The OPS has recently issued an advisory bulletin to advise owners and operators of natural gas transmission and hazardous liquid pipelines to consider external corrosion as a possible safety risk to newly constructed pipelines and to identify and remediate the detrimental effects of stray currents during and after construction. This action follows the discovery of substantial external corrosion on a newly constructed gas transmission pipeline. The pipeline had been in service a little over two years when this unexpected corrosion was revealed by a high-resolution, inline inspection tool. The pipe wall pitting was consistent with that caused by underground stray electrical current before a cathodic protection system is installed. In some isolated areas, the pipeline exhibited more than 50% wall loss. Corrosion due to stray current is most often found on pipelines that cross other underground structures (such as other pipelines) or that follow overhead electric transmission lines.
Advisory: Each operator of a natural gas transmission or hazardous liquid pipeline should determine whether new steel pipelines are susceptible to detrimental effects from stray electrical currents. Based on this evaluation, an operator should carefully monitor and take action to mitigate detrimental effects. The operator should give special attention to a new pipeline’s physical location, particularly a location that may subject the new pipeline to stray currents from other underground facilities, including other pipelines, and induced currents from electrical transmission lines, whether aboveground or underground. Operators are strongly encouraged to review their corrosion control programs and to have qualified corrosion personnel present during construction to identify, mitigate, and monitor any detrimental stray currents that might damage new pipelines.