Predicting the Progression of Wetness and Corrosion Under Insulation Damage in Aboveground Pipelines

ConocoPhillips Alaska, Inc. operates 800 miles of above ground pipelines on the North Slope of Alaska.  These lines have polyurethane foam insulation over bare steel, and are therefore susceptible to corrosion under insulation (CUI).  Radiographic and visual inspection data was analyzed for 73 miles of pipelines for which complete inspection data was available.  The analysis showed that the accumulated damage over time could be fit to a Weibull cumulative damage distribution.  Weibull curves generated from the 73 miles of pipelines were used to predict the number of CUI susceptible locations that would need repair or refurbishment each year for all 800 miles of pipelines in the field.  The Weibull curves appear to accurately predict the total number of CUI repairs and refurbishments that need to be done each year.  The model can be used as input to risk assessments and to support proactive maintenance strategies.  The model can also be used as background rationale for budgeting and optimization of manpower for inspection, repair and refurbishment activities.