INSPECTION OF PENETRATION DEPTH OF CHROMIZED STEEL PIPE

摘要

PURPOSE:To enable non-destructive and quick measurement of the pipe bodies to be inspected for the total number over the entire length by applying an eddy current testing method to detect the potential difference from a reference pipe body of which the penetration depth of a chromized steel pipe is known. CONSTITUTION:A bridge circuit BRG is constituted of coils L1, L2 wound on a bakelite bobbin 1 and elements B1, B2 for balance adjustment and AC is supplied thereto from an oscillator OSC. A coil L1 is first inserted onto a reference pipe body PS1 which is the same in outside diameter and wall thickness as the pipe body to be inspected and is not subjected to a chromizing treatment (penetration depth 0) and a coil L2 is inserted onto another reference pipe body PS2. The oscillator OSC is started and the circuit BRG is balanced by the elements B1, B2. The coil L2 is then removed from the body PS2 and is inserted onto the pipe body PT to be inspected while the coil L1 is held intact. Unbalanced potential is induced in the circuit BRG when AC is conducted to the coils L1, L2 in order to induce eddy current on the surfaces of both pipe bodies. The penetration depth of the chromized layer on the surface of the pipe body to be inspected is then discriminated from the detected unbalance potential.