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On a Dust Collector what about placing impeller before cyclone?

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Forum topic by WoodNSawdust posted 06-28-2015 09:58 PM 970 views 0 times favorited 17 replies Add to Favorites Watch
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WoodNSawdust

1417 posts in 643 days


06-28-2015 09:58 PM

Topic tags/keywords: dust collection super dust deputy wynn filter

From what I read adding a cyclone before the impeller decreases efficiency (cfm or suction?).

If the goal is to maximize dust collection and keep it out of the pleated filter (wynn nano filter) what would happen if I placed the impeller first and fed the output of the impeller into the input of the cyclone?

My equipment:
Harbor Freight 2HP dust collector
Oneida Super Dust Deputy cyclone
Wynn nano filter
30 gal metal trash can.

-- "I love it when a plan comes together" John "Hannibal" Smith


17 replies so far

View jerryminer's profile

jerryminer

528 posts in 908 days


#1 posted 06-28-2015 10:27 PM


.... what would happen if I placed the impeller first …..

The hard chunks that you want to drop out in the cyclone would hit the impeller instead

View bbasiaga's profile

bbasiaga

757 posts in 1462 days


#2 posted 06-28-2015 11:36 PM

The pressure drop of the Wynn filters is reported to be less than that of the original bag filter. So by replacing that bag you have pushed your fan farther out on the curve. Some think too far, meaning it will move more air than the motor is rated for, lowering the motor life. I have not tested either of these things myself as the fan curves (if they even exist) are not widely published.

Still, a common recommendation is to put a blast gate somewhere in the system and trim back the air flow to within spec for the machine. i have done that. The cyclone is a low pressure drop device, but it could serve some of that same purpose. I also put the Woodcraft version of the garabage can lid Thiene baffle before the blower. The motor runs without overheating, and i get reasonable dust collection. My portable contractor type TS is open in a lot of places, as is my Kreg benchtop router table. Collection is not good from either.

It works great from my jointer and planer, and has a noticeable impact on the bandsaw (which I thought was going to be the worst one but it is not).

Cyclones are relatively low pressure drop devices. And depending on how the fan is designed it may not matter much from a performance standpoint if it is in front of or behind the impeller. So In your shoes i would try it where it will protect the impeller and see if you get satisfactory results. If you dont like it, try it after the impeller and see if there is any difference. it would be a good experiment. You could further benchmark back to a system without the cyclone and see if that makes any differene.

But you’ll have options either way.
-Brian

-- Part of engineering is to know when to put your calculator down and pick up your tools.

View Kelly's profile

Kelly

1114 posts in 2411 days


#3 posted 06-29-2015 03:34 AM

I’d stop with the fact the cyclone protects the impeller.

View exelectrician's profile

exelectrician

2327 posts in 1894 days


#4 posted 06-29-2015 06:49 AM

Feed chunks of wood into your impeller and see and hear what happens… Learn by doing…

-- Love thy neighbour as thyself

View JeffP's profile

JeffP

573 posts in 858 days


#5 posted 06-29-2015 10:43 AM

Moving a restriction around in a closed system does NOT remove it from the system.

While, as stated elsewhere, the cyclone does not have anywhere near as much CFM reduction potential as a filter bag or similar…it does have some.

Where that reduction sits between the beginning of the system (where the DC hooks to a tool), along the length of the hose/pipe, just before the impeller, just after the impeller, right before the air escapes back into the wild…no difference at all.

A restriction at the very exit will make just as much of a difference in the air flow as the same type of restriction at the very beginning (or anywhere in between).

-- Last week I finally got my $*i# together. Unfortunately, it was in my shop, so I will probably never find it again.

View Fred Hargis's profile

Fred Hargis

3949 posts in 1960 days


#6 posted 06-29-2015 10:51 AM

Everything above…..your trying to invent something that has already been tried.

-- Our village hasn't lost it's idiot, he was elected to congress.

View crank49's profile

crank49

3981 posts in 2437 days


#7 posted 06-29-2015 01:26 PM

Makes no difference in efficiency if the fan is before the cyclone or after the cyclone. BUT, as already pointed out, the cyclone before the fan gives the chunks a chance to drop out of the flow before they get to the fan.There are simpler ways to accomplish this, but the cyclone would be a way.

If you put the fan impeller on top of the cyclone with the shaft vertical, a popular arrangement, be absolutely sure the fan rotation is the same as the spin of the vortex inside the cyclone. Getting this backwards will kill the efficiency, reduce the flow, reduce the static pressure and everything.

The addition of a cyclone to a good filter is a total waste of time, energy, and money, but if thats what you want, go for it.

-- Michael: Hillary has a long list of accomplishments, though most DAs would refer to them as felonies.

View josephf's profile

josephf

125 posts in 1563 days


#8 posted 06-29-2015 01:45 PM



The addition of a cyclone to a good filter is a total waste of time, energy, and money, but if thats what you want, go for it.

- crank49


I really must be reading something wrong here . the point of having the cyclone would be to keep from having to dirty up the filter and cut airflow .

View Fred Hargis's profile

Fred Hargis

3949 posts in 1960 days


#9 posted 06-29-2015 01:51 PM


I really must be reading something wrong here . the point of having the cyclone would be to keep from having to dirty up the filter and cut airflow .

- josephf

Yep, works well if the cyclone is properly built and keeps the fines out of the filter.

-- Our village hasn't lost it's idiot, he was elected to congress.

View gtbuzz's profile

gtbuzz

427 posts in 1908 days


#10 posted 06-29-2015 02:02 PM

As other people have already pointed out, moving it after the impeller doesn’t change anything really. You’re just increasing the back pressure.

I did it in a previous dust collector because it helped me keep the footprint smaller, but the big risk is that your impeller is unprotected. Accidentally sucked one jar of Shellawax one day while cleaning, and the next day I was converting it so the separator came before the impeller.

View crank49's profile

crank49

3981 posts in 2437 days


#11 posted 06-29-2015 03:19 PM

High efficiency cyclones that could catch finer particles exist, but require much more horsepower to operate than a comparable filter. High efficiency cyclones have pressure drops of over 10 inches static. Increasing pressure requires 3 times more horsepower than increasing volume.

Normal low to medium efficiency woodworking cyclones only catch larger particles.
The fine particulate still goes to the filter.
Fine particulate is what gets into the pores of the filter and cause blinding.
The proper way to avoid this is to increase the surface area of the filter media which reduces the velocity if the particles so they don’t get embedded into the pores in the first place.
Trying to capture the fine particles with a cyclone before they get to the filter is redundant and just adds to the operating cost.

There are several ways to capture air borne dust particles. Expansion chambers and drop out boxes, belt filters, pad filters, bag filters, cartridge filters, low medium and high efficiency cyclones, wet scrubbers, electrostatic participators and probably more. Each method has advantages and dis-advantages.

Cyclones are mostly used in industry when a filter won’t work because of sticky or hot dust. Grinding dust with sparks is a good example of a cyclone application.

In the case of low efficiency cyclones, low cost is a factor. A low pressure drop cyclone will have low efficiency, low building cost and low operating cost and is acceptable when dealing with non-hazardus dust. A high pressure drop cyclone will have high efficiency, be expensive to build and have high energy cost to run.

Cartridge filters are the best at capturing fine dust but are susceptible to catching fire in industrial settings because of the paper filter media. They are difficult to clean sometimes, depending on the dust type.

Bag filters are cheap, can have low pressure drop for low operating cost, but need a lot of surface area. A bag filter with performance comparable to a cartridge filter would require about 5 times the volume.

-- Michael: Hillary has a long list of accomplishments, though most DAs would refer to them as felonies.

View josephf's profile

josephf

125 posts in 1563 days


#12 posted 06-29-2015 04:51 PM

Crank 49 you maybe right that cyclones drop effeciency but filters seem to drop effeciency alot more .sure if you need a filter use the largest you can . i don’t ,both of my DC direct vent now. there is sense that i get from your writing that a cyclone is waist on a small DC .My experience has been extremely postitive ,i have never felt any less suction from adding a cyclone [big improvement direct venting ] .Besides two shall dc with cyclones i have 3 on vacuums . they have been very successful for me .

View Fred Hargis's profile

Fred Hargis

3949 posts in 1960 days


#13 posted 06-29-2015 05:33 PM

Cyclones do put a huge drag on the system, more so than filters unless they are really clogged. That’s why most of them have larger motors/impellers than a SS that moves the same air. They can also have a more efficient impeller design than a SS (which helps that larger motor/impeller thing) since they only have to worry about moving air, not be hit by debris. But they also have to have that tremendous air flow to do their separation, if they are choked down it just doesn’t work as well. I was in a shop last week where they guy took his Tempest cyclone and hooked it to 4” PVC to the tools. Something like that makes it work worse that it will otherwise. No doubt direct venting would be the cat’s arse….I’d sure do it if I could. But I don’t consider a cyclone a waste, though I do think they have to be considered of the overall scheme of what the owner may want in performance and budget.

-- Our village hasn't lost it's idiot, he was elected to congress.

View rwe2156's profile

rwe2156

2198 posts in 947 days


#14 posted 06-29-2015 07:14 PM

I thought a cyclone need negative pressure to work?

-- Everything is a prototype thats why its one of a kind!!

View BasementShop's profile

BasementShop

69 posts in 767 days


#15 posted 06-29-2015 07:35 PM

I built a dust separator and put it in front of my shop vacuum. The amount of dust getting to the filter on the shop vac was substantially reduced—the filter in my shop vac only gets dirty when I forget to empty the catch bucket under the separator—and the ability to vacuum wasn’t diminished “that much.” My shop is in basement and the shop vac is unaltered.

The dust separator is made from 2 buckets. The top bucket was cut so as to be about 1/3 its normal height (from the top so it would nest into the second bucket that catches the dust) with a side entry and a top exhaust back to the shop vac through the lid. The dust stream swirls around the circumference and drops chunks to dust into the catching bucket underneath.

I glued the bottom of the cut bucket to the top of the cut bucket with cuts around about half of the circumference. The difficult part is cutting in the entry port for it in the side of the cut bucket.

I put the dust collector on a little ‘cart’ with caster wheels and pull it across the shop to vacuum up at the lathe and to attach to the miter saw, table saw, and jointer /planer. I use it whenever I dry vacuum and can remove the hoses easily to convert for wet vacuuming should I ever need it to.

I envy those of you with larger shops and more hefty dust collection systems…

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