Coiled tubing (CT) strings are now regularly 35,000-ft. long. The seam weld in HSLA coiled oilfield tubing has been difficult to inspect for longitudinal imperfections and defects even with the use of UT. In-line ET units are ineffective on the tight defects found is the seam weld of this EW tubing. In this paper we present results from the use of phased array UT (PAUT) on the seam weld, and also on the 45° skelp-end welds that join the strips together before the tubes are milled. Magnetic flux leakage systems have evolved for both the final inspection after hydrostatic test, and for field inspections. Improvements to the suppression of excessive MFL from the seam welds is discussed, and some typical results of recent inspections are given.
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Woodlands, Tx. Stanley, R. K., “Magnetic Methods for Wall Thickness Measurement and Flaw Detection in Ferromagnetic Tubing and Plate,” Insight 38(1), pp 51-55.
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