Calculates full and partial vessel volumes for horizontal and vertical vessels. Calculates multi-level liquid volumes and residence times in horizontal and vertical vessels. Mist eliminator sizing estimation for typical mesh, vane and axial cyclone products. Sizing and selection of suitable inlet distributor for vertical and horizontal vessels. Liquid in gas droplet carryover calculator for horizontal and vertical vessels e. Design of fluidized-bed sand jet system and calculation of required headers and nozzles.
This poor separation creates serious filter problems. When used with fine filters these cyclones put out so much fine dust the filters clog very quickly. That clogging kills the airflow we need for good fine dust collection and quickly destroys our filters because the higher pressures force the fine sharp particles to cut and tear their way through the filters.
Cleaning does the same thing but faster. This why I only recommend traditional cyclones should only be used without filters and vented directly outside. It is also what inspired me to build a better separating cyclone. With a choice of giving up on a forty plus year woodworking hobby, I chose to spend my recovery time putting my three engineering degrees to work. I needed a solution that reduced how much dust went into the filter. Wearing a mask was not good enough because the fine dust lingers for months and would continue to get tracked into my home, office, and vehicles.
The shared knowledge from those dust collection firms who guarantee customer air quality all say we must capture the fine dust as it gets made then get rid of that dust.
The fire and building codes require that dust collectors and cyclones either be placed outside behind explosion and fire proof barriers or that these units be certified as fire and explosion proof. Getting that certification is so expensive that all of the more affordable commercial dust collectors and cyclones required putting them outside.
The ones setup for indoor use cost far more than my budget, plus required quarterly changing of many expensive cartridge filters. Most also used large commercial three phase motors that my home electrical service would not support without getting a phase convertor which was expensive.
This pushed me into doing more research on basic separation theory and cyclone design. My research convinced me that a cyclone was the best solution, but none of the seven fairly well studied cyclone designs offered a combination of fine separation with minimal power usage.
I went back to the basic swirl tube separation physics and cyclone design theory to come up with my own cyclone separator design.
I tilted the neutral vane inlet, added a helical baffle known as an air ramp, plus changed the inlet and cyclone geometry so the fine dust also got separated out. Although I had a much better working cyclone as of , it still took me a couple of years to design then build, test, and refine my design into its current configuration. The following shares some of that process. Although this is probably not that interesting to most, knowing much of this information will make the difference between your having a shop that looks clean and a shop whose air protects your health and the health of those close to you.
Rather than cover this information more than once, you can read it over on my web pages. Some university sites offer cyclone design optimization spreadsheets. To use one of these spreadsheets you need to know the airspeed and air volume we will be working with, the amount of material to be separated, and the sizing of this material.
These cyclone spreadsheet calculators will then compute the overall resistance for each of the different cyclone types along with expected separation efficiency.
Airspeed measured in feet per minute FPM defines what size and weight of chip we can pickup. Because woodworking makes a range of chip sizes we normally pick the airspeed for the largest type of material we use. During normal woodworking we make fairly large chips all the way down to very fine dust particles that are so small they are invisible. Major blower makers that provide equipment to use air and ducting to transport different types of material provide charts that tell us how much airspeed and the minimum pressures needed to transport various types of material.
For fine wood dust such as created when using fine sandpaper, we only need about 50 FPM airspeed to overcome normal room air currents and move this dust.
For typical sawdust we need to move the air at about FPM and for larger chips we need to move the air at about FPM. Ideally we should move right at FPM airspeed for picking up the normal range of wood chips.
Many air engineers design instead at FPM because this airspeed is ample to pick up the material most fire marshals consider dangerous. Air volume measured in cubic feet per minute CFM defines how big of an area we can collect over.
In short if we know what air speed we need and the size of the area we need to cover we can compute how many CFM we need. To just collect the same sawdust and chips we would otherwise sweep up with a broom, known as "chip collection", most large stationary small shop tools can use existing hoods and tool ports and get good "chip collection" with about CFM.
Tool makers like Fein and Festool have shown us we can get excellent fine dust collection with a big shop vacuum. To do so our tools must be built from the ground up to totally contain the dust. Unfortunately, most large stationary tools found in small shops are older designs that only have good "chip collection" built in. Air engineers have spent decades figuring out how to fix our older tools to get good fine dust collection.
To collect the fine dust on our typical older tool designs we must upgrade hoods, often provide larger dust collection ports, and provide a bubble of air around the working areas of the tools that pulls in the fine dust. Although that bubble only needs the air moving at 50 FPM and faster to overcome normal room air currents and pull in the fine dust, the size of this bubble is large, almost fifteen inches in every direction.
This large area is bad news because airspeed for sucked air drops at about the same rate as the surface area of a sphere expands meaning about four times Pi times the distance squared. So we need to move lots more air for good fine dust collection than is required for "chip collection". A moment of thought about how our vacuums work makes this pretty obvious. A vacuum nozzle only picks up right next to the nozzle and just moving a tiny bit away so reduces the airspeed we get no collection.
Air engineers calculated the minimum airflows at each size and type of large stationary tool then refined these values over decades of experience to create CFM requirement tables for each size and type of tool. We need a 7" for the ideal size to carry CFM.
If we use an oversized impeller and a little stronger motor we generate enough pressure to let us move this CFM in a 6" diameter duct. Knowing that 6" duct is readily available and inexpensive but larger is not available or readily available, I designed my blower to have enough pressure to move a real CFM in a 6" diameter duct. Static Pressure is how much overhead we need our blower to overcome to work in our shop.
Every length of duct, duct fitting, tool hood, tool port, and filter will add some resistance. This is a well-studied area and we can use a good static calculator such as the one provided on my pages here to get a good working estimate of the lowest and highest potential resistance or static pressure in our system.
That highest resistance is going to be our longest ducting run plus the highest resistance we expect from our filters. Filter resistance will change considerably over the life of a filter.
A clean brand-new filter passes the most air and has the least resistance. As a filter gets dirty the resistance goes up. Over time filters "season" meaning they build up a cake of fine dust in the filter pores that does not come out with normal machine shaking type cleaning.
A seasoned filter will often filter ten to twenty times better than a brand-new filter, but it will have a much higher resistance. Filter monitoring is done with a pressure gauge and recording the filter resistance after every cleaning. This fine dust trapped in our filter pores is made up of small sharp particles that will cut and tear their way through the filter matrix.
As the filter dirties the air pressure increases forcing these particles through faster speeding up this damage. Cleaning our filters forces these fine particles through the filter but even faster, so cleaning also quickly breaks down our filters.
Filters that get too dirty quickly fail and so do filters that are cleaned too often, plus most small shop woodworkers tend to over clean our filters causing them to fail even faster. This is why most large commercial installations use a pressure gauge and record the air pressure after every cleaning. That pressure will steadily rise as the filter "seasons" then fall off as the filter breaks down. They must replace filters when the pressure drops too low because the filter is no longer working well.
Filter rating is done in a variety of ways, but ASHRAE writes the rules for rating indoor filters designed to protect our health. ASHRAE requires indoor filters to be rated when clean and new which is when they pass the most air and the most fine dust.
Otherwise we would be using our lungs to filter the air in the sometimes up to two years it takes a small shop cyclone filter to fully season. Filter material makers also provide a filter rating that gives the expected level of filtering once the filter is fully seasoned, plus the resistance level for a fully seasoned filter. This resistance level is then used as part of the static calculations used to size the dust collection system.
Filter sizing is generally done based on recommendations from the filter makers based upon the fineness of the filter, the amount of airflow and amount of dust to be filtered. The medical experts recommend we filter wood dust to at least 0. The main filter makers say the 0. The thicker all spun bond material 0. If you read further the filter material makers further recommend using double the minimum filter area because that will reduce static pressure filter resistance four fold, extend filter life four fold, and reduce cleaning cycles four fold.
Typical small shop dust collectors with bag type filters generally have less than 50 square feet of filter area when with their claimed CFM of airflow actually need about square feet of these spun bond bag type filter area whether in a bag or cartridge. Most small shop cyclones claim CFM airflow and come with the poly cellulose blended cartridge filters that are typically under square feet in area when they really need a minimum of at least square feet of filter area.
Stock filters supplied by most small shop vendors end up being a mess of confused advertising and performance numbers. Most small shop vendors advertise their filtering level not when clean and new as required by ASHRAE, but instead based on a fully seasoned filtering level which leaves our lungs doing the filtering for sometimes two years and more while the filter seasons.
Most size their bag and cartridge filters based on clean and new air resistance which can be one tenth and less the actual working resistance of our filters when they fully season. This combination ends up with their providing far too small filters that quickly load up killing airflow and soon leaving us with filters that quickly fail and no longer provide us with good fine dust protection. Although this may make for more filter sales, it is not a very good way to care for their customers and invariably ends up using filters with far too much airflow robbing resistance.
Fan Tables let us use our calculated high and low resistance levels in combination with our required airflow to choose a blower housing that is the right size, an impeller fan sized to meet our airflow needs, and the right size motor.
Good fan tables also tell us the correct diameter for our blower opening which is also the same size we should use for our ducting main. The good ones like the ESSCO cyclone calculator will show the sizing and estimate the efficiency of each of the major well-known kinds of cyclones. We don't really need a fancy calculator because once we know our ducting size from our fan table we can multiply that by three to get the diameter of our cyclone. All the major cyclones then use this diameter dimension D to let us compute the sizes for all the other features of our cyclone.
Cyclone Efficiency is something that these calculators will predict, but almost all typical woodworking cyclones that we see outside almost every large woodworking facility provide a A micron particle is roughly one third the thickness of a coarse human hair. The woodworking industry considers particles sized under microns to be airborne dust because when blown outside they will quickly dissipate with no trace.
Virtually all woodworking cyclones provide exactly this same micron separation and are designed to simply drop the heavier sawdust and chips into a collection bin while blowing the fine dust away outside. This is also almost exactly the same separation efficiency found in trash can separator lids, except the trashcan separators need huge trashcans at the much larger airflows needed for good fine dust collection.
Cyclones can handle much larger air volumes in a smaller size. Although this micron separation may be ideal efficiency for a woodworking cyclone that blows the fine dust away outside, it is a very poor choice for running our air through fine filters. The problem is wood dust contains far too much of this fine airborne dust.
This dust ends up quickly plugging our filters killing the needed airflow, requiring constant cleaning, and leaves greatly reduced filter lives. So in conclusion we need a cyclone that minimizes air resistance and maximizes how much of the fine dust it separates. When I did my research, there were no such cyclone designs available for woodworking and no other kinds of cyclones provided the needed airflow and separation efficiencies without using greatly oversized motors and blowers.
Applying what I learned to the available small shop and even most larger facility cyclones showed woodworking fine dust collection is a mess. Only a couple of the largest dust collection vendors that actually certify and regularly test their customer air quality after installing a dust collection system provide good fine dust collection. Most instead provide cyclones that provide terrible separation, blowers that move far too little air, filters that filter so poorly the air should not be returned indoors, ducting that will not begin to move the airflows shown by decades of air engineering as the minimums needed for good fine dust collection, plus most don't even pay lip service to the key requirement of having to start with upgrading most tool hoods and ports.
This really did not make sense at all until I got deeper into the literature and discovered that dust collection is a strongly contested war between a few well-meaning medical experts versus our fourth largest group of employers in the country.
These folks continue to spend big dollars to purchase the best studies that money can buy which prove woodworking makes no fine dust, the fine dust made by woodworking has no negative health effects, and the exposure levels are so tiny as to be of no importance. These interests delayed the OSHA air quality standard for woodworking for nearly thirty years and forced this standard to be fifty times easier than recommended by the medical experts.
These same interests successfully challenged that easy OSHA standard before it even went fully into effect. In short, dust collection today for woodworking is almost entirely up to the customers to decide and then trust that the vendors will provide what they claim in their advertising. In small shop dust collection this situation is so dismal that the "best" magazine rated cyclone vendor puts out a cyclone that actually increases our airborne dust level in our shops to far higher than if we just worked with a fan running in an open doorway.
In summary small and large shop dust collection in the U. My personal testing of every major brand and size of small shop dust collector and cyclone found only the 3 hp and larger dust collectors and the 5 hp and larger cyclones moved enough air to even meet the relatively easy OSHA air quality requirements. I found most small shop cyclones now use portions of my earlier design shared on my Cyclone Modifications web pages, but all continue make serious design compromises to make them easier to build, to use a much less expensive and powerful motor, and to force fit them under an eight-foot-tall ceiling.
Not one of these units as of my testing done in provided a cyclone filter that when clean and new provided even micron filtering. All small shop vendor dust collector and cyclone vendors advertised maximum airflows that were more than double the airflows these systems provided in real use.
All small shop dust collector and cyclone filters ranged from five to twenty times too small for their claimed filtering level, and were even too small for their actual filtering levels. In short, small shop dust collection remains the same dismal mess it was when I got inspired in to come up with better solutions to help small shop workers better protect our health.
Every small shop vendor in sold cyclones with serious internal resistance problems that robbed about half the blower airflow, but even with the changes my friends and I came up with, but all other small shop cyclones continue to have such poor airflow, separation and filtering they often build dangerously high amounts of fine dust if vented indoors.
The top magazine recommended cyclone I installed in to protect my health less than two months later landed me in the hospital. The prior design problems coupled with poor separation and bad airflow helped me define what I wanted in a better cyclone. I still wanted a cyclone that protected the blower impeller and filter from material hits.
I wanted a unit that still fit under a typical eight foot ceiling that is 96" high. I wanted this cyclone to provide much better fine dust separation to permit using smaller and more affordable fine filters that quickly get ruined with cyclones that do not provide good separation.
I also wanted to power this cyclone with an affordable motor that would run on normal household current. Many of these design goals appeared mutually contradictory.
Reducing the cyclone height to fit it under an eight foot tall ceiling forces use of a prohibitively large motor. Increasing the cyclone size enough to use a smaller motor kills separation efficiency and keeps us from fitting the unit under an eight-foot-tall ceiling. Using a shorter cone length causes the cone to plug when processing larger chips and to suck the fine dust right out of the dust bin and put it into our filters.
The cone needs designed to reverse airflow direction so the natural air reversal point is just right to let the dust, chips and shavings fall while the cleaned air escapes upward. The cyclone research models all say the best fine dust separation occurs when the cone length is 3 times the upper cylinder diameter again creating a too tall cyclone.
I tried modifying the traditional cyclone design that all still sell, but nothing ended up with much better fine dust separation without creating a cyclone that was either too tall or needed too big of a motor. This pushed me back into the basic separation physics literature of which a cyclone is a special case of a "swirl tube". This information was not of that much help either because the traditional approach to getting better dust separation is to move the air faster.
The faster the air moves the more particles that a cyclone will spin out of that airstream. Unfortunately, my calculations showed I needed a This moved my thinking to looking at other options to get better separation. Almost all cyclones start with an inlet that comes in straight from the side. This causes the air to spin and relies upon gravity to pull down and drop the dust.
Minimizing the internal turbulence inside the cyclone lets the same airflow get rid of far more fine particles. Aiming that incoming airflow to push the dust down toward the dust bin further improves separation but creates a new set of problems. Since the bin and connection to the bottom of the cyclone is sealed, that downward moving spiral of air is going to reverse direction and head up and out the cyclone exit.
I needed to get that inlet aimed just right to minimize turbulence and adjust the cone sizing so the airflow reversed direction in just the right place. The traditional cyclone designs had already shown that making the cone dust chute outlet the same size as the cyclone inlet and making that cone three times as long as the cyclone diameter created the best fine dust separation for a cyclone with a perpendicular inlet.
For a tilted inlet I needed to calculate an ideal reversal point based upon my inlet angle and air speed. Unfortunately, the airspeed is not a constant but is near zero on the cyclone walls that are carrying the fine dust out and climbs close to the initial velocity from the inlet.
It was not easy as too high causes the cyclone to plug when processing larger chips and too low sucks the fine dust right out of the bin. Each different design and airspeed needs a different cone length. I found for my optimized design the ideal reversal point occurs 1. This creates a cyclone that will move a real CFM and will just barely fit under an 8' ceiling with a small dust bin.
This design minimizes internal turbulence decreasing cyclone overall resistance from the roughly 3. This much cleaner airflow allows this cyclone to provide a five times better fine dust separation efficiency. This means we can use smaller filters which is good news because good fine filters are expensive. It also means we are going to get many times the filter life and go far longer between filter cleaning cycles.
It also means that I can power this cyclone with a 5 hp motor and get better airflow and separation than other designs can get with far larger cyclones and motors. Moreover, when teamed up with an oversized impeller, this high efficiency allows using all 6" diameter ducting instead of needing to use 7" or in some cases even 8" ducts for good fine dust collection.
The additional pressure generated by this larger impeller also minimizes our hood and port changes to our tools. Another very positive benefit of this design is it ends up being scalable. Innumerable people have built and purchased little 6" diameter cyclones to use with their 2. The medical school testing on these smaller units ends up being just as impressive than the separation on the larger units.
These small 6" versions provide The real proof is in the results that woodworkers get with these in real use. Even shops that make multiple gallon drums of MDF dust daily find they can go six months and still see almost no fine dust in their filters.
The same is also true in terms of scaling this design to much larger. I designed one of these for a huge cement processing facility and they went from having to replace filters monthly to every five to six months, plus were able to use a much smaller horsepower motor.
The owner of that facility said his cost savings in energy and filters pays him back more than he spent to build this unit every three months. I've heard similar reports from a plastics maker, a coffee bean roasting firm, and innumerable woodworkers.
Many have even built these units with oversized cyclones to permit them to use smaller motors. Although I don't particularly like this idea because too much fine dust is not captured if the blower does not move enough air and separation efficiency goes way down, many successfully power my cyclone design with 1. Instead of building my recommended 18" diameter cyclone, those with 3 hp motors should make 20" diameter cyclones and those with 2 and even 1.
Often these bigger diameters end up requiring mounting the blower to the side as the result would be too tall with a top mounted blower, but regardless they still work very well. If you need a more powerful than 5 hp cyclone, have medical problems, or need to collect from more than one machine at a time, I recommend you seek professional engineering advice.
You might want to carefully consider your cyclone materials. We need to use a material that will wear well. Most commercial wood working cyclones tend to fail from wet abrasive dust causing rust out and wearing a hole on the inside of the cyclone where the dust and air first hits. Apparently, the wood hits hard enough to lose some moisture and generate heat. This creates a fast corrosion process aided by the sand blasting from the high silica content in sawdust and other materials sucked in.
Most industrial cyclones are made from coated heavy steel to keep the cost down. Because our small shop cyclones are generally much smaller we can make the whole unit of stainless steel, one of the new very tough plastics as the Clear Vue Cyclones used to use, or coat the contact area inside your cyclone. To work plastic or weld stainless, you do need specials tools, so most end up building from galvanized steel. If you make your cyclone from steel or stainless steel then you should use a replaceable rubber blast plate that sits right where the air first hits inside the cyclone to minimize the sandblasting wear.
My cyclone has a rubber sheet from some old cupboard liner glued on with polyester caulk where the material hits to provide a little extra protection. Alf Toy does some work with making signs and suggests using the tough and long-lasting sandblast resist sheets he uses in sign making to protect the inside wear spot on our cyclones.
He says, "We use this resist to mask off areas on sandblasted cedar signs and the same material is used with the even heavier sandblasting used to make granite gravestone markers. This tough adhesive backed rubberized material is easy to apply, holds up well and sticks tight enough that the high-pressure air from a sandblaster does not pull it loose.
The adhesive on the resist is the same as used on the vinyl material that sign makers use to make decals for automobile lettering which can last for 7 or more years. You should go to a gravestone store and ask for a foot square piece of resist or whatever size you need. Many just buy a small shop dust collector blower and use it to power their cyclone, but this is actually a very poor idea.
We size our blower to work against the expected pressure range. For our small shop cyclones this is typically from a low of about 4" of static pressure to a high of about 12". In short, the best approach is to size our blower then go looking for what makes the most sense.
For a cyclone what makes the most sense is an oversized blower housing and impeller attached to a good motor. I get a few people every week who want to power a cyclone with a typical air movement fan in the form of a big squirrel caged impeller, an inline duct fan, or some kind of bladed fan. Unfortunately, they also need to move this much air at a real 4" to 12" of pressure to do any good with a cyclone.
I engineered a special airfoil impeller that will provide up to about 8" of pressure which is just about the minimum for a one car garage sized shop.
Although these airfoils and other caged impellers are far more efficient, they are just plain not safe to use with woodworking dust. Woodworking makes long stringy curls and shavings that can get caught on any of the impellers that are not self-cleaning.
Material handling blowers are built to be self-cleaning and are the correct type of impeller for us to use. Likewise, with these being one of the less efficient impellers we need a big enough motor and large enough impeller to drive the air at the pressures we want.
My testing showed nothing less than a 14" diameter impeller will really move enough air. Over the normal pressure range in our shops the motor turning this sized impeller will pull as much as 3. With motors coming in 1, 1. Although we can get 3 hp motors that have an extended service factor allowing them to produce 3. In short I recommend a real 5 hp motor which lets us turn a real 15" diameter material handling wheel with the backward curved BC blades needed to minimize noise.
It seems only reasonable that the dust collector makers would sell just their motor blower units and maybe even sell a blower motor combination that was ideal for our cyclone sizing. Most say they sell blowers separately, but only a few do, and those charge as much if not more than buying a whole dust collector.
Jet, Wilke Machinery, PSI, RBI and Laguna Tools all sell motor blowers without having to buy a whole dust collector, but prices are high and the impellers are too small until you get into their larger units which come with more motor than most need. The 3 hp dust collectors with a 14" impeller provides a maximum CFM and these are the best compromise I could find. Unable to find what I wanted, I worked with a few vendors to provide the right sized blower wheels and motors to work best with my cyclone design.
More detail is on my Cyclone Building page. In addition to not offering very efficient blowers, you need to know most hobbyist blower vendors advertise extremes, not practical working efficiencies for motor horsepower and cubic feet per minute CFM output. Most dust collector and cyclone makers use what are known as compressor duty motors. Sadly, many of our small shop vendors rate their compressor motors like their shop vacuum motors based on how much they pull during startup.
A typical small shop 5 hp compressor motor is really a 3 hp motor when running but is designed to start a heavy load so will have a heavy duty starting circuit typical of a 5 hp motor. We need this heavy starting circuit to handle the high load while starting up our heavy impeller wheels. I gave up on the traditional small shop motor suppliers after having too many motors burn out and shifted recommending the Leeson American made real 5 hp compressor motors that can handle the heavy startup current and then run with a full 5 hp of capacity.
CFM is a similar case of what you see advertised by the small shop vendors is not what you are going to get. Current truth in advertising allows anyone to claim whatever they can show if even for only an instant. With clever inlets and no filters or cyclones, small shop vendors have figured out a way to rate their blowers at just about double what they can do for real in a working environment.
The reality is something very simple that sadly many small shop vendors don't understand themselves. Performance for small shop blowers almost always comes down to one simple thing, the diameter of the impeller. The reasons for this are:. Most have to use simple material movement impellers that are built like tanks to handle material hits from pieces of wood. Whenever our cyclone dust bins get full, all goes right through the impeller, so don't get sucked into buying an aluminum impeller that can explode when hit with a wood knot;.
Most use material movement impellers with backward curved blades because these provide the most efficiency with the least noise;. Experiments show that changing blade height over about one third the diameter of the impeller has little impact on impeller efficiency because each blade shadows following blades;. Experiments further show that blade length which establishes the diameter of the impeller is almost totally responsible for establishing impeller efficiency; so,.
These facts let you make an informed decision on what a blower can really produce instead of having to rely on totally useless sales claim information. With all virtually identical in performance, you can look at a good ACMA certified fan curve table for an industrial blower with the same size impeller running at RPM.
That table will instantly let you know not only the expected CFM at different resistances, but also the needed horsepower to drive an impeller at that load, and even the size of the inlet needed by that impeller.
If the sales claims don't match, please don't be surprised as many of today's hobbyist blowers appear to look pretty but their designs are so bad that almost any hobbyist with just a few minutes time can build a far better performer using the same impeller.
Dust collector makers have to protect their motors from burning up when allowed to run wide open with no airflow restrictions.
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