Industrial Dust collectors-A Complete Guide
Industrial Dust collectors are a critical component for a variety of manufacturing applications whether you need to collect sawdust from a woodshop, dust from blasting off a product surface, or a variety of other applications they can be critical to ensure both the quality of the products you produce as well as the safety of those that are in the areas products are in. When you’re considering a dust collector, it is important to understand your application and to evaluate the various factors that are relevant so you can choose the appropriate dust collector or at least know what might be the right dust collector for your application. In this article will discuss the most important factors to consider about dust collectors that you can determine may be right for you. For note, this article will be dedicated primarily to fabric dust collector designs and not include other collectors like wet scrubbers or electrostatic precipitator dust collectors.
Factor 1 – The Type of Dust or particle
Dust particles come in a variety of sizes from small too large. The size of the particle will be important in determining an appropriate air to cloth ratio as well as required filter efficiency. The air to cloth ratio refers to the volume of air (CFM) of air going through the filter media to the surface area (ft2). The type of dust you are filtering will typically have a recommended air to cloth ratio to be able to properly filter the dust. For example for blasting air to cloth ratios are often 2:1 but with other dusts like wood chips air to cloth ratios can be as high as 6:1. Ultimately the proper air to cloth ratio will depend on the dust you are collecting.
Air to cloth ratio is calculated as follows.
- Size of the bags or cartridges – For Round cartridges you take pi x the height and diameter of the collector cartridges in feet x the number of cartridges or bags
- Take the Air Flow of the Dust Collector and the Total area of the cartridges to determine air to cloth (example below)
You have 12 cartridges 10 feet tall by 1 foot wide: This would be 376.8 sq feet of face area (10*3.14*12). If airflow is 1000 CFM this would yield an approximate 2.65:1 Air to Cloth Ratio.
Why Air to Cloth Matters
ACR ratios matter for a variety of reasons. First the higher the ACR is the more filter media you will have in the dust collector which will result in a larger footprint for your dust collector.
Additionally, the higher air to cloth ratio will have to have a larger pressure differential which may require a larger fan motor to run the unit. Larger fan units can utilize more energy and lead to higher operating costs.
Higher air to cloth ratios will capture finer dust particles more effectively but can also lead to increased costs of changing out filters. Ultimately when selecting a dust collector, you will want to utilize air to cloth ratio that is high enough to capture the dust but not excessively high for your application.
Factor 2 – The Amount of Dust
The volume of dust your dust collector will handle is also critical. Dust collectors offer a variety of options in how dust can be cleared from the filters with typical options including manual or automatic clearing. For applications where dust will accumulate rapidly like in blasting or related productions settings it is usually a good idea to consider an automatic purging filter like a reverse air flow collector or pulse jet. There are other automatic purging options that are available like shaking dust collectors that are also an option (though these are usually less common). For lower volume applications a manually cleaned collector can be a good option.
Factor 3 – What is in the dust
The potential contaminants in the dust are important to know as well. Standard dust collectors can often be efficient enough to remove most contaminants and allow the air being pulled from the building to be returned. However with certain hazardous components, for example with chromates or other hazardous types of dust, you may need additional filtration with your dust collector or special filtration to safely handle the dust .
Other types of dust require special dust collector design considerations to ensure they are safe due to risk of flammability like in collecting aluminum dust. Additionally, certain types of dust collection can be hard on the dust collector and require design considerations to help keep the dust collector from being adversely effected. For example, blast dust collectors will often have design features like deflection plates to keep blast media from prematurely wearing the dust collector.
With the variety of dust that you can potentially have to collect it is important to match the collector to be appropriately designed to what will be included in the dust and what the collector may be exposed during operation. You will want to ensure your dust collector complys with OSHA directive CPL 03-00-008.
Factor 4 – The Size of the area dust will be collected from
Dust collectors are sized in CFM of air flow. The appropriate dust collector size will depend on the size of the area or areas you will be collecting dust from. For open areas you typically select a dust collector based on the area you are collecting and the way air will flow. For most open areas air flow will be calculated based on the opening of the face area (either width x height of the room or length x width of the floor depending on if the room will be a downdraft or crossdraft design) and a proper speed of air which can range from 50 – 125 FPM or higher depending on the dust that will be being filtered.
If you will be using a dust collector for multiple stations the calculations will differ. You will need to determine the size of the branches and the size of the main branch and determine that your dust collector is appropriately sized to provide enough airflow for the branches. You will also need to compensate for static pressures that come from elbows in the duct and similar variables. A good guide is provided here that will cover how to determine CFM with multiple stations based on different duct diameters.
Factor 5 – Controls
Certain collectors will offer optional electronic controls or visual gauges. These gauges will often allow you to monitor static drop across a filter surface which helps in determining when a dust collector filter is worn. This can be helpful to ensure you change your filters at appropriate intervals, potentially warn of a dust cartridge at risk for being blown, as well as to ensure that you have the dust collector reverse pulse properly tuned. Certain dust collectors will also have the ability to tune the pulse pressure and interval which can be important in ensuring that the collector works effectively.
Ultimately dust collectors involve a fair amount of consideration to ensure your facility is properly ventilated of dust. If you have questions about dust collection for your facility contact us and we can help clarify your questions.
For woodshops : The Complete Guide to Wood Shop Dust Control