Electromagnetic flux leakage inspection system for ferromagnetic tubes

Claim 1

Apparatus for inspecting, in-situ, a heat exchanger tube, comprising: (a) means for inducing into the wall of a tube a resultant magnetic field produced by the vectorial addition of a first and a second magnetic field, said means including: (i) a scanner for traversing the tube having a hollow cylindrical body, said hollow cylindrical body being provided with an outwardly protruding rim at either end extending toward said tube to guide said scanner when scanning the tube from the bore of the tube; (ii) a first solenoid coil, carried by said body in close proximity to the wall of the tube, suitable for being energized by a first electrical source to generate said first magnetic field; (iii) a second solenoid coil, suitable for being energized by a second electrical source for generating said second magnetic field, said second solenoid coil disposed within and carried by said hollow cylindrical body perpendicular to said first solenoid coil; and (b) an array of sensors mounted on said first solenoid coil around the outer circumference thereof to be spaced away from the wall of said tube, generating output signals responsive to the leakage flux produced by a flaw in the wall of the tube.