Interpretation of CIS Potential Profile with Respect to ECDA Methodology

Indirect inspection is used to identify and define the severity of coating faults, other anomalies, and areas at which corrosion activity may have occurred or may be occurring on underground pipelines. Of the several indirect inspection methods that are commonly used, close-interval survey (CIS) is considered the most widely accepted and accurate method for ECDA severity classification. For valid interpretation of the CIS inspection results, the pipeline operator must consider the specific conditions along the pipeline and the expertise level of personnel analyzing the inspection data when defining classification criteria. For CIS potential profiles, typical criteria used to assess severity include the magnitude of potential change or dip, separation distance between on and off potentials, and whether the on and off potentials are above or below cathodic protection (CP) criteria. Depending on the experience of the individual, interpretation and classification of this data can often be inconsistent. This paper discusses the interpretation of CIS potential profile data based on practical experience using ECDA methodology under various pipeline conditions.