New EC- and UT-systems for the in-service-inspection of austenitic and dissimilar weldmentsat elevated temperatures
Neue Wirbelstrom- und Ultraschallsysteme für die wiederkehrende Prüfung austenitischer und Misch-Schweißnähte bei erhöhten Temperaturen
The described EC-inspection system works with four frequencies (30kHz-2MHz) simultaneously fed into the inspection coil. The mixing of the resulting measuring signals is otimized to characterize and to size fatigue and corrosion cracks in austenitic weldments. To solve this task it is necessary to suppress the disturbing conditions growing from the coil lift-off. The applied sensors are designed for an elevated temperature (250xC). For the inspection of the inner near surface zone of the two circumferential welds HORIZONTALLY POLARIZED SHEAR (SH)-waves, excited and detected by EMUS-probes, are used. The probes are optimized to fulfill htree different inspection functions and are designed to operate at 150xC. SH-waves are used because of their ability for gracing incidence and their advantageous features for the inspection of anisotropic abd coarse grained dissimilar welds.