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Thread: Dust Collection - my latest two cents worth

  1. #1

    Dust Collection - my latest two cents worth

    Emails this morning scolded me for not posting this as a new thread, plus leaving a few things off. Here is an updated version of what I shared at the end of the last cyclone thread. bill

    Making a dust collection decision requires you to first decide on what it is you want to do. If you just want a shop with no chips, then just about any hobbyist 1.5 hp or larger dust collector or cyclone will work well for you because you only need about 450 CFM airflow for chip collection. If you seriously want to get the airborne fine dust in your shop under control then you have a whole different set of concerns. You can go to my web pages and study for yourself the dangers of fine dust and what it takes to control, collect and get rid of it.

    Many local safety standards require putting commercial cyclones and dust collectors outside. That works well because these outside units let the fine dust blow away outdoors. For hobbyists, exhausting outside is illegal in many areas. It can be hard on the pocketbook to send our heated and cooled air outside and our air conditioning equipment will mostly not keep up. The noise and debris can upset neighbors. Some types of chips and dust kill plants. Blowing our shop air outside can also suck deadly carbon monoxide backward through the vents on our heaters, stoves, water heaters, and other fired appliances into our shop air. Putting these units outside also often requires making them a special enclosure. Many hobbyists choose to just bring these outdoor units inside.

    When hobbyist started bringing these downscaled commercial dust collectors, cyclones, and small shop vacuums inside it created a serious hidden problem. These smaller units make great “chip collectors” that will leave our shops spotlessly clean except for a coating of the unhealthiest finest dust on everything. That coating comes from moving too little air to gather the fine dust as it is made and too open filters that blow the finest unhealthiest dust right through. Unlike commercial firms that blow this fine dust away outside, hobbyists trap the dust inside. This fine dust builds and lingers for months getting even more dangerous as molds, mildew, and fungus break it down. Our tools and even dust collection systems become “dust pumps” that recycle previously made dust. Government testing of hobbyist shops that turn professional shows most end up with fine airborne dust levels over ten thousand times greater than permitted in commercial facilities. We as hobbyists often receive more fine dust exposure in a few hours of dusty woodworking than a commercial woodworker will get in a year.

    With almost no hobbyist tools, dust collectors, cyclones or ducting setup for anything but "chip collection" getting good fine dust collection takes a lot of work. We have to remake most of our tool hoods and tool ports. We need a good downdraft table and portable dust collection hood. We need a much bigger blower that moves a real 800 to 1000 CFM at each major tool. We need larger lower resistance ducting than most hobbyists vendors sell and cannot use commercial ducting designs because the smaller down drops kill the airflow in our mains building up dust piles. These piles pose a fire hazard and will eventually ruin our impellers, motor bearings, and filters from breaking loose and slamming around. We also need to either exhaust the dusty air outside or run it through fine filters.

    We can't just run the dusty air through a filter. Meeting government commercial air quality standards that many now think are not tight enough requires filtering all particles down to 0.5-microns in size. My doctor and many other health professionals recommend filtering down to 0.2-microns. We also must have enough surface area so the filters do not plug too quickly and kill the airflow needed for good fine dust collection. Most can only provide enough filter surface area by using large cartridge filters. Fast moving wood chips quickly plug and punch holes in cartridge filters as too many are now finding with their cartridge dust collectors. Cleaning rapidly also wears holes in these expensive cartridges.

    Protecting these filters can be done with a drop box, meaning a huge pipe with so much area that the airflow drops below what will keep the chips entrained (kept airborne), or using a cyclone separator. Trashcan lid separators are a type of drop box that many hobbyists find work well for “chip collection”. Unfortunately, the higher 800 to 1000 CFM airflows needed for good fine dust collection scour the cans clean unless the trashcan separators become huge. Most find a 5’2” diameter seven foot tall or larger trashcan separator too big, so instead turn to cyclones for separation.

    The huge cyclones we see outside most large commercial woodworking facilities are agricultural cyclone designs that work well. They provide almost exactly the same 85% separation efficiency by weight that our far less expensive trashcan separator lids provide for “chip collection”. These cyclones were designed to separate dirt and sand from cotton. They use very high internal turbulence to smash the dirt and sand loose from the cotton fiber. After breaking the heavier stuff loose it gets slung by spinning air off to the cyclone sides and gravity pulls it into a collection bin. Close to 100% of the fine cotton fiber blows right out the top of the cyclone. When used for woodworking, high internal turbulence smashes the fine dust from the heavier chips. Close to 100% of the heavier chips and sawdust drop into a bin and near 100% of the fine airborne dust away into the outside air.

    Sadly hobbyist vendors discovered that if they feed their cyclones only large heavy chips, say from planers, they can advertise close to 100% separation efficiency for cyclones that provide 85% separation efficiency. Feeding these same cyclones all fine dust, say from MDF, puts close to 100% of the dust into the filters.

    It is no secret that almost all hobbyist cyclones are downscaled copies of agricultural cyclone designs sold by Delta to small commercial shops for decades. These units require a 7.5 to 15 hp motor for the same sized cyclones that hobbyists try to power with 1.5 to 3 hp motors today. With lots of help we worked through countless design changes to improve these hobbyist agricultural cyclone separation efficiencies. We learned most hobbyist vendors did not know the cone on the bottom of the cyclone requires just the right shape and proportions to keep that heavier material from causing plugs or getting sucked back into the exiting air stream. We learned inlet size, shape, length, and angle is critical. We also learned that the incredibly high turbulence was not needed if we wanted to separate off all the dust. With clever modifications we got these cyclones from 85% efficient by weight to the low nineties.

    That was just not good enough. In spite of adopting many of our recommended changes, hobbyist vendors continue to sell cyclones that require more time to fix than building a cyclone from scratch, plus cutting up a brand new unit just hurts too much. Hobbyist cyclones still constantly plug their undersized filters, pass much of the finest unhealthiest dust right through their too open filters, fail to move enough air for good fine dust collection, and fail to move enough air for good separation with anything less than 3 hp or larger motors.

    Larry Adcock with his WoodSucker II design, my design plans available off my web pages for free, and cyclones based on my design sold by Clear Vue Cyclones made major steps forward. Larry used a more efficient caged impeller and I used an airfoil impeller. Both move 3 hp air volumes with a 2 hp motor. We also both got our separation efficiency up into the middle ninety percentile before filtering. My continued testing moved me away from the caged and airfoil impellers. They generate so little air pressure they only have enough power to collect from small shops plus they need regular cleaning. I refocused my design enhancements into building an overall more efficient cyclone and blower. Everyone who uses the result can attest to their air movement and separation efficiency.

    Meanwhile, if you won’t use large enough ducting, upgrade your machine hoods, move enough air and use fine enough filters, just buy a good 1.5 to 2 hp dust collector and be happy, because your cyclone is not going to give what is needed for good fine dust collection.

    bill
    Last edited by Bill Pentz; 09-09-2005 at 12:12 PM.

  2. #2
    Join Date
    Jun 2005
    Location
    Woonsocket, Rhode Island
    Posts
    45
    Hello Bill,

    As your website is, so are your posts.....full of valuable information.
    Thank you.

    Regards,
    George

  3. #3
    I am unhappy to hear that you received negative email.


    I am very happy you took your time to post at the thread I started, and again here.

    In fact, after your post to my thread, I went back to your web site and started to read again. I liked the experiment with the small clear tube and breathing. I will pour through the information again this afternoon and this weekend. Maybe some folks think like I did... it is only dust. Seems mother nature has a way of removing those from the gene pool.

  4. #4
    Thanks Bill for this very usefull information and your tireless efforts in this area.

    Bob
    bob m

  5. #5
    Join Date
    Dec 2004
    Location
    Delaware Valley, PA
    Posts
    476
    Quote Originally Posted by Bill Pentz

    These smaller units make great “chip collectors” that will leave our shops spotlessly clean except for a coating of the unhealthiest finest dust on everything. [snip]

    This fine dust builds and lingers for months getting even more dangerous as molds, mildew, and fungus break it down. [snip]

    Government testing of hobbyist shops that turn professional shows most end up with fine airborne dust levels over ten thousand times greater than permitted in commercial facilities. [snip]

    We as hobbyists often receive more fine dust exposure in a few hours of dusty woodworking than a commercial woodworker will get in a year. [snip]
    Bill, it seems like you've done quite a bit of research in this area. I've done some searches on google and pubmed, but I guess I'm not good at framing search terms, because I came up with no references to reliable scientific sources of info on these issues. There are some books and magazine articles for hobbyists and small shop operators, but the ones I've read fail to cite the sources of their info. I've been on your web site a few times and was unable to find it there.

    Would you mind posting your sources for this info? Thanks in advance.
    What this world needs is a good retreat.
    --Captain Beefheart

  6. #6
    John,

    I used to keep many links to medical articles on my web pages, but keeping them up became overwhelming, so I now suggest people do their own searches. Finding about the health risks of fine wood dust is pretty easy. Just do a few Google searches (fine wood dust hazards) and (PM 2.5 health hazards). Reading and making sense of the better medical articles is not quite so easy, but still doable.

    The second part of your question is the same one that threw me when I got started. I only did a little woodworking now and then and already used most of the best available in hobbyist dust collection with fine filter bags, so figured my exposure and risk was tiny. Yes, I ignored the coating of fine dust everywhere on my tools that also joined us inside our attached home. It was not until an OSHA inspector friend came over and educated me by showing with his test gear that I could believe the problem was so bad. Just turning on my cyclone with no woodworking at all raised the airborne dust levels in my shop thousands of times over allowable limits in commercial facilities. Do I have credible reference studies to back this up, no just my test results because nobody else has spent the time and money to do independent testing. Regardless, if you think about why this is a problem most don’t question these results:
    1. Unlike commercial concerns that have long blown fine airborne dust outdoors, hobbyists keep the dust trapped indoors.
    2. Our tools and hoods fail to control and protect the fine dust before it can spread.
    3. Our dust collectors move too little air to capture the fine dust at the source.
    4. Our small ducting will not support the airflow needed for good fine dust collection.
    5. Our too open filters turn our cyclones, dust collectors, air cleaners, and shop vacuums into “dust pumps” that constantly blow the finest unhealthiest dust right through.
    6. This dust builds and lingers for months getting cycled back into the air every time we turn on our dust collection or other tools.
    7. While sitting around this fine dust builds up irritating molds, mildew and fungi that break it down into smaller even more dangerous airborne particles.


    The third part of your question you did not ask is do we really need to move 800 to 1000 CFM for collecting the fine dust while 450 CFM does a great job collecting the heavier dust? The answer is yes and we all know why from using our shop vacuums. Sucked air only collects over a tiny area because airspeed drops off at pi times the cube of the distance. Getting the needed 50 FPM airspeed out far enough to capture the fine dust requires moving a lot more air than just gathering the chips forced by our tool hoods right into our collection pipes. My web pages share more information with the calculations and testing results.

    Hope this helps.

    bill

  7. #7
    David Less Guest

    Blowers

    I refocused my design enhancements into building an overall more efficient cyclone and blower.
    Quote Originally Posted by Bill Pentz
    l
    Bill,

    Is this the same cyclone/blower type that can be purchased through Clear Vue using a 5 HP motor??

    Thanks for the help and the wonderful research that you have done and provided.

    David

  8. #8
    Join Date
    Dec 2004
    Location
    Herndon, VA
    Posts
    547
    Bill - As usual your inforamtion is greatly appreciated. I have a Jet 1.5 DC with the AFF aftermarket bags. My duct work is 6" to 5" main run and either 5" or 4" at the machines (Oneida designed). It's in a small basement shop so the longest run is maybe 18'. I also run a AFS to clean the air. I know the AFS discussion has been somewhat controversial but my guess is it can't really hurt since it is picking up dust in the air.

    The cyclone would be a better setup and will be on the short list of upgrades.

    What does this type of setup present in terms of health hazards? Are you comparing dual bag DCs to cyclones based on the 30 micron stock bags?

    I actually find the two worst offends for dust collection are the CMS and the table saw. My CMS dc needs to be redesigned to surround the saw better. With the TS I get more dust coming off the top of the table than I woul dliek to see. That can be corrected with an overarm guard.

    Thanks, Mike

  9. #9
    David,

    Yes, Ed Morgano with Clear Vue Cyclones makes his plastic cyclones based upon my designs. Unlike other vendors who just plain lift my work, Ed is kind enough to pay me a small commission on sales to help with the fairly high overhead of my continuing dust collection testing, design, and web page work.

    bill

  10. #10
    Join Date
    Dec 2004
    Location
    Delaware Valley, PA
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    476
    Bill, thanks for the links. It's amazing what a difference it makes when you change the search terms on google. This area is of personal interest to me, because my wife has a pretty severe respiratory condition.
    What this world needs is a good retreat.
    --Captain Beefheart

  11. #11
    Michael,

    Your 1.5 hp dust collector makes a great unit to hook with a short 6” diameter flex hose directly to your tools and then blow all outside, otherwise it quickly becomes challenged as a fine dust collector. The typical 4” of resistance from just a large hose, hood, and filters reduces the typical 1100 maximum CFM to a working bare 800 CFM for this size collector. Adding ducting and fine minimal resistance filters, or a smaller 4” hose or small 4” tool port pushes the overhead up enough that you lose the airflow needed for good fine dust collection.

    Many hobbyists get “sucked” into using commercial ducting designs that look nice but work poorly. Unlike a commercial shop designed with a blower big enough to power all down drops open at once, most hobbyists only have the power for a small dust collection blower. These hobbyist blowers can only move enough air for a single run at a time. With air at typical dust collection pressures more like water that will hardly compress at all, any obstruction or short length of pipe acts just like our valves on our garden hoses and kill the flow. The Dwyer Instruments testing pages show that ten diameters of a smaller duct will kill the overall system airflow down to what that small pipe can support. For example my Jet DC-1100 dust collector that moves a real maximum 1100 CFM will only move 452 CFM through a short length of 4” pipe. The velocity is more than ample to keep the vertical down drop clear, but when that 452 CFM hits the main the airspeed is too low to keep the duct from building up dangerous dust piles.

    I have long used a good air cleaner in my shop. It is worthless for protecting me as I work, but it does keep the volumes of fine dust from building up and helps keep my cars that get parked in the same area cleaner. Although I could do the same job with my cyclone and fine filters, the cost to run it the six plus hours needed would be prohibitive, plus unlike my aircleaner, the cyclone fails to properly stir the air, so keeps cleaning the same "racetrack" of air over and over.

    ASHRAE recommends that we use a pre-filter or separator before our fine dust filters to keep them from plugging too quickly. They also recommend the filter area be at least 1 square foot of filter area for every 2 CFM of airflow. We use the cyclones to protect these fine cartridge filters from getting plugged too quickly and from material hits punching holes. My doctor and many other health professionals recommend those of us with respiratory concerns use 0.2-micron filters. Again, you still need to upgrade tool hoods, ports, ducting, and cyclone to make these filters do the job on fine dust collection.

    I fully agree with you on our table saws and miter saws pumping out lots of dust. Both need collection at the blade guard and either under or behind the blade. I suggest on my web pages use of 6” down drop that goes to a 5” lower port and 3.5” upper hose for both types of saws. The worst dust producer in my shop is not any of my big iron, but instead my powerful hand held power sanders that swing from 5" to 10” sanding discs. They make so much fine dust, the only way to avoid a fine dust problem is to work outside with a mask on.

    bill

  12. #12
    Thanks again for all your efforts, Bill.

    I've been testing some of the DCs for the local guys and every time I do, their eyes open wide when they can see for themselves the penalities of using too small ducting or poorly constructed duct runs.

    Restrictive tools are another issue that I've been trying to make people aware of which leads to better hood design. You know something can be made better when I have a strong DC and have measured over 1400cfm in my 7" main duct.....then add on a 7x6 reducer, some flex hose and bolt it up to a custom made 6" port on a benchtop planer and the cfm will drop to 780cfm.

    Over 600 cfm was lost! A chunk of that will be through the ducting, but even more was lost because of the hood design and the limited openings in the tools.

    You get the same loss of airflow if you use the factory port on a Performax 16-32 sander.

    I've exchanged several e-mails with Don Beale about hood designs and he has encouraged me to get more into this area. He wanted to do it but has no time and wants me to run with it. I'll do that when I get the house renovations done and I'll keep you posted.

    Cheers,

    Allan

  13. #13
    Join Date
    Dec 2003
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    West of Ft. Worth, TX
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    Bill, good to see you posting again here at the creek! I think I can safely say we are all very appreciative of the work you have done in this area. There will always be debates as to which unit is best, we all know that. But if the awareness you have raised about this problem helps some of us healthwise, then you have done a marvelous service to us and our families.
    By the way, I now have my Clear Vue up, but still no power to the shop to get it running yet. As a side note, the motor on my unit is about 3 inches from the roof decking at the peak of a gabled end. Is there a "best" method of getting air on it to keep it cool? After some discussions here at the creek with several others, I have decided to put a powered roof vent close to the unit that will help expel heat from the attic, but am curious if there is a preferred method from your experience.
    Thanks again for your valuable information. Jim.

  14. #14
    Jim,

    You probably will not need to do anything for extra cooling, but should keep an eye on the motor temperature. If it gets too hot, then wire up a little muffin fan to blow more air over the motor top.

    *smile*

    bill

  15. #15
    Join Date
    Mar 2005
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    Bill---I suppose a number of us new buyers would be interested in your opinion of Oneida's 2 HP Gorilla cyclone. For those of us working in basement shops, there aren't a lot of options due to low ceilings. Your design was ruled out for lack of height. I must go back to your site to refresh my memory on ductwork recommendations. Is anyone making larger than stock dust ports for things such as table saws? For those of us who don't work with metal, tool modifications are a daunting task.

    Dan
    Last edited by Dan Forman; 09-10-2005 at 5:11 AM.
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    Critiques on works posted are always welcome

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