Work was performed to assess corrosion damage on a pipeline suspension bridge transporting liquid products.
Corrosion had been previously detected and characterized using in-line inspection methods. The inspection
results were graded and it was noted that several regions had corrosion levels that were of concern. The
pipeline company requested that an evaluation be performed on the pipeline bridge that had been constructed
during the 1950s.
Evaluation involved construction of a detailed finite element model of the suspension bridge including details
on the carrier pipe, an additional support pipe, primary catenary cable, and other supporting cables and wires.
The analysis included variations in pipe wall thickness in relation to data collected from the in-line inspection
tool run. Loading included gravity, internal pressure, and wind loads. Analysis stress results were then
compared to design limit based on the rules of ASME B31.4. The final evaluation revealed that a very
specific band of conditions (namely pressure and wind speed) were required to ensure the continued safe
operation of the line. Recognizing the need to maintain the required operating pressure, coupled with the
inability to control wind speed, led the pipeline company to make repairs to regions of the pipeline where
stresses exceeded the code limits. This project was a clear demonstration of how inspection, analysis, and
repair methods can work together to ensure the safe operation of pipelines.