Corrosion in/on Pullboxes, Hubs, Conduit, etc.

[pjholguin]

If you are going this route you need to pay attention to field cuts and threading, these points need to have the PVC coating repaired to close as possible to the original coating and exposed threads and field threads need to be protected from corrosion using approved sealants. FWIW

PJHolguin

Okay lets suppose that we decide to replace the RMC with PVC coated metal conduit as made by Thomas & Betts. This type of conduit is neither pure metallic or pure PVC. How would you support this conduit? Would you support it at 10 foot intervals as you would with RMC or would you support it in accordance with NEC Table 352.30? The existing conduit system is 3" diameter.

 

[petersonra]

Typically PVC-coated GRC and supported at intervals just like GRC (RMC).

no different than painting the conduit IMO. it is still listed as rigid.

 

[petersonra]

bump

 

[Smart $]

no different than painting the conduit IMO. it is still listed as rigid.

Are just referring to the listing or its long-term performance in the environment. IMO, much better than simply painting RMC.


...But then again that would depend a bit on what you paint it with and how thick. 100 coats of suitable epoxy might just hold up better than PVC-coated.

 

[mgookin]

Just curious - not that it really matters. Is this a lighting circuit or emergency call stations or something else? What's your voltage in it?

 

[erickench]

Just curious - not that it really matters. Is this a lighting circuit or emergency call stations or something else? What's your voltage in it?

They're 277 Volt lighting feeders located on a high bridge. Does anyway know the consequences of corroded hubs? I would think that they would create bad bonding between the raceway and the pull box/conduit body.

 

[petersonra]

They're 277 Volt lighting feeders located on a high bridge. Does anyway know the consequences of corroded hubs? I would think that they would create bad bonding between the raceway and the pull box/conduit body.

I doubt it. The threads bite into each other and form a pretty good bond.

The rust is on the outside.

 

[GoldDigger]

I doubt it. The threads bite into each other and form a pretty good bond.

The rust is on the outside.

The bonding would only get bad if the threads were not tightened gas tight in the first place or if the corrosion went all the way through the pipe or conduit body and caused it to lose mechanical integrity.

 

[junkhound]

Wire brush and paint with galvacon (95% zinc powder paint). Used that stuff on some places in HI in the 80s, think it is still good.