Direct Current Voltage Survey (Dcvg)
Corrosion; Depletion or disruption physically due to the electrochemical reaction of a metal or alloy with the environment in which it is present.
Abrasion, corrosion and defect are observed in the insulation of pipelines based on electrochemical, physical and environmental factors. DCVG is based on point detection and sizing of insulation coating defects which are caused by corrosion on pipelines and which negatively affect cathodic protection.
DCVG is based on measuring the voltage changes on the earth via the Cu / CuSO4 reference electrode on the line while the DC voltage is applied to the pipe line in the certain period by the intelligent circuit breaker connected to the cathodic protection system of the external current source (Transformer Rectifier). While the 0 gradient point that we determine gives us the error center, the magnetic field spread around gives us the current density and the size of damage, based on the calculations. By using Measuring Boxes (Sacrificial Anodes),this method is also effective for pipelines cathodically unprotected or temporarily protected.
The good part of the DCVG technique is that the existing pipeline utilizes the Cathodic Protection system wherever possible in its normal setting and therefore the results reflect the close interaction between the effectiveness of the Cathodic Protection and the deterioration of the protective coating in individual plating faults. This is a very powerful knowledge in the struggle against corrosion. None of the alternative current or Electromagnetic Techniques offer such a direct working ability.
DCVG technique can be applied for gas, petroleum, chemical and water boron lines in streets, process plants and refineries, in rivers and estuaries, in marshlands and parallel pipeline systems. DCVG can also be used at measuring the protective coating on the telephone and power cables. In the case of new pipings, it is recommended to apply a DCVG immediately after laying the pipeline, so that the contractor can repair any possible coating faults.
Related calculations are used to determine the sizes, diameters and repair priorities of defects detected by DCVG. According to the NACE-0207-2007, NACE SP 0502-2008 - NACE TG294 standards, the efficiency and evaluation of cathodic protection are presented to you by direct survey service or practical training.