Choosing the Right Dust Collector Filters

Daniel Ginzburg, director of aftermarket, RoboVent

Cartridge dust collectors are a practical and reliable choice for most powder and bulk solids applications. Choosing the right filters--and caring for them properly--will greatly enhance the effectiveness and energy efficiency of the dust collection solution.

What Kind of Filters Do You Need?

Powder and bulk solids dust collection covers a broad range of dust types, from ultrafine and potentially toxic chemical compounds to heavy, abrasive mineral powders. Different types of powder and bulk solids dust will require different filtration strategies. Choosing the right dust collector filters depends on the answer to several critical questions, including (but not limited to) the following. 

1. What are the physical properties of the dust?

Properties such as particle size distribution and morphology will impact filter selection: dust that is heavy, coarse, and abrasive may require a different type of filter media than ultrafine powder. Abrasive dust may also require specialized engineering of the dust collection system to protect the filters (e.g. baffles or dropout boxes).

2. Is the dust wet, sticky, or oily?

Some dust is naturally oily, sticky, or hygroscopic (attracted to water). If the environment is hot and humid, this will also impact the moisture content of the dust. These factors will impact filter loading and how easy it is to pulse dust off the filters. Specialized filter media and coatings can help extend filter life when collecting moist or sticky dust.

3. What is the volume of dust created?

The higher the dust load, the more filter media (in square feet) will be needed per unit of airflow (cu ft/min). This is known as the air-to-cloth ratio and is an important consideration in dust collector sizing and filter selection.

4. How toxic or hazardous is the dust?

Dust that is highly toxic or hazardous to human health will require a more aggressive filtration strategy than less hazardous dust. The dust collector filters must be able to filter out enough of the material to protect workers and meet Permissible Exposure Limits (PELs) set by the Occupational Safety and Health Administration (OSHA) or other regulatory bodies. For example, the dust collection system may require secondary HEPA filtration or BIBO (bag in/bag out) filter changes.

5. How clean does the production environment need to be?

In addition to protecting humans on the production line, it is important to consider the overall cleanliness needs of the process. If cross-contamination is a concern, or processes must be completed in cleanroom or near-cleanroom conditions, higher-efficiency filtration will be needed.

6. Is the dust combustible or staticky?

Combustible dust requires special care in collection, and that includes selection of filter media. The use of anti-static filter media may be recommended if dust tends to produce static or presents a self-combustion risk.

7. What kind of maintenance is required to maintain the filters?

Maintenance is another important consideration when selecting cartridge filters. Cheaper filters made with lower-quality filter material may cost less upfront, but they will need to be replaced more often as they become loaded or develop microtears and holes from abrasive material (maintenance requirements will also depend on the characteristics of the dust being collected and environmental factors, such as humidity).

Understanding Filtration Efficiency

Filtration efficiency is one of the most important factors to consider when selecting cartridge dust collector filters for powder and bulk solids applications. Two common metrics used to assess filtration efficiency are the Minimum Efficiency Reporting Value (MERV) and High-Efficiency Particulate Air (HEPA) ratings.

MERV Ratings

The MERV rating, set by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), is a widely used measure of filtration efficiency. MERV ratings range from 1 to 20; a higher MERV rating indicates that the filter is able to capture a higher percentage of particles of various sizes (3–10 microns, 1-3 microns, or 0.3 – 1 microns). Filters rated MERV 17 and above are equivalent to HEPA filtration. Most dust collector cartridge filters are rated between MERV 11 and MERV 16.

HEPA Ratings

HEPA filters--and their even higher-efficiency cousins, Ultra-Low Particulate Air (ULPA) filters--are used when applications require filtration efficiency above MERV 16. To qualify as HEPA by US government standards, an air filter must remove 99.97% of particles that have a size of 0.3 microns. ULPA filters must capture 99.999% of particles 0.12 microns or larger and are used when cleanroom conditions are required. Cartridge dust collectors are sometimes equipped with a HEPA after-filter to collect fine contaminants that make their way past the cartridge filter.

Filtration Efficiency Tradeoffs

While choosing cartridges with the highest filtration efficiency available may seem like an attractive option, there are tradeoffs to consider when selecting higher-efficiency filters.

Because of these tradeoffs, it does not make sense to select dust collector cartridge filters with a higher efficiency rating than needed by the application. Filter selection will depend on the size of the particulate to be captured and the degree of capture efficiency needed. This will be determined by the cleanliness required by the application and/or the hazard level of the dust; higher filtration efficiency will be needed to meet stringent PELs for toxic or hazardous dust, for example. An engineering partner can help you determine the best filtration efficiency for your application.

Progressive Filtration

Progressive filtration, also known as staged or multi-stage filtration, is a strategy used in dust collection systems where air is passed through a series of filters with increasing filtration efficiency. The concept is to remove the larger particles using less expensive, lower-efficiency filters, and then progressively remove smaller particles in later stages using higher-efficiency filters. This approach has several benefits, including:

Powders and bulk materials with a wide range of particle sizes will often benefit from a progressive filtration strategy.

Filter Media Options

Cartridge filters come in various types, each with its own set of properties designed to capture and hold specific kinds of dust particles.

The Importance of Filter Quality

The quality of a cartridge filter is a critical factor that directly impacts the performance and efficiency of the dust collection system. High-quality filters not only provide superior filtration performance, but they also tend to last longer, require less maintenance, and provide better overall value in the long run. In addition to looking at the filter media type and filtration efficiency (MERV rating), consider:

Extending the Life of Your Dust Collector Filters

Choosing the right filter for your application will go a long way towards maximizing filter life and optimizing the efficiency of your dust collection system. Proper maintenance and care are also essential to ensure proper performance of your filters. There are several important steps to take:

Summary

If you’re not seeing the performance that you would like from your dust collection system, start by looking at your filtration strategy. Changing your filter media, adding pre-filters or after-filters, or optimizing your filter pulsing cycles could make a big difference—and is much cheaper than buying a new dust collector. Don't hesitate to seek expert advice if needed. Remember, the right filtration strategy not only enhances system performance but also promotes a safer and healthier working environment.

Daniel Ginzburg is director of aftermarket, RoboVent (Sterling Heights, MI). For more information, call 877-959-7639 or visit www.robovent.com.