Schweißnahtprüfung mit Fernfeld-Wirbelstrom-Prüftechnik

A feasability study of the remote field eddy current technique has been performed investigating the inspection of circumferential sleeve tube welds in steam generator tubing. Exciting coil and receiving coil is an inner bobbin coil. The receiving coil is a small, sensitive differential pick-up coil with a ferrite core. The signal from the receiver coil is successively fe dinto a phase shifter, an attenuator, a differential amplifiet and a lock-in amplifier. Images showing signal amplitude and phase as a function of the receiving coil position allow to differentiate between good and bad qualities of sleeve tube welds.