welding specs for commercial stove hood duct...

Date 05-14-2014 19:01

If it were me, I guess my first call would be to the local county/city health department.
I love it when a new and different subject comes on to the table.
I did repair one several years ago, but just "welded her up" (GTAW) with a Miller MaxStar 150 and never gave it a second thought.

By knslash (*)

Date 05-15-2014 02:08

In my state, (New Mexico), commercial range hoods are goverened by the National Fire Protection Act codes. I have built and installed more than a few over the years in school cafeterias and restuarants. The NFPA is very specific as to joint design, welding, and testing of the duct work. You would be wise to contact your local or state mechanical inspector before starting, it might save you a lot headaches and money in the long run. Plus, if you intend to do more hoods in the future it would not be wise to get on the mechanical inspector's bad side right off the get-go.

By knslash (*)

Date 05-15-2014 02:16

Found it. Look at NFPA96. this code covers ventilation and fire suppression of private and commercial kitchens. Hope this helps.

By Stringer (***)

Date 05-15-2014 03:16 Edited 05-15-2014 03:46

I've installed at least a dozen and I have some materials to draw from but it's a sketchy deal because it's sheet metal construction. I recommend a heliarc setup so you can 309L from stainless hood to duct work (16 guage mild steel) and ER 70s-2 to minimize porosity on the mild steel parts. Biggest issue is clearance and ability to see what you're welding. What you can't get from the outside you may be able to get from the inside.
Slope and areas where grease can collect are issues and must be addressed because grease fires are not just another safety lecture. They can cause deadly destruction. That said, some of the nuts and bolts issues are chaining up argon (there's never a good place) and aquiring adequate electricity for welding.
Please let me edit this post with the addendum that all my 'installs' were unsupervised. On more than one occasion I was the only human on the site. I am incidentally a CWI and as luck would have it I have never encountered other inspectors in my "grease duct career". It's usually a lonely job, but it's a very good job that is not talked about enough.

By TimGary (****)

Date 05-15-2014 12:26

NFPA96

see attached

Attachment: NFPA96Requirementsforductwork1.pdf (66k)

Attachment: Doc1.docx (376k)

By 803056

Date 05-16-2014 02:43

Good information Tim.

Al

By Metarinka (****)

Date 05-16-2014 20:47

I used to build hoods, other people have mentioned the fire and building codes, usually there was no direct weld quality code, but for food safe and aesthetic reasons we would blend all outside corners and not leave tight radii so that it was easier to clean.

By Cumminsguy71 (*****)

Date 05-17-2014 00:34

I have not built the hoods but have been in on a few installs and even ran duct up 5 floors, across the roof to some vent, unit, I don't know, really didn't care. Guy was cheapskate, I was broke and took the measly $600 he offered while his crew of morons piddle farted around wasting time.

The only code I was aware of, working thru mechanical companies, weld it so it don't leak. I was in my infancy in the business so did not know much about "code". Although the fire marshal had to come out and inspect everything.

By kcd616

Date 05-17-2014 05:08

ok
here is how it goes
you put in plans and prints for what you do
local area building code accepts them
they inspect your work
it is all up to local area code and inspectors as to what it is
ie when I started welding in Los Angeles
aws cert was a waste of money :surprised:

LA city cert was the one you wanted
now times have changed
but still local building code apply
hope this helps
sincerely,
Kent

l