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

  1. #16
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    Ole, you are correct with your system numbers but the problem is that at over 8" SP the flow drops like a rock. Given the resistence of the cyclone, the filters as they fill given the surface area, the long runs with 270 to 360 degrees of bend, the flex at the end, you might be lucky to to stay at 8". If the real world ends up with SP of 10 or 11 you are dead in the water and have no plan B other than sell a used unit. Given that Todd has taken some hit already he might want to hook it up and measure the cfm but if it turns out all he can get is 500-750 he will have spent a lot for pretty crappy results. My experience with the cfm requiements of most machines is that they are low as well. almost all will benefit from 5000-6000 fpm. Dave

  2. #17
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    I had a look at O's curve that you linked too Ole, and not being an expert perhaps am missing something - but as earlier don't understand how it's possible to get 785CFM at 8in WG with 2HP. Or the 1,349CFM at 2.3in WG the same curve mentions. Especially when that's presumably for the as delivered 2HP system - the fan, cyclone and filter combined and tested as a unit.

    I'm more used to working with Cincinatti Fan's model SPB fan series data as representative of typical dust system fan performance - which so far as I know is for the fan on it's own in a stock test set up.

    As before the highest CFM they list at 2HP for any sort of 6in inlet fan is 1,108CFM at 1in WG - this is for a 12x2 7/8 in impeller. That's such a low pressure as to be almost useless for our purposes (i.e. upping the pressure drop to a useful number will drop the CFM so much that it's an irrelevant number), and despite a lower CFM than the above being claimed does not include the additional pressure drop of a cyclone and filters.

    It's not clear exactly what size of impeller O use, but it's a fairly conventional BC radial judging by the picture. It's just possible that there is something different about it, but all being equal Cincinatti don't seem to list any impeller size that does better than the 1,108CFM at 1in WG and 2HP mentioned before.

    You're right that the pressure drops for everything will fall away rapidly as the CFM drops.

    The 5in WG/100ft of duct run Cincinatti list for 6in steel ducting at 4,000CFM for example (but you have to extrapolate from published data to get to this because it's outside of any normal operating range) drops away to perhaps 1.5 to 2in WG at 350CFM.

    The pressure drops created by the cyclone and filter will presumably drop accordingly (I've seen no published data), with the result that by the time the whole lot is totalled and something is allowed for entry and exhaust losses you might hope to get away with something like 5 or 6in WG - even with the sort of pretty long runs Todd's number suggest.

    There's several major problems at that though as already pointed out. First as David fingered straight away the seemingly respectable approaching 400CFM this gives at 8in WG (which number gives some cushion) has (according to Cincinatti) dropped to a pretty useless less than 200CFM by 9in WG.

    Secondly this 380CFM amounts to only 1,900ft/min in a 6in duct which seems unlikely to give reliable transportation of anything except very fine and light dust in small quantities. The duct diameter is in essence too large for a 2HP fan to drive it properly over the sort of distance Todd mentioned.

    Finally there's at best only a minimal cushion in there for duct leakage/misalignments, unexpectedly high duct losses due to factors like machine hoods/extra bends, and most importantly of all filter blinding. (HEPA flters may increase their pressure drop by up to x4 over their life) If it works it'll just about manage basic chip collection, and a minor step up in pressure drop may kill even that.

    The bottom line if all of this is true is that a 2HP ducted cyclone system is at best going to be unreliable and pretty unpredictable (at the level of accuracy of this discussion) in its performance on long ducting runs like this - although the situation would improve significantly if the ducts were kept short and the pressure drop very low.

    Anyway... that's just one view. We each decide what we do.

    ian
    Last edited by ian maybury; 03-17-2012 at 6:36 PM.

  3. #18
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    My concern here is that you are using incorrect assumptions to in effect say that a 2 hp cyclone just won't work and that is simply not true. Ask most anyone with a 2 hp cyclone from most any manufacturer if they are generally satisfied with the performance and you will get a resounding yes, with maybe a few wishing for more horsepower simply because that is what guys do. But in these days of energy conservation, saying that you must have a 5 hp DC or you are wasting your time is not the kind of direction we should be going.

    You seem to ignore specific fan curves based on empirical data in favor of looking at curves from Cincinnati Fan. I can't explain the difference, but to dismiss the data provided by the manufacturers and independent test groups is almost suggesting a conspiracy.

    By the way, my 2 hp cyclone, the yellow one, will move offcuts nearly 7 feet vertically up a 6" duct after negotiating two 90 degree bends and 8 feet of 6" horizontal duct then though a wye and a double bend in a 7" aluminum flex pipe before being deposited in the dust bin. So I am thinking the cyclone is pulling at least 4000 fpm and 800 cfm. Surprise: when I ran that particular run thru Bill's calculator I got 6.95" of loss at 785 cfm, which puts it almost exactly on the fan curve for my yellow 2 hp DC.

    You quote 5" of loss per 100 feet of 6" duct per Cincinnati Fan. Using Bill's calculator with just 100 feet of 6" duct and 4000 fpm velocity gives 4.28" of loss per 100 feet so those numbers are reasonable. However if you input 350 cfm in 100 feet of 6" duct in Bill's calculator you will get 0.92" of loss per 100 feet of 6" duct, almost negligible.

    I am only responding because I really hate to see this misinformation and resulting conclusions floating about the Internet, which then to someone looking for their first cyclone becomes gospel because they didn't do their homework. As a result they buy the big hulking 5 hp DC because they are convinced that anything else just won't work. Now if they are running a 26" drum or belt sander, by all means go big or go home.

  4. #19
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    I have a 2 H.P Dust Gorilla(refused to mount the silly decal!!) with 6" spiral main pipe in my woodworking machine room. It works quite well for my 10" table saw,8" jointer,16" planer and 18" Delta thickness sander. The farthest thing from it is my 14" Delta bandsaw,which I reach with a 4" drop. About 24 feet away.

    The unit works fine,BUT,you might want to consider the NOISE that even a 2 hp unit puts out. It is rated at 74 decibels,but that is nonsense. It could be the 8' ceiling,and 16'x22' original single car garage I have the "mess makers"in,but the unit is quite loud. I have a radio that has a decibel reading on its dial,and 74 db on the radio is child's play compared to the dust collector.

    I think 5 hp would be entirely too loud to put up with without wearing hearing protection.

    My main room is 30'x40',but I have my metal working machine shop in there,and try to keep it clean of dust. My dust collector is at the rear wall of the small garage which I added the big building on to. Right beside the dust filter,I had a 18" shuttered 3 speed fan mounted into the wall. Got it from Enco,and I don't see why they cost like they do,as it's motor is Chinese. It WILL move about 5200 FPM of air on full,though. I only turn it on low,though,and it makes a mild breeze going towards the rear of the room,away from the big room. Any fly stuff is floated in that direction,as well as anything that might get through the filter. It works pretty well to have that extra fan.

  5. #20
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    It is always tough to determine what works for the other guy. The only way to really know what you have is to measure the flow and get the actual cfm. I have every Onieda system curve and am surprised at the difference among the 2,2.5, and 3hp gorilla systems. The 2.5 and 3 seem to have much more capacity at higher SP which is what scares me about the 2 hp unit. The problem I have with calculating pressure loss vs using measurements- and i'm a bean counter in real life- is that I don't know the actual pressure loss of each cyclone or the filters and the additional loss as the filters clog. The more efficient the cyclone at separating dust the higher the pressure drop. Cyclone efficiency can range from 2" to 10+" of drop so in effect the better the cyclone the larger the blower needed to operate it. The longer cone fine dust cyclones keep the filters cleaner but at a pressure drop cost. It is pretty easy to calculate the pipe and fitting loss, less easy to figure out the machine hood efficiency, and mainly a guess as to the cyclone loss. If you assume 2-3" filter loss and 2-4" cyclone loss those guesses can really screw you up if wrong. Ole, sounds like yours works for your machines although a Dylos type monitor would tell if the air gets worse when the machines are running or better. I agree that the 5 hp is likely overkill in Todds application but with a fan curve that provides 750+ cfm at 8" and about 200 cfm at 9" there isn't much room for error. Dave

  6. #21
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    Quote Originally Posted by george wilson View Post
    The unit works fine,BUT,you might want to consider the NOISE that even a 2 hp unit puts out. It is rated at 74 decibels,but that is nonsense. It could be the 8' ceiling,and 16'x22' original single car garage I have the "mess makers"in,but the unit is quite loud. I have a radio that has a decibel reading on its dial,and 74 db on the radio is child's play compared to the dust collector.

    George, The dB rating numbers on the radio are at best useful only for relative volume changes and will not relate at all to actual absolute sound levels. Yes the DC's can be loud, but they can also be quieted enough to make a huge difference by enclosing them in a silenced closet. http://www.youtube.com/watch?v=8X8qwMqm3Ek

  7. #22
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    I've no experience Ole of your system, and have not used the calculator you mention. It was however Bill that tipped me off to the accuracy of the Cincinatti data - it corresponds very closely with the numbers i linked in the 'basics' page that he himself published.

    That said nobody has said that 2HP doesn't work, the caution was that with the sort of long ducting runs Todd mentioned with multiple bends, the possibility of unforeseen further restrictions and the fact that filters quickly add resistance as they get dirty there is a significant risk that he could on occasion have ended up at pressures very close to the 8 or 9in at which a 12in impeller drops from maybe 350CFM to much less.

    You on the other hand are running what sounds like short ducting runs with few bends, with part in 7in dia. If as is possible with clean filters your total pressure drop is the 4in or so region the Cincinatti tables have a 12x2 7/8 impeller doing 930CFM which is a very respectable number - with enough cushion to tolerate some extra restriction as the filters blind up. Add 4in of pressure drop to that though and you would probably be back down to the previously mentioned 370CFM, add another inch and you would be below 200CFM.

    It's consequently all in the pressure drop, and the unfortunate fact about that is that the estimation of it is a fairly approximate affair. Which necessitates building in factor of safety at the design stage.

    It's possible that my guesstimated numbers are overly cautious, but knowing that even an inch or two change in pressure drop (the difference between dirty and clean HEPA filters is it seems alone potentially 4in WG) could potentially have such a marked effect on CFM in the region he was likely to be operating in there were not going to be too many takers to guarantee he would experience no problems at 2HP.

    It's normal engineering practice in these situations to build in some cushion to guard against such possibilities. Adding impeller size (and hence the HP to drive it) rapidly lifts one clear of potential problems. Step up to 14in dia and you're knocking on the door of 1,000CFM at 8inWG at 2.3HP - so a 3HP motor would do a better job and leave some protection against the risk of problems.

    Against that 1,000CFM would shove the pressure drop well over the 5.13in WG/100ft, meaning that the total pressure drop could exceed 8inWG so that 3HP might actually deliver something more like 6 or 700CFM over Todd's runs - reducing as the filters blind up.

    That's in turn going to be marginal if you're running a big old planer like what David does, or are keen to maximise the air cleaning/fine dust capture effect - so there's reasons to go higher at times too.

    ian
    Last edited by ian maybury; 03-18-2012 at 12:42 AM.

  8. #23
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    David as ever says with more impact in a few words what I'm busily trying to explain and then justify with some numbers.

    Noise can be a bit of an issue all right George. That said bigger systems don't necessarily sound significantly noisier to my ear than smaller ones, just a bit deeper in tone. How it measures might be a different matter - we don't always perceive sound levels in the same way as the dB scales read them.

    I suspect that much like predicting pressure drop and CFM it's subject to variables that are hard to precisely tie down. Balance and vibration of parts, and transmission of that vibration into the system and building structures is probably a significant part of it - the plastic Clear Vue cyclone could possibly do better in that regard than a metal one. Some build sound proofed enclosures.

    As before I took care to isolate my '5HP' blower and cyclone from the inlet and exhaust ducting using flexible hose, and got a very nice reduction in noise and softening of the tone by double soft mounting my fan and cyclone assembly. The Clear view set up hangs it on rubber bungs on threaded rods screwed into the mounting bracket. I added polyethylene pads under the feet of my non standard floor mounted ply mounting bracket.

    The double sprung mount principle is well proven and used on spin dryers and lots of machines, although getting it optimised requires calculating the optimum spring stiffnesses and suspended weights. I just took a shot at it to see what would happen....

    4 view.jpgcyclone assembled in mounting .jpgsoft mounting.jpg

  9. #24
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    I am not a dust collector expert,only ever having the one of my own. I'm concerned about heat buildup by putting my 2 hp unit enclosed.

    I think my unit has always had a bad control in it since new,because I cannot start it more than about 3 times an hour,or the motor cuts off. I need to call the makers about this.

  10. #25
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    Hi Todd, I have a few comments;

    1) ignore HP ratings for fans, they are of no use except for the fan engineer. You could put a 5,000HP synchronous motor on my cyclone and it wouldn't move any more than the 1.5HP motor that's on it.

    2) Your cyclone is capable of 1,000 CFM at 6" water column. In a hobby shop, 1,000 CFM will support your machines unless you buy large industrial stuff.

    3) write down what you need for your machines,

    -500CFM for a table saw cabinet, 200 to 300 CFM for the over blade collection

    - 500 to 700 CFM for a good size stationary planer

    - 500 to 700 CFM for a shaper

    - 500 to 800 CFM for a sander.

    See a pattern emerging? You need somewhere around 800 CFM maximum.

    Plugging 1,000 CFM into the calculator with 7" pipe and the following'

    - 1 hood

    - 4 right angle elbows

    - 3 Wye fittings

    - 50 feet of pipe

    It yields 3.71" water column, yet your cyclone is capable of that air flow at 6" water column.

    You have a bigger machine than you need, if you use larger than 6 inch pipe................Regards, Rod.

  11. #26
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    Rod, you are ignoring the cyclone which adds 3+ and the filters which will add 2-4 depending on area and how clean they are. The 3.71 may well be 8.71 or higher which why Ian and I have been saying it is on the marginal side. That doesn't even account for losses or flex that will add more resistence. Dave

  12. #27
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    Hi Todd,

    Welcome to the world of Dust collection threads.

    I hope you are finding some useful information.

    An update on my system: I redid some piping and sealed all the connections to reduce restrictions and losses, and this did significantly improve performance. I vent to the outside though so if going through filters I would still deem it inadequate. I havent determined yet if the current performance is acceptable for me (need more use).

    You can always just use yours and see how it goes. Since its a used unit already, you wont lose much resale value if you decide to upgrade later.

  13. #28
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    Quote Originally Posted by David Kumm View Post
    Rod, you are ignoring the cyclone which adds 3+ and the filters which will add 2-4 depending on area and how clean they are. The 3.71 may well be 8.71 or higher which why Ian and I have been saying it is on the marginal side. That doesn't even account for losses or flex that will add more resistence. Dave
    Hi David, of course I'm ignoring the cyclone and filter, the Oneida curves are for the complete cyclone with filter, no need to account for them............Rod.

  14. #29
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    Quote Originally Posted by Rod Sheridan View Post
    Hi David, of course I'm ignoring the cyclone and filter, the Oneida curves are for the complete cyclone with filter, no need to account for them............Rod.
    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

  15. #30
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    I sold the 2 HP SDG today. I made no misrepresentations to the buyer. He wanted it for a very short run setup and understood that when he puts his final shop together he will most likely need a more powerful DC.

    Now which DC to buy?

    I like the professional looks of the Oneida but the Clear Vue is a heavy favorite. It is less expensive but as I understand it, requires other items to be purchased, and requires some fussing around to set it up. I would definitely paint the wood pieces to give it a more professional appearance. Lots of pictures in Clear Vue gallery. I totally understand wiring, so that is not a problem at all. I wired to code (and was inspected) my entire house and new garage shop.

    Oneida has two 5HP units. The 5 HP SDG has an 8" input port, if I connect my 6" system what happens to performance? Oneida also has the new Smart Pro. Very nice comes with almost everything, remote starter (not sure I care once I get my dust gate triggers operational, but in the mean time will be nice), infrared dust sensor. It has a 7" input port (maybe better when connecting 6"?) but is very pricey. I have no idea what the infinitely variable fan curve means. Is it worth the splurge?

    The beauty of the clear Vue is that it is sized for 6" duct, and PVC at that!. Seems like a lot of people have this setup so I would be in good company. I have to buy more and fuss more but will cost less than the Smart Pro, not sure it will cost less than the 5 HP SDG..

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