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Lookup NU author(s): Dr Julia Race,
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In order to develop effective integrity management plans for corroding pipelines, operators need to be able to estimate realistic internal and external corrosion growth rates. Indeed, corrosion growth rate data is an essential input into future integrity assessments, rehabilitation planning and the determination of safe and cost effective reassessment intervals. The rate of the external corrosion reaction in pipelines is influenced by a number of factors including the water content of the soil, the soluble salts present, the pH of the corrosion environment and the degree of oxygenation. Therefore the prediction of external rates is complex and there is currently no method for estimating corrosion rates using empirical equations. This paper describes a scoring model that has been developed to estimate external corrosion growth rates for pipelines where rates cannot be estimated using more conventional methods i.e., from repeat in-line inspection data. The model considers the effect of the different variables that contribute to external corrosion and ranks them according to their effect on the corrosion growth rate to produce a corrosion rate score. The methodology has been validated by linking the calculated corrosion rate scores to known corrosion rate distributions that have been measured by comparison of the results from multiple in-line inspection runs. The development of the corrosion rate database and the results of the analysis of the database are reviewed and discussed. Initial results from the preliminary corrosion rate model are presented in the paper and further planned developments in the model are outlined. The paper also demonstrates how the estimated corrosion rates can be used for the establishment of reassessment intervals for DA, ILI and hydrotesting, comparing the benefits of this approach with current industry recommended practice and guidance.
Author(s): Race JM, Dawson SJ, Stanley LM, Kariyawasam S
Publication type: Conference Proceedings (inc. Abstract)
Publication status: Unknown
Conference Name: Pipeline Pigging and Integrity Management Conference
Year of Conference: 2007