STEEL PIPE WALL THICKNESS MEASUREMENT BY PULSED EDDY CURRENT


11th International Conference on CANDU® Maintenance and Nuclear Components - 2017 Oct. 01-04

Presented at:
11th International Conference on CANDU® Maintenance and Nuclear Components
2017 Oct. 01-04
Location:
Toronto, ON Canada
Session Title:
Advances in Inspection and Monitoring Techniques 1 - Specialised Tools

Authors:
K. Faurschou (Royal Military College)
R. Underhill (Royal Military College)
J. Morelli (Queen's University)
T. Krause (Royal Military College)
  

Abstract

Non-destructive inspection of bulk wall loss in ferromagnetic steel pipe is a common requirement across multiple industries. In the nuclear industry, pulsed eddy current has potential applications for tile holes and balance of plant inspections where insulated pipe is present. Currently, inspection on this type of component is typically done with ultrasonic testing, which requires a coupling agent and removal of any insulation. Pulsed eddy current (PEC) technique does not require direct contact and has a larger spot size, thereby facilitating more rapid inspection. Three different types of PEC send-receive probes were examined for inspection of a section of steel pipe with a step wall reduction. PEC data was taken at different distances from the inner surface of the pipe so that sensitivity of wall loss measurement to liftoff (distance of the probe from the near surface) could be assessed. The PEC signal was analyzed by fitting the tail of the transient decay with an exponential curve, with curve fitting parameters correlated to wall thickness variation. An analytical model was developed and partially validated in order to examine a wider range of factors than is practical with a lab setup, such as probe parameters, and magnetic permeability and conductivity of the steel. The modelled data was also used to perform a sensitivity analysis on probe parameters in order to streamline further probe development and to determine optimal probe parameters for specific applications.

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