Welding Exhaust 1

[carlosgw]

Owner wants a 10'X10' welding area in the corner of their shop. If it is 10' high and I treat it like a walk-in hood with one open side and exhaust on the wall opposite that's 10,000CFM (based on 100FPM). I'm trying to talk them into local exhaust.
Anyone do anything similar?

 

[berkshire]

Need more information to consider local exhaust.
How many welders are working in the booth?
What welding process i.e. Stick, Mig, Tig.
The last two methods are sensitive to drafts in the work area.
B.E.

The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor

 

[willard3]

The ACGIH handbook has this information for the required ventilation.

It is not a local exhaust and treating it like it is a bad idea.

 

[carlosgw]

ACGIH and OSHA encourage local exhaust for welding (my copy of Industrial Ventilation is older but I can't believe it has changed).
Am I missing something?

This is for a machinery repair shop in an industrial plant. It is not an assembly area where the welding is the same all the time.

 

[317069]

you said" that's 10,000CFM (based on 100FPM)"
how did you select a required cfm based on the air velocity?
I googled some information about weld fume control and found on the following link

http://www.lincolnelectric.com/en-us/equipment/weld-fume-control/Documents/e1360.pdf

there is a hood package with product data, the size is (13'x 6.5')
which is about 85 sq.ft, they said that it needs 3500 cfm.

 

[carlosgw]

A 10' X 10' work area. Sat 10' high so the face is 10'X10'.
Now that you say it I am not sure where I got 100FPM. The place I thought it was in Industrial Ventilation actually says 125CFM/SF face which is worse.
Thanks for the cut. I will check it out.
I have been looking at a Plymovent local exhaust unit.

 

[berkshire]

carlosgw
I have used the Plymovent units. They are generally wall mounted with a boom and counterweight for the duct. Used properly they will keep a shop free of smoke and fumes.
B.E.

The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor

 

[BronYrAur]

I don't have enough time to give a detailed response or to help you with any calculations, but here is what I did once before. Please forgive the extremely rough sketch as I just threw it together in a minute.

Capturing fumes is all about the "capture velocity". I don't recall what the velocity is for welding fumes, but you are on the right track with your thinking. Now, here's where I think my idea will help you:

Construct a hood to cover the entire 10'x10' welding area, but put a plate in the bottom of the hood so that most of the opening in blanked off. You will have to weld straps or come up with a way to support the plate. This will leave you with just a perimeter slot around the 10'x10' welding area. How big should the slot be? I don't know off hand, but probably 2" wide. You will need to consult an Industrial Ventilation handbook for the cals.

With this setup, you only need to have enough capture velocity across the slots and not throughout the overall 10'x10' area. This dramatically reduces the total CFM! Any fumes that hit the plate will migrate horizontally and get sucked up through the slot.

I put a light on the the one I designed because the hood was blocking the overhead lighting.

If you have a door open or a fan blowing, etc, the fumes may be blown out of the welding area and not get captured. Likewise, if the hood it too high, the fumes may escape before being captured by the slot velocity.

Hope this helps!

 

[chicopee]

Which metals are you expecting to weld?

 

[carlosgw]

The owner has been convinced that local exhaust is the way to go.

 

[mauricestoker]

The 100 fpm sounds like a reasonable figure, if you have a "capture distance" included. Difference between cpature distance of 6" vs. 9" can be large.