Abstract: First and second magnetic poles are provided, which have end surfaces brought close and in opposition to a material to be examined. These magnetic poles are magnetized by a DC exciter coil such that the magnetic poles have opposite polarities. The first magnetic pole is provided at its end surface with a pair of cumulatively connected transmitting coils, and the second magnetic pole is provided at its end surface with a pair of differentially connected receiving coils. The transmitting coils are connected to a pulser which generates a pulse current, and the receiving coils are connected to a differential amplifier. An electromagnetic ultrasonic wave generated by the transmitting coils are received by the receiving coils, amplified by the differential amplifier, and thereafter supplied to a synchroscope and an automatic detector.

Abstract: A method for detecting the flow instability in steam generators is provided. First, a number of limit values on the differential pressure between the water-side inlet and outlet of the steam generator are determined at different feedwater flow rates. The limit values define the onset of the flow instability. By connecting the thus determined limit values, a boundary line defining the occurrence of the flow instability is obtained. Second, it is checked whether the measured differential pressure between the inlet and outlet at an actual feedwater flow rate is above or below the boundary line so as to determine if the flow instability has occurred or not in the steam generator. An apparatus for accomplishing the method is also provided.

Abstract: A supersonic or ultrasonic wave flaw detector in which acoustic boundaries of flaws and/or abnormality of materials within an object to be inspected is detected by supersonic or ultrasonic waves and the position and shape of such a flaw and/or abnormality are displayed. A hard object to be inspected is sector-scanned with a supersonic wave beam with a variable-angle beam probe in direct contact with the object. In a range of comparatively small incident angles at which the longitudinal wave mainly penetrates the object, sectional images due to echo signals of the longitudinal wave are displayed on a display screen with scanning lines representative of the transmission speed and direction of the longitudinal wave. In the range of large incident angles where the shear wave penetrates the object, on the other hand, sectional images due to the echo signals of the shear wave are displayed on the display screen with scanning lines representative of the transmission speed and direction of the shear wave.