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Challenges in Analyzing ECDA Indirect Inspections Data

Published: 20140309 by NACE International
Author(s): Sorin Segall
Co-Author(s): Robert Gummow P.Eng, John Shore P.Eng

The analysis of indirect inspection data is a critical factor in conducting a successful External Corrosion Direct Assessment (ECDA) process. Any “out of range” data must be validated prior to being con­sidered an ECDA indication. Furthermore, standard methods of validating the accuracy of the field data must be reviewed when special conditions are present.

This paper covers a number of lessons learned by dealing with less well-known sources of measure­ment error, during nine years of ECDA application on more than 100 projects.

Topics like “clipped” gradients during the DC Voltage Gradient (DCVG) Survey, AC current drain by well casings during influence testing, and sharp drops in potential indicating the presence of an under­ground isolating flange are discussed in detail in this paper.

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