VALIDATION OF EXTERNAL CORROSION DIRECT ASSESSMENT WITH INLINE INSPECTION IN GAS TRANSMISSION PIPELINE

摘要

External Corrosion Direct Assessment (ECDA) methods are widely adopted in the gas industry recently to verify the integrity of pipeline. ECDA is defined as a continuous improvement process. The validity of the assessment should be confirmed by comparison of the excavation results with the prioritization of indication. ECDA is usually applied to the un-piggable section of pipeline. As a result, a comparison of ECDA and ILI on the same section of pipeline is not reported frequently. We performed both ECDA and ILI survey over the same section of the pipe to validate ECDA. We can conclude that the reliability of the ECDA may be weakened by the severe cathodic shielding of disbonded coating. It is an inherent disadvantage of indirect survey methods which relies on the distribution of cathodic protection current.