Abstract: A non-destructive method and apparatus for inspecting materials in excess of 500.degree. C. includes a dual transducer disposed upon a delay line suitable for operation at the elevated temperatures. The delay line is divided into two parts acoustically isolated and is cooled by a fluid to maintain the surface upon which the transducers are mounted at a safe operating temperature.

Abstract: Apparatus and method for measuring the thickness of a test piece by obtaining the acoustic velocity of the test piece where an ultrasonic wave is refracted into the test piece at a first point and the wave travels substantially parallel to the surface and the transit time to a second point where the wave is refracted out of the test piece is measured. The distance between the first and second points is known and the ultrasonic wave is initially transmitted into a member of different acoustic velocity than the test piece to produce the subsurface wave in the test piece.

Abstract: As an ultrasonic transducer is continuously rotated about a pipe which is fed axially through a water-filled cavity, it sends sufficient periodic pulses to the pipe to cover essentially the entire pipe surface. The transducer also receives reflections from the outside and inside walls of the pipe from which information about pipe qualities is derived. A thickness processor module employs precision peak detectors in various circuits, including one in which flaw conditions are compared on successive rotation of the transducer in order to verify the presence of a flaw before an alarm is indicated. The thickness processor module may also provide display information about maximum and minimum values, average values, and eccentricity. In addition to the precision peak detector, there is also provided a rate of change filter which monitors rate of change of wall information and detects flaws by any major rate of change.