Dust collection using a venturi ?

[Glenn Roberts]

I have a question that someone might be able to answer. Can the output of a blower ( from a dust collector) be used to create a venturi effect and suck even more dust out of the surrounding air?
eg: by adding a wye fitting ( or 2) in the main exhaust duct.
Has anyone tried this? Seems like the energy of the exhaust air is wasted.
I am wondering if the venturi effect ( assuming it works) 'might' help catch the very fine dust (not shavings or chips etc)

Any comments very welcome.

[David Hostetler]

Not sure how this would work. A venturi is a restriction in the line, usually used on the back side to reduce pressure and atomize a liquid as in the venturi an a carburetor barrel.

I am just not certain of how this would work to provide any positive benefit. All I see is potential restriction...

[Jimmy Coull]

Glenn,
I don't think that it would work only because the air used for the draw(from a blower) has a capability of being compressed. When I worked in the power industry we used sluicing water, that was pumped through a venturi to draw the fly ash, that we were collecting from burning coal, and bringing it out to a holding pond for collection. The fly ash was very fine and this method worked very well for years. But as I said, the water wasn't compressible like air from a DC would be, so I'm not sure it would work.

Nice idea though.

Jimmy

[Paul Atkins]

Have you noticed that an air nozzle with the 'saftey nozzle' blows more air than the straight nozzle? Not really a restriction in the tube, just some extra holes. Try it.

[David G Baker]

I have a venturi device for moving small parts, it is powered by an air compressor. The pick up line is 3/4". I purchased it to use to pick up metal shavings from my lathe, drill presses and mill. It takes a compressor that produces a large volume of air so I haven't hooked it up yet because I haven't purchased the large compressor. I don't see why a venturi system wouldn't work if you can move enough air and have large enough openings but the cost may not make sense.

[David Epperson]

I have a question that someone might be able to answer. Can the output of a blower ( from a dust collector) be used to create a venturi effect and suck even more dust out of the surrounding air?
eg: by adding a wye fitting ( or 2) in the main exhaust duct.
Has anyone tried this? Seems like the energy of the exhaust air is wasted.
I am wondering if the venturi effect ( assuming it works) 'might' help catch the very fine dust (not shavings or chips etc)

Any comments very welcome.

I would say yes, and no.
A DC blower could be used to induce a low velocity draft that would move fines to an exhaust location, but I do not think that using the blower that is already in use for dust collection would work very well.
A venturi works by the effect of a high pressure, high velocity stream being used to entrain the surrounding air into a much larger volume, but lower velocity and lower pressure stream.
Like you infered, after the "ventuti" you would no longer have sufficient air movement force to maintain chip movement - though the fines would still be able to be conveyed.

[Glenn Roberts]

thanks for the responses thus far. I will try out the idea to see if it works. I should mention that the fitting would be in the exhuast line (after a Bill Pentz type cyclone etc) with no filters , and going outside. So the exhaust would not have any restriction and would be short so no worry about losses.

I wonder if any suction might just help with the very fine dust that hangs in the air. ( not chips) so the 'extra' line would go into the workshop space ( eg: at a lathe etc)

Further comments please

[Frank Hagan]

I'm more familiar with venturis in water, where a gradual restriction in pipe size is terminated with a sudden re-enlargement; it is at this point of restriction-to-enlargement that we would place an air supply to entrain air into spa jets.

I think the problem with just a standard wye will be that the air pressure inside the exhaust pipe is higher than the air pressure in the room. If you can draw the room air farther down into the center of the stream of air by having a tube from the wye extend toward the exhaust terminal a few inches ... maybe a 2" diameter "injection pipe" from the wye, positioned in the center of your 6" DC exhaust pipe, and extended a couple of inches toward the exhaust port (a 45° ell might work on the end of a short section of pipe). This might create a true venturi effect; as air compresses around the "injection pipe", it will build up higher pressure behind the pipe. Where it forms an eddy after the end of the injection pipe it creates a lower pressure area that might draw in room air.

Might be easier to use the rapid loss in pressure as the air exits the exhaust terminal at your wall. Position the wye right at the wall and you might get a venturi effect instead of pushing air back into the room without having to use an injection pipe to create the area of lower pressure.

[Glenn Roberts]

Frank, thanks for the ideas I will try both ideas.
Glenn

[Frank Hagan]

Let us know if it works. Its an interesting concept.

[harry strasil]

aren't you trying to make an eductor, its used on chemical spray rigs to suck chemicals into a tank and on fire trucks to suck foam into the line for fighting oil and gas fires.

[Glenn Roberts]

harry, thanks for the advice. I used the word venturi loosely. I hope people understand what I mean