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Electromagnetic Testing

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In pipe inspection, flux leakage testing is used to look for corrosion pits and<br />

cracks. The locally thinned area puts a higher magnetic flux distribution in the<br />

space nearer to the flux detection device. This relative increase in field<br />

strength can be measured. Any discontinuity with its major axis parallel to the<br />

direction of the flux flowing in the material has little chance of being detected<br />

using this method. The pull speed of the flux leakage testing probe must be<br />

maintained at a fairly constant rate or the accuracy of the test is decreased<br />

even further. Pipeline inspections are performed with what are called smart<br />

pigs (Figure 8.2). These devices can simultaneously carry out multiple<br />

nondestructive testing tests. The most common is flux leakage testing.<br />

Charlie Chong/ Fion Zhang

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