Approach to Assessment of Corrosion Growth in Pipelines

Two key components of corrosion growth assessment in pipelines are accurate determination of corrosion growth rate and application of corrosion growth to future integrity of a pipeline. PII has developed a corrosion growth assessment tool, Run Comparison (RunCom) software that allows accurate determination of corrosion growth. RunCom compares the raw signals of the same defect present in two inspection runs to report the real active corrosion defects and their growth with less error. Since variations in corrosion growth along the pipeline can be significant, a single value of average or maximum corrosion growth rate does not represent the corrosion condition of the pipeline and could result in a conservative or non-conservative conclusion for future integrity. PII introduces a Decision Tree Analysis method to categorize the corroded regions along the pipeline and calculate the mean corrosion growth rates in these specific areas. Relationships between corrosion growth rate and defect geometry are also identified. The influence of soil, drainage, and topography on corrosion rates is examined to determine representative corrosion growth rates along the pipeline. A systematic approach incorporating statistical analysis with mechanistic understanding of corrosion for preliminary corrosion assessment of pipeline systems is discussed.