Optimizing Air Compressor
By Published On: December 13, 2023Views: 62

Proper maintenance of a dust collector is crucial for extending filter life and ensuring the lowest possible energy consumption. Owners and operators of dust collectors may sometimes consider replacing only damaged filters instead of all filters as a cost-saving measure. While this seemingly simpler and quicker solution may appear economically sound, it can actually lead to more frequent filter replacements, longer downtime, and higher electricity costs, ultimately increasing overall expenses.

The Importance of the Proper Air Filtration Ratio

The size of a dust collector depends on various parameters, including the specific particles it needs to remove from the airflow and the total airflow volume. Air-to-media ratio (AMR), or filtration airspeed, refers to the ratio of the airflow to be filtered to the total available filtering surface area of the dust collector. Generally, the smaller the particles to be filtered, the lower the recommended filtration airspeed. This is partly true because smaller particles pose unique challenges to filtration.

Firstly, smaller particles accumulate more densely on the filter surface, resulting in smaller gaps available for gas to pass through the captured dust. This increases resistance and the frequency of necessary filter cleaning. Lower filtration airspeed allows more gaps between particles during accumulation, reducing resistance and lowering the frequency of filter cleaning.

Secondly, smaller particles are more likely to penetrate the outer fibers of the filter and may embed in the filter media. While not impossible, reversing this deep filtration phenomenon is challenging and leads to a permanent increase in pressure on the media, requiring replacement. Lower filtration airspeed reduces the energy that carries small particles into the media, reducing the chances of deep filtration and extending filter life.

Note that particles (or dust) accumulating on the filter’s surface area will limit the size of the pores through which airflow passes. Some of these limitations can be resolved by effective periodic cleaning when resistance increases, but even excellent surface filtration filters will eventually face a long-term increase in resistance or pressure drop.

Surface Filtration Media

(Surface Filtration Media)

Deep Filtration Media

(Deep Filtration Media)

The inevitable increase in pressure drop is often a design consideration when determining fan size. When selecting a fan, one must anticipate the eventual pressure drop it will experience when replacing filters to ensure it can provide the designed airflow throughout the filter’s entire lifespan. This usually means including an additional static pressure of four to six inches to handle the eventual pressure drop increase over the filter’s lifespan.

To ensure that the fan does not introduce too much airflow when the filter is clean and there is no final static pressure, designers should incorporate airflow control valves or other methods to regulate airflow. One method is to combine airflow controllers with variable frequency drives (VFDs) to control airflow at the designed level when the filter resistance is low.

So, why is replacing some filters not a wise decision?

Replacing some filters is not an ideal option because during operation, the resistance on all filters in the dust collector is uniform. However, when installing only a single new filter, its resistance is much lower than that of other dirty filters. In fact, the resistance of a new filter to the designed flow is usually less than 1 inch, while the resistance of old filters to the designed flow is three to four times that value. If only one new filter is installed in the dust collector, and other filters already have a certain resistance due to dust accumulation, the airflow through the new filter will significantly increase until the resistance on the new filter equals that on the dirty filters.

The airflow through the new filter does not conform to the appropriate design flow ratio but far exceeds the designed flow. Therefore, the new filter will immediately experience deep filtration, significantly shortening its lifespan and increasing pressure drop during dust collector operation.

The shortened lifespan of the replaced filters will affect all other filters, potentially requiring the purchase of more filters and leading to longer downtime. Additionally, operating the dust collector at higher pressure drops increases compressed air consumption and requires more energy to maintain the airflow through the dust collector.

Advantages of Replacing All Filters

Replacing all filters ensures consistent pressure drop across all filters in the dust collector, maintaining airflow at an appropriate level and minimizing pressure drop. The consistent pressure drop achieved by replacing all filters allows operators to control the filtration airspeed through all filters, saving compressed air and minimizing the frequency of cleaning filters, thus extending filter life.

It also makes it easier to maintain the designed airflow, keeping the AMR appropriate and minimizing deep filtration of the filter media. Reducing deep filtration can extend filter life, ultimately saving expenses in the long run.

Furthermore, do not overlook the possibility that the damaged filter to be replaced is not the only damaged filter in the dust collector. Replacing only one filter while continuing to use other locally damaged filters will result in other damaged filters becoming unusable in the following days or weeks.

Delaying the replacement of old filters means operators must increasingly frequently stop the system and investigate multiple filter failures, increasing downtime and labor costs. It forces the dust collector to operate for a longer time with increased pressure drop due to blocked and damaged filters, leading to increased operating costs.

Purpose: When you find that one of the filter elements in your dust collector is damaged, consider the relative age of the filter elements and the potential advantages of using a new set of filter elements to reduce the operating pressure drop of the dust collector.

Consider how you can avoid additional unscheduled downtime and maintenance costs, and remember that sometimes it is a better investment to replace all the cartridges that are going to be used up than to replace only the ones that are no longer usable.

If your air compressor is having problems, read these pages here for general information, but be sure to check out the air compressor troubleshooting section.

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