Applications of Brazed-Type Ultrasonic Probes for High and Low Temperature uses

Abstract Brazed-type ultrasonic probes have been developed to extend the allowable service temperature drastically. These probes are constructed by brazing method not only for bonding an element with a protection plate or a probe shoe delay but also for acting as heat resisting electrodes, an element sandwiches therebetween. It has been demonstrated that these probes can continuously endure the temperature up to 550°C for a long period of time and also down to -269°C in liquid Helium without any coolant. These brazed-type probes were used successfully to monitor the plate thickness in the environment of corrosion and erosion at high-temperature. Double element probes are used by direct contact method for in-operation inspection. Probes directly jointed by stud-welding on the actual piping of plants can register continuously the small variations of plate thickness. Material degradation of 475°C embrittlement of two phase stainless steel (25CrNiI.5Mo) was studied to monitor continuously the velocity of sound in material by this brazed-type search unit in a furnace. The same kinds of acoustic emission sensors were discussed, too.