Direct Current Voltage Gradient (DCVG) survey is an accurate method available to size and locate pipe coating defects. The technique is based on measuring the voltage gradients in the soil above a cathodically protected pipeline. Once the Alpha technician has recorded the DCVG measurements and GPS locations, the %IR {Percent Intensity (current) of Resistance} values are calculated. Depending on the degree of magnitude of the %IR, a determination can be made where physical examination and repair are necessary. The DCVG technique is one of the two most important inspection tools used in the ECDA concept to inspect buried pipelines, the other is CIPS. Both DCVG and CIPS utilize the pipeline’s CP system.
Survey results vary from the obvious to the smallest coating defect.
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