Dust Collector too small (HP) and locating in garage create dust on cars?

[David Kumm]

Todd, how could you do that. We were still arguing about whether it would work. The Oneida smart has a vfd with software that adjusts the airflow to compensate so in effect it speeds up the motor if needed. You can get that by buying a three phase motor and running it a vfd. A change of 3hz increases or decreases my airflow by about 13%. It isn't a bad option if you find a good used Torit, Dustvent, or Sternvent 3-5 hp system which tend to be three phase. For your application the Oneida hi vac 5 hp is overkill and the regular 5 might be as well. On the other hand the 5 hp motor will run on less amps if the ducting restricts it so you aren't wasting all that much energy. I like the steel in the Oneida but the clearvue cyclone design is more efficient at fine dust separation. In fact that cyclone was developed primarily for the fine dust so it excells at that. If I were buying the clearvue I would buy the Max cyclone for $200 more to get the 8" inlet and then reduce to what made sense. If you decide to add a drum sander or bigger shaper down the road you will only need to swap out the main line. Having said all of that I have a Torit 20-5 cyclone with an Oneida stand alone blower-5hp three phase and run it off a vfd. That is more than you need but I have less $ in it than what a new Oneida 2000 would cost, and I still have the original Torit blower and motor as a backup. Dave

[ray hampton]

I do not wish to HiJack this post but how can we compare the furnace with its 12x6 duct work to this business of dust collector ? if the dust collector duct work were 12x6 " how big motor will you need

[ian maybury]

Far be it from me to question makers curves either Rod (says he), and it's clear from what you and others have said that the unit works well over shorter ducting runs. But as I posted before I'd love to hear why it is that the curve seems to say it manages to move more air on 2HP through a filter and a cyclone than probably similar stand alone fans from another respected manufacturer.

My guess as before Todd is that hooking smaller ducting to a somewhat larger cyclone inlet won't have any significant downside in terms of system performance, and may actually help the cyclone (if it's a shortish one) by reducing the inlet velocity a little. i.e. the ducting will determine most of the pressure drop. Going the other direction the opposite would likely be true though.

The good news about these big units is that by and large they are much more tolerant of small increases in pressure drop.

A VFD can be a very real advantage if it's set up the right way - it costs a bit, but it offers the possibility of controlling the start up current, less wear and tear on frequently started motors, easy remote control using low cost commercially available key fob operated radio switches with low power relays - and of course speed control to adjust CFM and pressure output. It probably depends to a degree on the installation, but upping the fan RPM to get more pressure (for restrictive tools) is only an option up to a point due to mechanical limitations and increased noise. Dropping a little can make a big difference to noise with no obvious effect on dust collection.

How useful the extra pressure the higher RPM gives might be (bear in mind that a 15 or 16in impeller is still already moving decent quantities of air to 15in WG or a bit more) depends on how high the fan goes vs likely needs - it's unlikely to get even close to vacuum levels. I'd want to check if buying a commercially supplied unit with a built in VFD that it didn't have built in limitations to what you can do with it - it's not as an alternative very hard to buy a freely re-programmable and full feature VFD yourself and fit it to whatever system you want.

The big difference between ventilation and dust collection Ray (which I guess you know) is that in dust collection we need to maintain a high enough air speed in the duct to give reliable transportation - around 4,000ft/min. This will sharply drop the CFM available from most low pressure fans. It's as before possible to persuade a smaller fan to punch above it's weight by running larger ducting, but then it becomes a question of how far can you safely shade it in dropping below the recommended 4,000ft/min number. Most smaller dust systems end up running at lower air speeds than is ideal...

The other factor I'd want to look at if buying a larger commercial cyclone is its shape. None of them seem to publish good data on their fine dust retention capability, but as David has said there are some longer/taller units about that seem to more closely mirror industrial practice, and other more squat ones. It's hard to know if this is significant, but it's hard to think that the industrial units are not the way they are for a reason...

ian

[David Kumm]

Hi Ian. It's tough to figure out the curve numbers with any consistency. The 5 hp belt driven straight fan curve on the Oneida site tops out at less SP than the entire 5 hp system curve for their 2000. The difference in blowers might account for it but the fan curve shows a max of 10 sp and the DD system curve goes over 12" before adding the cyclone that runs about 3". The chart says the readings are without filters but the numbers are the same as the cfm with filters posted. As to cyclone design it seems that most hobby units are sized to fit under an 8' ceiling and that limits the effectiveness in fine dust removal. I think that is one reason the clearvue uses an 18" diameter for their systems as the relationship between the cone length and diameter seems to be key. The problem in fabricating the smaller diameter with a bigger unit is the need then to convert the 8" inlet to a rectangular shape about 13" x 4" to maintain the area but keep the flow against the outer wall and between it and the inner neutral vane. cyclones with a round or square intake need to be larger diameter to avoid the turbulence created if the air flows directly against the vane. That in turn means the cone must be proportionaely shorter and separation suffers. How much I don't know because it takes a lot smarter guy than me to figure it out. Dave

[Ole Anderson]

Speaking of fan curves, could someone please post or link the data for the 5 hp CV cylcone?

[ian maybury]

There sure doesn't seem to be a lot of consistency in test methods David, or comparability of test numbers. It's as you say why it's a bit risky to sail too close to the wind in estimating CFM and pressure drops without being able to draw on experience of a very similar installation. Add in that there's a shortage of pressure drop info on filters and cyclones and it gets even less precise. I've a suspicion too that there's possibly a trade off like what you say - but likewise rely on hearsay.

One of the issues Ole with the 16in Clear Vue fan is that there isn't a curve published for it. (at least not that I've seen) I've encouraged the new owners to get the necessary testing done and publish the data. Likewise on the retention performance of their cyclone. It seems a pity that it hasn't been done, in that if the cyclone actually does perform better than the shorties it's a pity not to be in a position to be able to quantify it.

None of the cyclone makers seem to do so. Perhaps it's because it risks creating a hostage to fortune in circumstances where the type of dust, conditions of use and nature of installations are not well controlled. I've a feeling too that minor variations in the set up can have significant effects when the issue is the dropping out of very fine dusts which are right at the limits of cyclone capability. The industrial manufacturers seem to (?) do it on an application specific basis - starting with a particle size count and other analysis of a sample of your dust.

David has made the point before that it'd make sense to use a credible and independent third party test house, in that it should strip out the 'you would say that, wouldn't you' perception from the situation.

I've relied on Bill Pentz's numbers, and on the curves for similar size and RPM fans published by Cincinatti fan - they seem to correspond pretty closely. The cyclone is reportedly based on a well proven industrial model (he mentions the source somewhere), it's longish proportions are certainly pretty similar to those done by some of the industrial suppliers for use on fine dusts.

ian

[Michael W. Clark]

Todd,
FYI, if you have 45' of straight duct, 360 degrees of elbows, and pull 1000 CFM through a 6" duct, you will need about 5"wg at the cyclone inlet. I'm like others, I find it hard to believe that the Oneida unit can develop 6"wg SP at the cyclone inlet with only a 2HP motor. If you need 5" SP at the cyclone inlet, and you need another 5"DP for the cylone, filter, and ducting between, you will need at least a 3HP motor and then you are probably into the safety factor of it (I get 3.14 BHP at 50% efficiency).

Have you looked at the Grizzly cyclone units? They are also all metal construction and look to have a good L/D ratio (tall and skinny).

If the CV is getting the small dust, it will also do better on the big dust as long as the cone discharge and inlet arrangement does not create a plugging concern for large chips.

There was a mention earlier on this thread about energy consumption. If you go David's route and locate the fan after a good cyclone, you may be able to use a more efficient fan. A BI (backward inclined) fan wheel will deliver more CFM at less HP than the Radial fan wheel types. The BI fan cannot handle large chunks of material without damage, but if its after the cyclone this shouldn't be an issue. It will be handling some particulate after the cyclone, but it is doubtful that you will use it enough as a hobbiest to errode the fan wheel. For example, if you use a BI fan at 70% efficiency, you only need 2.3 BHP at the flow and loss conditions above, so a 3HP would work.

David, I am still not familiar with the "nuetral vane". I looked at the Pentz site and it looks like an extension of inlet to get the airstream past the outlet pipe. This is probably necessary on the tangential inlet style of the hobby cyclones. Otherwise, you would errode the outlet pipe and could get some "short-circuiting" of the inlet air straight into the outlet pipe. The industrial cyclones I'm familiar with have involute inlets where the inside of the inlet is actually on the OD of the cyclone body.

I think the smart Oneida system is some type of HP control using a VFD. I think the fan speed changes to maximize current draw. Thus, you would always have the maximum suction available at the flow being delivered. They probably have a larger fan than the motor can handle under normal circumstances (dust collection). They can then increase speed under low volume conditions (floor vacuuming) and increas the SP. Not sure, I saw this before and was curious how it worked. This is a common concept used on hydraulic pumps where you need power under load (low flow and high pressure), and a quick return under no load (high flow and low pressure).

Mike

[Todd Brewer]

Todd,

Have you looked at the Grizzly cyclone units? They are also all metal construction and look to have a good L/D ratio (tall and skinny).

Mike

Mike, thanks for the tip. I just checked out the Grizzly's. From what I'm reading, I don't think I will get anything other than a 5 HP.

For the price of the 5HP Grizzly I would spend a few hundred more to get the Oneida Smart Pro, or spend a lot less and get the Clear Vue.

Fascinated by this discussion, wish I understood 1/2 of it.

[David Kumm]

Mike, thanks for the tip. I just checked out the Grizzly's. From what I'm reading, I don't think I will get anything other than a 5 HP.

For the price of the 5HP Grizzly I would spend a few hundred more to get the Oneida Smart Pro, or spend a lot less and get the Clear Vue.

Fascinated by this discussion, wish I understood 1/2 of it.

Cyclone design is pretty similar to Oneida and Pennstate. Downside would be the motor and perhaps the filter material. Dave

[Rod Sheridan]

Rod, I see what you are saying. The Oneida system curves are supposed to have taken the cyclone and filters into account so when they show 730 cfm at about 7+" they are only speaking of the duct and flex loss. My mistake. I do have some suspicion however about those system curves as they have always seemed in line with the Cincinnatti fan curve data which led me to believe - evidently in error- that you had to add the cyclone and filter pressure to the totals. I went on the CF direct drive backward inclined fan table and could find a bunch of 12" diameter fans that provided 800 cfm at 7" at 2hp but could find none that came even close at 10-11". The ratings at 2" on the CF table seemed similar to the Oneida system ratings at 2.3" which to be comparable should be about 5" on the fan rating chart.

Rod, I'm agreeing that you were using the Oneida tables correctly but I'm going to look more at the numbers. Pentz always argued that the DC companies juiced their ratings by running the motors over amperage and using larger particle filters. I always discounted that analysis but there is something that needs more explination. Dave

Hi, having installed and measured the airflow on two different Oneida models, I found their curves to be accurate.

I was extremely impressed with the sophisticated blade shape on the impeller, it has a changing radius and profile, something I haven't seen on other impellers.

The better the fan efficiency, the less power it needs to produce the same airflow and pressures. In my opinion you really are getting a better designed machine for your money...........regards, Rod.

[Michael W. Clark]

Oneida must have a BI wheel and a low DP cyclone design to get the performance.

[ian maybury]

That's interesting Rod. There's certainly scope for a lot more output from a 2HP fan if the impeller is significantly more efficient - the typical item is only about 40% it seems.

ian

[Rod Sheridan]

Oneida must have a BI wheel and a low DP cyclone design to get the performance.

Hi, the wheel is backward inclined..............Rod.

[Michael W. Clark]

Hi, the wheel is backward inclined..............Rod.

So you have 70%+ efficiency instead of 40%, makes a difference.

[David Kumm]

Thanks, Rod. I knew the Oneida fans were BI because I use one on my system but didn't give them credit for that kind of increase in efficiency. Makes me think that when I get less busy I need to put my straight blade Torit fan in the housing and try to measure the difference. The cfm at higher resistence is the issue. The Oneida 5 hp system curve looks to be much closer to my expectations than did the 2 hp one. It would be really helpful to know all the companies test. What length of input pipe, type of filters, and amp draw at various cfm and sp. Might only be interesting to me. Dave