Direct Current Voltage Gradient - DCVG Survey

DCVG surveys play a critical role in safeguarding buried pipelines and preventing costly failures. As pipelines age coatings deteriorate and if corrosion control is not being provided, the rate of corrosion can be excessively rapid in some soils, salt water or where it is exposed. For buried pipelines, coatings alone are inadequate and corrosion defects will likely occur. DCVG survey technique is being performed to detect coating defects, calculate the level of severity and measure the effectiveness of the cathodic protection in place without damaging the pipeline.

When a DC signal is applied to a pipeline, current flow through the soil towards the coating defect generates a Voltage Gradient. By observing the direction of these gradients, the location of coating faults may be identified. Once defect is located, one can determine its importance by measuring the potential lost from the defect epicenter to remote earth. The PD is expressed as a fraction of total potential shift to the pipeline.

DCVG Survey (Direct Current Voltage Gradient)

DCVG: Pinpointing Pipeline Issues

Location of pipeline.
Detection of cable fault location.
Delineation of coating defects.
Behavior of coating defect.
Severity & Nature of coating defect.
Stray Current Interference.
Checking of Insulating Flanges.

Benefits of DCVG Survey

DCVG technique provides accurate and reliable. The high sensitivity of this technique permits even the smallest defect to be located.
Accurate to the extent of ± 0.1 meter of their actual location.
High resolution in “pinpointing and sizing” the coating defect.
Determine Anodic and Cathodic behavior of the coating defect.

Case Studies