Circumferential current field testing system with TMR sensor array for non-contact detection and estimation of cracks on power plant piping

Piping is a critical component in power plant, which is subject to surface thermal fatigue cracks. Due to the high temperature and the presence of coatings, conventional non-destructive testing methods are unsuitable to detect the thermal fatigue cracks on power plant piping. This paper presents a novel circumferential current field testing system for the non-contact detection and estimation of cracks on power plant piping. A 3D dynamic finite element method model is developed to obtain the characteristic signals and optimize the inducing frequency. The circumferential uniform current field testing system with tunnel magneto resistance (TMR) sensor array is set up and the crack detection experiments are carried out. The results show that the circumferential current field testing system with TMR sensor array can achieve non-contact, visual and efficient detection of cracks on power plant piping in a one pass scan. The depth and length of cracks can be estimated by the proposed calibration method.