07179 CIS Data Enhanced by Soils Modeling

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Product Number: 51300-07179-SG

ISBN: 07179 2007 CP

Author: E.B. Clark

Publication Date: 2007

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This paper uses field data from a variety of dig sites to evaluate whether soils data could be used in a model to predict locations where external corrosion would be an issue, as one approach to enhance the ECDA process. If by adding soils data to the previously collected ECDA datasets it could be shown that areas suffering corrosion could be predicted consistently, then operators would have an additional tool at their disposal to help maintain the country’s natural gas pipeline infrastructure safely and reliably. The approach targeted soils-corrosivity, because if corrosivity dominated a very simple model would be viable as a screening tool – with such a model then viable when other data is not available, unreliable, or difficult to obtain. Soil corrosivity was characterized in terms of a model that couples soils type with topography and drainage, with consideration also given to a simpler approach based on pH and resistivity. The results indicated that there is essentially no correlation between corrosion susceptibility based on soilscorrosivity expressed in terms of these two models. While an attempt was made to calibrate these measures of susceptibility using ILI data for corrosion incidence and severity, the frequency of corrosion for the sites evaluated was limited, which confounded this process. It follows that corrosivity alone cannot be viewed as the dominant factor controlling corrosion susceptibility. This absence of correlation is not surprising given the effectiveness of CP and coating integrity for the six sites used in this evaluation. The results indicate that if soils models are to be useful in guiding ECDA conducted in accordance with NACE Standard RP0502-2002 they must consider CP and coating integrity.