It works well, is plenty strong, is easy to shape, and it costs 1/3 or less the cost of the other forms of pipe. Also, over time junk will go into those pipes and they will be a nightmare to clean or replace. He found a very elegant solution that gives far better airflow than we get with even the nice tapered reducers shown above. Note this system uses a 3+ hp blower needed to support an 8" diameter main with only 6" down drops. Also, for maximum efficiency, particularly with a cyclone, this layout keeps a straight run that is at least 4' or longer going into the inlet. Our problem was so severe that we had sparks jumping 1 1/4" from our piping that would leave burn marks on your skin. Another solution for hanging duct is to use stranded metal cable (called wire rope) with special clamps that let you adjust the length. in stock. Using a piece of insulated HVAC flexible duct on the exhaust part of your blower will also help. Back as a hobbyist when PVC pipe was cheap I built a nice ducting system from the agricultural PVC that is readily available in this area. For tools that have two ports like a table saw, use a 5" duct to the larger cabinet port and a 4" to the smaller blade guard port. Our smaller blowers also require us to use properly sized duct with long sweeping big radius curves or 90-degree joints broken up with a straight run between two 45-degree joints. I started off using HVAC snap lock duct and quickly learned I don't like fighting with snap lock and I had to use the heavier 26-gauge because just like with one of the cyclones I built, standard 30-gauge collapses if the system gets turned on with no blast gates open. I hot melt glued in big neodymium super magnets on the front of that sweep to collect nails and screws before they get sucked up. Neither I (Bill Pentz), American Air Filter, nor any other references or links on these pages will accept any liability for the applicability of this information to your specific situation or any damages or injury caused to people or property from the use of this information or from any associated links. Additionally, duct itself adds resistance that can also seriously hurt our flows, so a good ducting design uses all the right sized ducting components and provides the shortest straightest runs possible with minimal sharp bends or joints. Although most buy stainless metal band screw type clamps for securing their flex hose, standard stainless steel band clamps work poorly. If you use a small section of flex hose between your ducting and your blower and cyclone that will also make a huge difference. Many choose to use this class of pipe because it is readily available in or can be ordered by some of the larger hardware stores. In small shop systems when we calculate the overall static pressure we normally just add up the resistance levels for each piece starting with our tool hood, then ducting with fittings, then separator if used followed by filter resistance. In areas where we need to install drainage or that do lots of irrigation for agriculture, we often have some other less expensive thinner walled pipe options. Our phone lines are open from 9am-5pm central time, Monday through Friday. Our chop saws, miter saws, sliding compound miter saws and radial arm saws all pose one of the more difficult fine dust collection challenges. Also notice that in spite of some vendor claims, these values show that PVC moves more air with less friction than even equal sized spiral ducting. When I bought a set of air gauges and did some testing, I realized that my trashcan separator was not good news at all. Without choking on that tiny piece, try to breathe through it. For almost all small shop systems this works out to using the same sized duct for the mains as the down drops. If your ducting is too small, then it instead of your blower defines the CFM that your system can provide at your machines to pick up the dust. There are many different types of wyes, but the best are going to be those that are smooth and either the most gentle angle or longest radius. Moreover, few of these fittings seal real well or are that smooth inside. Use a Large End Coupling (female) or short piece of spiral pipe for connecting fitting to fitting. Woodworking makes huge amounts of fine dust compared to how little it takes to exceed these standards and harm our health. The resistance and size of the duct will define the airflow. That guard rested on the wood and blocked the fast moving airstream that was spraying the fine dust all over. Note it does not take much curve at all to make a huge difference. I had so much ducting the cost to buy actual dust collection wyes with the correct ends was too high, so I invested around $100 buying on sale an inexpensive Harbor Freight knockoff of a Pexto machine that let me crimp the female joints into male then flatten and expand the male joints into female. For saw blades I strongly recommend use of hoods that incorporate at least a splitter or riving knives plus use anti-kickback pawls. Wood shaper emissions are usually controlled by an exhaust hood located at the back edge of the work table which allows the operator to freely move the work piece over the table. From those working from home who need high quality air filters, to the other essential businesses we supply products to, we're here for you. That same airflow only provides 1310 FPM in a 7" main and 1003 FPM in an 8" main. Although that charge can shock you, the experts say it is not ample to cause an explosion in hobbyist based systems. Those cracks made for a moisture problem that was not compatible with my galvanized ducting. Many choose to use the inexpensive sheet metal HVAC wyes found in home centers, but these have far more resistance and potential to cause plugging than what is appropriate for dust collection. I bought on-line a large spool and a pound of ferrules for what it would have cost me to buy just a few pieces from a boat store. One of the better known that many woodworkers have used successfully is the Gripple System. To get that length I drew a full sized circle, then divided the circle into sixths, then twelfths, then twenty-fourths. Wood dust is a known carcinogen and requires a dust collection system and/or other safety measures to remain risk-free. To support the minimum 1000 CFM we need for fine dust collection, we need to upgrade our 4" ducting and tool port connections to a total area the same as the opening area of a 7" duct or we must use a bigger more powerful blower that generates the pressure to pull ample air through a smaller duct. To make sense of this on my other pages I share a simple experimental game moving a balloon and two straws. That totally eliminated the massive static electrical discharges and earned me a bonus!" When you have the tape through the PVC, stick the aluminum tape to the end of the PVC pipe. When it is all the way through stick the tape to the inside top of the pipe using a tennis ball to smooth it down as far as I can reach. The next best is smooth walled laser welded steel pipe followed by top quality metal spiral dust collection ducting and fittings then HVAC metal duct, followed at a far distance by corrugated metal pipe and flex hose. The standard 4" connections on our larger hobbyist machines kill the CFM below what we need to collect the fine dust. I've helped build one of these type shops and did most right, but also learned a few lessons the hard way. Fortunately, the better air engineering firms who certify that their customer shops will pass the air quality tests have been kind enough along with the EPA to share different hood designs that we know work well. Most small shop users will have to upgrade their tool dust ports themselves and use the wrong types of ports. Our employees dreaded working with the equipment. Nothing short of a strong vacuum generates the pressure needed to pull the air through a small blade guard port. Yes, it kills the dust collection performance. Sadly, most small shop vendors sell blowers that do not perform nearly as well, so the commercial blower tables often show much better than what we can buy from our small shop vendors. Grizzly, PSI and others also carry 6" flex in a few different grades as do most local hosing suppliers. Many publish their information on the Internet such as Cincinnati Fan Engineering Data. Eventually I changed to two different approaches after realizing I was mostly making 45 degree wye fittings in 6" PVC. I already got a price quote from Paul, and I see that the Delta motors are still available via eBay. It almost made it, but his metal calipers got turned sideways at the second bend and jammed in so hard it locked in place. Good "chip collection" collects the same sawdust that we get with a broom, and good fine dust collection provides good "chip collection" plus also collects the fine dust ample to keep our air quality below one of the different air quality standards. The clamp threads through a thin slot I cut in the side of the block. Cutting curved slots into the sanding pad as shown relieves the pressure caused by the extra suction and provides additional dust control at the pad edges. I also mounted my square wash tub to the rotating portion of my saw so when the blade rotates the tub stays centered behind the blade. It is easy to just stick the tape on the outside of the pipe. I drill out those connections, then use a piece of angle iron and hammer to square up the corners with the top and bottom set at the width of the outlet I want it to mate with. As shown some configurations are far better than others. Because improperly designed ducting can cause fires, fail to meet local codes, etc., these drawings, plans, procedures and words are for information only. If you are just starting I recommend going right to the 16" impeller and skipping these air volume problems. I put my pipe on my workbench oriented with where I want the tape on top. There are all kinds of different PVC pipes out there. Wynn Environmental carries affordable clear good quality 6" PVC hose and would recommend going with them in 25' lengths. Bottom line, if you have today's normal dust collector and cyclone blowers, you are limited to either living with 785 CFM airflow with 6" diameter ducting or you can get your 1000 CFM with the 7" diameter ducting but will have some plugging in vertical runs. There are lots of ways to mount your ducting to the ceiling or wall. Go with overhead ducting so you don't have to pull dust up at the end of the run by the blower. I bought a bunch of HVAC parts and am copying forum advice you gave others. The wrong pipe size, leaks, fittings that change the air to abruptly, overly long runs, an inefficient separator, and a poorly designed cyclone can each cost far more CFM loss. These hoods then also must move a large volume of air around the working areas of our tools. So little air was moved I went back to using my powerful shop vacuum on all tools with small ports. That left me with a 4" port for my blade guard and a 4" port on my saw cabinet. Light 24 Gauge 45 Degree Saddle Tap Tee perfect for a small hobby shop with a max 3 HP dust collector. I found a heavy paperclip and shop vacuum works wonders, but need to clean every few months. The traditional approach for hanging duct some distance from the ceiling is to attach galvanized wire to the ceiling or to a metal pipe then around our ducting. Lesser quality hose with rougher ribs can be purchased through Grizzly. A 4" port will only support about 350 CFM, but the airflow charts say we need 550 CFM for good fine dust collection. In terms of the transition to the blower, you can go to my Transitions section above and see how to build a sheet metal transition that will go from either round or square to either round or square. One of these tests was at an engineer friend's shop with the testing coming out worse than ugly. A 2 HP dust collector capable of 1200 CFM is lucky to provide 450 CFM. That is plenty for good chip collection at most small shop stationary machines, but far short of the 1000 CFM I recommend for good fine dust collection. I found the best prices at Wynn Environmental (thanks Jack Diemer) and next best from Amazon. The same is true of our ducting. My new home with its own shop in a large separate building and elevated floor inspired me to foolishly place the ducting under the floor. We are shipping orders on time, with no delay in manufacturing. Now 'tape' the backing to the rod then stretch the aluminum tape tightly angling it towards the top of the PVC piping (12 o'clock position). I used a second compass that is set to the length of an arc that is 1/24th of a circle. |
There are many who are interested in having automated blast gates that open when you turn your machine on and close when you turn your machine off. They invariably have to share why we need bigger duct to move enough air and few small shop owners take kindly to being told they are going to have to remake most of their tool hoods and ports for the result to be effective. Polypropylene fibers traveling through 3" or 4" PVC piping creates massive amounts of static electricity. That makes the dust more awkward to empty, but safer and the metal flex duct is much less expensive. Pictured to the right is a commercial Rosseau hood that does the same job. We are in an interesting time right now where the computer world is changing so fast that this leaves an opportunity for woodworkers. I found on both the metal and PVC pipe, use of standard 2" aluminum duct tape found in home and HVAC stores provides great seals that do not leak or come apart. It was a bear to find on Amazon and often not in stock (search for "jet hose"). OUCH! Created: May 9, 2001
My friend who has done this for years made this look too easy. We use this chart to pick two different diameters that equal or slightly exceed the area of the incoming ducting. Most air engineers that are just interested in getting sawdust build systems targeted to get an airspeed of 4000 FPM in the main. In some cases we cannot amply fix our tools, so we must use them with a powerful downdraft table. With a little solder that copper wire is there for life! Keeping workshops clean and free of debris is crucial to the health and safety of woodworkers. "With regards to cyclone noise, I work in automotive and one product which probably be good for reducing cyclone noise is what we call peel and stick mastic. The starting tie gets a large loop to hold one end of the duct. If you bolt directly to your framing, most of the noise is fairly low frequency so like a subwoofer will go all over your shop and house if they are attached. Your actions are your responsibility, VERIFY and CHECK information out before proceeding, and don't attempt anything without the required skills. Most cannot because it has too much resistance. The result in terms of efficiency is not too bad for each joint, but unless you are careful the total can add up to terrible performance. Typical small shop dust collector and cyclone blowers only generate about half of their maximum possible pressure when working, so run in the 4" to 6" of pressure range when working. Dust collection systems rarely move air at much over 40 miles an hour. (Thanks Grant Erwin!). Contractor saws also need good collection below the blade, but most lack the enclosures needed to control the dust sprayed below the blade. I also have slowly been adding other hood designs that work well: Random Orbital Sanders NIOSH Recommendation. After living under the crawl space with every change, I said never again, plus there were condensation problems that ended up rapidly rusting and corroding my duct. They provide simple formulas and approaches to help design our ducting to move the needed air with ample volume and speed at each tool. Personally, if you cannot afford nice spiral smooth interior walled ducting and smooth snap on fittings, this is my next favorite choice. Shipping ducting is tough because it is so bulky it gets shipped with heavier items. If your ducting is too large you might not maintain the airspeed needed to keep sawdust and chips from building up and blocking your ducting. This dust control device is not currently commercially available, but is patented so you can make these changes for your own unit but cannot go into commercial production. If you're interested in Nordfab Laser Welded Clamp Together Ducting my friends at Air Cleaning Specialists Inc. (ACS) (866) 455-2130 are happy to work with hobbyist and small shop owners interested in a clamp together duct system. Otherwise buying this type of blast gate is difficult without a commercial license to buy from a wholesaler. (Thanks Amer from Amer's Woodworking)
Almost all hobbyists and six out of seven professional woodworkers work in small shops that are not government inspected or covered by any standards except what we choose to put in place for ourselves. Just about every woodworking machine and hand tool operation launches fine dust particles airborne. All wye (Y type) takeoffs need narrow angles. Our on-site staff will follow the appropriate best practices and guidelines set forth by OSHA's latest release of "Guidance on Preparing Workplaces for COVID-19.". They provide undersized insufficient horsepower blowers, improperly sized ducting with poorly designed and made fittings, blast gates, and tool hoods. What do you use and what do your recommend? If you have this kind of set up, you should never clean your shop floor or other areas that might have metal or stone bits with your dust collector. After digging into the engineering behind cyclones, I realized that almost all small shop cyclones were copies of the same original design. They found we need the same airspeed to pick up the chips as we do to keep them moving in vertical ducting runs. One system I tested had so many leaks from installing the gates backward that he had less than half the total airflow that we got after reversing the gates so they sealed well. I'm just in the preliminary stages of planning a cyclone dust collector based on your airfoil blower. Neither the author nor any other references or links on these pages will accept any liability for any damages or injury caused to people or property from use of this information or from any associated links. Because my plans are scalable, your evolutions will change based on cyclone and blower sizes. If you have not already read at least the Home and Medical Risks pages, you should read those pages first to better understand fine dust risks and how poorly most do at providing good protection. This makes sure that stuff does not build up in down drops with closed gates to create plugging. His mixed combination of Imperial and Metric sized ports on his tools required lots of different reducers and expanders to work with his 6" mains. I learned to start with the longest side and draw a line then follow the circle around as I turn the disc.". I admit my saw guard soon got removed and ignored because taking it on and off to ensure my cuts were aligned correctly was too much trouble. Copyright 2022 Air Handling Systems | All Rights Reserved | Site by: Dust Collection Frequently Asked Questions. Click here to view more information about the ACS ducting design service. After retiring I fell in love with woodworking, have just finished building a large shop, and am slowly adding one machine after another. It was found that, in spite of this control, large amounts of wood dust were still emitted into the workroom. Use a Small End Coupling (male) for connecting pipe to pipe and flexible hose to pipe. These surplus computer floor squares and uprights are readily available for little cost. but I still constantly struggled with the new upper filter bag getting so full of dust it felt like cement and would barely pass air. In short, for good fine dust collection we almost always have to rebuild our hoods and use larger ports. You seem to say that 4" ducting, categorically, is not sufficient. This same approach works equally well with the nylon cable ties. Now go back to the small piece and try to breathe through it quickly. Even with venting outside, the peer reviewed medical research shows the more fine dust we take in the greater the short- and long-term health damage and this research also shows even with their much lower exposures almost all large facility woodworkers develop serious dust triggered health problems and significant loss of respiratory capacity. The easiest way to install the nylon cable ties is to use screw in mounts designed to work with these ties. I had to do this with my airfoil impeller as it will stall if I let the pressure get too high. SDR-35 is the "common name" for the 4" and 6" range of this product that has thinner walls than normal schedule 40. Why? This page translates the engineering ducting solutions that the experts who guarantee customer air quality use. It also is a huge help in cleaning my shop when used with a ShopSmith vacuum attachment. Most of these saws only come with a small vacuum sized port that cannot be easily modified. Looking at these fold lines from the circle inlet gives us the actual length of a base of right triangle whose height will be the length of the fitting. I used those extra tabs to solder a 2" ring onto the circular part to mate with my PVC. This time I used all 6" Sewer and Drain 2729 PVC because it is inexpensive, has the least resistance, and the fittings slide tightly onto 6" HVAC fittings. Just a little hand sanding on the hole leaves a near perfect joint. At the same time using PVC poses a serious fire danger for those who use a tiny blower and large PVC pipe. They have built enclosures with enough room to access the cyclone using either two layers of sheetrock inside and a third outside or sheetrock outside and a 3M construction sound deadening board inside. In readily available 4" and 6" PVC pipe there are two regularly used classes of "drain piping", this includes DWV (drain waste, vent) and PVC schedule 40. Without doing any woodworking at all, our just moving around in his very clean looking shop stirred up enough of the fine invisible dust that his shop failed the EPA, medical and European air quality standards. Connect the rest of the ties loosely. With the small shop blowers all being equal or less in performance, this creates a problem. Frequently Asked Ducting Questions (FAQs). This results in very smooth clean transitions without all the nonsense of expensive transitions. Some have had problems with this technique. The most common problem with duct piles is when they break loose they slam down the duct hard enough to blow apart our ducting joints and go right through separators then destroy blower impellers, bearings and filters. The 2729 PVC is rated for many times the pressure that even large industrial blowers generate. This angle forms a right triangle as tall as the height of the fitting and base taken with a set of dividers from that view picture. It only takes a few tries to get it down pat. It works well to power my downdraft table, collect chips from my router table and larger tools, and pick up the leaves that constantly get blown into my garage shop. They had as small as 1" diameter down drops which measured with only 22 CFM airflow letting all collect in the mains. Take a look at my for more details on how to build your own muffler. Different suppliers make pipe of different thickness so not all will fit together. Government testing shows on average just one hour inside a small shop that vents its dust collection inside results in more fine dust exposure than large facility commercial workers receive in months of full-time work. I had multiple sales people tell me their elbows were only for dust collection. (my thanks to Dave for reminding me that under typical dust collector pressures air is virtually incompressible). My current shop is in my garage and up until recently was also a mix of 6" mains and smaller down drops. In place of the blade guard that came with his over arm blade guard system my friend added a pretty amazing product. Nope. This is especially true if you buy duct with the built in seals. I wanted my tape inside and tape outside to end up right next to each other with just the PVC in between so I could use a screw and nut to ground the two layers together. We have maintained all proper design characteristics of the industrial piping. After years of changes my technique now uses heavy wide long nylon cable ties and screw in mounting brackets. Brent Dugan was the Maintenance Supervisor/Plant Engineer for a large 'Meltblown' polypropylene manufacturer (oil sorbents) for 9 years.