Pulsed Eddy Current Inspection of Wall Loss in Steam Generator Trefoil Broach Supports
- Resource Type
- Periodical
- Authors
- Mokros, S.G.; Underhill, P.R.; Morelli, J.E.; Krause, T.W.
- Source
- IEEE Sensors Journal IEEE Sensors J. Sensors Journal, IEEE. 17(2):444-449 Jan, 2017
- Subject
- Signal Processing and Analysis
Communication, Networking and Broadcast Technologies
Components, Circuits, Devices and Systems
Robotics and Control Systems
Electron tubes
Coils
Probes
Ligaments
Steel
Eddy currents
Inspection
Pulsed eddy current
broach support
steel wall loss
steam generator
- Language
- ISSN
- 1530-437X
1558-1748
2379-9153
Inspection for corrosion in steam generator (SG) tube support structures is a significant component of monitoring SG condition, since support degradation can lead to SG tube flaws, and thereby further SG deterioration. A pulsed eddy current probe was developed to augment SG inspection at carbon steel trefoil broach supports. The probe demonstrated capability to measure far side wall loss as small as 20% of the original 2.7-mm-thick broach support ligament from within the Alloy 800 SG tube. A power law fit of the data was found to describe signal variation at later times under conditions of varying wall thickness and lift-off. The associated power law exponent varied linearly with wall thickness and was observed to be largely independent of lift-off and angular orientation of the probe, identifying it as a potential parameter for ligament wall thickness monitoring. Voltage response integrated over time also provided a low-noise means of measuring the wall loss when lift-off variation and misalignment were not present.