Direct current voltage gradient: a survey in which CP current is pulsed and a technician walks the line with two reference electrodes on probes and a sensitive center-zero meter. Current flowing to a coating holiday creates a voltage gradient in the soil, the needle swings toward it, and the operator pins down the epicenter. The signal size, expressed as percent IR, ranks each holiday for excavation.
DCVG picked up a 45 percent IR indication in the road ditch, that one's getting a bell hole.
Also heard as
- DC voltage gradient survey
Related terms
Holiday
Pinhole, void or bare spot in a coating that leaves the metal underneath exposed.
CIS
Close interval survey: potential readings taken every metre or so along a pipeline to find protection gaps.
Bell hole
Excavation dug around a short section of buried pipe so crews can inspect, repair or connect to it.
ILI
In-line inspection: sending instrumented tools through a pipeline to measure wall loss, dents and cracks.