Nondestructive evaluation of pipes and tubes using magnetostrictive

Abstract

A method and apparatus for the inspection of ferromagnetic and non-ferromagnetic pipes, tubes or other cylindrical shell structures utilizing the magnetostrictive effect to detect defects such as corrosion pits, wall thinning, and cracks within the structure under evaluation. The apparatus and method constitute an active testing application, wherein 1) a transmitting coil element generates a mechanical pulse within a cylindrical shell structure through the magnetostrictive effect and a second coil detects reflected mechanical waves within the pipe, this by the inverse magnetostrictive effect, or 2) a single sensor functions as both transmitter and detector. The present invention also anticipates a passive monitoring application with a detection coil that continuously monitors ferromagnetic or non-ferromagnetic tubes, pipes, etc., for mechanical or acoustic wave emissions and either records this monitored information or alerts the appropriate personnel to the existence of mechanical or acoustic wave emissions indicative of deterioration. Non-ferromagnetic pipes, tubes, etc., are made amenable to inspection by attaching a layer of ferromagnetic material such as nickel on either the inner or outer walls of the pipes, tubes, etc. by plating or bonding such material in a local area where the sensor is to be placed.