A clean working environment starts with proper dust collection.
Between OSHA regulations, long-term health risks and the desire for a pleasant place to work, dust collection is an important topic for any woodworker. To help companies get the most effective and efficient dust collection possible, we have asked several suppliers to share their best practices tips.
Q. How can a woodworking shop keep the energy consumption of its dust collection system to a minimum while still getting adequate dust removal?
A. Rob Williamson, service division manager, Dantherm Filtration Inc.: An efficient way to save on energy consumption and achieve peak dust collection efficiency is by use of an âon demandâ-type dust collection system.
For years, companies have used blast gates to manually stop the draw of dust collection on equipment when it is not in use. Those blast gates required the shop employees to manually open and close the gates when the equipment was and was not being used. The dust collector and its fan were still running at the same rate, thus still using too much energy.
Today, with automatic blast gate options, you can attach electronic blast gates that are centrally controlled. This system will automatically open and close blast gates on production machines as they are started up and shut down. The system will also maintain the minimum velocity required in your ducting system. Based on the machines in operation, you also can use a system with a control technology that provides only the required dust collection needed by increasing and decreasing the fan speed through a Variable Frequency Drive (VFD) controlling the fan motor, thus using far less energy.
You can also âzoneâ your dust collection operations. This would be setting up a system that also can shut down or turn on dust collection throughout your plant in âzonesâ where and when it is needed.
A. Michael Gerardi, general manager, Scientific Dust Collectors: A woodworking shop can keep its energy consumption to a minimum by first making sure that the system is correctly balanced. In addition, by installing blast gates at each pickup point and a damper on the fan outlet, the system can be balanced to ensure good dust collection using the minimum horsepower required.
Even though a fan has a fixed horsepower motor, the operating brake horsepower (BHP) is the amount of energy being consumed. By balancing the system, the least amount of brake horsepower is used, thus saving energy.
If you want to improve the system even further, a variable frequency drive (VFD) can be used to further refine the amount of horsepower being used and still get sufficient extraction. In another simplified way, the end user should adjust the fan flow so that he is getting acceptable pickup at the farthest point in the plant. Often times, too much suction is being used and energy is wasted.
A. Curt Corum, sales manager, Air Handling Systems: Run equipment on 3-phase when ever possible. If machines are in clusters, hook up groupings with separate dust collectors instead of one large central collector.
If a few machines are requiring a small diameter, such as 4 inches, and are quite a distance from the main trunk line, service them with small portable units. Additional horsepower from the blower will be required to provide dust collection to this equipment due to the high level of resistance in the branch run. The cost of the ducting will be more or equal to a small portable unit. These machines typically do not run that often, but the main blower will need a few extra horsepower when they are in operation.
Machines that do not run for a prolonged period of time, such as CNC routers or moulders, should have their own dedicated unit. If they only run an hour or two per day, a dedicated unit will be running just for that period. It is better to keep a unit running instead of turning it on and off several times in a short period of time. Start-up amps use five times the energy of running amps.
Do not spread machines out more than necessary. The more duct work, the higher the level of resistance, which equals more horsepower needed to deliver the CFM required.
A. Robert Witter, president, Oneida Air Systems: Correct duct layout and sizing is critical in controlling horsepower requirements in dust collection systems. Air velocities in ducts for woodworking dust collection systems should be between parameters of 3,500 to 4,500 feet per minute (FPM) to effectively convey wood waste material and keep energy requirements at a minimum. Excessively high air velocities in ducts increase friction losses exponentially or, put another way, moving 800 CFM in a 4-inch-diameter duct requires four times the horsepower requirement of moving 800 CFM in a 6-inch duct.
Unbalanced or undersized ducting increases static pressure demand while decreasing air volume (CFM). Use the correct diameter pipe for the proper air flow requirements at the tool to efficiently entrain material into the hood. For example, a 20-inch planer that specifies 800 CFM to collect waste efficiently needs a 6-inch-diameter delivery pipe. The American Conference of Governmental Industrial Hygienists (ACGIH) industrial ventilation guide lists CFM requirement charts for most woodworking tools.
Q. What is the best way to obtain long filter life in your collector?
A. Williamson: On a woodworking dust collection system, the best way to maintain filter efficiency and realize extended filter life is to correctly size the dust collector during the design phase. After the system is installed, performing recommended maintenance on the cleaning system and dust collector in general is crucial for optimum filter life.
A. Gerardi: In any system, the way to achieve longer filter life is to pay attention to the cleaning system. Is the correct amount of compressed air regulated at the collector? Ninety to 100 psi is sufficient. Too low a compressed air supply will reduce filter life. Too high a compressed air supply will also reduce life.
Probably the best way to prolong filter life in a dust collector is to make sure that the compressed air used for cleaning is clean and dry. The cleaner and drier the compressed air is, the longer the filters will last. Proper maintenance will also serve to prolong filter life. Routinely draining the manifold tank of any accumulated moisture and ensuring that all the air valves are working properly will most definitely aid in extending filter life.
A. Corum: Keep the filters as dry as possible. High humidity has a tendency to degrade filter material rapidly. Also, moisture will cake the filter material and substantially reduce air flow. Do not throw splinters or sharp chips at the filters. Spin out all coarse debris with a cyclone.
A. Witter: For open-filter style systems, air flow and particle collection efficiency can be greatly increased by using the correct proportion of filter media for your dust collectorâs air volume. Wood dust collection systems should have in the neighborhood of a 10-to-1 air-to-cloth ratio. This means for every 10 CFM, use roughly 1 square foot of filter media. Keeping the air-to-cloth ratio allows the air to move slowly across the filter media, keeping the pressure drop or energy loss to a minimum.
As filters load with a dust cake, pressure drop across the filter media increases and the overall system airflow decreases. Set a regular cleaning maintenance schedule for your filter media. Keeping the pressure drop across the filter low will result in less overall system energy costs and better dust collection at your woodworking tools. Dust collection systems set up with 20-, 30- or even 40-to-1 air-to-cloth ratios wonât ever be energy efficient or produce good return air quality.
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