This most recent development in ultrasonic testing (UT) is the first of its kind anywhere in the world, and has significantly improved the possibilities of comprehensively testing seamless steel tubes at full production speed.
Hot-rolled seamless steel tubes are advanced high-tech products. Especially in the oil and gas industry, but also in power plants, tubes are subject to the most stringent quality requirements. A full-body test for surface imperfections is part of the normal scope of testing.
Due to the high elongation involved in the production process, most of the surface imperfections on hot-rolled seamless tubes are positioned in a predominantly longitudinal direction, but also oriented at higher angles. So far, the phased-array UT process with additional paint-brush technology has enabled the detection at full production speed of defects positioned up to 45° to the longitudinal axis. This configuration is used, for example, at Vallourec's Barreiro works in Brazil, and ranks among the most advanced automatic ultrasonic test facilities for seamless steel tubes.
However, the existence of surface imperfections at higher angles can by no means be ruled out. Ideally, tubes should be checked for defects with all conceivable orientations. With the process used until now, a large number of probes would be required to cover the whole circle (360°) of potential defect orientations, as each of the probes can only test a small section. Given the high costs involved regarding the probes, electronics and mechanical features, the facility would no longer operate economically.
The new 2D phased-array facility with ShapeUT™ technology detects defects in all directions
The 2D phased-array probes and the ShapeUT™ operating mode avoid this disadvantage. In the ShapeUT™ operating mode, the shape of the sound can be changed in a way that the full circle can be included in the test, so natural defects at all angles from 0° to 360° can be detected. To increase testing speed, additional probes have been installed for the high-resolution wall thickness measurement and testing for laminations as well as for defects with a transverse orientation.
Up until now, defects located
beyond the 45° position could
not be detected in a single test run.
The new 2D phased-array testing technology
in conjunction with the ShapedUTTM operating
mode can detect surface imperfections through 360°.
For the plug rolling mill in Düsseldorf-Rath, the new technology has been implemented as a 2-carriage portal solution with a separate calibration and production section. Besides the quality benefits enabling defect detection through 360°, this layout allows for optimum setting and production times as well as maximum flexibility in terms of plant utilization. While the tubes on one carriage are being tested, the other carriage can either be set up for the next test lot, or can be used as a second carriage in the production area, to enhance the speed of testing.
The new 360° technology also requires new techniques to ensure correct and economic calibration of the UT facility in the production environment. Accordingly, the Vallourec Research Center France (VRCF) in Aulnoye developed an alternative calibration method which has meanwhile been patented. The acceptance tests of the UT bench featured outstanding reproducibility as a criterion for the quality of the measurements.
After a development period of just under three years, the installation of the ultrasonic test facility following its successful release, took less than two months. This included its integration into the production flow under restricted space conditions, as well as its connection to the works IT systems for automatic order data input and storage of the test results.
The plug-rolling mill at the Düsseldorf-Rath location currently operates the world's most advanced automatic ultrasonic test facility for seamless steel tubes.