department of education terminology

inline dust separator

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The spinning air throws the heavier materials outward to the cyclone walls. Cyclone separators can go longer between dumpings because all separation occurs above the collection bin. Designing a good fine dust separation into a cyclone compatible with indoor use with fine filters requires a whole different design and considerable work. Additionally, all impellers can build up heavy deposits of dust and sap, so should regularly be inspected and cleaned because too much of a buildup of sawdust and resin can create an out of balance condition that can ruin motor bearings and cause our impellers, especially the light weight ones to fail and possibly fly apart. He unfortunately gave me some bad advice when he recommended installing a good quality ceiling mount air cleaner. Blower impellers are chosen both to address the noise issues and how dirty the air they need to move. My doctor says those without my allergies should use 0.5-micron certified cartridges. Air starved means the blower has an impeller that is too small to overcome the resistance it is working against, so it just loafs along moving a minimum of air. Air trapped in the fast moving impeller slings out the sides out creating a very high suction in the center that keeps drawing more air in through the filter. Almost all go with use of a cyclone separator as the only other really viable option other than buying a commercial dust collection system. Channels in this separator's low-profile lid direct air into a spiral motion within the bucket or bin, slowing the air's speed so debris settles out. They use cyclonic separation to spin the air inside the trashcan causing the heavier particles to go to the can walls where it will eventually drop. Otherwise, any small ducting runs or restrictions will get severely kill the airflow just like partially opening a water valve. Collect and store dust in metal cans to avoid fires. That cleaned air then spirals up through the center of the cyclone then exits through the cyclone outlet. It is best to orient our filters vertically so the filters wear more evenly. The problem is when brought indoors these types of filters which are still the standard on most small shop equipment are "dust pumps" that fill our air with huge amounts of fine dust. Air is sucked into the side of a blower and hits the impeller. I also had to engineer my own blower then test various motor and impeller combinations to power my cyclone and move enough air to ensure moving the air needed at our larger tools for good fine dust collection. More than 40 lbs. Many don't want to mess with this overhead and just use the less efficient material movement impellers. Air movement volumes are measured in cubic feet per minute (CFM). Government requirements forced large commercial woodworking facilities to leave "chip collection" behind in favor of fine dust collection in the late eighties. Fans move air by turning different kinds and shapes of blades ranging from flat like a ceiling fan to complex spiral and airfoil shapes. Cyclones are well understood with many computer modeling programs available to help optimize their designs to separate two different weights of materials. Most of us use a blower built into either a dust collector or cyclone based dust collection system. Moreover, because most stationary tools leak dust careful testing by air engineers shows we need closer to 1000 CFM for effective fine dust collection at our larger and dustier tools to pull in the slow moving dust before it gets dispersed by normal room air currents. The exiting air creates a vacuum that pulls more air through the blower casing or shroud known as the blower housing inlet. Inline fans are another type of HVAC fan. Without protection the odds are close to 100% that you and even those close to you will eventually develop some fine wood dust related health problems. A few instead put some form of restriction on either the blower inlet or outlet to limit how much air can pass. The larger the cyclone diameter the less resistance and smaller blower we can use.

If you do not care, then ignore all the rest and go buy at least a 1.5 hp dust collector or larger depending upon your shop size and ducting. The finer filters clog far more quickly so need a much greater filter area or some way to separate off much of the dust before it can reach and clog the filters. Some vendors avoid and ignore this concern by simply supplying wide open filters that pass most of the airborne dust right through. The less honest vendors make things worse by making up their own filtering claims and forgetting to include the needed airflow information. An effective exhaust fan should move enough CFM to change out all the air in your shop at least once every three minutes. Often we add a trashcan separator to our dust collectors as shown. Copying an outdoor commercial cyclone with high built in turbulence is just plain dumb as that high turbulence is only there to break the fine from heavier dust. They make terrible dust collector blowers because they cannot generate the pressures needed to overcome the resistance of our hoods, ports, ducting, separators, and filters. To get that you need a 5 hp motor coupled to a 15" or 16" diameter impeller. For those who are braver, there is an excellent inexpensive book, How to Design & Build Centrifugal Fans by David Gingery on making and balancing your own blower.

Sucked air instead comes from all directions at once, so the airspeed for sucked air falls off very quickly. Additionally, that inlet needs to be small enough that we never get into an open air situation where the blower motor tries to push so much air it quickly burns up. These vendors continue to make short, often round cyclone inlets to reduce manufacturing cost. It took designing a whole new type of inlet to carefully use a laminar flow to stabilize and start the air stream right on the side of the cyclone. Moreover, unlike dust collectors, the air most vacuum impellers move also provides the motor cooling, so any blocked airflow kills motor cooling and will quickly burn up motors. Also make sure you check out Dust Collection Electrical and Safety. In addition to these being the wrong cyclones to copy, the vendors have made these cyclones work even more poorly by adding additional compromises to address a few small shop realities: Most small shop users have limited money to spend on their cyclones. At my vendor's advice I replaced their garbage internal cyclone filter with an even bigger and finer top quality filter than they offered. When challenged with no additional 240 volt power in my shop, I chose to use an even more efficient caged impeller I had custom made. Although small shop woodworkers often need exhaust and cooling fans, most fans are not suitable for dusty use or able to power a cyclone or dust collector. I also had bad experiences with a few other professionally made aluminum and plastic impellers letting go not quite so dramatically. Most dust collection fan performance is measured in Imperial units (feet, inches, and pounds). With no oversight except what we exercise with our purchasing decisions, most small shop vendors claim to sell fine filters but instead deliver undersized far too open filters. Smaller bins fill faster, but handle easier for dumping, so decide which is more important: frequency or convenience. Everyone else is also looking for the same single phase 3 or 5 HP motor-blowers. Vacuums use universal motors turning at very high speeds, typically 18,000 rotations per minute and faster. Early dust collection systems used bag filters where the dirty air was blown into the bags and the bags were kept clean with a shaker that turned off the airflow for a bit and shook the bags out. Between frequent cleaning, holes punched by flying chips, and pushing the fine dust right through, even the better cartridge and bag filters rapidly open to pass most airborne dust. Typical small shop trashcan separators work well until you have a system that moves more than about 450 CFM. There is considerable debate on whether or not to buy a wet-dry or only dry vacuum. They tend to be a far better solution for powered tools because of that additional smoothness, longevity, and lower cost.



The problem is at low dust collection pressures air is virtually incompressible, so any small opening acts like a partially closed water valve and kills our airflow. This is an interesting balancing act. Without a smooth evenly opening curve, you get performance killing pressure waves and bad vibrations that can ruin motor bearings and cause the impeller to fly apart. Big? Similarly, games can be played by removing filters, using oversized hoses, leaving the collection bin off, etc. Likewise cleaning wear and holes from being hit by sharp chips also quickly open up these filters, so even fine filters soon freely pass most of the finest unhealthiest dust.

The cleaning we need to do to protect our filters not only gives regular "dust baths" in the very dust we need to avoid, but also quickly wears out filters. Most will do like me and start with a cheap small garage vacuum then buy at least two more larger vacuum before they realize that getting a good vacuum is a must for good fine dust collection. Although the most powerful and perhaps the nicest are the larger Festool vacuums, I instead recommend the slightly less powerful but still expensive big Fein vacuums with the cartridge filter. Those with 1 HP to 2 HP will support 5" diameter ducting. The two coupler components fit standard 4" dust hose as well as the Dust Right Handle system (sold separately).

With that all said is a filter box what I recommend? Nah. Small shop dust collectors, often called hobbyist dust collectors, are downscaled versions of outdoor commercial dust collectors designed to move just barely enough air to collect sawdust and chips from one machine at a time. Fans are rated based upon their performance measured in terms of how much air gets moved, at what speed, and at what pressure. The problem with cyclones is not just making their normally less than good quality copies. Look for a separator with a foam-rubber or soft-rubber gasket that seals the lid against air leaks, ensuring maximum suction. Their disadvantages are they cannot take direct material hits and will clog quickly unless you use a pre-filter or separator. Engineering practices rate filter performance when clean and new and rate filter resistance when the filter builds up a semi permanent cake of fine dust that lodges in the filter strands. Vacuums show us an important difference between blowing and sucking air. Skip to the beginning of the images gallery. With most filters now equally coated and effective when you blow from either the inside or outside, you can build your filter setup either way. Where? In practice the airflow inside a dust collector is so violently turbulent that chips and even small blocks constantly crash into and frequently poke holes into our filters. Even with its heavy steel impeller, it still needs regularly checked and cleaned. Sadly, when we started testing with our meters, we found all the major name ceiling mounted air cleaners came with filters that do a great job getting rid of the visible dust that ruins our finishes, but most freely pass the unhealthiest fine invisible dust. In addition to the normal problems with buildup of strings and shavings, airfoil impellers (AI) also have a serious problem with stalling if they don't have enough airflow or the pressure gets too high. Just like a big subwoofer it goes right through walls and ceilings (I know thinking about my daughter as a teen with a big subwoofer in her room and later her car).

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inline dust separator