Choosing And Using A Dust Collector

By: Dennis Perkins

There's lots of options when considering dust collection in your shop. We'll help you sort through them and choose the right dust collector for your needs.

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Adding a dust collector may be one of the best investments you can make for your health and safety. High-quality collectors are available at several different price levels. But the collectors marketed for home woodworkers have very different capabilities. So it's easy for a woodworker to be confused.

I tried out a few dust collectors that represent the different sizes and styles. Rather than using expensive test equipment, I simply tried to find out how well each performed on common shop tasks like collecting chips from a planer.

I also set up different configurations of ductwork to see just how well each would perform in realistic shop situations. Here are some tips and suggestions for choosing and employing a dust collector to your best advantage.

SIZE MATTERS. The first thing to consider when shopping for a dust collector is the size of the unit. If you have a very small shop, you probably don't want to give up the floor space required by the larger collectors. On the other hand, in a large shop with several stationary tools, a larger collector, like a shop vacuum, might be the only way to capture the chips and dust.

In addition to the size of the collector, you'll find two important ratings: the horsepower (hp) of the motor, and the cubic feet per minute (CFM) of airflow the unit is capable of generating. The higher the airflow, the greater the capability of the collector. The good news is there are enough options on the market to suit just about any size shop.

SMALL. A 3/4 -hp, 650 CFM collector, like the wall-mounted unit shown below might be the perfect solution for a small shop. It's small enough to move around the shop as needed and conveniently hangs on the wall, out of the way of your tools.

In spite of its small size, I found this type of unit worked very well. With a ten-foot section of hose attached, it collects planer and jointer shavings very well. And since it's so easy to move, you'll probably never need to use a longer hose. This is a big step up from trying to collect dust with a shop vacuum. With it's reasonable price point, it won't break the bank either.

On the downside, the filter bag also doubles as the collection bag. This means that the air has to move through the dust on its return path into the shop. And the 30-micron bag allows quite a bit of fine dust back into the air. Fortunately, Rockler also sells a 5-micron replacement bag.

MEDIUM. The next step up is a collector like the one shown below. Typically equipped with a 1-hp motor and rated to generate around 700 CFM, this style is a good choice for a small shop with only a few stationary power tools.

Collectors of this size also use disposable plastic collection bags for the chips and dust. This not only separates the chip collection from the air filtration, but it makes them a lot easier to keep clean than having to empty and clean a cloth bag.

This type of collector works well with up to 15 feet of hose, but is still too small to serve a duct system connected to more than one tool at a time. Another limitation of this size and style collector is that most only have a single inlet.

Units similar to this are sold by a number of different manufacturers. But the thing I like about the Steel City collector is that it comes with a 1-micron filter bag as standard equipment.

LARGE. If you have a larger shop and want to set up a duct system connected to multiple tools, the 1 1/2 -hp, - CFM models, like the one shown in the main photo are just the ticket. Collectors of this size are about as large as you can go without requiring 220-volt service to your shop.

In addition to providing plenty of collection power, many manufacturers offer pleated filter cartridges to replace the bag-style filters. These cartridges capture dust down to 1 micron and the pleated filter provides an extremely large surface area to improve filtration.

As you can see in this photo, the Jet canister also features "sweepers" to help remove dust from the pleats. Just give the handle a few turns and paddles will knock loose most of the dust.

With these larger collectors you can set up fixed collection ducts for added convenience. I'll show you a few ideas for setting up a collection network on the next.

DUCTING YOUR SHOP

While it's fine to rely on swapping a length of hose between tools in a small shop, in a larger setting this will get old in a hurry. One of the biggest benefits a larger dust collector offers is that it has the power to run a fixed system of collection ducts throughout your shop. This means you can hook up a collection pipe to each of your stationary tools and capture the dust and chips with the flip of a switch.

DUCTING MATERIALS. To set up your shop with permanent ductwork, you'll first need to decide what type of ducting to use. Once again, you have a few options to choose from depending on your budget and situation.

METAL DUCTS. In large production shops and other industrial settings, metal ductwork is standard. This is the OSHA-approved solution - and it's a good one. Metal ductwork offers a couple of advantages. First, the smooth walls allow air to move with little resistance. Second, since the metal is grounded, there's no need to be concerned about a static discharge sparking the dust inside the collector and causing a fire. (I'll address this concern a little later.)

The only problem with metal ductwork is that it's expensive. For example, a high-quality Y-fitting can cost over $100. That puts the total cost of a collection system out of reach for most home shops. It's important to understand that the metal ductwork sold at the home center for furnace ducting isn't designed for this application. It's too light and can collapse when under negative pressure.

FLEXIBLE HOSE. Dust collector manufacturers also offer black plastic fittings to be used with hose as a ducting option. In my view, this is the least-effective solution. Hose is not very efficient over long runs. The corrugated interior walls create turbulence in the airflow, reducing the performance.

PVC. For good airflow at an economical price, many users turn to 4" PVC pipe. In addition to the low cost, PVC is available at most home centers. And as you can see in the photos below, elbows, Y-fittings, and connectors can be used with straight pipe to build a complete collection system. The key to putting together a PVC system is a special adapter from Rockler to make the initial connection to the collector. After that, it's easy to build just about any configuration.

STATIC DISCHARGE. One concern about using PVC is the possibility of static electricity building up and causing a spark in your collector. Studies suggest this is highly unlikely to happen with dust collectors in a home shop.

To alleviate any fears, you can always use copper wire to ground the ducts. In fact, grounding kits, like the one shown above, are available for this very purpose. You'll find grounding the system helps prevent annoying shocks as well.

START WITH A LAYOUT. No matter which type of material you choose, adding ducting isn't difficult. But it does require a good plan before you begin. And the planning process might make you rethink the way you lay out the tools in your shop. You'll find any collection system works best when you keep the duct runs as short as possible.

A good place to start is to make a scale drawing of your shop and tools to experiment with different layouts. The drawing above is a good example. Try to keep the biggest dust producers closest to the collector and add a blast gate for each tool.

BLAST GATES. To channel your dust collector's airflow from a particular tool, you need to be able to close off the unused portions of the network. The easiest way to do this is to incorporate blast gates (photo below) into the design. Blast gates are simply sliding doors that fit between two sections of pipe. By closing the door, you reduce the airflow in the network, focusing it on an open gate.

Even though the 1 1/2 -hp collectors are powerful, it's still a good idea to only have one gate open at a time to keep up a strong airflow to pull dust and chips.

I find it's best to place a gate on each stationary tool, positioning it for easy accessibility. Sometimes this means placing it on a branch in the duct work, as shown above. But there are times when it pays to have the gate right at the tool's dust port for convenience and ease of use.

USE GENTLE BENDS. Another general rule for keeping your system at its highest efficiency is to avoid 90º bends when possible. You can usually incorporate two 45º elbows instead and accomplish the same result, but without restricting airflow as much. A gradual bend is also less likely to get clogged with debris. The photo below shows you what I mean.

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SYSTEM MAINTENANCE. No matter how careful you are about laying out and installing the ductwork, there are still things that can cause it to lose some of its collection power over time. Fortunately, most of these can be prevented with simple checks and maintenance.

For example, any blockages in the ductwork will cause a severe restriction. That's why I leave a few connections with only a friction fit and no glue. This way, you can easily remove a duct to check for and remove obstructions. It's also a good idea to periodically inspect all your hoses and ducts for leaks.

COLLECTOR EFFICIENCY. Dust collectors rely on a large volume of air coming in and going out to create airflow. When the collection bag fills up, that volume is decreased and so is the effectiveness of your collector. I usually empty the bag when it's half full.

Another frequent cause of reduced airflow is dust buildup in the filter bag or canister. For bags, you can remove them and in most cases even wash them to remove excessive buildup. But with a canister filter, you'll need to pull it off and give it a thorough cleaning from time to time. A shop vacuum works great for this.

No matter what size or style you choose, you're sure to appreciate the convenience of a dust collector in your shop. By keeping chips off the floor and dust out of the air, it will make it safer too.

Worth a Look: Cyclone Lid

Large dust collectors often incorporate a cyclone separator to collect the larger chips before they arrive at the impeller and bag. For home shops, a simple plastic lid for a trash barrel can provide the same benefit.

A hose from the collector fits on the top and a second hose is routed to the tool. This way, large chips are collected in the barrel. Since it's easier to empty the barrel than it is to remove and replace the bag, this can be a handy addition to your system.

Perhaps you&#;ve upgraded your workshop with larger, more powerful equipment, or you&#;ve just begun your journey into the wonderful world of woodworking. You might be asking, &#;just how big of a dust collector do I need?&#;

Inhaling dust of any kind can be the cause of harmful respiratory illness. As such, it is crucial to ensure you understand how to size a dust collector so as to safeguard the health and safety of yourself, those around you and any other machinery in the environment.

Fortunately, your dust collector&#;s necessary size can be determined through just a few simple calculations that will tell you the required flow capacity, how much static pressure loss can be overcome, and how big the ductwork needs to be.

As Queensland&#;s leading providers of dust collectors, Searose Environmental endeavours to ensure the safety of your working environment. Our team of specialists provide professional design, supply, installation and dust collector servicing solutions to suit any and all of your dust extraction and dust control needs.

What Is a Dust Collector?

A dust collector is used to improve air quality in industrial, commercial, workshop and factory areas by collecting dust and other air impurities. Moreover, dust collectors also capture wood shavings and chips on top of the dust particles you can&#;t see.

A dust collector system consists of many parts and filters, as well as reverse pulse cleaning, shaker motors, electronic controls, subduct lines, flexible hoses, pressure transducers, a centrifugal fan, reverse blow fans, rotary valves and control dampers.

How Does a Dust Collector Work?

So just how does a dust collector work? Dust collectors are intentionally designed to purify and filter hazardous particles released within a working environment.

Dust collectors work by vacuuming up dust particles from the air before moving them through the system&#;s ductwork into a collection area. From here, the dirty air is pushed through a filter that splits the substances before exuding purified air back into the airspace.

How Big of a Dust Collector Do I Need?

It cannot be understated just how important it is to have an adequately sized dust collector within the workspace. A dust collector that is too small will fail to effectively capture harmful substances, exposing you and your colleagues to potential health risks. A dust extraction system that is too big will take away space that could be otherwise used for more equipment, incite unnecessary running costs or damage your ductwork.

When asking how big of a dust collector you should install, your attention should turn to calculating what the maximum airflow through the system will be. You can deduce this by listing all the tools that will connect to the dust collecting system. A CFM calculation should accompany each device.

CFM stands for &#;cubic feet per minute&#; and refers to how much airflow each part requires for the effective disposal of dust particles. CFM is the essential aspect to consider in understanding &#;how big of a dust collector do I need?&#; as your dust extraction system must be able to cope with the required CFM.

How to Calculate CFM

The answer to the question &#;how big of a dust collector do I need?&#; lies within CFM. Once the maximum CFM is discovered, we know how big the dust control equipment must be to adequately protect those in the environment. There are several different ways we can calculate CFM:

1. Research Typical Airflow Values Online

Most machines used in industrial spaces and workshops will have a standard accompanying CFM value that you can research online. However, the individual parts within your workshop may vary from this estimation, perhaps due to size, make or type. This method should be used more as a guide rather than a definitive value.  

2. Look It Up in the Instructional Manual That Comes with Your Tools

Check the manual that comes with your respective tool, as the manufacturer may have accurately calculated the CFM already. You can then spend the time that calculations would otherwise take on using the machinery itself!

3. Manual Calculation

Calculating the CFM needed for your dust collector does not require mathematic expertise, but it will take a number of calculations. Following this guide, you should have no more doubts about how to size a dust collector for your workshop.

Firstly, you must measure flow velocity. Flow velocity is determined with the following equation:

V = x &#;ΔP (square root of velocity pressure)

Note: velocity pressure can be measured by a pressure sensor.

Example: V = x &#;0.75 = 0.866

x 0.866 = 3,468.

Flow velocity = 3,468 ft/min.

Secondly, you must determine the cross-sectional duct area. If the duct is rectangular, simply times the duct width by duct height in feet.

If the duct is circular, you must measure the diameter. Convert the diameter into feet before halving this value for the radius. Proceeding this, you must multiply the radius squared by pie (3.14).

Example: An 18&#; diameter round duct. 18&#; diameter = 1.5ft2. Therefore, the radius = 0.75

A = π x r²

r2 = 0.752 = 0.

A = π x 0. = 1.77ft2

Finally, you must determine the airflow in CFM by multiplying your two measurements together.

Airflow in CFM = Flow velocity in feet per minute (FVPM) x Duct cross-sectional area (A)

Example: 3,468 ft/min x 1.77ft2 = 6,128 CFM.

Therefore, your CFM would be 6,128 using this example.

Note: The most significant CFM number out of all your tools will be the minimum benchmark for what is required in size for your dust collector.

The final step in your calculation requires you to determine the static pressure loss within the system&#;s ductwork. Static pressure is representative of the friction between the air moving within your ductwork and the surrounding walls. In order to make the air move toward purification, the blower must be able to overcome the friction inside. The more angles and indents inside your ductwork, the greater the loss of static pressure.

To calculate, first consider each branch separately. Measure the length of that branch duct in feet. Add up the branches as well as your central duct to calculate your total static pressure loss. Make sure that every piece of ductwork inside your dust collector is considered. Now that you know how to size a dust collector, you can begin to search for a dust collector that exceeds these measurements.

Searose &#; The Experts in Dust Control

Have you calculated your maximum CFM flow and figured out how big of a dust collector that you need? Have you cleared out some space in your workshop? Now it&#;s time to select the right dust collector for you. At Searose Environmental, we custom design dust collection systems that are unmatched in performance and reliability. Shop our full range of dust collectors today or enquire with our team on 48 48 49. Searose Environmental can also provide leading dust control Brisbane installation and dust collector maintenance services that are sure to keep your focus on the work at hand.

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