Rewarding individual operators and operations as a group means recognizing them for their performance and acknowledging them for their contributions to the goals of their organization. Group recognition is usually tied to lagging metrics. Asset reliability is a good example of this. It is important to indicate the key performance indicators.

Key Takeaways:

  • Rewarding reliability-boosting behaviors will encourage an environment of more reliability-boosting behaviors.
  • To maintain high levels of performance operators must shift from a reactive mindset to a proactive mindset.
  • Preserving asset reliability leads to increase productivity and more sustainability.

“Proactive operators are innovative problem solvers.”

Purchasing Filters & Cages: Inventory Management for Dust Collection System Parts

A Quick Guide for Purchasing Professionals

Purchasing consumable parts for industrial systems like filters and cages for a baghouse dust collector can be a challenge. Part of the job of a purchasing professional, supply chain manager, or material planner is to ensure there are enough parts on hand so they will be available when needed, while minimizing inventory and expedite costs.

You certainly don’t want to wait until your dust collector goes down due to a damaged filter or a required changeout to go out and try to purchase filters and cages – lead times can vary wildly (up to 16 weeks for some specialty items) due to global raw material availability, supply chain issues, and the general demand for your item. Ensuring your supply of parts comes down to inventory management.

Every supply chain professional understands the basic concept of inventory management and safety stock, but how should you ensure you have the correct inventory for your dust collection system parts (generally, filters and cages)?

Here’s a general process that you can follow:

  1. Determine the standard lead time: Lead time is the time it takes for the supplier to deliver the part after you place an order, and this is a critical variable. You can ask for the lead time or use historical data if you have it.
  2. Analyze demand: Analyze the historical demand for the part to understand how much the demand for filters fluctuates. This analysis will help you determine the average demand rate, the variability in demand, and the peak demand periods.
  3. Determine the reorder point: The reorder point is the inventory level at which you need to place an order to avoid stock-outs. The reorder point can be calculated as:

Reorder Point = (Lead Time x Average Demand) + Safety Stock

The safety stock is the additional inventory that you keep on hand to cover unexpected demand or supply chain disruptions.

Inventory reorder points

  1. Calculate the economic order quantity (EOQ): The EOQ is the optimal order quantity that minimizes the total inventory costs, including ordering costs and holding costs. The EOQ can be calculated as:

EOQ = sqrt((2 x Annual Demand x Ordering Cost) / Holding Cost)


  • Annual Demand is the total demand for the part in a year
  • Ordering Cost is the cost of placing an order, including processing and transportation costs
  • Holding Cost is the cost of holding inventory, including storage, insurance, and obsolescence costs
  1. Determine the reorder frequency: The reorder frequency is how often you need to place an order to maintain the appropriate inventory level. The reorder frequency can be calculated as:

Reorder Frequency = Annual Demand / EOQ


  1. Review and adjust regularly: It is essential to review and adjust the inventory level regularly (ideally quarterly, but at least yearly) based on changes in demand, lead time, and supply chain risks. Regular reviews will help you ensure that the appropriate level of inventory is maintained to meet demand and minimize inventory costs, and you are never left scrambling to find a part you need.

Would you like help understanding current lead times for your filters, cages, and other dust collection system parts?

Contact Us Today to Talk to One of Our Baghouse Experts.

6 baghouse hopper dust discharge styles

Many problems arise over how to properly dispose of dust in the baghouse once it is collected. Improper dust disposal can directly impact the operation of your baghouse. Storing dust in your baghouse hopper is a terrible idea. Dust collector hoppers are designed for temporary storage only. If collected dust builds up in the hopper it can cause several problems.

  1. It directly causes filter bag abrasion, the wearing holes near the bottoms of the bags. This happens because the rising dust levels disrupts the carefully engineered airflow mechanics within the baghouse. When high speed air is pulled across the surface of a pile of dust in the hopper it picks the dust back up (i.e. dust reentrainment) and essentially throws it back at the filter. The effect is much like sandblasting your filter bags, something no bags will ever be able to withstand.
  2. Large amounts of dust can provide ample fuel for fires or even combustible dust explosions. Sparks and embers can make their way into the unit from cutting, grinding or other friction generating processes as well venting of furnaces and other heat sources. These ignition sources can ignite bags upon reaching the baghouse or pass through to the hopper. In either case, large amounts of dust in the hopper provide ample fuel for continuing a fire or making it much worse.
  3. Excess hopper buildup will block off the baghouse and cause a loss of suction throughout the system. Loss of suction at pickup points can shutdown entire plant processes, damage equipment and even cause environmental safety hazards and increase emissions levels past permissible limits.

Clearly, failure to keep the discharge working efficiency can have serious consequences. So how can you make sure your discharge system meets the needs of your baghouse?


6 baghouse hopper dust discharge stylesDifferent Baghouse Discharge Systems

Let’s review a few common dust discharge methods and some guidelines for choosing the best option for your application.
#1, 3 – Covered Box or Drum with venting
An enclosure (usually a box or container) directly underneath the discharge holds the dust. To prevent dusting and back pressure issues the enclosure is vented by (a) a small vent with filter attached to it or (b) with a duct vent piped back to the collector or the inlet duct. Simple system, but requires maintenance to remove collected dust or else it can backup into the discharge (blocking the system) and overflow the container. Good for systems with light dust loads and nonhazardous materials.

#2, 5, 6 – Removable Storage Containers
Uses drums or bags to collect dust from discharge. When filled, technicians remove them by hand or using a forklift for disposal and then replace them with a new container. Good choice for easily handled, non-toxic dusts. Can also be useful for products that then get shipped by truck from plant (e.g. fly ash sold to cement plants, etc.) Requires technicians to monitor fill levels and replace as needed.

A dust transport method for baghouse discharges is by screw conveyor

The most common automated dust transport method for baghouse discharges is by screw conveyor

#4 – Discharge to conveying system
Preferred where possible, this method ensures the prompt removal of discharged dust. This proves the best solution for large units with heavy dust loads and applications requiring dust to be transported far from the collector after disposal such as hazardous material disposal, or for reuse in process. On the downside, it is more expensive than other methods and requires additional maintenance costs to maintain system.


We have seen that the best method of hopper discharge varies from application to application and from unit to unit. However, this does not mean that all discharge methods work for all baghouses. As outlined above, serious problems arise when the baghouse hopper discharge system is not adequate to the dust loads passing through the unit. Additionally, the disposal methods may require more man power than available at the plant and lead to spillage and other issues.

These issues can be avoided by not leaving the dust discharge method to chance. Review the operating parameters, dust loading rates, dust characteristics and eventual use of the dust (including disposal in landfill) before selecting a discharge method. has helped many plants retrofit their existing dust collectors with new hopper discharges, dust transportation and removal. Contact us today and let us advise you on how to improve your discharge system and thereby improve your dust collector efficiency today!

Need Help With Your Hopper Discharge? has helped many plants retrofit their existing dust collectors with new hopper discharges, dust transportation and removal. Contact us today and let us advise you on how to improve your discharge system and thereby improve your dust collector efficiency today!

In this design guide we have reviewed a relatively simple baghouse dust collection system with few variables. Even at this level it is still recommend to consult with an experienced dust collector OEM like before making any equipment purchase. There may be additional factors to consider before determining the final sizing, design, construction and installation of a dust collection system.

Common Additional Considerations

  • Recirculating air back into facility
  • Balancing system with blast gates
  • Combustible and toxic dust
  • Filter styles
  • Dust discharge (manual or automatic)
  • Option for VRD fans

Recirculating Air Back Into The Facility

Recirculating air from the dust collector exhaust can prove practical in areas with cold climates to conserve heat. Make sure to include a ambient air return line to balance the airflows and prevent carbon monoxide poisoning. Additionally, any return duct needs to be sizes at least 2 inches larger than the main duct entrance and its SP added to the system total. Additionally, OSHA and other applicable safety regulatory bodies require any recirculated air to pass through a HEPA after filter.



Combustible Dust and/or Toxic Compounds Hazards

Many types of dust, including many woods are toxic, so take special care to choose a filtering system that will provide optimal safety. Facilities that handle combustible dusts must take special precautions to avoid potentially serious safety hazards from forming within their dust collection system. The National Fire Code issued by the NFPA (National Fire Protection Agency), OSHA combustible dust emphasis program, and the OSHA General Duty Clause and many other similar local and state regulations now require a combination of explosion/fire prevention and/or protection devices for any dust collection system handling combustible dusts. Prevention devices include spark arrestors, abort gates, high-speed sprinklers, inert gas or injection systems, and more. Protection devices include explosion vents, high-speed sprinklers and dry extinguishing injection systems. Fire experts should be consulted for any system potentially handling combustible dusts.

Filter Styles

Pleated Filters - Top and Bottom Load

New filter styles such as pleated filter elements can improve operation, reliability and collection efficiency while also lower operating costs (less compressed air to clean, last longer) compared to traditional bag and cage technology. They also allow for much smaller units (thus cheaper to build) while still having better air to cloth ratios compared to bags since they also provide more filter cloth in a smaller area.

Bags, cartridges or pleated filter elements are three common filter styles used in baghouse dust collectors. Cartridges are rarely used in new systems except for a handful of OEMs due to high cost and difficulty sourcing replacements. Bags and cages are the most versatile being able to work in the widest range of applications including temperatures up to 500F. In newer systems, pleated filter elements (sometimes called pleated filters) provide a much larger filter cloth area in a smaller space compared to bags (usually 3 times as much filter in half the space). They are widely manufactured and are only marginally more expensive than bag and cages. In addition, they provide superior performance, require less cleaning energy (i.e. compressed air) and provide less pressure drop over a longer service life. And due to their smaller size, collector units can be made smaller. (See our case study showing benefits of converting from bag/cage technology to pleated filter elements)

Best Practices to Increase efficiency and Reduce Size

Try to capture dust as close as possible to source to reduce size requirements. More directed venting better solution than venting large area as volumes increase rapidly when venting entire spaces e.g. Venting one machine at 600 CFM = 6 bag unit vs. venting entire room of 30’ x 30’ x 10’ = 9,000 cubic feet of air = 125 bag unit @ 3:1 ratio Oversizing for future expansion Good idea to size in additional 10% capacity for later. Minimal added costs upfront to add additional capacity, resizing later much more expensive (10:1 ratio roughly)

Balancing System Using Blast Gates

Blast gates should be installed on all branch lines to maintain system balance. Their proper use should also be part of regular training for dust collector operation.

Clean Out Traps

If your system has areas where long slivers of material could possibly hang-up and cause a clog, install a clean-out near that area.

Determining Required Capacity For Secondary Sources

6 baghouse hopper dust discharge styles

Various options exist for disposing of dust from the baghouse hopper. Here are 6 discharge methods

After adding all primary lines together determine how much extra capacity you want to install for secondary lines. If secondary branches are run sparingly then its possible to not include them in the calculation. When they need to be used you can divert some of the capacity from the primary branches (by shutting them down and blocking those ducts using a damper valve). Be realistic when calculating your needs and size appropriately.

Consider Variable Frequency Drive (VFD) Fans

VFD fans allow for more control over system performance and potential energy savings when loads constantly change.

Dust Discharge Options

The most basic discharge is a manual slide gate, that is activated manually by personnel. If dust loads are light or the system is infrequently used this may be the most economical option. However, failure to keep the baghouse hopper clean and result in major operational problems and damage the filters. Another option is for a rotary airlock that automatically cleans the hopper. This eliminates the need for a technician to manually clean the hopper, but comes at a price tag in the $2,000 – $3,000 range.

Ready To Size Your Dust Collection System?

Thank you for reading our online guide to sizing your dust collection system. After considering this information should be able to estimate what size dust collection system your facility needs. With this information in hand you can begin the bidding process for your new system. experts are ready to help if you have any questions. Please feel free to call at (702) 848-3990, contact us via our online form, or visit our resources section for more helpful dust collector information.

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 Baghouse Design Guide Overview

Example of a dust collection system layout for a woodworking shop.

We continue from our last article where we reviewed the 4 key design variables of airflow (in CFM), static pressure/resistance, air velocity and air to cloth ratio. Now we can begin calculating these variables for our new dust collection system. When we are finished we will know exactly how large of a baghouse we will need (including how much filter area required) along with our fan output (x airflow @ y static pressure).

The sizing and design process can be divided into two stages. The first stage involves sizing your duct work for adequate volume (CFM) and velocity (ft/m) for the type of dust you will be handling. Then in the second phase you calculate the static pressure (SP) of your system to determine the size of your baghouse (how many filters and what size) and power of your system fan. If you already have a ductwork system and want simply to replace an existing baghouse/fan combo, you still need to calculate the CFM and static resistance from the existing ductwork system to properly size the baghouse and/or fan.

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Step 1 – Find the Minimum Conveying Velocity (ft/m) of Your Product

Determine from a reputable source the minimum conveying velocity for the material the system will handle. The box on the right lists several common materials and their recommend conveying velocities. Most materials require between 3,500 ft/m to 5,000 ft/m. A more extensive list can be found on

Step 2 – Identify Total Number of Primary and Secondary Sources

Sizing your system requires you to determine how many much airflow you need at each location. Begin by making a list of all the equipment you plan to vent with the dust collection system. Identify your primary and secondary sources that you will connect to the system.

Primary Sources need constant venting whenever system is running. Some facilities may have only one large source to vent (e.g. a single boiler, furnace, etc.). Others may have many different systems but each one requires its own system as the different equipment cannot be connected for some reason (e.g. gypsum plants, cement plants, process applications)

Secondary Sources do not always run concurrently without primary sources and sometimes shutdown completely. Secondary sources are common in wood/metal milling, fabrication and manufacturing shops. For example, a woodworking shop uses several different pieces of equipment such as saws, lathes and sanders requiring dust collection. While the large saw and lathe run continuously everyday (primary), a small specialty-use sander and a planner are only used once or twice a week (secondary) and never at the same time as each other. In this example, you would size your system to handle the two primary sources (saw and lathe) and only one of the two secondary sources (sander and planer) as they will never run at the same time. Plan with the objective of defining the heaviest use scenario so you can size your system to meet it. Incorporating pickup points that see limited or infrequent use may result in an oversized the system, which increases its total cost to purchase, operate and maintain. Plan wisely, as increasing capacity post installation is nearly impossible. A good rule of thumb is to oversize the system by roughly 10% to ensure proper operation and accommodate any future expansions.

Primary or Secondary Source?

  • Take care to correctly classify each piece of equipment
  • Classifying all sources as primary sources will result in an unnecessarily large system, increasing initial installation costs and making it more costly to operate in the long run.
  • Classifying too many sources as secondary sources will result in an undersized system, resulting in insufficient capacity for normal operations. This will produce production bottlenecks or inadequate venting leading to health/safety hazards.[/box]

Step 3 – Calculate Total CFM Required for Each Branch

In the next step, determine how much CFM you need at each branch of your system. If your source equipment has a built in collar or port identify the diameter (if rectangular calculate the total cross sectional of the duct and convert to round equivalent). On larger sources such as kilns, furnaces or process equipment or for sources with custom-designed venting determine CFM required by consulting with the equipment OEM or by using industry-best practice methods. (Consult a dust collection expert experienced in the specific application for advice.) Finally, using the chart in this section find your duct size and match to column with the required conveying velocity to find the needed CFM for each branch.

Determining CFM for Each Branch in Our Example System – To illustrate we have prepared a sample system layout for consideration of this design step (See illustration below. We will continue to use this same example throughout the following 3 sections.)

Here we have a woodworking shop with a total of (5) pickup points. We have a sander, backdraft table, planer and two floor pickups. Next we determine the CFM required for each branch by duct diameter and then matching it to the appropriate conveying velocity required for wood (see chart in previous section)

  • (1) Sander = 4” OD @ 4,000 ft/m = 350 CFM (rounded)
  • (1)Planer = 5” OD @ 4,000 ft/m = 550 CFM (rounded)
  • (1)Backdraft table = 6” OD @ 4,000 ft/m = 780 CFM (rounded)
  • (2) Floor pickups = 4” OD @ 4,500 ft/m = 400 CFM (For reference only, secondary sources are not counted towards final total.) Expert Tips Many types of equipment come with built-in connections for dust collection. These ports are sized by the manufacturer to provide sufficient ventilation while operating the equipment. Simply confirm the diameter of the port to calculate the required CFM (using chart in this section) for the unit.

Step 4 – Create a System Layout and Size Your Main Trunk

Now we need to create a layout of the ductwork system, deciding where it will connect to each machine and where we will place the dust collector. This will determine what size ducts we need including our main trunk line. To help illustrate these concepts we will continue to refer to our sample system first described in the previous section.

Steps to Layout Your System and Size Your Main Trunk

  1. Make rough floor plan showing the location of each piece of equipment
  2. Sketch layout of ductwork connecting each piece of equipment together and running all the way back to the dust collector
  3. Where two primary branches meet combine the CFM require by each branch (using figures from previous step) and calculate the duct size needed to provide sufficient CFM for both branches at the required air velocity (where needed round up to next largest duct size)

Example of a dust collection system layout for a woodworking shop.

Make Floor Plan of Equipment – Take your primary and secondary sources and make a rough floor plan of every piece of equipment. Once you have every source in its approximate location map out the ductwork connection each piece back to the collector. Try to locate your dust collector in a central, convenient location. Safety regulations covering applications involving combustible dusts (e.g. wood, metals, grains, etc.) may mandate placing the baghouse outside or on an exterior wall (along with explosion venting to the outside).

Create Rough Layout of Ductwork System – Now each piece of equipment needs to be connected together and run back to the baghouse. Start at the source farthest away from your collector. Using the CFM requirements you calculated for each branch in the previous step, note the diameter of the duct required and map it out running towards the collector to the point where the next branch connects. Additionally, note the length of each run of duct (important for next step).

Where the next branch connects add the CFM of both lines together and determine what size duct you need for that amount of CFM at the required velocity in ft/m. Increase the size of the duct accordingly and continue mapping the trunk forward. Repeat the process and increase the duct size only at each spot where a primary source connects to the main trunk. Continuing mapping your main trunk (making sure to connect to all primary and secondary sources) until you reach the collector.

Example of a dust collection system layout for a woodworking shop.

Sample shop layout – Notice our calculations for the required CFM, air velocity and the total static resistance generated by the system. Now you can determine the required filter area (i.e. number of filters in the collector) and the fan power. 

Determining Duct Size for Each Branch and Main Trunk in Our Example System – First, we begin with the farthest source the sander. Its built in connection port is 4”, so we begin with a 4” duct leading out of it. Then we continue running it where it connects with the 5” duct coming from the planer. (NOTE We do not increase the size where it meets the Floor Pickup, as this is a secondary source.) By combining 4” duct requiring 350 CFM and the 5” duct requiring 550 CFM, we get 900 CFM +/- at 4,000 ft/m (see previous section for more details). Where these two combine we need a duct to handle at least 900 CFM@ 4,000 ft/m. According to our chart, this falls between a 6” and 7” duct. Per best practice, we will move up and oversize the duct slightly to ensure sufficient airflow and allow for possible expansion later.

Continuing on the 7” duct next combines with the 6” duct running from the backdraft table. The 6” duct requires 780 CFM +/- and the 7” duct requires 1068 CFM. Again, the total combined CFM falls in between the 9” and 10” OD duct, so we size up to 10”. Finally, with all the primary sources connected, the system requires at least 1,680 CFM @ 4,000 ft/m.

Now we have sufficient CFM for all of our primary branches. We also have a safe amount of oversizing to ensure adequate operation and provide a cushion for any possible future expansion. To accommodate the other secondary branches we can install blast gates on all the branches and close off other lines. Expert Tips:

  1.  Try to keep the largest equipment closest to where you will place your dust collector.
  2. Try to run your ductwork in the shortest possible route.
  3. Always size up if the required CFM falls between two duct sizes. This allows for future expansion.
  4. Only increase the duct size when a primary source branch connects, but do not forget to run trunk so that all the secondary sources can connect as well.
  5. Consult fire/safety regulations may require the dust collector be located on an external wall or outside.[/box]

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Step 5 – Calculate The Static Pressure (i.e. Static Resistance) of Your System

Static pressure or static resistance (measured in inches of water w.g.) refers to the amount of resistance to airflow created friction and channeling of air through the ductwork. For the system to work the system fan must overcome the resistance created by the ductwork and the baghouse. Accurately calculating the static pressure or SP of the system is crucial for the system to function correctly. To determine the total SP of your system you must add the SP generated by following three elements together:

  • The branch with the great SP (also known as the Worst Branch)
  • The SP of the main trunk line, including any fire protection/prevention devices
  • The resistance created by the dust collector(s). This would include any precleaners (cyclones, knockout chambers, etc.) as well as the filters within the baghouse.

Calculate the SP of all your branches and identify the one with the greatest amount of resistance in w.g. (Likely the branch farthest from the unit with have the highest SP, but not always.) Only figure the SP of the worse branch into your calculations for the entire system’s SP. Next, move on to the main trunk line. Calculate the resistance created by the duct diameter and the length of each section, along with any elbows, splits, or other connections. Finally, identify the SP generated by the dust collector(s), which in most cases will be only a baghouse. For most baghouses plan on a maximum of 5”-7” of resistance (most baghouses should run between 3”-5” differential pressure, but sizing slightly above this figure is conservative and allows for some flexibility).

Steps to Calculate System Static Pressure (i.e. Static Resistance)

  1. Identify the branch with the highest static pressure (Worst Branch)
  2. Calculate the SP of the main trunk line
  3. Determine SP of dust collector

Determining Static Pressure for Each Branch, Main Trunk and The Baghouse in Our Example System

Step 1 – Find the Branch with the Highest SP – Starting at each piece of equipment work back through to the main trunk and determine the total SP of each branch. In our example, the sander branch has the great resistance.

  • Entry loss at equipment adaptor of 1.5” (constant)
  • 10’ of 4”OD duct
    • Reference Table 2-3 shows 100’ of 4” OD duct @ 4,000 ft/m = 7.03”
    • 10’ = 7.03 x .1 (for 10’ feet out of 100’) = 0.70” SP
  • (1) 90° elbow
    • Reference Table 2-4 shows (1) 90° elbow of 4” OD is equivalent of 6’ of straight pipe
    • 6’ of 4 OD = 0.28” SP
  • 25’ of 4” OD duct
    • Reference Table 2-3 shows 100’ of 4” OD duct @ 4,000 ft/m = 7.03”
    • 25’ = 7.03 x .25 (for 25’ feet out of 100’) = 1.76” SP
    • 1.5” + 0.70” + 0.28” + 1.76” = 4.24” Total SP for sander branch

Step 2 – Calculate SP of Main Trunk Line – In our example our ductwork has 50’ of 7” OD duct, followed by 30’ of 10” OD duct at 4,000 ft/m.

  • 50’ of 7” OD duct
    • Reference Table 2-3 shows 100’ of 7” OD duct @ 4,000 ft/m = 3.55”
    • 50’ = 3.55 x .5 (for 50’ feet out of 100’) = 1.78” SP
  • 30’ of 10” OD duct
    • Reference Table 2-3 shows 100’ of 10” OD duct @ 4,000 ft/m = 2.30”
    • 30’ = 2.30 x .3 (for 30’ feet out of 100’) = 0.69” SP
  • 1.78” + 0.69” = 2.47” SP Total SP for main trunk line

Step 3 – Calculate SP for Dust Collector – Each type of dust collectors generates different SP. For this figure, it is best to consult with an experienced baghouse OEM such as For our example we will assume a SP of 6” for a baghouse dust collector. Note: Baghouses are normally designed to operate between 3” – 5” of differential pressure. recommends being conservative with this estimate and designing in extra capacity to provide a cushion for normal operational ups and downs.

  • 6” Total SP for baghouse

Total SP for our example system:

  • 4.24” for worst branch
  • 2.47” for main trunk line
  • 6” for baghouse
  • = 12.71” total system SP

Now we have all the data needed for completing our system. The dust collection system must provide a minimum airflow of 1,680 CFM through a 10” trunk duct at air velocity 4,000 ft/m with a static pressure of at least 12.71” w.g.

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Next Section – Part 4 – Additional Considerations for Dust Collection System Design

 Baghouse Design Guide Overview dust collector technical Drawings - S-TA 9-144 Models

For a dust collection system to function adequately engineers must design and operate the system to maintain the (4) key design parameters of airflow (measured in CFM), airflow velocity (measured in FPM), Static Pressure/Static Resistance and Air to Cloth Ratio (or A/C). Changes to any of these key system parameters will result in systemwide performance issues. All four of these parameters are fluid and directly affect the others. Maintaining all at proper levels requires careful engineering, operation and maintenance. Lets review these four parameters one by one.

Airflow in CFM (Cubic Feet per Minute)

CFM – What Is it? – How much air the system moves is measured in Cubic Feet per Minute or CFM. (Related terms include ACFM for Actual Cubic Feet per Minute and SCFM for Standard Cubic Feet per Minute). Most often baghouses are sized and categorized according to CFM. In general, the larger the space being vented or the greater the number of pickup points in the system the more CFM required. The CFM generated by the system fan can be fixed or adjusted (Variable Frequency Drive or VFD Fans). However, total CFM generated by a fan can be affected changes in altitude, ductwork restrictions and sizing as well as resistance to flow created by the system (ductwork + filters).

Why Important? – Without sufficient CFM the sources will not be vented adequately. Poor venting directly causes damage to equipment, high emissions, loss of reclaimed product and hazardous environment (especially of concern in facilities handling combustible dusts or hazardous materials). Low CFM can also negatively affect air velocity, air to cloth ratio, and vacuum pressure, other key design parameters.

Vacuum Pressure (Suction) & Static Pressure (Static Resistance)

What Are Static Pressure and Static Resistance? – Vacuum pressure or suction is measured in inches of water gauge, w.g. and is the basis of a properly functioning dust collection system. The system fan must supply enough suction to pull the materials from the collection point(s) all the way through the ductwork to the baghouse and then through the filters and out to exhaust. To do that it must overcome the resistance to flow created by the filters and the ductwork. Conversely, static pressure or static resistance is a measurement of resistance generated by the ductwork and the filters in baghouse. This also is measured in inches of water gauge.

Why Important? – Without sufficient CFM the sources will not be vented adequately. Poor venting directly causes damage to equipment, high emissions, loss of reclaimed product and hazardous environment (especially of concern in facilities handling combustible dusts or hazardous materials). Low CFM can also negatively affect air velocity, air to cloth ratio, and vacuum pressure, other key design parameters.

Air Velocity and Minimum Conveying Velocity

What are Air Velocity and Minimum Conveying Velocity? – Air velocity within the system is measured in feet per minute, or ft/m. The system must be carefully engineered to keep the air speed within an acceptable range to prevent two major issues. Air speed is related to CFM as follows: ft/m = CFM ÷ cross sectional of duct (i.e. size of duct).

Dust builds up within the ductwork when the air velocity is too low causing blockages and affecting airflow and performance.

Dust builds up within the ductwork when the air velocity is too low causing blockages and affecting airflow and performance.

Why Important? – High air velocity can quickly wear holes the ductwork by means of abrasion (especially abrasive dusts like metals, ceramics, etc.) or can break up delicate conveyed products such as processed foods (cereals), pharmaceuticals, and others. Of greater concern is low air velocity, which can cause dust buildup within the ductwork and lead to poor dust capture at inlets. For a dust to travel suspended in air it must most at or above the minimum conveying velocity for that product. If it drops below that minimum speed at any point in the ductwork the dust will begin to settle or dropout of the airstream, which then accumulate into large piles that eventually choke off the duct. These accumulations of dust within the ductwork create major safety hazards. When combined with an ignition source (such as a spark or ember) they provide ample fuel for a combustible dust fire or explosion, which then can propagate throughout the entire system, being continually fed by dust accumulations further downstream until it reaches the dust collector. Additionally, these accumulations can eventually become so large that the duct collapses under the added weight.

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Air to Cloth Ratio

What is Dust Collector Air to Cloth Ratio? – The ratio of gas volume (ACFM) to total cloth area (sq. ft.) of the baghouse. First calculate the total cloth area of your collector by calculating the total filter area of each filter (bag diameter x 3.14 x length ÷ 144 [for number of inches in a square foot] = filter cloth area) and then multiply that figure by the total number of bags in the collector. Take the CFM of the system and divide it by the total filter cloth area to get your air to cloth ratio.

Why Important? – For the baghouse to capture the dust from the airstream the unit must have a sufficient number of filters. As you push more air through the same amount of filter material the collection efficiency goes down. Maintaining an adequate air to cloth ratio enables the baghouse to operate at peak efficiencies, collecting more than 99.9% all dust particles that pass through it. For most applications, anything less than near peak efficiency will result in excessive emissions, violating pollution regulations and creating hazardous environment for workers and neighbors.

Putting All 4 Variables Together and Designing Your System

Now that we have discussed the 4 key design considerations, we will now see how to design a baghouse dust collection system so as to maintain all 4 of these parameters within acceptable ranges to ensure proper operation. Our next section is titled: Design Process for Your Baghouse Dust Collection System

Next Section – Part 3 – Design Process for Your Baghouse Dust Collection System

 Baghouse Design Guide Overview dust collector design and sizing

Dust collection systems play a vital role in many commercial and industrial facilities. Whether part of a system process, used to capture harmful pollutants from furnaces/boilers, to convey dry bulk product or to maintain a clean and safe work environment, dust collection systems need to function at near constant peak efficiency for facilities to operate safely and productively. While maintenance and proper operation play a large role in keeping these systems running properly, many facilities face challenges due to improper system design and engineering.

Many users rely on outside vendors or so-called “experts” with little to no actual dust collection experience to design and engineer a system for them. Other times vendors may purposefully undersize a system in order to undercut other potential suppliers regardless of how it actually performs in the end for their customer. Still others design their own system in-house thinking it an easy process that just any engineer can accomplish with little to no outside guidance. These cases frequently end with an inadequate dust collection system that cannot meet the needs of the process, resulting in high emissions, lowered productivity, hazardous work environments or all three! So what can facilities do to ensure they do not encounter these same issues?

Need Help Designing Your Baghouse?

Looking for help designing your dust collection system? Let our us use our 40+ years of expertise to help you select the right system for your application.

In our experience, an educated user benefits the most and becomes best customer. With that in mind, we have prepared this guide (broken into 4 major sections) to assist users in designing and properly sizing a dust collection system. By following the direction in this guide closely, you can effectively estimate what kind of system you require and then use this information as a basis for gathering quotes and additional assistance.

This guide is NOT an exhaustive course on dust collector design. Each system presents unique circumstances that affect the general operation of a baghouse system. As such, the guidelines present in this guide should be used only to estimate the sizing of your system. A qualified, and experienced dust collection system OEM should be consulted before purchasing any equipment or making design changes.

Now let’s get right into it! First we start with the four key dust collector design variables.

Next Section – Part 2 – The Four Key Baghouse System Design Variables

 Baghouse Design Guide Overview

Key Points to This Guide

  • Many So-called “Baghouse Experts” know little about proper dust collection design and operation OEMs and sales reps frequently undersize systems to win contracts leaving customers with a system that does not work
  • Educated clients can determine the general size they need and use it as a basis to compare quotes from multiple sources
  • Understanding principles of dust collection system design enables facilities to make better decisions regarding baghouse maintenance, operation and safety
  • Designing a baghouse with the correct variables CFM, air velocity, static/vacuum pressure/resistance, number of pickups

    How large of a baghouse do you need? How do you determine how many filters you need? What air to cloth ratio meets your needs? How much vacuum pressure (static pressure) do you need in the system fan? How much CFM do you need?

    These are just some of the questions that may arise when working with dust collection systems are your facility. When designing a new system plant engineers need to decide how large of a system they require before they begin getting quotes from vendors.

    A danger exists when facilities ask outside vendors to design a system for them. Many so-called “dust collection experts” are really just sales rep organizations that have little technical background or engineering experience with these systems. As such, they will often sell whatever product lines they have with little regard for making sure it is the best fit for your specific application. Others vendors purposefully recommend undersized systems in order to undercut other vendors on pricing, regardless of how the end system performs for the customer.

    Plant personnel can easily avoid being sold an undersized dust collection system by conducting research in advance to get a general idea of what size system they need. Then they can use this estimated sizing information as a basis for getting quotes from multiple vendors.
    For this reason, has prepared a detailed series of articles to help educate users on how to properly size their baghouse system. Each article in this series will cover a different step in the process of determining your dust collection needs for your system. This article series will primarily be of use to plant personnel looking to install new baghouses and ductwork systems. However, the information can also be used when troubleshooting existing systems (where capacity may not be sufficient) or when looking to expand capacity on existing systems.

    Click here to download the complete eBook: How To Size a Baghouse Dust Collection System.


    Next Section – Part 1 – Why You Need to Properly Size Your Baghouse System

     Baghouse Design Guide Overview

    A entry level triboelectric broken bag detection system - Courtesy of

    By Dominick DalSanto

    Quickly finding and replacing leaking filters is crucial for keeping a baghouse operating at peak efficiency. The longer you take to replace the leaking filter the more likely you will have to report the event to your air quality control regulatory agency (reportable event) and the more abatement costs you will incur.

    How Broken Bag Detectors Work

    How Triboelectric Dust Detection Systems Work

    How triboelectric bag leak detection systems work – Courtesy of

    Triboelectric broken bag detectors measure the amount of static electricity generated by dust particles in an airstream. Dust particles generate an electrical current when they encounter the insulated metal probe in the ductwork. A dust particle directly impacting the probe creates a DC signal while a particle passing near to the probe generates an AC signal. The latest generation of triboelectric detectors (such as the Auburn Systems’ TRIBO series) unify both signals and then output a measurement of particle concentration to a nearby control panel or transmit it to a PLC.

    Using a Triboelectric Broken Bag Detector as Early Warning

    Most leaking baghouse filters begin as small holes or rips that overtime become worse and worse. Catching a leak quickly is crucial. The longer a leak persists the worse it becomes, often quickly causing a plant to exceed its maximum PM 2.5 emissions limits set out in its air permit. Additionally, abatement requirements quickly increase as a leak continues over time.

    Older optical emissions monitors (i.e. opacity meters) and optical bag leak detectors can only detect a filter leaking so badly damaged that the increase in emissions exceeds 10% opacity (often greater than the maximum permissible levels for many air permits).

    Triboelectric systems are sensitive enough to detect even the smallest of increases in dust emissions such as when a bag first begins leaking. Operators can then examine the realtime trending emissions data to see whether it was a sudden spike indicates a damaged bag (such as from quickly worn hole) or slow rise indicating wearing filters.


    Using Broken Bag Detector to Pinpoint Which Filters Are Leaking

    An added advantage of triboelectric bag leak detectors is they can enable operators and maintenance technicians to pinpoint exactly which bags are leaking and need to be replaced.

    Personnel should carefully monitoring emissions while cleaning system runs. When emissions spike during one cleaning cycle it means that leaking filters are present. Using this method, maintenance personnel can trace the leaking filters down to a specific baghouse, compartment and even row (pulse jet only) of bags. This saves time and money over traditional dye leak testing.

    However, on older units, or when first beginning to troubleshoot a unit dye leak testing should still form part of your maintenance schedule. Dye leak testing can pinpoint multiple leaks at once, and in structural components as well as filters.

    By quickly pinpointing leaking filters maintenance staff also reduce the amount of abatement required after the leak is fixed.

    Below is the sample data from a test conducted to determine the differences in performance between a triboelectric leak detection system and a typical optical system (opacity meter). Notice the huge difference in response time and abatement required.

    Leak Test ResultsTriboelectric Bag Leak DetectorOptical System
    Estimated Time to:
    Detect LeakLess than 1 Hour2-3 days
    Locate Leaking Filter(s)Less than 1 Minute2-3 Man Hours (dye leak test)
    Clean Up LeakLess than 1 Man-Hour8-10 Man Hours
    Estimated Size of:
    Hole Detected1/4”8”
    Dust Accumulation2.6 cubic feet60 cubic feet
    Dust Clean Up ToolShopvacShovels


    Reduce Baghouse System Downtime

    When a baghouse goes down it often brings much down with it, from specific equipment to entire production lines to even entire plants due to emissions or health and safety issues. Preventing unscheduled baghouse shutdowns directly impacts the bottom line. In some facilities, losses from just one down day can add up to tens of thousands of dollars in lost production, fines and other costs. Therefore, investing in the maintenance and upkeep of these baghouse systems is well worth the initial capital costs.

    Triboelectric dust monitoring system often prove one of the most cost-effect ways to improve dust collector maintenance and operation. With the ability to monitor emissions in realtime and trends over time, operators can better assess the condition and operation of their baghouses than those who rely solely on differential pressure.

    For example, by carefully analyzing the triboelectric data trends maintenance planners can accurately predict when filters will no longer achieve their require collection efficiency and need a changeout. Further, they can begin preparations for the changeout in advance, sourcing filters and cages, obtaining contract labor for the changeout and scheduling the changeout for the next most convenient time (e.g. yearly maintenance shutdown). Compare this with the added costs and stress involved when a changeout is done at the last minute!

    Additionally, as mentioned above, triboelectric bag leak detectors also prevent downtime by quickly alerting plant personnel to any leaks as soon as they begin to form. By catching leaks before they become serious plants can avoid stoppages for abatement, repair and any possible fines or sanctions from air quality regulators.

    Recap of the Key Points

    • Triboelectric bag leak detectors directly impact the bottom line of your baghouse by improving maintenance efficiency, reducing downtime
    • Increased detection range means finding leaks quicker, before they become reportable events
    • See when filters first begin to fail allows predictive maintenance planning to reduce inconvenient shutdowns
    • Find leaking filter bags quicker, pinpoint down to specific unit, compartment and row without a dye leak test
    • Comply with MACT standards that require triboelectric broken bag detectors over opacity meters

    Interested in a Triboelectric Broken Bag Detection System?

    If you would like to know more about our line of triboelectric broken bag detectors  and how they can benefit your facility contact us today for a free consultation and quote!

    Baghouse maintenance from personnel