A big proportion of heat exchangers in the industry are made from carbon steel tubing, and that carbon steel is prone to the apparition of pits and other defects caused by corrosion, in the free span and near or under support plates.
Missing the detection and characterization of key defects in heat exchanger tube bundles can prolong costly factory shutdowns during routine maintenance at petrochemical plants. Even worse, unfound flaws can cause an unexpected shutdown during production.
Remote-field testing technology is one of the standard technologies used in the petrochemical industry to inspect heat exchangers – however, one key drawback of conventional RFT is the region of insensitivity, or "blind zone", near support plates and tube sheets.
Due to the nature of the electromagnetic field generated by the probe, the support plates block field penetration through the tube as the probe passes under the support. When corrosion or pitting occurs near these supports, the signal becomes masked, and the defects can be missed even by experienced analysts. If the corrosion or pitting exceeds the tolerance threshold required by the plant, then corroded and even leaking tubes might be put back into service at the cost of reduced efficiency and could potentially cause further problems down the line.
Read more at Eddyfi.com.