- since 1996 -
|NDT.net Issue - 2010-03 - NEWS |
|An ultrasonic testing portal for heavy-wall seamless tubes within a diameter range from 178 - 419 mm, a wall thickness range from 20 - 100 mm and a tube length from 4 - 15 m is presented in this article. During the inspection, the tube is scanned with helical testing traces. While the tube is rotating, the probes are linearly guided along its longitudinal axis and coupled onto the tube surface in the 12 o'clock position. Special about the testing system is the way to couple the ultrasound into the tube. Water jet coupling (also called squirter technique) is used, which means that the water path between probe and tube surface is in the order of several centimetres. |
In total, five probes holders are used. Four probe holders contain the probes for longitudinal and transverse defects and one probe holder is for straight-beam testing to measure the wall thickness and to detect laminations. All probes are phased array probes. Phased arrays allow a convenient electronic adjustment of the ultrasonic incidence angle. Therefore, optimal angles can be chosen for the detection of internal and external longitudinal defects - especially important for heavy-wall tubes. For the detection of transverse defects, phased array probes are used which can produce overlapping sound beams. Thus, a high reliability in detection is achieved and the amplitude deviation in dynamic mode is reduced.
The probe holders are gimbal mounted and are flexibly guided along the tube surface. The guiding elements (rollers made of hardened steel) do not have to be changed for varying tube diameter due to the jet coupling technique. This results in short change-over times and a long-lasting mechanical set-up.
A modern phased array testing electronics with 192 parallel testing channels is used.
The testing mechanics was completely designed and assembled in-house in the KARL DEUTSCH systems workshop in Wuppertal, Germany and the machine was fully tested before shipment in order to reduce the installation period at the customer's plant. The total length of the machine is approx. 25 m. One short tube segment (800mm) and one longer sample tube (6m) can be seen on the photograph. Artificial defects were machined into both tubes. The short tube segment is used for the dynamic system calibration with full testing speed. Afterwards, the defects in the long tube were used to verify the system settings.
View of the testing machine in the systems workshop before shipment.
A = testing electronics, B = probe holders, C = testing portal, D = calibration station, and E = production tube.
KARL DEUTSCH Prüf- und Messgerätebau GmbH + Co KG