Roland Electronic has developed a new sensor with the special capability of detecting weld seams in thickwalled ERW tubes and positioning the tubes for ultrasonic testing purposes.

The final step in the production of electric resistance welded tubes - ERW tubes - is ultrasonic testing of the weld seam of the finished tubes. For this process step the tubes have to be turned either manually or automatically in order to position the weld seam exactly in the middle between the two ultrasonic probes.

The automatic weld seam detection and positioning is generally done with optical sensors. The reliability of this positioning depends very much on the optical properties of the tube surface and can vary accordingly.

Roland Electronic has been in the business of weld seam detection and positioning with magnetic sensors for over 15 years, however, until now primarily for smaller diameter tubes being processed in tube bending and hydroforming machinery.

Roland Electronic has now developed the very powerful Weld Seam Detector NS24 specifically for the detection and positioning of weld seams for ultrasonic testing on thickwalled ERW tubes. This weld seam detection system is based on the magnetic leaking flux principle and therefore completely independent of the optical properties of the tube surface.

The picture shows the Weld Seam Detector NS24 with a thickwalled ERW tube.

 This sensor is designed in such a way that the sensor element adjusts itself automatically to the different tube diameters. The analysis of the sensor signals is done in the tried and proven control unit SND40 originally designed for the smaller diameter weld seam sensors. The signal diagram shows the very clear delineation of the weld seam signal from noise and is based on proprietary analysis and filter algorithm.

The sensor NS24 is suited for tube diameters up to 600 mm (24 in.) and wall thicknesses up to 12.5 mm
(.5 in.). The enhancement of the sensor to cover thicker walls is under development.