Radially focused eddy current sensor for detection of longitudinal flaws in metallic tubes

US5942894A · kind A · utility

Assignee

• The United States of America as represented by the Administrator of the National Aeronautics and Space Administration · US

Inventors

• Russell A. Wincheski · Williamsburg, US
• John W. Simpson · Madison, US
• James P. Fulton · Hampton, US
• Shridhar Champaknath Nath · Gaithersburg, US
• Ronald G. Todhunter · Grafton, US
• Min Namkung · Yorktown, US

Key dates

• Filing date: Sep 13, 1995
• Grant date: Aug 24, 1999
• Expiry date: Sep 13, 2015

Classification

• Technology area (CPC G): Physics
• CPC primary: G01N27/902
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

A radially focused eddy current sensor detects longitudinal flaws in a metal tube. A drive coil induces eddy currents within the wall of the metal tube. A pick-up coil is spaced apart from the drive coil along the length of the metal tube. The pick-up coil is positioned with one end thereof lying adjacent the wall of the metal tube such that the pick-up coil's longitudinal axis is perpendicular to the wall of the metal tube. To isolate the pick-up coil from the magnetic flux of the drive coil and the flux from the induced eddy currents, except the eddy currents diverted by a longitudinal flaw, an electrically conducting material high in magnetic permeability surrounds all of the pick-up coil except its one end that is adjacent the walls of the metal tube. The electrically conducting material can extend into and through the drive coil in a coaxial relationship therewith.