| 摘要 |
PURPOSE:To facilitate the detection of a fine defect at a weld part of a weld- seamed tube, by making a part of a coil bobbin of a through type eddy current flaw detection element thinner than other parts thereof to bring the weld part near the thinner part. CONSTITUTION:An eddy current flaw detection element 13 which comprises a coil bobbin 11 having a cylindrical bobbin with a thinner part and a coil 12 is used to perform an eddy current flaw detection on a welded cylindrical tube 2 having a weld part 1. The coil 12 is connected to an eddy current flaw detector body with a wire 14 and a welded cylindrical tube 2 is passed through the eddy current flaw detection element 13 in such a manner that a length-wise weld part 1 is brought near the thinner part of the bobbin 11. An eddy current I generated in the welded cylindrical tube 2 flows unevenly to concentrate most on the weld part 1. Any fine weld defect can affect the flow of the eddy current generated so greatly as to obtain a large detection signal. Thus, the detection signal other than the weld-seamed defect will be suppressed drastically to improve the S/N ratio. |
