| 摘要 |
PROBLEM TO BE SOLVED: To improve workability in pinhole testing of an outer cable.SOLUTION: A pinhole testing machine consists of a ground plate 10 as an indirect ground, a semi-annular brush electrode 11, and a detector 13 to which the ground plate 10 and a brush electrode are connected via cables 12a, 12b. The ground plate covers and is fixed to a surface outer periphery of a PC steel material B, which constitutes an outer cable, a voltage of 3 kV is applied between the ground plate and the brush electrode, and the brush electrode is moved in the peripheral surface longitudinal direction of the PC steel material. This movement performs testing of a half peripheral surface of the PC steel material in a forward path, and moves the brush electrode 11 by a half periphery to perform testing of an opposite half peripheral surface in a return path. When a pin hole exists in a clad of epoxy resin 1b according to the movement of the brush electrode, electric discharge occurs between the brush electrode and a steel element wire 1a via the pin hole, a current flows in a loop circuit consisting of the PC steel material, the ground plate, a cable, a detector, a cable, and the brush electrode, an ammeter detects the current, and a lamp is lighted or the like in the detector to notify a user of the presence of the pin hole. |
