting magnetic field generated in the weld and surrounding substrate. Analysis of these disturbances indicates where cracks or other irregularities exist. The Greek company Zenon incorporated an array of ACFM sensors into a probe christened the Robot Inspector. The sensors are positioned in the probe such that the entire weld cap can easily be scanned in one pass. The probe geometry is flexible enough for use with a variety of weld types, such as butt, fillet and overlapping welds. Furthermore, the number of sensors can be optimised to address defects both parallel and transverse to the weld. The probe prototype was tested during the GROWTH Programme project and was found to be particularly effective in the detection of defects not only in the weld material but also in the surrounding substrate. In particular, cracks on the substrate surface deriving from toe cracking were easily identified. Organisations interested in learning more about the ACFM sensor array or the Robot Inspector should come into contact with Zenon.
