# Stainless Steel Conduit?



## chenley (Feb 20, 2007)

We got an e-mail last Friday from a contractor who is coming in to install quite a bit of equipment for one of our new production lines here. 

They are asking if stainless steel conduit that will be welded together and at junction boxes is acceptable in Kentucky. At least 85% of all our other equipment is installed in this matter due to it being a dairy production plant. I have e-mailed our local AHJ and looked through the codebook (NEC2008). Still have not received a response from our inspector and the closest thing I can find in the codebook is 300.18(B). 

All I can think of is that if the SS conduit is UL listed and is made to be welded at connections that it will be fine.

I'd greatly appreciate any help or ideas on this issue. 

Thanks,

Cameron Henley


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## BBQ (Nov 16, 2010)

I do not know of any NEC exception that allows the welding of conduit.


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## chenley (Feb 20, 2007)

Well now that I'm home, I looked through the 2009 white book. On page 111 there is Rigid Nonferrous Metallic Conduit (DYWV) although it doesn't say anything about SS there. It is in the Index as SS and that it has to adhere to Artlicle 344 for the NEC. Where the NEC does not say anything about welding the conduit together.


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## LJSMITH1 (May 4, 2009)

Listed Stainless Steel EMT should be used with Listed SS EMT fittings. Cal Conduit sells both....

http://calbrite.com/


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## MDShunk (Jan 7, 2007)

BBQ said:


> I do not know of any NEC exception that allows the welding of conduit.


Someone should draft one. I can't think of any reason why non-ferrous conduits should not be able to be welded, other than the code prohibition against it.


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## Jlarson (Jun 28, 2009)

MDShunk said:


> Someone should draft one. I can't think of any reason why non-ferrous conduits should not be able to be welded, other than the code prohibition against it.


Yeah, I wouldn't mind TIG welding SS conduit, it would work better than fittings in some situations.


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## MDShunk (Jan 7, 2007)

Jlarson said:


> Yeah, I wouldn't mind TIG welding SS conduit, it would work better than fittings in some situations.


I'm thinking food safety as substantiation. There is no metallic conduit system that food, dairy, and pharmaceutical businesses are completely happy with from a sanitation standpoint, simply because of fittings and/or threads. I think you and I have both probably seen how PVC holds up to harsh chemicals... it turns to dust. TIG would pretty much have to be the process anyhow. Besides, if I was welding fittings, I'd rather drag around a little wee TIG box than a big honking welder anyhow.


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## Jlarson (Jun 28, 2009)

MDShunk said:


> I'm thinking food safety as substantiation. There is no metallic conduit system that food, dairy, and pharmaceutical businesses are completely happy with from a sanitation standpoint, simply because of fittings and/or threads. I think you and I have both probably seen how PVC holds up to harsh chemicals... it turns to dust. TIG would pretty much have to be the process anyhow. Besides, if I was welding fittings, I'd rather drag around a little wee TIG box than a big honking welder anyhow.


Yeah, a small TIG unit and a cylinder wouldn't be too bad to move around, put it all on a cart and it would be just as easy if not easier than dragging a threader around.


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## chenley (Feb 20, 2007)

That is why the question came up if it was allowed. Most of all our equipment has stainless steel conduit that is tig welded together running to it. It would be sprayed down with heavy chemicals 2-3 times a day to keep the sanitation up to par. 

The question came to me from the corporate engineer in Dallas. He was not sure if Kentucky had an amendment against running welded SS conduit. Kentucky as far as I know has adopted the NEC2008 in it's fullest without any amendments.


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## MDShunk (Jan 7, 2007)

chenley said:


> That is why the question came up if it was allowed. Most of all our equipment has stainless steel conduit that is tig welded together running to it. It would be sprayed down with heavy chemicals 2-3 times a day to keep the sanitation up to par.
> 
> The question came to me from the corporate engineer in Dallas. He was not sure if Kentucky had an amendment against running welded SS conduit. Kentucky as far as I know has adopted the NEC2008 in it's fullest without any amendments.


Kentucky doesn't need an amendment against it, since it's already prohibited by the NEC.

Check out 300.18(B). It's illegal EVERYWHERE, unless they have an amendment specifically permitting welded conduit connections. That said, if the "Equipment" is part of a UL Assembly, or built under NFPA 79, welded connections seem to be permitted. The field conduit connections, however, are under the NEC.


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## mattsilkwood (Sep 21, 2008)

Pretty interesting idea.


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## BBQ (Nov 16, 2010)

MDShunk said:


> Kentucky doesn't need an amendment against it, since it's already prohibited by the NEC.
> 
> Check out 300.18(B). It's illegal EVERYWHERE, unless they have an amendment specifically permitting welded conduit connections.


This is what is confusing me as in his opening post he said he knew about that section.


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## MDShunk (Jan 7, 2007)

mattsilkwood said:


> Pretty interesting idea.


Fact is, it's done here and there already anyhow. Government work sometimes makes you buzz a blob on every connection.


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## BBQ (Nov 16, 2010)

I have welded up custom wireway fittings.

In one case I really needed an "F" with close dimension between the legs.

One "T", one 90 and a mig took care of it.


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## mattsilkwood (Sep 21, 2008)

MDShunk said:


> Fact is, it's done here and there already anyhow. Government work sometimes makes you buzz a blob on every connection.


 I've never seen on any job I've been on. I can see from a sanitary or security standpoint, it doesn't get any better.


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## frenchelectrican (Mar 15, 2007)

I know from European side we do allow to weld stainless steell conduit however we have few quirks is how far you can weld due some conduit can become FNG due get some slag inside the conduit and ruin the whole thing.

It did not happend to me yet but for food processing plants they should have some type of guideline what type of welding or coupling they allow in the States.

I know in Our codes {FEC} we can use compression fitting but I am not a strong fan with the dammed thing at all especally in Food area.

Merci.
Marc


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## BBQ (Nov 16, 2010)

MDShunk said:


> Someone should draft one. I can't think of any reason why non-ferrous conduits should not be able to be welded, other than the code prohibition against it.



I think they are worried about a crappy welder damaging the inside of the conduit.


Here is the only ROP I could find about it, this was for the 2002 NEC.



> *3- 89 - (300-18(b)): Reject
> 
> SUBMITTER: *Randolph O. Lovelace, City of Orlando, FL
> 
> ...





> *300.18(B) Welding.* Metal raceways shall not be supported, terminated,
> or connected by welding to the raceway unless
> specifically designed to be or otherwise specifically permitted
> to be in this Code.


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## MDShunk (Jan 7, 2007)

BBQ said:


> I think they are worried about a crappy welder damaging the inside of the conduit.
> 
> 
> Here is the only ROP I could find about it, this was for the 2002 NEC.


Luckily, there's a spec for that already, as it relates to the welding of sanitary piping. The proposal could say, "welded in accordance with xxxxxx spec", but I've never noticed that the NEC references any other spec except in FPN's and appendices.


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## Wingnut (Jan 31, 2010)

We use too get stainless in 20' sticks which would eliminate (alot of)couplings all together.


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## rbalex (Nov 24, 2010)

As the original author of what has since become 300.18(B), I intentionally attempted to establish a principal rather than a rigid rule. I didn't want a litany of exceptions or cross-references.

I submit that a manufacture of stainless steel raceway may certify that their product is “…specifically designed to be…” field welded if they choose to – _listed_ for it or not. The UL standard that applies (UL 67) neither checks for applicability nor prohibits field welding but it does permit “…special lengths … with or without a coupling for specific applications or uses.” Of course, the manufacturer would need to provide any appropriate welding procedures.

The problem is we have become so “_listing_ or _labeling” _paranoid that sound engineering judgment is all but thrown out.


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## chenley (Feb 20, 2007)

The engineer is wanting to go with PVC coated Rigid conduit now. 

How long has 300.18(B) been in the NEC? I see it in 2005 and 2008, I don't have any previous versions of the NEC though.

We have equipment that had SS conduit run to it that is at least 15 years old. The last project that was completed at the site 10 years ago was ran in RMC. Just wondering if it was ever allowed and if it was, why was it changed?


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## rbalex (Nov 24, 2010)

It was originally 300-18(b) in the 1999 NEC


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