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Re: (T3) temp spray booth


On 7 Jun 2001, at 19:16, Chazpix@aol.com wrote:

> Good thought Jim, but there are a couple of problems with the "in
> blowing". The main  fear is the accumulation of vapors and
> atomized paint inside the booth creating vortices. It is
> absolutely imperative that overspray be withdrawn from the field
> immediately,otherwise it has a tendency to swirl around and over
> the car, collect any dust or impurities(undercarriages are
> notorious for dirt!) dry, then settle(or be blown) back on the wet
> finish.(BIG TIME PITA!) 

We're in complete agreement on most of your points. My only 
claim would be that the air flow is ~the same whether the fan is 
pushing or pulling. In the overall picture, it really doesn't matter 
where you put the various elements in the chain: the fans provide 
some pressure boost and the filters have resistance to flow. From 
this the flow rate can be calculated.  

> In 25+ years of painting I never have seen a booth with two fans.
> Are you thinking  about a separate heating source? Have used a
> heated booth,but the elements were built into a one-fan system. 

The place where I used to work had a nice booth that had a fan 
exhaust (belt driven to keep the motor out of the vapor stream) and 
a makeup air unit which had its own fan. The latter had 
thermostatically controlled heaters  

> The air is filtered twice in pro booths, incoming(the doors are
> fitted w/fine mesh type) and the receiving end(freeflowing,
> disposable styrofoam collectors(for EPA regs) I have found that
> installing any type of filter over (or behind) the fan
> substantially reduces the air flow. 

Right, the incoming filters are there to remove dirt, and the outgoing 
filters are to collect the overspray.  

> The ultimate is what's called a "downdraft" booth,where the
> exhaust ports are actually under the car as it is parked inside.
> These are VERY nice! Overspray gets sucked right down off of the
> vehicle(along with any dirt underneath) Dry is even & quick,and
> leaves a super clean finish.(unfortunately they run about $60-70K
> to build!) 

Our old painter used to use a downdraft booth, but it only filtered 
the overspray. It had no roof, only exhaust. It was open so that the 
machine tools that they painted could be hoisted in there with a 
crane. No real concern about dirt. I realize this is not the usual       
setup.  ;-)

-
*******************************
Jim Adney, jadney@vwtype3.org
Madison, Wisconsin, USA
*******************************

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