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DC Voltage Gradient Survey (DCVG)
Coatings and cathodic protection are relied upon for
corrosion control on underground pipelines. The coating is the
primary barrier with the cathodic protection providing back-up protection.
Increasing coating deterioration results in a greater demand upon the
cathodic protection system. Coating breakdown occurs virtually from
the day the pipeline is installed due to man-made or environmental
factors. Increasing cathodic protection current outputs will not
necessarily provide the desired protection, indeed, in some instances the
problem can become more acute due to over-protection and subsequent
cathodic disbondment.
Developments in pipeline coating surveys over the last
20 years have led to an increased use of DC methods as an alternative to
the Pearson type AC technique. In Australia and New Zealand the DC
voltage gradient survey method has been established as the preferred
technique. Close interval potential surveys have been popular in
past years in some countries due to their superior results over the
Pearson method and unavailability of DC voltage gradient survey
technology.
SCCS'
PCS-2000 meets the requirements for equipment in NACE RP0502-2002
section 6.
NACE Standard
Recommended
Practice
Pipeline External
Corrosion
Direct Assessment
Methodology
The PCS-2000 DCVG
meter is capable of operating in all conditions and can cover between 10
and 18km per day.
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