vacuum hood design
vacuum hood design
(OP)
I am working on designing a vacuum hood for cleaning sand, coal ash, and brick chips. A dust collector system is the preferred way of cleaning, but I have to design a hood to create enough vacuum to pick up the particles as it sweeps over an uneven surface. I have to have at least a 5/8" opening to collect the particles, but the hood has to be close to 60" wide, and thus creating enough suction on one end, but not enough on the far end, since the inlet for the system has to be on one side or the other. Any suggestions as to how to design the hood to get even vacuum across over the entire hood?





RE: vacuum hood design
However, being an ME, you should recognize that it's the pressure differential that drives the air flow; hence, the "vacuum" cannot possibly be uniform within the hood.
I can't tell from your posting what kind of sand, but most sands require pretty manly airflows to get them to move, which might be counterproductive to whatever the user is actually doing. I'm thinking along the lines of 40 mph wind?
Perhaps you might consider a grill as a worksurface, i.e., something that's mostly holes that are small enough to prevent your objects from falling through, but will allow your dust and sand to fall through and get sucked away.
TTFN
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RE: vacuum hood design
You might want to look a bead blasting cabinet design.
The standard fume hood in a laboratory creates a draft across the working surface by using duct fans and normally a room with positive pressure to assist the draft. There is essentially no vacuum in these hoods only a draft. Anytime that would create a vacuum to accommodate your materials would be complex system.
RE: vacuum hood design
RE: vacuum hood design
TTFN
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RE: vacuum hood design
RE: vacuum hood design
Think street sweeper. They use large roller brushes to kick the dirt up and into the suction mechanism.
RE: vacuum hood design
Look at all their products as there are several possibilities like the air amplifier to exhaust the dust.
http://www.exair.com/Cultures/en-
US/Primary+Navigation/Products/Air+Nozzles/
http://www.vortec.com/curtain_transvectors.php
RE: vacuum hood design
Coupled with unclesyd's comments:
Have you looked into a "push-pull" system; or rather a system that "blows" compressed air from a source across the work surface "into" a vacuum system tuned to pick up the same volume?
RE: vacuum hood design
You might look at a tapered tube design with a narrow slot in the side of the tube. Make the area of the tube equal to the sum of the area of the length of the slot.
You could put several of these across the pickup area if one by itself will not work. You would need a face velocity of at least 4000 fpm.
B.E.
RE: vacuum hood design
RE: vacuum hood design
Your only plausible option is to have a re-positionable duct that you can move around within the hood that places its inlet near your work piece. If the duct were something like 3" diameter, it would be much more manageable.
TTFN
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RE: vacuum hood design
1.What "capture velocity" do you you think you need to pick up this dust and move it into your hood? 100 feet/min?
500 feet/min?
2. How far away is the hood slot or nozzle from the most remote dust particle that you want to collect? One foot? Two feet? 3 inches?
If you can answer these questions, I can tell you the flow you need, assuming the hood is 5 feet long as you say.
You can achieve even distribution across the hood face with a properly designed hood plenum. The Industrial Ventilation Manual, published by the American Conference of Government Industrial Hygienists (ACGIH) describes how to do it.
Peter Ott
www.utieng.com
RE: vacuum hood design
RE: vacuum hood design
The downdraft table can be used as a working surface, or it can be placed under a section of conveyor that allows the debris to fall thru under the action of gravity plus the airflow of the table, depending upon your process and production volume.
RE: vacuum hood design
If not street sweeper then how about the attatchment on your vacuum/hoover at home with the bristles?
KENAT, probably the least qualified checker you'll ever meet...