Corrosion is a leading cause of pipeline failures; it is reported that nearly 30% of all pipeline failures in a 30 year period 1971 and 2001 in Europe where due to external corrosion of underground or underwater pipelines. Leaks due to corrosion of pipelines result in huge economic losses and damage to the environment and can result in loss of life.
With the publication of the NACE International Recommended Practice RP0502-2002 Standard Recommended Practice Pipeline External Corrosion Direct Assessment Methodology, pipeline operators are required to utilise a minimum of two indirect method tools to assess the effectives of the corrosion control method(s) on underground and underwater pipelines. The NACE International Standard Practice SP0207-2007 Standard Practice Performing Close-Interval Potential Surveys and DC Surface Potential Gradient Surveys on Buried or Submerged Metallic Pipelines, has now defined the methods for undertaking CIPS and DCVG surveys.
These standards require the pipeline operator to select indirect inspection tools based on their ability to detect corrosion activity and/or coating holidays reliably under the specific conditions to be encountered. The pipeline operator should select indirect inspection tools that are complementary. The operator should select the indirect inspection tools such that the strengths of one tool compensate for the limitations of another.
Undertaking a combined CIPS and DCVG survey satisfies the requirement for indirect inspection under RP0502-2002. The CIPS and DCVG surveys are complimentary and compensate for the weakness of each survey system, thus meeting the requirement of ECDA.
Pipeline operators that adopt these standards as there corrosion control procedures should see a significant reduction in external corrosion of pipelines
and a consequential reduction in leaks.
World Piplines November 2007
J. Peter Nicholson
Cathodic Technology Limited
Bolton Ontario Canada