1. 118
WED.4.C.1 83)
Improvements to Surface Detection Algorithms
for the TFM Beam Former
R.L. ten Grotenhuis1
, R. Fernandez-Gonzalez2
, N. Saeed1,3
, M. Wang2
,
A. Hong1
, A. Sakuta1
and T. Zulueta2
1
Ontario Power Generation, Inspection & Maintenance Division, 800 Kipling Ave. Toronto, Canada
2
University of Toronto, Institute of Biomaterials and Biomedical Engineering, Toronto, Canada
3
University of Toronto, Division of Engineering Science, Toronto, Canada
Ontario Power Generation’s (OPG) Matrix Inspection Technique (MIT) is based upon the combination of the
Full Matrix Capture (FMC) UT acquisition technique with the Total Focus Method (TFM) beamformer. This
recent development has yielded outstanding results in several CANDU field inspection campaigns from 2010
to present. The inspection coverage and resolution of pressure boundary fitting to fitting weld geometries is
unsurpassed in the TFM derived intensity map images. Current work directed towards the Inspection
Qualification of the MIT system has provided an opportunity to re-examine the edge detection strategy
applied to the TFM images. Previous versions of the Neovision TFM beamformer employed the Canny edge
detector. The Canny detector is acknowledged as an excellent general-purpose algorithm however requires
judicious selection of operating parameters as well as carefully constructed ‘wrapper’ logic to provide stable
results in the MIT application. Unique characteristics and specific features are typically observed in high
quality TFM intensity map images. It is believed these characteristics could be exploited by a bespoke edge
detector in a way that affords greater robustness in the final result. The new strategy was implemented to
address several challenging scenarios highlighted in field based OPEX. Suppression of ring-down noise,
rejection of grating lobe artefacts, and identification of isolated discontinuities are issues specifically
addressed by the new edge detector. Modification of the wrapper logic also permitted isolation of features of
the weld pool ripple, the constituent data provided by contributions across the elevation direction of the
transducer. Isolation of these features in turn enables superior imaging of the weld volume. This paper
describes the development of an enhanced edge detector and the resultant performance on data sets
obtained from the field.
Keywords: Total Focus Method, Beam Former, Surface Detection.
* Corresponding author: ray.tengrotenhuis@opg.com