Loction and Size Detection of Buried Pipe Anti-Corrosion Coating Defect in Nuclear Power Plant

The directed current potential gradient method was used to detect the location and size of the buried pipe anti-corrosion coating defects. The distribution regulation of the surface potential difference above the buried pipe anti-corrosion coating defect and the relationship between defect diameter and surface potential difference were analyzed. Based on the experimental research results, three checking and calculating methods for the defects of buried pipe anti-corrosion coating were presented, and their accuracy was compared. The results show that the ratio of surface potential difference to on-off potential difference above the defect, surface potential difference and surface potential gradient equipotential line showed a good linear relationship with anti-corrosion coating defect diameter, and their fit goodness were higher than 95%. Among the three diameter checking calculation methods, the accuracy of ΔU/ΔE/D was the highest, ΔU/D was the second, and R/D was the lowest. The accuracy of double defect check calculation was obviously better than that of single defect check calculation.