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PRCI PR-3-611
- The Development of an Ultralow Frequency Eddy Current Instrument for the Detection and Sizing of Stress Corrosion Cracks
- Report / Survey by Pipeline Research Council International, 01/01/1988
- Publisher: PRCI
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L51566e
Battelle Memorial Institute
Need: Eddy current testing has received only limited application to ferrous materials because the high permeability of the material in combination with the normally high frequency of the eddy current instrument results in a very small depth of penetration of the eddy currents into the material.
Result: The objectives of this research program were threefold. The first goal was to develop an eddy current instrument with frequencies low enough to penetrate pipeline steel. The second was to use the new instrument to develop techniques for locating stress corrosion cracks (SCC) on coated pipelines without requiring the removal of the coating. Our last goal was to develop methods of characterizing SCC; i.e. determining the lengths and depths of the defects.
Benefit: We accomplished two out of these three goals; we were able to build the instrument and use it to detect SCC in pipelines. Simple defect characterization algorithms (measuring defect length and depth) have been more difficult to develop. At present we can estimate the depth of "long" defects (relative to the coil diameter) but have problems with shorter ones.
Battelle Memorial Institute
Need: Eddy current testing has received only limited application to ferrous materials because the high permeability of the material in combination with the normally high frequency of the eddy current instrument results in a very small depth of penetration of the eddy currents into the material.
Result: The objectives of this research program were threefold. The first goal was to develop an eddy current instrument with frequencies low enough to penetrate pipeline steel. The second was to use the new instrument to develop techniques for locating stress corrosion cracks (SCC) on coated pipelines without requiring the removal of the coating. Our last goal was to develop methods of characterizing SCC; i.e. determining the lengths and depths of the defects.
Benefit: We accomplished two out of these three goals; we were able to build the instrument and use it to detect SCC in pipelines. Simple defect characterization algorithms (measuring defect length and depth) have been more difficult to develop. At present we can estimate the depth of "long" defects (relative to the coil diameter) but have problems with shorter ones.
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