| 摘要 |
PURPOSE:To enable a non-destructive measurement of the thickness of a metal or the size of a flaw by using the direction of a coil impedance change occured as a reference when a coil exciting frequency is varied by a designated small amount. CONSTITUTION:For example, when measuring the thickness of a liner, first, an output (Q1x, Q1y) of an eddy current flaw detecting device 5 is measured using a liner coated pipe of which liner thickness is already known as a test specimen, and next, (Q2x, Q2y) is measured at the same measuring location while varying an exciting frequency by a constant minute under the condition of maintaining a constant amount of lift-off amount. From these values, the frequency change direction H and its perpendicular direction V are determined. Then, when measuring is started, a liner coated pipe 1 to be inspected is rotated in peripheral direction by a rotating device 2 and a prove 3 is moved in axial direction by a driving device 4. The probe 3 is an insert type probe and equipped with an absolute value type coil. An impedance change of this coil is converted to a voltage by the eddy current flaw detecting device 5. This voltage is converted to a liner thickness by a calculation device 6 and the liner thickness is displayed at a display device 7.
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