An engineer wants us to weld 4" conduit nipples to a bulkhead plate for exiting a freezer building. The plate would intersect the nipples halfway....so half the nipple sticks outside...half inside.

Welding on conduits (even while no wire inside) just seems wrong, but I'm not sure there is no reason we can't do this.

Any thoughts?

Try looking at 300.18(B) and see if that helps at all.

Also welding galvanized steel creates a poisonous white cloud of zinc oxide, I believe.

Dave

It always looked yellow to me but you better be wearing a respirator anyway.
300.18(B) is the real answer. Good call Mike

What would be wrong with a "Myers " bulkhead fitting. Time you figure your welders time it might be cheaper to use bulkhead fittings.

300.18 (B)

Aha! Sometimes these guys direct us to do some of the screwiest things...so basic that it seems hard to immediately answer why it is wrong.

On the gas...we do weld HDG brackets all the time (outside) so I knew about that. Good comment though.

What I proposed to the Eng. was nipples thru the wall (wall is 6" thick with ins. core and galv. skin) with O-Z Gedney CDS? sealing bushings (the feeder is 3-500mcm per phase in tray up to wall on either side). Then have mechanical guys flange/seal around conduits as they see fit (I think we can get them pretty tight). They are worried about thermal loss. This is a cold storage building. Or a EYD with Chico on either side.

Thanks for help. I haven't even had time to break open the code book till just now. Crazy lately...working 6-7 days most weeks. Wife is real happy....<sarcasm>

Possible solution is to weld a metal sleeve in the bulkhead and use a Link Seal between the sleeve and the conduit.

In naval use, we weld steel stuffing tubes and swage tubes to bulkheads all the time. Provides a full watertight and mechanical seal. And if used with a grounding adapter, provides full EMI/EMP protection, too. They all come with threads for attaching conduit adapters and anything else you might need. This might be an option too, if your engineer insists upon welding!

I just signed up for an auto welding class to help with my hobbies. Anyway I seen in the textbook you can weld galvenized steel (without grinding it off) but it looked much more difficult to get a good weld for many reasons. The big tip was you got to crank the welder setting higher than normal.

Isnt metal also thermally conductive as well as electricaly? Sounds like some sort of sleeve like iwire posted would be better for the purpose. Even a big gapping hole and a can of foam would be better IMO.

Also heres an interesting code and kinda funny when you see why its there, or not too funny depending on the situation. 300.7

Funny one: Jelly jar light filled with water.

Not funny: Rotted out disconnect falls apart when the AC mech LOTO's his switch, and and finds that it only partialy opens as it falls apart inside from rust.