The alternative MAOP Rule requires the use of non-shielding coating. What coatings does PHMSA consider to be non-shielding?
For the purpose of the alternative MAOP Rule, a non-shielding coating is a coating that allows cathodic protection (CP) currents to pass through the coating and along the outside surface of pipe and which is an oxygen barrier, even if the coating has disbonded from the pipe surface. An example of such a coating is Fusion Bonded Epoxy (FBE) which does allow CP currents to reach the external surface of the pipe, even if the coating disbonds from the pipe surface. The intent of the alternative MAOP Rule is for operators to use modern external coatings that do not impede CP. Also, PHMSA would consider a two-part epoxy girth weld field joint coating or repair coating as a non-shielding coating. Some examples of shielding coatings are polyethylene tapes, shrink sleeves, coal tar mastics, asphalts, etc. These coatings can prevent CP currents from reaching the pipe when they disbond from the pipe surface. The use of shielding coatings is not the intent of the alternative MAOP Rule.
Related Questions
- Are certain types of pipelines or pipeline conditions prohibited from using the alternative MAOP Rule to operate at higher operating stress levels?
- Does PHMSA expect the operator of an alternative MAOP pipeline to run geometry and high resolution MFL tools at separate time intervals?
- Why are mill test reports required for the alternative MAOP rule?
