An industrial dust collector is an environmental product and therefore inherently “green”. But there are many ways a properly designed dust collection system can contribute to sustainability beyond cleaning up dust and fumes. This white paper will focus on the top 10 tips for achieving sustainability with your dust collector.
by John Dauber, Vice President of Sales Camfil APC
1— Make sure the dust collector is designed to achieve environmental compliance.
For years, many plants have dealt with welding fumes and other airborne contaminants by exhausting them outside. The EPA National Emission Standard for Hazardous Air Pollutants (NESHAP) Rule 6x, which went into effect in 2011, changes all that. The regulation encompasses all manufacturing processes using materials that contain 0.1 percent of cadmium, lead, nickel or chromium and any material that contains 1 percent manganese (which is true of most welding applications). Simply stated, in any 20-minute test period, there can be no more than three minutes of visible emissions (zero opacity) from these types of processes. The regulation spells out the monitoring and test methods required for compliance and outlines control techniques that may be used.
One corrective strategy is the use of a dust and fume collector with high efficiency cartridge filtration. Cartridge filtration is identified in the regulation as an acceptable control device to eliminate visible emissions, and will in many cases be the solution of choice.
If you opt to recirculate the filtered air downstream of the dust collector rather than exhausting it outside, the indoor air must still comply with OSHA permissible exposure limits (PELs). OSHA has established PELs for hundreds of dusts based on 8‐hour time weighted average (TWA) exposure.
How do you know if your people are adequately protected by a dust collector that complies with OSHA and EPA emission thresholds? The equipment supplier should provide a written guarantee stating the maximum emissions rate for the equipment over an 8‐hour TWA.
2 — Avoid thinking “smaller is better” when sizing a dust collector.
Though a small car is greener than a big gas guzzler, the analogy does not hold true when it comes to dust collection equipment. A dust collector must be properly sized to run dependably and efficiently at the required air flow. If a collector is undersized, a host of problems can result: The operating pressure drop may be too high, filters may be overloaded and require frequent changeout, and larger maintenance problems may surface. When this occurs, operating costs and energy usage can actually be higher with a smaller unit.
3 — Look for a heavy duty dust collector with a higher pressure rating.
4 — Look for a dust collector manufactured using sustainable materials and processes.
Some dust collectors are manufactured using environmentally friendly paint finishes and other construction materials that contribute to sustainability. Energy-efficient components in the system can also make for a greener machine, as you will see in several of the tips that follow. Ask your dust collection supplier to provide a sustainability report or other documented evidence of the company’s green manufacturing initiatives. Also ask whether energy-efficient/premium components are
offered as standard or added-cost options.
5 — Don’t rely on filter percentage efficiencies or MERV ratings to predict environmental compliance.
Sometimes equipment suppliers talk about “removing 99.9 percent of contaminants” of a certain particle
size, or they state filter efficiency as a MERV rating. Although these measures are useful for comparing
different filters, the EPA and OSHA don’t care about percentage efficiency claims: They want to know that emissions will be at or below required thresholds. Ask the filter manufacturer for a written guarantee of emissions performance stated as grains per cubic foot.
6 — Reduce change-out frequency with longlife filters.
No matter how maintenance-friendly a collector may be, the less service needed, the better — especially in hazardous dust applications. Extended-life cartridge filters available in today’s market reduce filter change-out frequency — minimizing worker exposure to dust, saving on maintenance and
disposal costs, and reducing landfill impact. Some suppliers even offer written guarantees on filter life.
A misconception exists that the more media a filter contains, the longer it will last. Actually, the amount of media contained in a filter is not as important as the amount of usable media surface area. Many filters contain media packed so tightly into the cartridge that most of it is not available for filtering. New open-pleat designs offer better utilization of the media using less media area per filter. Air flow through the filter is improved, for reduced pressure drop and energy savings. Open-pleat filters also respond better to pulse-cleaning and use less compressed air, saving further on energy and lasting longer for lower replacement and disposal costs.
For maximum life, open-pleat filters with nano fiber media are often an excellent choice. An outer layer of nano fibers acts as a pre-filter to the base media, capturing most of the dust at the surface before it imbeds in the filter. This technology increases the filter’s cleaning ability — reducing pressure drop and improving energy efficiency while further extending filter service life.
7 — Use a variable frequency drive to control fan speed.
When running a dust collector with a constant speed fan (i.e., with no energy control device), the amount of air moving through the collector will vary during the service life of the filters. Why does this occur? When filters are clean and differential pressure is at its lowest, more air blows through the system than required, essentially wasting energy. As filters become loaded with dust, static pressure is increased and less air is moved as a result. Thus, filters use more energy in the early stages of service life and less in the final stages.
One way to reduce this problem is via a mechanical damper at the blower outlet. Depending on the type
of filters used, periodic adjustment of the damper to regulate air flow can save an average of 1” w.g. of
static pressure over the life of the filter.
A far more effective approach is the use of a VFD to electrically control fan speed. When filters are new, the VFD will decrease fan speed to obtain the desired air flow. When filters become loaded, the fan is sped up to maintain a constant air flow. The electrical control is highly efficient in maintaining desired air flow, and energy consumption is greatly decreased.
The use of a VFD has been proven to save an average of 4” w.g. of static pressure over the life of the filter. The added capital cost of installing a VFD on a dust collector will vary. However, the return on
investment is typically under one year. By helping reduce the spike in overall energy consumption, use of a VFD may also lower your utility rate.
8 — Use a premium efficiency fan motor for further energy savings.
Designed for cooler operation and more efficient performance, a premium efficiency motor can pay for itself in reduced electrical power use. As with VFDs, added savings are often possible through
rebates and incentive programs offered by many electric utilities. Premium motors can be used in combination with VFDs for optimum fan speed control and energy savings.
9 — Don’t use a programmable logic controller (PLC) to control pulse-cleaning of filters.
Though PLCs are popular for use with a variety of manufacturing processes, they are not well-suited
to controlling pulse-cleaning of dust collector filter cartridges. Pulse-cleaning relies on very brief (i.e.,
150-millisecond), high-energy bursts of compressed air to blow dirt off the filter surfaces. With a PLC, the valve typically opens too slowly for proper pulsing to occur. To optimize cleaning and ensure reliable and efficient dust collector operation, use a timer board designed for filter pulsing. The timer board can be used independently or tied into your PLC.
10 — Conduct a total cost of ownership (TCO) analysis of the filters.
When choosing a cartridge dust collector filter, a Total Cost of Ownership (TCO) calculation allows you to make the most economical and sustainable choice. Similar to life-cycle costing, TCO is a step-by-step evaluation that pinpoints the three main components of filter cost: energy, consumables and maintenance/disposal. To choose the most economical and sustainable filter, you need to do a TCO calculation that takes all these components into account. A TCO evaluation will often show that filters with a lower initial price tag may end up costing thousands of dollars a year more in energy and operating expenses.
Ask your dust collection supplier to help you use this data to compare the real costs of operating a
dust collector with different filters. A TCO analysis can save money and energy for years to come, whether you are designing a new dust collection system or refurbishing an old one.
For more information about Total Cost of Ownership for a Farr Gold Series dust and fume collector, visit the Camfil APC website.
