Dust suspends how long!?

[Larry Kunkler]

Dave,

I see your point. But, my thinking is as follows

In my system, a full stream of very clean air is coming from a ceiling mounted ambient air filtration system based on a 650cfm "Elicient turbine blower" that draws only 160 W and is nearly silent. It pulls air through a 4 sq ft two stage filter system with the final stage at about merv 14. The output from this unit (6" dia. adjustable duct) is directed just over my shoulder (and breathing area) and into a large (18"w x 12"h) high flow rate (all 6" ducting) DC intake. The airstream pushes and/or entrains almost all of the sanding dust from finishing processes on the lathe into the intake of the dc to be removed from shop air.

If you have really clean shop air to begin with, another way to accomplish the same thing is to mount a muffin fan or/=, over your shoulder, opposite the dc intake, blowing dust into the dc intake. I am ok with giving up a bit of ambient air filter function to know that I'm breathing the cleanest air possible.

My main dc system consists of a 220v, 3hp bolwer sitting directly on top of a large (22" dia) custom made, Pentz type, cyclone, exhausting (nearly clean air) into a Wynn 9L300 final filter that feeds very clean replacement air back into the shop.

Benefits of my push-pull collection system:

1) You get to breathe the cleanest air

2) Dust collection effeciency is excellent. Better than any pull only collection can possibly do.

3) Due to #2 above, you get to breathe much cleaner shop air and your shop (and home) stay much cleaner.

BTW, NASA determined that it takes about 1 hour for a 1u particle to fall 1 foot in still air. every time you walk through your shop youo stirr up the dust and re-load the air with particulate. So the other part of the process is to keep your shop very clean using as neer to a HEPA vacuum as you c an get.

Bottom line, collect the dust at the source. If it gets into the air...you're screwed....kunk

[David C. Roseman]

Kunk, thanks for elaborating. Now I understand your setup, and it sounds very efficient, indeed.

I've used the "push-pull" approach in an unrefined way when spraying lacquer in a confined room: A box fan in one window blowing out, and one in another window blowing in. But I hadn't thought about applying it to collecting dust in the shop from an individual machine, and certainly not in terms of cfm fall-off of blown air vs. vacuum-intake air. Makes sense. And having the "pushed air" coming from a clean-air source over your shoulder makes it ideal for any machine or station where we're in one place for longer periods of time. Especially a lathe, bench sander, sanding station, pyrography station, etc. Need to give some thought to adding some localized "push" to my own system.

David