Not just another dust collection system question....... VFD/flow related

[David Kumm]

I'm still thinking Larry will run it faster than 63% when using the machines anyway. that big Unitronex will need 2000 cfm to handle the dust. Big shapers with big cutters generate chips a mile away from the dust port so he will use more of that 10 hp than he thinks. Based on my experiments I'd guess 50 hz is about as low as he will go unless just cleaning the air like an ambient. The extra energy cost isn't as significant as the saving from the slow start available with the vfd. Dave

[Michael W. Clark]

I'm thinking the separation rate will drop at a fairly linear rate, and resistance will drop at an exponential rate, related to reductions in CFM.

Not trying to argue with you, I just don't think separation will suffer as badly as I think you might.

Hi Phil, I see where you are coming from, I didn't mean to come across argumentative. I apologize if I did.

I can't speak directly to Larry's cyclone, but I know most industrial cyclones really drop efficiency as the air flow drops. It is more exponential than linear. Typical design range is +/-10%, even on that difference, the efficiency can be very noticable and is usually stated at the different conditions for custom equipment. Air flow is just one variable, cyclone efficiency depends on a lot of variables.

I do industrial air pollution control equipment (including high efficiency cyclones) in my day job. I often have to think in terms of downstream loading instead of just cyclone collection efficiency. For example, if you have a cyclone that is 99% efficient (total collection by weight), you have 1% leaving the cyclone and going into the equipment downstream. If you increase the cyclone efficiency to 99.5%, you now have 0.5% leaving the cyclone. You have increased the cyclone efficiency only by 0.5% (which may take a lot more cyclone), but you have reduced the loading downstream by 50%. Vice versa, if you cut the efficiency down to 75% from 99%, you have increased the downstream loading 24X, all other things being constant, which we know they rarely are.

Larry, if you have any pictures, it would be interesting to see. Just the fan and motor sound like a steal for that price.

Mike

[Phil Thien]

Hi Phil, I see where you are coming from, I didn't mean to come across argumentative. I apologize if I did.

Oh no, you aren't at all.

But, if exponential increases in CFM are required for linear increases in fine-dust separation rates, then linear decreases in CFM shouldn't cause exponential drops in separation rates, should they?

Either way, I do agree that there are many factors. And I still think at the heart of it this is a one-man shop that will see occasional use. What would be a design failure for a commercial shop used 40+ hours a week may be hardly significant in a shop used a few hours every couple of days.

[Michael W. Clark]

It has to do with the efficiency curve of the cyclone and dust particle sizes. Do a google search for "cyclone fractional efficiency curve". The first and fourth images illustrate it very well. The large particles are easier, but the small particles are more difficult and require much more effort to collect. Getting the last 0.5% is more difficult than getting the first 0.5% because it is all fine particles.

I agree, for $250, hard to go wrong. You can also choke off the flow with a gate and get energy savings. It is not as good as with a drive and it is noisier, but would cut the flow and give you an idea if there are any issues if you are wanting to check it out before getting a drive. Me, I would want all the air I could get without over amping the fan, but I'm not paying the electric bill either.

Mike

[Phil Thien]

The large particles are easier, but the small particles are more difficult and require much more effort to collect. Getting the last 0.5% is more difficult than getting the first 0.5% because it is all fine particles.

Exactly. He will be giving-up the finest of the fines. Whether that is a problem depends I suppose on the tools he uses and the usage they see.

Running a 10-HP motor would only run about a dollar an hour (assuming $0.09/KwHr), wouldn't it? I mean if the entire point of this exercise is to save money I'd seriously consider how many hours I'd be running the unit and I'd just run it flat-out. Even if I was going to run the thing 40 hours/week, any savings from reducing the RPM may only save me $10-$15/week. I don't know what the VFD would cost but when you consider the cost of the drive and the work installing it and the unknowns in terms of separation, it seems like a lot of screwing around for $10-$15/week (if run 40 hours/week). And if you're running 5-10 hours a week the payback for the VFD isn't going to come very quickly.

[Larry Edgerton]

Interesting points. Keep in mind that the primary reason for the VFD conversion would be so I can run the dust collector without the converter. About half of my tools are single phase, so I can work quite a bit without having to run the converter. Being able to slow it down is just a bonus.I am not dead set on any particular RPM, as Dave has said, I will just adjust it till it works. I have no idea about what this system generates for flow as there is no tags on it. It is a nicely made unit, obviously professionally built, but as far as CFM, have no clue. Michael, I will get some pictures and better measurements this weekend. I assume that I will have to keep a minimum of open ports to keep the flow up with this system and would be interested to hear what you have to say on that matter. Again, I will get a list of dimensions.

I have been reading on VFD's and it is a confusing subject as so many of them are integrated into automation and have features that I do not need. I wish I was more into it but I have a hard time concentrating after a couple of hours, just does not interest me. Electrical systems at this level are a profession on their own, and at some point I will have to get some help but am trying to learn more before I get some help in here. I was reading on a couple of factory maintenance forums, and wow! There are so many terms that I do not know what they mean that I am soon lost. I'm just trying to get smart enough to ask the right questions. I know a couple of guys that work on this kind of stuff but they work for oil companies and are not budget minded I guess you could say. They can easily come up with solutions that I can not afford. Easiest solution would be to have three phase power brought in but that is $37k. I just had a 400 amp service put in but the closest three phase is two miles away.

Gotta get to work, Larry

[David Kumm]

Keep in mind that on a large vfd you will find 3 phase input models rather than single phase input. Almost all will run on single phase with two of the three inputs wired up. The vfd needs to be close to twice the size or rated for 1.5-2X the input amps ie a 45 amp input- 42 amp output would be needed to run your 25 amp motor or close. I think the ratio is 1.73-1 or in my simple world 2-1. Dave

[Michael W. Clark]

I thought energy was the primary concern from quote in the post. The least expensive way would be a rotary converter to get the fan going. I assume the fan is 220V 3ph? If it is 480V/3ph, then you will need a transformer or VFD. (I think a VFD would do that?)

If you have enough equipment to require a 400A service, the energy cost/savings may not be noticeable as Phil suggests.

If your baghouse doesn't already have it, put a differential pressure gauge or switch on it. Monitor the pressrue drop. At the end of the day, it doesn't matter what the cyclone does, its only function is to reduce loading to the baghouse and reduced cleaning cycles to save filter life. Too much loading could plug the filter and make it where it cannot clean itself effectively (I assume it is automatic cleaning, pulse jet or shaker). With the pressure gauge, you would know you had a problem. The high pressure drop across the baghouse will reduce air flow, but if you run it continuously for a long time, the high filter velocity will blind the bags and they will have to be replaced.

[Ryan Mooney]

How does this look?

http://www.factorymation.com/Product...0-2010-N1.html

Like it probably won't work..

TECO MA7200 AC Drive, 10 HP, 230V 3 PH Input, 230V 3 PH Output, 32FLA, NEMA 1

Hmm.. Davids point about the larger ones mostly having 3PH input is a possible concern.. I did find a couple on ebay that took single phase so they're out there - I didn't see any at factorymation in the 10hp range in single phase input..

[Larry Edgerton]

Keep in mind that on a large vfd you will find 3 phase input models rather than single phase input. Almost all will run on single phase with two of the three inputs wired up. The vfd needs to be close to twice the size or rated for 1.5-2X the input amps ie a 45 amp input- 42 amp output would be needed to run your 25 amp motor or close. I think the ratio is 1.73-1 or in my simple world 2-1. Dave

Looking at my notes that is the exact number the tech at Factorymation gave me Dave, and I rounded up to 20hp myself. So your memory is still intact.

Ryan, They don't really say you can do it in the web site for some reason but it can be done using a bigger, and more expensive unit. So I'm told.

Michael, Cutting down on energy would be great but is not an absolute. I do have a friend who works for a REA that told me to be prepared for large increases in electrical energy costs in the next two to three years and that is in the back of my mind I must admit. I will dial it down till it stops doing its job.

The 400 amp service is more than I need, now, but who can predict the future? I may buy another wide belt down the road. And, I like overkill.

The baghouse is trash. There is enough there that I can hang the bags and see how it works, and use that information to design and to weld up another one to suite my needs. There is nothing there for cleaning, that is something I will have to invent and build at a later date. I just need to get this thing up and working so I can move into my larger shop. I need to do some more research. Eventually I would like the both the hopper under the cyclone and the hopper under the bags to be able to be emptied from the outside with my tractor. For the bags I am picturing a sealed box at the bottom that the bags clamp to, and a sealed drawer that opens from the outside to empty it. Any leaks will be to the outside that way to my way of thinking. I'm thinking big drawers basically that I can clip to the quick change on the tractor and dump. I appreciate your input, and if you know of any good reading for a lay person by all means shout it out. I read all of Bill Pentz's writings but his is more on small scale setups and cyclone design, which is already carved in stone in my case.

Keeping heating cost down is also a consideration as I am above the 45th parallel. My last shop got up to about $2000 on a bad month and this shop/home complex is all about low overhead.

On the minimum flow thing. I was thinking that I could run a duct to a overhead ambient air filter instead of just wasting spent energy in the times I do not need all the CFM this thing has to offer. Am I correct in thinking that choking this big a collector down to say one 5 inch when running said machine would be a bad thing for cyclone efficiency and motor life?

Dinners done, Larry

[Michael W. Clark]

Hi Larry, post some pictures when you get a chance. Unless the bag house is rotten or eroded away, it can probably be repaired if you are handy with a welder and metal fabrication. Even if you only have a functional cyclone and fan for $250, it's still more than gloat worthy.

[Larry Edgerton]

I have some pictures but have to figure out how to get them out of Windows 8. Hate Win 8.......

I had a memory fault, the impeller is about 18", the impeller housing is roughly 26"average by 9" deep. The main body is 24"wide by 22" long. The cone is 22" at the top to 12" at the bottom and 30" long. Intake is 7"x14", exhaust is 9"x12". Bag house had 4-14"x10' bags. When I shoved a camera up the center tube and snapped a picture it appears that the impeller is built like an impeller in a turbocharger rather than simple straight blades.


I welded up a new plenum for the exhaust, the old one had been run over by something.

I'll get my wife on the picture thing, I have not been able to post pictures since I bought this PC. I miss Win 98.

Gotta get to work.....Larry

[Rick Fisher]

Hey Larry ..

I was at the Vegas woodworking show.. I think I was at the Baldor booth but either way, it was a Baldor Gold motor. It was about a 5hp motor and they had it on a dial, connected to a VFD. The motor was turning so slow you could see the shaft turn.. I am talking 100 rpm.

I played with it a bit and then spoke to the fella at the booth. I asked him if the motor was at risk for overheating. He said nope. He explained that these motors where much more durable than people thought. He said the load would cause more heat than the RPM .. I was puzzled.

I always heard that slowing the motor too much caused it to overheat. This fella said otherwise and his proof was on display.

He then told me that to actually overheat that motor, the outside casing would be so hot you couldn't touch it and the motor would still be fine. He explained the difference between work related heat and over-current or shorting.. Anyway .. it was impressive ..

I think you should go Phase Perfect but that the Air Compressor and dust collector should be run on VFD's so they don't hog Phase Perfect electricity .. 10Hp is a massive dust collector .. Good for you.

[Ryan Mooney]

Ryan, They don't really say you can do it in the web site for some reason but it can be done using a bigger, and more expensive unit. So I'm told.

Hrm, I can't find any wiring instructions for running the TECO drives at single phase with current derating although its certainly plausible that you can. Doing the bogo math I'm seeing you need something like a 60a input circuit to run the 10HP motor off of single phase input so something more like the 20HP drive would be needed (its 64a input which is the closest they have): http://www.factorymation.com/Product...0-2020-N1.html You might be able to get away with the 15HP drive if you were 100% certain you'd never run anywhere near full load (again using napkin bogo math but I think that comes out to around 85% of peak so around 51hz +- what I'm sure are huge errors on my part).

If you do end up wiring one up like that I'll certainly be interested to hear how it goes.

[Larry Edgerton]

Rick, you have had that Phase Perfect for a while now, still doing its job with no issues? From what I have been able to find out VFD's run at either end of the scale do in fact cause heat buildup, and on an old motor [Like mine] it can be an issue. What is different is that motors are made with that in mind now and have better materials and vastly better insulation on wires and so forth. Some motors will say"VFD compatible" or some similar phase. This is related to heat. I have no doubt that the motor in question will not be a problem, but I don't think he told you the whole story. Baldor is making VFD's now.

Ryan, I called Factorymation and talked to a tech for a while, that is where I got that information. And in ads such as this they make reference to it. http://www.ebay.com/itm/Hitachi-WJ20...-/231027875515 What has me concerned is that it is sellers making these claims and not manufacturers. I can find no reference by a VFD manufacturer that this can be done so I am wondering? If this is a real possibility with no drawbacks wouldn't a manufacturer want to increase sales and advertise as such? I do not trust salesmen any farther than I can throw them, and have not even found a link to one working in this manner. I have a small VFD doing this but it was sold that way, in the spec sheet. Maybe they just figure that anyone that is running this big of a motor would have three phase, and I'm sure most are.

So.... with the fact that I have to double the size, and basically double the cost I am rethinking running machines on VFDs instead of a converter. If I find that it is approved and warrenty is still in effect, well then maybe. But the cost savings disappeared with that little tidbit of information. I still want to run the Dust collector on a VFD but will have to think about a Phase Perfect. I thought by now Phase Perfect would have some competition and prices would be coming down, but does not seem to be the case.

Larry