Americas 
Dust collectors have become an increasingly critical tool in today's industrial environments. Their primary function is to safeguard the health and safety of your workers and protect your equipment from the harmful impact of dust and particulates. The performance and efficiency of these systems rely heavily on how they are designed, installed and maintained. That's where air-to-cloth ratio comes in.
One of the key factors to keeping your dust collector operating efficiently over its lifetime is selecting the right dust collector filters. In past blogs, we’ve talked about how to save on dust collector filters and how to choose the right kind of filter media. Nevertheless, understanding the concept of the air-to-cloth ratio is indispensable to determine the most suitable filter for your dust collector.
Selecting a dust collector filter with an inappropriate air-to-cloth ratio may put your workers at risk. An inadequate filtration efficiency may result in increased exposure to particulates, which can potentially trigger various health problems. Similarly, poor dust filtering may create an environment conducive to explosions. Hence, it's crucial to ensure the correct air-to-cloth ratio for your dust collector to protect your workers' health and maintain a safe work environment. Here are a few important things to understand.
What is Air-to-Cloth Ratio?
Simply put, the air-to-cloth ratio (also called the "air-to-media" ratio) of a filter represents the volume of air flowing through each square foot of filter media every minute. To calculate this ratio for your dust collector, divide the total airflow in cubic feet per minute (CFM) by the total square footage of the filter media present in all the cartridges.
Why is the Air-to-Cloth Ratio Important?
- It helps in increasing the lifespan of the filter cartridges
- It enhances the overall efficiency of the filter cartridges
- It cuts the costs related to system maintenance because less time is needed to change out filter cartridges
- It prevents unnecessary spending on filter cartridges
Determining the Ideal Air-To-Cloth Ratio
The general rule of thumb is that the higher the airflow and dust concentration in your environment, the more square feet of filter media you need. Consequently, a high volume of airflow and dust warrants a lower air-to-cloth ratio.
It is important to get your air-to-cloth ratio right. An excessively high air-to-cloth ratio may overload the filter quickly, driving dust deeply into the filter faster than it can be pulse cleaned. This process leads to a build-up of negative pressure, which in turn makes cleaning less effective. The result? Filters get clogged rapidly and need to be replaced more frequently, driving up both the cost of consumables and the time and resources spent on maintenance.
A lower air-to-cloth ratio can help alleviate these issues. However, if the ratio drops too low, meaning there's an excess of filter media for the volume of particulates collected, it could drastically reduce your dust collector's efficiency. This video explains air-to-cloth ratio in greater detail.
More Media Isn’t Necessarily Better
Contrary to popular belief, having more filter media doesn't always equate to better performance. Many manufacturers try to cram as much media as possible into their filters to maximize the square footage within each cartridge. This approach often leads to a filter being so densely packed with media that it becomes inefficient.
When the pleats are packed too tightly, a large portion of the media becomes unusable because it is shielded from the airstream and hence unavailable for filtering. Then the filter can't load as much dust, and pulse cleaning becomes significantly less efficient. Recognizing this issue, Camfil, a leading manufacturer of clean air solutions, sought to develop a more effective solution for dust collector filters.
Pleating Technology Matters
In response to the ongoing challenges of maintaining efficient dust collector filter performance, Camfil created a patented pleating technology known as HemiPleat®. This patented innovation uses plastic bead separators to hold the pleats open and ensure consistent spacing, resulting in a notable increase in filter efficiency.
The goal of HemiPleat technology is to expose more square footage of filter media to the airstream. Strips of plastic beads are added to keep all the pleats more open and evenly spaced. There is more media available to capture dust particles, and it is easier for those particles to be ejected with each burst of reverse pulse cleaning air. This raises the overall filtration capacity of your dust collector and thus its efficiency.
The open-pleat design characteristic of HemiPleat filters facilitates a much higher airflow per square foot of media. This means that more dust can be loaded onto the filter and then released when pulse cleaned. The ability to handle more dust not only improves the filter's capacity but also reduces the need for frequent replacements, providing substantial cost savings.
Moreover, the breathable and open design of HemiPleat filters ensures a lower pressure drop. This is a significant advantage, as lower pressure drop translates to reduced demand on the dust collector's motor, thus resulting in significant energy savings. With HemiPleat’s open pleat design, your dust collector will be able to use every square foot of its media, improving its air-to-cloth ratio.
Additionally, HemiPleat filters help conserve compressed air, which is a critical resource in many industrial environments. By reducing the amount of compressed air used for the pulse-cleaning process, the filters contribute to more efficient operation and further cost savings.
Size and Configuration
All cartridge-style dust collectors are sized based on air-to-cloth ratio to set the performance life expectancy. Different styles and different filter element configurations create attributes that influence performance life. We will define performance life as the dust collector’s ability to maintain the design process flow as a dependent of air-to-cloth ratio (or filtration rate).
The dust collector system is responsible for maintaining filter element pressure drop within a given range. When the filter element pressure drop moves above this range, the dust collection system flow will decline, thus losing its ability to maintain the design capture velocity and transport velocity. Without the proper velocities, dust will not be captured or transported to the dust collector.
Types of Filter Media
Different media used in filter cartridges have different filtering properties, which can affect the ideal air-to-cloth ratio for a specific system. There are primarily two types of filter media used in the process of dry dust collection. The first is cellulose, a nonwoven blend of cellulosic materials. The second is spunbond, a mix of synthetic polyester or a polyester silicone blend.
Cellulose is typically the more cost-effective of the two, with a usual blend of 80% paper and 20% synthetic fiber. It is suitable for most applications, demonstrating a relatively high performance even under high temperature conditions.
On the other hand, spunbond media is made entirely of synthetic fibers, enabling it to work effectively even at higher temperatures. Notably durable, spunbond media also demonstrates good resilience when exposed to moisture during the manufacturing process.
Both types of media can be enhanced with special treatments for improved performance, including features like fire retardance, moisture resistance and the ability to capture nanoparticles. For more filter media information, check out the segment “Dust Collector Filter Media Selection” by Randi Huckaby, Camfil APC’s Product Manager for Dry Filtration, on Camfil’s Let’s Talk Clean Air podcast.
Emphasizing Health and Safety
HemiPleat filters have been thoughtfully designed to foster a healthier, cleaner working environment. The open-pleat design of HemiPleat filters allows your dust collector to fully utilize every inch of its air-to-cloth ratio, optimizing the dust collection process and ensuring the best possible filtration efficiency.
When HemiPleat filters are integrated into your dust collection system, it leads to substantial savings of both time and money. By reducing energy usage and the demand for compressed air, the operational costs associated with your dust collector are significantly minimized. Additionally, by reducing the frequency of filter replacements and related maintenance downtime, HemiPleat filters enhance productivity and efficiency.
But the ultimate benefit lies in the improved safety and health conditions of your workplace. As your dust collector works more efficiently, the levels of airborne dust and particulates in your facility are reduced, promoting cleaner air and contributing to the overall health and wellbeing of your employees.
HemiPleat filters are designed to create a safer, cleaner work environment. You’ll save time and money on energy usage, compressed air, filter replacements and downtime while your dust collector works more efficiently to keep your employees safe. For help selecting the right HemiPleat filter for your application, speak with a product expert at Camfil APC.
