On May 7, 1:47 am, Rick Frazier wrote:
wrote:
I'm concerned about the dust hazard in my shop and am trying to make
my shop more dust-proof and have done the following:
- Built a cyclone dc.
- Built a ambient dust collector to filter the dust floating in the
air.
- Just bought a Trend Airshield Pro to protect my face/lungs.

Now, I am wanting to exhaust as much dust to the outside of my shop as
possible. I searched the Internet for information on exhaust fans
similar to the ones used by sawmills, but they are expensive and
large. I'm also thinking about venting the dust/chips from my cyclone
dc outside. My shop is 24x32x8 high and in the country, so dust
discharged outside shouldn't be a problem. I may make a collection box
outside to collect the dust/chips if I go that route.

My questions:
1. Can I build a exhaust fan unit to discharge dusty air from my shop
to the outside? If so, how large a fan and does it have to be a slow-
speed fan? Or will a gable vent fan work?
2. Is it O.K. To do away with the collection bin located below the
cyclone? And do away with the filters? And just have everything go
outside?

Rob

1: First, look at whether you have opportunity for natural cross
ventilation... If you have a window on one side of the shop and a door
or another window on the other side, just opening both should provide
some sort of cross air flow that will help out a lot (assuming you don't
have things locked up tight due to heating or cooling considerations).

If you have a decent dust extractor you shouldn't have much dust hanging
around, even while you are power sanding on the lathe. (I do a fair bit
of turning on a lathe with 42" swing and can generate a LOT of dust, but
rarely have to deal with breathing much of it.) The volume of your shop
is only 6144 cubic feet, and even a 1000 cu ft/minute dust extractor
would (theoretically) change all of the air every six minutes or so...
My current shop is similar in size, but doesn't have a lowered ceiling,
so the volume is about 13000 cubic feet. With reasonable air flow, I
don't have much issue with dust, except for the workbench, which is
directly under the "exhaust path", so to speak.

If you don't have any built-in cross ventilation (like decent,
consistent wind on one side of the shop and some windows or doors to
make it work), then just about any sort of air mover will help. Here
bigger is better, and slow moving fans are just quieter. With no close
neighbors, if your spouse doesn't mind you could use just about
anything. At one place I lived in San Jose, CA I picked up a ton of
those square muffin fans used in the computer industry for a pittance,
and just bolted them to metal strapping to fill an old screen door
frame. It sounded like a jet plane getting ready to take off, but moved
somewhere between 8000 and 10000 cubic feet of air a minute. You could
even feel the breeze standing in one of the two open garage doors (no
matter if the wind was blowing towards the garage, the air still moved
out... One neighbor just about had a heart attack because he though I
had a jet engine in the garage and was worried it would get loose and
destroy the neighborhood. We made a deal. He'd turn his stereo off by
10PM and I'd turn off my fans... A while later I found a bunch of
similar fans that were much quieter and he didn't even know I had them
on. They only moved around 3 or 4000 cubic feet a minute, but still
kept the garage pretty dust free. There was a fair bit of dust on the
driveway, but some judicious re-aiming of the sprinklers made it all go
away every morning when the lawn got watered... At another time, when I
was doing some custom paint on classic cars, I filled one garage door
with furnace filters to catch most of the paint and sprayed away inside.
Nearly nothing on the driveway for the sprinklers to deal with and
using the quiet fans so I wasn't spraying in a hurricane, things worked
out fine. Of course, with all of the current EPA regulations on
volatile organic vapors, you couldn't get away with that now (and can't
even buy the lacquer any more...), but that was another time and place.

2: You can't do without the collection bin at the bottom of the
cyclone, but you can probably do without the exhaust filters, especially
if you exhaust to the outdoors. If you do exhaust outdoors, make sure
you have a low-restriction source of "make up" air, such as a window or
door near your lathe. That way, clean air comes in from outside and is
blown out by your dust extractor/Cyclone. If you've got a working
cyclone, you should have any visible dust and certainly no chunks coming
out. This should all be going into the collection bin.

At my last shop, I had a cheap 1000 cu ft/min DE attached to a homemade
cyclone (55 gallon drum with typical home-made cyclone style input and
output out the top, with the DE sucking the output of the cyclone. The
output of the DE was so clean that I ran without filter at all, and
after 6 months barely had a light dust inside the (leaky) shed where the
DE exhausted (outside of the shop)... Removing the filter bag also made
a positive difference in the overall performance of the DE/Cyclone
combination, as the factory filter bag cut off a fair amount of the
airflow...

In my current shop, I haven't had the cash to purchase a new DE or
Cyclone to install yet, (which makes running a 15" belt sander noisy as
my only dust sucker is a shop vac that barely keeps up with the volume
of the wide belt)... However, other items, and particularly my Lathe
that does generate significant dust while sanding, aren't a real problem
because I have great cross ventilation. Air comes in a garage door near
the lathe and out through one man sized door at one corner of the shop,
(same side). I stand in a relative bubble of clear air, but my poor
bench catches a ton of dust if I leave much out on it to disturb the
airflow. The other side of the shop gets a bit of dusting now and then,
but once a month or so a quick dust-off with an air hose and everything
is all right for awhile.

There are a lot of possible solutions, particularly if you haven't got
any close neighbors. The most important is protecting your health. If
you're using the airshield, you shouldn't have any problems with your
lungs, and nearly anything else you do will help reduce the amount of
dust in the environment, which will only make the job of the airshield
easier.

Not mentioned yet is the potential for an explosive atmosphere under the
right conditions... If you've got an exposed flame of any kind (water
heater or furnace pilot, furnace burner, etc.) you've got to make sure
you don't get too high a concentration of dust in the air, as it can be
explosive under the right conditions. (Ever wonder why a flour mill has
one side almost all windows? Let's just say it keeps the rest of the
building intact if they hit that magic concentration of flour dust with
an ignition source present...) I know it's difficult to get to that
level in the average shop, but stranger things have happened.

I think you're basically on the right track, or you wouldn't have
purchased the airshield... Keep up the good work, and take care turning!

--Rick

Thanks for the information. I didn't know that my cyclone had to have
a dust collection bin as my thought was to do away with it and duct
the dust collected outside by running a discharge hose out through the
outside wall. Glad you told me that I need the bin. I would have hate
to cut a hole in the wall for nothing.
My workshop is a detached garage so I plan on opening at least one
garage door and the entry door, but in winter I hope to use an exhaust
fan attached on the inside of a window, so I can open and close it
when I want. I think I'll start out with about a household-type 12
inch fan for an exhaust fan and see how that works and then move up to
a larger one if I need to.

Rob