Hydrogen H2 under Type B steel repair sleeve - pipeline - Cathodic Protection CP

[awol]

Has anyone experienced the development of hydrogen between the carrier pipe and the fully welded Type B steel repair sleeve? With enough hydrogen produced to dent the carrier pipe due to a thicker steel sleeve? Can an overdriven CP system produce hydrogen from the carrier pipe under a steel sleeve? Or because the steel pipe and steel sleeve are electrically connected, the CP acts on both equally.

Maybe same scenario as a blister within a pipeline wall. Or maybe not. Thanks, AWOL

 

[brimmer]

I have never heard of this occurring. I don't see how you would get enough hydrogen and pressure build up between the sleeve. If there were hydrogen atoms they should just diffuse in and out of the pipe and sleeve, I don't see why they would stop between the sleeve and pipe, unless there is some sort of applied barrier on the pipe surface under the sleeve to prevent the atoms from moving. If there was an excess of hydrogen from the CP system at the sleeve location, atoms would have to diffuse through the sleeve first, then into the pipe. It seems to me the sleeve might help prevent hydrogen from getting to the pipe itself. If you already have an impurity/discontinuity in the pipe under the sleeve that has the hydrogren in it I suppose more hydrogen atoms could migrate to this location and continue to grow the blister.
I am just guessing here, but I would say there was a dent in the pipeline and someone has put a B-Sleeve overtop as a repiar, the dent hasn't formed after the sleeve was put on. Or there was already hydrogen blistering there and someone put a B-Sleeve over as a repair.