Abstract: A running apparatus within a pipe runs such that a center axis of a main body of the running apparatus is automatically coincided with a center axis of the pipe during running, and smoothly runs within a curved pipe.

Abstract: A flaw sensor for a metal pipe has an exciting coil for generating remote field eddy currents in the pipe. First and second groups of receiving coils are spaced from the exciting coil by respective distances along the axis of the pipe in a region of the generated remote field eddy currents. The first and second groups have respective pluralities of receiving coils with axes perpendicular to the pipe axis and disposed circumferentially about the pipe axis at predetermined angular increments wherein the receiving coils of the second group are staggered relative to the receiving coils of the first group. A third receiving coil is disposed coaxially with the pipe at still another distance from the exciting coil along the pipe axis but also in the region of the generated remote field eddy currents.