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Piping Hydros, to coat or not to coat?

Piping Hydros, to coat or not to coat?

Piping Hydros, to coat or not to coat?

Hello folks.

This might be a more suitable query in another forum, apologies if so... I was hoping I could draw on your experience in regards to protectice coatings and piping hydros.

We're about to launch into a significant amount of piping work in a plant revamp [Australian site]. It's been our practice to date to leave all piping welds [shop or field] uncoated until the piping successfully passes a hydro test. This is on the understanding that a pinhole/pore failure in a weld may not necessarily be picked up by RT and is also undetectable in a hydro situation if the weld is coated due to being plugged by the coating system.

We're considering a proposal to modify this practice by way of prime coating all shop spooling prior to hydro. This means that the final hydro will be carried out once all closure welds have been done and the piping is fully installed in the field. The field welds will be left unpainted until after the hydro, at which time the piping will be fully coated to the appropriate protective coating specification.

B31.3 stipulates uncoated welds for Cat M fluids or sensitive leak tests - neither which apply to us. This clause actually struck me as odd given the pin hole plugging that can occur with a coating system. Wonder why the committee has let that one go past?

Anyway, I'd appreciate it greatly if you would share the gist of the piping hydro practice on your sites?

Thanks in advance.


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