Wall Thickness Measurement of 1230 degree C Hot Tube Blanks with a New Type of Laser Ultrasonic System.

The wall thickness of hot tube blanks at approx. 1230 degree C has been measured with a laser ultrasonic system during production. The short pulse of a high-power laser was used for ultrasound generation in the blank. For recording purposes, the back echoes have been detected and recorded interferometrically by means of the light of a second laser, backscattered by the tube wall. At a production rate of about 2 m/s, the thickness variation was measured point-by-point at 25 cm intervals over a generating line. The measuring distance amounts to about 5 m.