Oversize Dust Collector? Oneida V System 3HP vs. 5HP

[Jerry Cummins]

In case anyone is interested. http://desmoines.craigslist.org/tls/3169810425.html

[Ben Martin]

In case anyone is interested. http://desmoines.craigslist.org/tls/3169810425.html

I do have family in Des Moines. Too big of a hassle to get it South though...

[Ryan Brucks]

just FYI that Clearvue indeed published fan curves for the 1800 and Max a few months ago.

http://www.clearvuecyclones.com/Bull...3&d=1337614552

of course we could easily launch into a full length discussion analyzing the different numbers. I have talked with them about the results and its clear that the MAX is well suited for lower pressure ranges. For some reason it's not really performing better at the higher pressures despite the larger impeller.

What I did was use the CV1800 body with the 16" impeller. Seems to be the best of both worlds if you aren't going to be under 7" WC (and pretty much everyone is going to be over 7" wc unless they have two 6" gates open). BillP told me that the 1800 has far better fine dust separation than the MAX and the only reason to consider the max is for under 7" wc.

I'm not sure what's going on, but I attribute it to the fact tradeoffs were made to get the higher theoretical MAX cfm. For one, (as BillP told me), if they were to optimize the MAX for the 16" impeller, it would have to be LARGER, too large to fit in the average 8' ceilings, so that was out. So instead compromises were made. The inlet was enlarged at the expense of making the tube connecting cyclone/blower smaller. I think this is to blame for the reduced fine dust separation capability (higher velocity air escaping the cyclone equals more chance of particles taking the trip).

I also wonder if it could merely be an artifact of testing procedures that won't reproduce in the real world.

For example, testing 6" and 8" pipe at the same SP makes little sense... in the real world you'd reduce SP by increasing duct size, but these tests all use the same length of pipe. So the 8" test needed a smaller restriction on the line to get the same SP... meaning they needlessly increased VOLUME... and that messes with pressure.

[ian maybury]

I didn't know they had published anything Ryan (i even checked a few weeks ago, but expected it to be in the information or education sections of the site) so I based my view on the Cincinatti Fan curve for a similar sized impeller. Which does perform significantly better.

There's something very odd about those curves, in that the 16in impeller performs no better than the 15in - worse actually. It's even down as doing better on a 6in pipe than the 16in does on an 8in. Not just in terms of pressure, but also CFM.

It was a couple of years ago, and there were no curves specific to it at the time - but Bill and the then owners steered me towards the 16in as having better performance all round.

There were problems with the older curves that CV had - something about the power supply not having been right.

It seems like there's something sub optimal about the design of the bigger impeller, or the use of it in the their housing - or somebody screwed up.

ian

[Ryan Brucks]

These are probably the same old curves that had problems. I asked James Bushey about them and he said they were done before the Busheys were involved....back under Ed Morgana (probably said that wrong).

He said they didn't want to release these and only did so because of the number of requests... And he said he kind of regrets publishing them.

It would help to see curves with the 16" impeller on the 1800 body and likewise curves with the Max and 15" impeller but that will probably never happen.

I agree the 16" impeller should give better cfm across the range... That's the main reason I went 1800/16 instead of just Max. I was just hoping for a slight improvement at higher sp.

[David Kumm]

Ryan, I've seen the curves too and while not perfect there isn't much info there. A 16" BI fan won't be much different from the Oneida 16" fan. The CV cyclone has a little less resistance but was engineered for 1200-1400 cfm. The larger impeller will create higher velocity at the inlet which will likely reduce the fine dust efficiency somewhat, particularly if the outlet is reduced but if running a sander and the port restricts the cfm is probably doesn't matter all that much. When I ran a 5 hp system with a 15" impeller with a 20" Torit I got pretty good dust separation. When I upgraded to a 7.5 hp with a 15.75x6.25 straight fan the cfm went to 1800-2200 with my 8" and 7" mains. That is a little fast for the cyclone so for fine dust I restrict it down until I can install a 24" Air Sentry i picked up for $200. If we could get the Busheys to manufacture some larger cyclones I think they would sell. The 8' ceiling restriction creates lots of design compromises. I sometimes think we should be looking at push through cyclones when installing in reduced height situations rather than using shorter cyclones and depending so much on the filters to do the work. Dave

[Chris Parks]

I have been told that the only reason the larger impeller was used was to increase flow at 2800 rpm and no other reason. The fact that the US uses it at 3400rpm most probably falls under the heading of bigger must be better.

[Michael W. Clark]

Hey Michael didn't I say the same thing in my post that it's easier to choke off the dust collection to a machine with and oversize collecter than it is to add and wish you had more suction with and under size unit!

Alan, yes you did and I said again in the post right above that and may have said it again earlier.

I was mostly commenting on the hood pressure concept. It probably was more confusing than helpful.

Mike

[Michael W. Clark]

I'm not sure what's going on, but I attribute it to the fact tradeoffs were made to get the higher theoretical MAX cfm. For one, (as BillP told me), if they were to optimize the MAX for the 16" impeller, it would have to be LARGER, too large to fit in the average 8' ceilings, so that was out. So instead compromises were made. The inlet was enlarged at the expense of making the tube connecting cyclone/blower smaller. I think this is to blame for the reduced fine dust separation capability (higher velocity air escaping the cyclone equals more chance of particles taking the trip).

I'm not familiar with these two cyclones like you and Ian are, but based on the conversation, I think you are correct.

If you want a cyclone to handle more flow and you simply enlarge the inlet, your efficiency will typically go down. The primary reason for this is that the residence time in the cyclone has been reduced. The hobby cyclones with round tangential inlets suffer due to the inlet being located so close to the outlet pipe. The industrial cyclones we provide do not use this type of inlet due to lower efficiency and increased wear on the outlet pipe. We use an inlet that wraps around the OD of the body (involute) and has a rectangular cross-section instead of round.

Generally speaking, if you reduce the size of the outlet pipe (diameter) the efficiency and pressure drop go up. There is a limit, if you reduce the outltet pipe diamter too much, the vortex is too strong and can re-entrain particulate. The length of the outlet pipe also has an effect on collection efficiency, too long is bad and too short is bad.

We have to admit, as critical as we are of all of the offerings, hobby cyclone suppliers are selling to a niche market. There are space constraints, power constraints, noise limits, and the largest constraint...sales price. Often, I read on here where someone ultimately chooses between supplier A and supplier B because there was a sale and one was $200 cheaper. We can't run a particle size distribution for that!

I still would like to see the hobby cyclone suppliers provide a performance curve for their equipment and it seems several are starting to attempt it. The other thing that would be most helpful is to provide guidance to the intended operating range for their systems. A cyclone designed for 1200 CFM is not going to be near as good at 750 CFM.

Mike

[Michael W. Clark]

It's meanwhile i suspect fairly unusual to run a fan all that much faster than 3,450RPM on a VFD - not because it's not possible mechanically, but because of noise.

Shout if you know better, but i'm guessing that if the Smart impeller was more than an inch or so smaller in diameter than say a 16in dia item run at 3,450RPM that it could struggle to do much better on pressure.

Put another way. Whether you achieve the tip speed through extra RPM or through extra diameter is it possibly the noise that sets the practical upper limit?

Anybody?

Hi Ian, not saying I know better, but there are some fan selection charts for small industrial fans at 5000+ RPM. Usually, the larger the fan, the lower the max speed. AMCA fans are also classed. The higher the class, the higher the maximum safe speed. I think it ultimately has to do with the mechanical design and integrity of the fan. I doubt a VFD would push a 3450 RPM motor to 5000 RPM, these are likely belt driven with a speed-up arrangement.

Twin City Fan - Radial Blades

Mike

[David Kumm]

For those interested I did put an anemometer on my mediocre 20 gal shop vac and got about 6500 fpm through a ten ft hose. My DC pulls about 8500 fpm through the same hose but I'm running a 7.5 hp pressure blower so I think it unlikely a 5 hp or less BI impeller will outperform a quality vac with a 2.25 hose. Dave

[Joe Jensen]

For those interested I did put an anemometer on my mediocre 20 gal shop vac and got about 6500 fpm through a ten ft hose. My DC pulls about 8500 fpm through the same hose but I'm running a 7.5 hp pressure blower so I think it unlikely a 5 hp or less BI impeller will outperform a quality vac with a 2.25 hose. Dave

Cool. I bought an anemometer for testing and I haven't tried the shop vac hose comparison. Everyone is asleep in the house now so I'll try to remember to do it Saturday.

[Ben Martin]

Well look what showed up today...



Now to figure out how to get it off the truck!

[J. Greg Jones]

Congrats Ben, it will be interesting to follow your experience with the installation. Yesterday I ordered a V-3000 and there is a lot of good information in this thread that helped me make my decision. Mine should be here in 3 weeks. Good luck!

[Ben Martin]

Greg,

Congrats!

Oneida failed to mention how absolutely massive the box would be, I was assuming that that cyclone would be laying down.

My truck has an 8' bed for reference, I expect that the box is at least 8' tall...

I am pretty close to having the lights up in my shop, after that a bit of conduit work and than I will be starting on the installation. I need to see if any of my neighbors has a fork lift!

Ben