Direct Current Voltage Gradient (DCVG)

Direct Current Voltage Gradient (DCVG) Surveys are a non-destructive technique used to inspect the electrical continuity and quality of protective coatings on pipelines. The survey measures the electrical potential difference between the coating and the pipeline substrate, which is an indication of the coating's continuity and ability to protect the pipeline from corrosion. The survey can be performed using specialized DCVG instruments that are connected to the pipeline, and the results are recorded in a digital format for further analysis. NACE standards that apply to Direct Current Voltage Gradient (DCVG) Surveys for coating inspection. NACE SP0502 and NACE RP0472 provide guidelines and recommendations for the use of DCVG surveys for evaluating pipeline coatings. These standards cover the use of DCVG surveys in both laboratory and field conditions and outline best practices for ensuring accurate and reliable results.

This technique is widely used in the pipeline industry as a means of determining the presence and severity of coating defects, such as holidays, cracks, and other damage. The survey can be performed on both buried and above-ground pipelines, and it is often performed in conjunction with other inspection techniques, such as visual inspections, ultrasonic thickness measurements, and holiday detection, to provide a comprehensive understanding of the coating's condition. By identifying coating defects early, DCVG surveys can help to prevent corrosion and extend the service life of pipelines.