APPARATUS FOR DETECTING SURFACE FLAW OF PIPELINE BY ELECTROMAGNETIC INDUCTION

摘要

APPARATUS FOR DETECTING INNER SURFACE FLAW OF EACH PIPE CONSTITUTING PIPELINE An apparatus for detecting an inner surface flaw of each pipe constituting a pipeline, which comprises: a pig capable of travelling through a pipeline and being provided with the following elements: a cylindrical primary coil coaxial with the pipe, the density of a magnetic flux of an AC magnetic field of the primary coil varying in response to an inner surface flaw of the pipe; a plurality of cylindrical secondary coils arranged at prescribed intervals in the circumferential direction of the pipe between the outer peripheral surface of the primary coil and the inner peripheral surface of the pipe, each secondary coil having the axis parallel to the axis of the primary coil, and producing an AC voltage proportional to the density of a component parallel to the axis of each secondary coil, of the magnetic flux of the AC magnetic field of the primary coil; and a signal processing circuit for processing the AC voltage signals from the secondary coils to detect the presence and the depth of the inner surface flaw of the pipe.