Photos by Manufacturers; Lead photo by Mark D. Goldman
Managing wood chips and dust is essential in all workshops. In smaller shops that don’t use machinery to any great extent, a small shop vacuum, perhaps paired with an overhead air cleaner, might be all that’s required. However, in a typical shop equipped with the usual array of wood processing equipment – table saw, bandsaw, planer, jointer, and so on – you need a more capable dust collection system. Ideally you want a system that’s effective at two things: handling large volumes of wood chips, and keeping as much of the fine dust particles out of the shop air, and your lungs.
Most woodworkers will be familiar with single-stage dust collectors, as they’ve been around for eons. They’re still the most popular collector for small workshops. They consist of a motor connected to an impeller (a hub with a series of blades). Wood chips and dust-laden air are drawn in through the impeller. The wood chips and heavier dust particles fall into a waste container (often a plastic bag, sometimes a canister). Air, typically laden with very fine dust particles, is vented out through a filter, which can be a fabric bag, or a rigid pleated canister, and back into your shop.
A typical single-stage collector will have an air flow capacity of about 500 cubic feet of air per minute (CFM). It works best when the ducting in a shop is very short, with minimal bends and elbows. The amount of dust that is expelled into the shop air depends on the effectiveness of the filter. Most cloth bags are rated at 30 microns (the size of dust particles they can screen out), while a typical canister filter is rated at about 1 micron. However, you really need to protect your lungs from the smallest dust particles, down to about 0.3 microns.
Today, cyclone collectors are gaining in popularity. Unlike single-stage collectors, they treat wood chips and dust in two steps, which is why they are often referred to as two-stage collectors. The body of a cyclone collector incorporates a cylindrical funnel (aka the cone). The impeller, which typically sits on top of the collector, creates cyclonic (centrifugal) action, causing the air to spin around in the funnel. Heavy wood chips fall down the funnel into a waste container, while the lighter dust particles are drawn up through the impeller into a filter canister. As air is vented out through the filter into the shop, the fine dust particles fall into a waste bin, or are trapped in the pleats of the filter. All cyclones are equipped with canister filters – standard filters (sometimes referred to as ‘high-efficiency’ filters) remove dust down to 1 micron; HEPA filters remove the most insidious dust particles, down to 0.3 micron. Considering it’s the smaller dust particles that cause the damage to our lungs, this is an important consideration.
This two-stage process of pre-separating the heavier material means that the filter will clog up much slower than with a single-stage collector. Less clogging helps to move more air through the collector system.
There are six cyclone brands widely available in Canada. They offer models with motors ranging from 1.5 to 10 HP. We have listed the 1.5 HP models in the chart. Any of them are capable of handling the dust extraction requirements for most small professional and avid hobbyist shops, which typically use one machine at a time. If you work in a shop that runs multiple machines at the same time, and has long ducting, then you’ll want to look at larger cyclone models.
For all collectors to work efficiently (not just cyclones), they need to generate a high volume of air with enough velocity to move the chips and dust from shop machines, through the ducting, and into the collector. Otherwise, the debris can pile up in the bends and elbows, or at the blast gates. This is why you want a high CFM rating for the collector.
However, as the air moves through the ducting it encounters resistance in the form of friction from the internal walls of the ductwork and the various bends and elbows. This resistance is referred to as static pressure (SP) loss, and is measured in inches of water (water lift). Once air starts moving through the ducting, static pressure begins to increase, and airflow decreases.
The CFM levels in the chart are reported at zero static pressure loss (0″ of water lift), and range from a low of 775 CFM for the Grizzly up to 1,250 CFM for the CWI. Water lift, which is listed at zero CFM, ranges from a low of just over 7″ for the Laguna, up to 10″ for the Grizzly.
You might think of just choosing the collector with the highest CFM and water lift specs. However, the CFM requirements of the machinery you use, the diameter and length of your ducting, and the number and type of connections installed on the ducting, will affect the performance of your collection system. You can calculate the CFM requirements and SP loss for your existing (or planned) shop to ensure that the collector you choose will meet your needs. See the sidebar (Calculating Static Pressure Loss), or consult one of the online resources, such as air handling systems (www.airhand.com/designing).
Of course, there will be a range of other factors to consider when choosing a dust collector.
Like cigarette smoke, sun exposure and asbestos fibers, it’s the long-term effects of breathing in very fine dust that has the greatest potential detrimental impact on your health. Any dust collector, or shop vacuum for that matter, equipped with a HEPA filter, will provide the best protection from fine dust. The CWI, Grizzly, and Oneida all use HEPA filters, while the other three brands have standard canister filters. There are after-market HEPA canister filters that you can purchase, and some manufacturers can upgrade models with HEPA filters.
All the canister filters, except the Oneida, are equipped with a flapper handle that makes it easier and more effective to clean the filter than using compressed air.
There is a noticeable increase in airflow between a canister filter and a traditional cloth bag filter. This is due to the relatively large surface area of the cartridge filter.
You can save time with a larger waste drum, though it may be a moot point if you don’t generate a lot of wood chips in your shop. At 18 gallons, the CWI, King Canada, and Laguna have the smallest drums. The General and Grizzly drums are 50 percent larger, while the Oneida drum tops the scales at 35 gallons. All the drums except for the Oneida are equipped with wheels, so you can roll them about. You can let the debris fall into the drum, and then empty it outdoors, or install a plastic bag into the drum, making disposal easier and cleaner.
These collectors take up anywhere from about 8 to 16 square feet of space. The CWI, Grizzly, King Canada, and Laguna will fit into an areas 2’ by 4’, with a bit of room to spare. They’ll also comfortably reside in shops with ceilings as low as 6 feet, enabling you to tuck them under stairs, or install shelving overhead for extra storage. The General and Oneida require a larger footprint. For the Oneida you’ll also need a ceiling height of just over 7’.
The CWI, General, King Canada and Oneida collectors can be plugged into a standard 15-amp circuit. More than likely it will have to be a dedicated circuit (not used simultaneously by any other device while the collector is running). Both the Grizzly and the Laguna require a 110 volt, 20 Amp circuit – for these make sure you either have an available circuit, or can add one to your service panel.
For anyone who works in a home basement or attached garage, noise is always a concern. Current standards suggest that a noise level of around 85 dB is the threshold at which hearing protection becomes necessary to avoid long-term hearing damage. The CWI, King Canada, Laguna, and Oneida units are well below that level, at between 73 and 75 dB, at 10 feet from the collector. The General and Grizzly approach the standards at 83 and 84 dB, respectively. However, since any collector is going to be used simultaneously with another shop machine, the overall dB levels will be considerably higher, necessitating some form of hearing protection.
While we often get caught up in the initial purchase price, it’s important to consider the return on your investment over the anticipated life span of the product. Like many, if not most shop machines, a cyclone collector should last the independent woodworker or hobbyist woodworker a lifetime. The two crucial components that might need replacement are the motor and start switch. Both are easily replaced. In my experience, a motor that is indeed defective is most likely to fizzle out very early on – likely the first time you start the machine. All the manufacturers’ warranties cover this eventuality for the first year of operation.
Consumables (plastic waste bags) do add marginally to the overall cost of ownership, while the canister filters should last for about as long as you own the collector.
If you don’t have a whole shop dust collection system, but rely on a shop vacuum (aka dust extractor) you can increase its efficiency by adding a ‘pre-separator’, essentially converting it into a two-stage collector. The pre-separator is just a collector drum installed between your vacuum and shop machinery. If you go this route, make sure you use a thick walled drum to prevent the drum walls from collapsing. While you could use any lid with the drum, a specially designed cyclone lid will better enhance cyclonic action in the drum. The larger wood chips are diverted into the drum, while the finer dust is sucked into your vacuum. A benefit of a pre-separator is that you won’t have to clean the vacuum filter quite as often, and your vacuum will maintain better suction for a longer period of time. Plus, you won’t have to empty the vacuum waste bag nearly as often. You can assemble your own pre-separator system from bits and pieces, or purchase a ready-to-go unit such as the Oneida Dust Deputy or the Clear Vue Mini System CV06, available from Stockroom Supply.
You can calculate the SP loss for each machine in your shop. Calculate the number of feet of duct between the machine and collector. To this add 6′ for each 90º elbow along the line, 3′ for each 45º elbow, and 7′ for each T-fitting. Then multiply the number of feet by .055 if you will be using 4″ ducting, .042 for 5″ ducting or .035 for 6″ ducting. The result is the static pressure loss for the machine. Let’s look at a shop that has a table saw connected to a collector via 4″ diameter ducting that is 18-feet from a collector, and has one 90º elbow. Using our formula above – (18 + 6) x .05the SP for the table saw will be 1.32. You need to do this for each machine that is connected to your collector, add 1.0 SP for air leakage, and then tally the total, which will be the SP loss for your dust collection system. For optimum efficiency, the collector you choose should have a water lift rating equal to or greater than the SP loss you have calculated.
Carl Duguay - [email protected]
Carl is a Victoria-based furniture maker and the web editor at Canadian Woodworking & Home Improvement.