Spray Ventilation

[Len Rosenberg]

I am about to start using a FUJI HVLP turbine unit to do spray finishing, water borne and oil based. I will be doing this in my basement work shop, and want to make sure I have adequate ventilation. The workshop has three windows, each at the top of the wall. One will be open for intake, another for exhaust. I will use a three sided spray "booth" made from styrofoam panels. The middle one will have a cut out, and in back of it will be a fan unit, with flexible ducting run from the fan unit out the exhaust window. I will be using a very light filter over the cut out so the fan blades do not get covered with spray particles. My question is how many CFM do I need the fan to exhaust? I'm looking at two models from Ramfan, the 8" is rated at 980 CFM, and the 12" at 2500 CFM. The ducting run will be about 15 feet long.

Thanks for any advice!

[Allan Speers]

No answer to that question, but I assume you will be using spark-proof fans, yes?

[Len Rosenberg]

Yes, absolutely. Although they are far more expensive.

[John TenEyck]

More is almost always better. Spray booths are designed with a minimum face velocity of 100 fpm. So if you have a booth with an 8' wide x 8' high front on it you would 6400 CFM to have 100 fpm. With that 980 CFM you could have an open area of 9.8 Ft^2 (just over 3' x 3'), and the 2500 CFM fan could handle a frontal area of 5' x 5'.

OK, now for what's practical. I use my 1400 CFM dust collector fan as my temporary spray booth exhaust. Curiously, I've never heard of anyone else doing this, but I've been using it with waterbased and shellac products ONLY for about 4 years now and it works great. I just bypass the bags, run an inlet hose from the back of my booth to the inlet of the fan, and run another hose from the fan outlet out a nearby window. An added benefit of this approach is you don't need, nor want, any filters. WB and shellac products are dry before they get to the fan and just pass through with no buildup. I leave a window open to bring in make up air. I can spray non stop as long as I want with no build up of over spray in my shop air, so 1400 CFM is enough even though the booth is 7' high and 8' wide. I use a 10 CFM @ 40 psi HVLP gun and often spray large projects like a pantry, dresser, or china cabinet.

So, with that as background, the 2500 CFM option you outlined would be more than large enough for most any size booth you would want to construct unless your turbine has a much higher output than my HVLP gun. But I would not spray oil based products because the over spray is going to make a sticky mess on anything it lands on.

John

[Len Rosenberg]

Thanks, that's great info, much appreciated.

Len

[Alan Lightstone]

I'm trying to remember which explosion proof fan I used for mine, but the 2500 cfm size rings a bell.

Works great sucking through 3 large side-by-side paint filters.

Handles anything my Fuji HVLP can throw at it.

You should use hearing protection - it's pretty loud, especially with the HVLP turbine's high pitched whine on top of it.