Ultrasonic Arra Ys for Fla W Characteriza Tion at High Temperature

There is a real and increasing need to monitor the presence and growth of cracks in key regions ofplant within the nuclear, gas and chemical industries [1]. A rugged, permanently attached sensor, capable of operating at temperatures in excess of 400° C, would have substantial benefits, since it would reduce the down-time costs incurred through the forced inspection of known or suspected flaws. By carefully measuring crack growth insitu, under plant operating conditions, remedial action can be taken, either during planned outages of the plant, or when the crack depth exceeds criticallimits.