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Welding on conduits #68828
08/17/06 03:27 PM
08/17/06 03:27 PM
Amazingmg  Offline OP
Joined: May 2005
Posts: 42
Florida, USA
An engineer wants us to weld 4" conduit nipples to a bulkhead plate for exiting a freezer building. The plate would intersect the nipples 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?

Work Gear for Electricians and the Trades
Re: Welding on conduits #68829
08/17/06 03:57 PM
08/17/06 03:57 PM
macmikeman  Offline
Joined: Jul 2002
Posts: 717
Honolulu, Hawaii
Try looking at 300.18(B) and see if that helps at all.

Re: Welding on conduits #68830
08/17/06 04:06 PM
08/17/06 04:06 PM
Tiger  Offline
Joined: May 2005
Posts: 706
Crystal Lake, IL USA
Also welding galvanized steel creates a poisonous white cloud of zinc oxide, I believe.


Re: Welding on conduits #68831
08/17/06 04:22 PM
08/17/06 04:22 PM
gfretwell  Offline

Joined: Jul 2004
Posts: 9,343
It always looked yellow to me but you better be wearing a respirator anyway.
300.18(B) is the real answer. Good call Mike

Greg Fretwell
Re: Welding on conduits #68832
08/17/06 05:37 PM
08/17/06 05:37 PM
hypress  Offline
Joined: Jul 2004
Posts: 129
Charleston WV
What would be wrong with a "Myers " bulkhead fitting. Time you figure your welders time it might be cheaper to use bulkhead fittings.

Re: Welding on conduits #68833
08/19/06 02:28 PM
08/19/06 02:28 PM
Amazingmg  Offline OP
Joined: May 2005
Posts: 42
Florida, USA
300.18 (B)

Aha! Sometimes these guys direct us to do some of the screwiest 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> [Linked Image]

Re: Welding on conduits #68834
08/20/06 12:46 PM
08/20/06 12:46 PM
iwire  Offline
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
Possible solution is to weld a metal sleeve in the bulkhead and use a Link Seal between the sleeve and the conduit.

Bob Badger
Construction & Maintenance Electrician
Re: Welding on conduits #68835
08/20/06 02:51 PM
08/20/06 02:51 PM
SteveFehr  Offline
Joined: Mar 2005
Posts: 1,213
Chesapeake, VA
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!

Re: Welding on conduits #68836
08/21/06 10:29 PM
08/21/06 10:29 PM
Active 1  Offline
Joined: Feb 2003
Posts: 687
Grayslake IL, USA
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.

Re: Welding on conduits #68837
08/23/06 03:11 AM
08/23/06 03:11 AM
e57  Offline
Joined: May 2003
Posts: 2,876
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.

Mark Heller
"Well - I oughta....." -Jackie Gleason


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