NEC 300.6 and PVC coated rigid

[rob569]

I have a contractor that built a water treatment building for my company, while inspecting some of their vendor supplied corrosive skids(sulfric acid and caustic) I noticed that the vendor had a skid that was handling sulfric acid and did not have coated rigid conduit and fittings and on other skids handling corrosive fluids (caustic), they did, but the contractor's electricians installed rigid conduit instead of the PVC coated rigid conduit.

This was done becuase the vendor sent an email stating that it was ok, as look as the skids don't leak and if it does it is cleaned up promptly (I don't know how he thinks that will be accomplished).

To make matters worse the vendor had already supplied a drawing detail to address this very issue, stating that, where there are skids that handle corrosive fluids use PVC coated rigid (schedule 40) when installing conduits.

They are now trying to get the vendor to change the detail on the drawing.
NEC 300.6 does not specifically speak on when to use PVC coated rigid and why, just that in corrosive environments use suitable material for the area.

My question for you is there anywhere in the NEC or other code books that give specific instruction on installing coated conduit for corrosive areas and why?

 

[petersonra]

Why not just buy some brush on PVC coating and paint the conduit?

PVC coated rigid (schedule 40)

Is this PVC schedule 40 or PVC coated rigid?

 

[Pierre C Belarge]

See 501.10 for the permitted wiring methods.

I am not sure that brushing on some coating is acceptable, but I would imagine there are products I have never seen or heard of that may fit the need.

 

[noonan]

I think you have it covered with 300.6 "materials suitable for the environment in which they are to be installed".

 

[lakee911]

I am not sure that brushing on some coating is acceptable, but I would imagine there are products I have never seen or heard of that may fit the need.

There is typically they're used for patching up nicks, scratches, wrench marks. They're probably not intended to be used to provide protection for a whole conduit/fitting. It's much thinner than factory coating too.

I did some punch listing this past summer and found some fittings painted up this way. Fitting was already rusting under that and paint flaking off. This was in a H2S environment. I can't locate a pic though.

Jason

 

[petersonra]

See 501.10 for the permitted wiring methods.

I am not sure that brushing on some coating is acceptable, but I would imagine there are products I have never seen or heard of that may fit the need.

The OP never said this was a classified area.

There is a whole series of coatings made just for this kind of environment. The equipment skids themselves are often coated with it.

 

[Pwelch]

You might find 344.10(a)(b) helpful. The enamel on rigid metal conduit is not suitable for severe corrosive influences. Rigid metal conduit is suitable for severe corrosive influences, where protected by corrosion protection and judged suitable for the condition( that's where pvc coated comes into play).