Echograph Ultrasonic Testing of Helical Submerged Arc-welded Pipes

Summary Borusan Mannesmann Boru is the largest pipe producer in Turkey having a production capacity of a million tons of welded pipes and employing more than 1200 people. The company was founded in 1958 and more than 50% of the shares are privately owned. A new spiral pipe plant is under construction in Gemlik, Turkey. The main line supplier was Danieli W+K with plants in Italy and Germany. The inauguration of the new plant is planned for September 2011. Full production will start in early 2012. The Gemlik plant is located directly at the sea which facilitates transportation of raw materials and finished pipes by ship. Three ultrasonic testing systems from KARL DEUTSCH were ordered to fulfil the highest requirements of the oil and gas industries. The test of the pipe body is performed in the strip stage before welding. The strip widths range from 1100 to 2050 mm. The testing speed corresponds with the uncoiling process, i.e. max. 10 m/min. The test specifications in recent years require a high percentage of ultrasonic coverage. In order to reach a solution with 100% coverage without any mechanical oscillation a total of 41 probe holders was chosen. Each probe holder contains a special broad-beam probe with one common transmitter and two receivers (TR-probe with 2 test channels), thus providing a test track of more than 50 mm per probe. Steel rollers guide the two outmost probe holders along the strip edges. Three additional probes are provided to measure the wall thickness at both strip edges and the strip middle. Thus, a total of 85 test channels is provided. The test results can be viewed online in real-time during the test. Each probe can be monitored either in the strip chart representation (amplitude versus strip length) or in the C-scan representation (top view of strip with colour-coded amplitudes). Since an endless strip is tested, the results scroll through the screen. The spatial resolution can be chosen by the operator as convenient for the supervision of the test. The test mechanics can be moved offline above a test plate with artificial defects where a dynamic calibration with full test speed can be performed. After the strip test, the pipe forming and welding process takes place. The pipe diameters range between 20 and 64” (508 mm – 1625.6 mm) and the wall thicknesses between 6.35 mm and 25.4 mm. The pipes are then cut to their final length and undergo a first ultrasonic test with 6 ultrasonic probes. Longitudinal and transverse defect detection are the respective test tasks. The weld crown is automatically tracked by a laser-based seam tracking system which keeps the probe pairs centered with respect to the weld. A line laser pointer produces an illumination parallel to the weld crown which is always monitored by a camera. The camera image is transferred to the operator panel and is checked by the operator for proper functioning. The test mechanics is mounted to a machine stand with horizontal boom. The boom must be adjusted in height in accordance with the pipe diameter to be tested. The pipe is transported by a carriage where linear and rotational speed must be chosen such that the test position of the weld is always in twelve o’clock position.