Test system detects defects as small as 5 percent of tube wall

July 29, 2014

Magnetic Analysis Corp. has developed a 19.6-in. transverse/longitudinal flux leakage Rotoflux® test system for a new tube mill at an OCTG producer in Russia. It is designed to detect seams, laps, pits, scabs, rolling skins, cracks, weld line defects, and transverse and longitudinal defects as small as 5 percent of the wall on the OD and ID.

The rotary is the largest diameter that the company has made. It required new mechanical designs to provide for the greater magnetization and detection capabilities, along with substantially new software. The company also designed a new demagnetizer to meet the customer’s requirements.

The system also features wireless transmission of test signals between the rotating test probes and the stationary electronics.

During the test, the pipe first passes through the multiplexed, 48-channel Rotoflux TRFX Transverse flux leakage rotary, where it receives a high level of magnetic saturation that creates intense magnetic flux flow within the material. Some of this flux extends or leaks beyond the tube surface when interrupted by a surface or internal defect. This leakage flux generates test signals that are detected by the test probes rotating around the pipe. The signals are wirelessly channeled to the system’s test electronics for analyzing, processing, and data management, followed by display in real time on-screen.

The pipe then passes through the multiplexed, 24-channel LRFX longitudinal rotary to detect signals from longitudinally oriented seam-type defects, followed by the demagnetizer to remove any residual magnetization. A fully automated flaw tracking system with end suppression is used to control output sorting, alarm, and marker functions.

This system handles tube and pipe from 5 to 19.6 in. in wall thicknesses from 0.23 to 1.57 in. at speeds up to 200 FPM. Straight or upset ends can be tested.



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