The airflow in a dust collection system is extremely important, since the air collected at the hoods is removing the dust from the affected areas.  This air is then sent to the dust collector to remove the dust from it.  While it is always desirable to use the least amount of air as possible in your dust collection system, you must have enough air so that it is actually doing the job it is meant to.   If not enough air is going through the system, you will not capture all the dust from the pickup areas, thereby allowing dust to escape into the facility, cause health / nuisance issues and/or fire hazards.  If the airflow is too high, you could be picking up product/ raw materials, wasting energy and increasing maintenance issues.

There are many reasons that the airflow through a dust collection system can change.  A few of them include:

• Environmental changes – temperature, humidity, etc.
• Changes in the system – such as opening/ closing dampers, dust buildup in the ductwork, damage to the ductwork and/or hoods.
• Dust collection issues – such a plugged filters, old filters, holes in the filter, etc.
• Damage to the exhaust fan – such as bearings, damaged impellers, etc.

Unlike liquids, there is no easy and inexpensive way to monitor airflow in a dust collection system.  The most common way is to periodically manually measure the airflow by inserting a pitot tube in the ductwork and measuring the air velocity.  The airflow is then calculated.

One option to monitor your airflow is to install a cyclone pre-filter ahead of the filters.  A cyclone’s pressure drop increases as the airflow increases in them.  Usually the manufacturer of the cyclone can provide a curve, showing the relationship between the pressure drop and the airflow.  So if you monitor the pressure drop through the cyclone, you will notice if the airflow suddenly increases or decreases.  And if the pressure drop drifts too far from a certain pressure drop you will know to troubleshoot the system.

To learn more about the different types of Dust Collection methods,  please contact our experts at 440-543-7400 or click on the button below to get our whitepaper: Top 5 Questions To Ask When Considering A Cyclone Dust Collector.

Dry dust collectors and humidity don’t react well together.  Baghouses and cartridge collectors operate by having dirty (dusty) air enter the housing.  Multiple filters (bags or cartridges) are located in the housing.  The air travels through the filter and then exits the dust collector.  The filters are a mesh of fibers that allow air to travel through small holes, while dust is too large to pass.  The dust builds up a layer (dust cake), further limiting the subsequent dust’s ability to pass through while allowing the air to pass.  From time to time the dust collector will clean the filters by shaking them or using compressed air to expand them.  This causes the outer layer of the dust cake to fall off.

Humidity can cause problems in the process described above.  Humidity is a way to express the amount of water in the air, (the higher the humidity, the higher the amount of water in the air).  When high humidity air enters a dust collector with fabric filters, there is a chance that the water vapor will condense and create water droplets or the dust on the filters will absorb the water as the airflow passes through.  Many dusts change their physical properties when the water content increases.  Some become sticky, some become hard like concrete, etc.  When this happens to the dust cake, it affects the ability of the air to pass through and the ability of the dust to fall off during cleaning.

When dust becomes sticky, it will adhere to neighboring dust particles and not want to fall during cleaning.  Dust that becomes hard (like concrete) will prevent air from passing through.  When one of these issues develop in a dust collector the pressure drop across the dust collector will increase.  Over time, an increased pressure drop will lower the airflow being pulled through the system.  This will decrease the airflow being picked up at hoods, therefore lowering dust collection at where operators are located.

Humidity can also be introduced in the dust collector in the compressed air.  When air is compressed, the temperature of the air increases, thereby increasing the water content of the air.  The compressed air is at its saturation point.  As the air moves through the line, it cools, thereby condensing water in the system.  If additional drying technology isn’t installed, the compressed air will have water droplets in it as it is used in the dust collectors.  This will cause the filter cake to wet and cause issues as described above.  This is why it is important to dry compressed air when dealing with dust that is affected by water.

However, sometimes no matter how you treat your compressed air, you continue to have issues.  This could be because the airline travels outside and in winter time it gets very cold. It could be because you are located near a large body of water, and humidity is high.  One way to minimize the effect on your dust collector is to minimize the dust getting to your dust collector.  Cyclone pre-filters are ideal for these applications.  Cyclones collect dust and water droplets using centrifugal motion.  This means they aren’t affected by the changes to the dust as a filter is.  Cyclone pre-filters can often remove up to 80% of the dust before a dust collector with filters.  This means you can lower the number of water droplets going into your dust collector and minimize the cleaning required, thereby not getting as much water from the compressed air system. 

To learn more about the different types of Dust Collection methods,  please contact our experts at 440-543-7400 or click on the button below to get our whitepaper, Top 5 Reasons to Use a Cyclone as a Pre-Filter.

Look under almost any dust collector and you will see a rotary airlock valve spinning its rotor and emptying the collected contents from the hopper. These valves have long been used to maintain a seal in vacuum dust collection systems while simultaneously providing an escape route for the dust. The advantages of a rotary airlock for dust collectors include, automatic hopper emptying, minimal vacuum pressure loss, and the many options available to meet specific application needs. Rotary valves can be custom fit to handle high temperatures, harsh chemical environments, and abrasive materials. Rotary valves do however, have a few major drawbacks.

Because rotary airlocks are sealed tight to the atmosphere they can be very difficult to clean. Cleaning a rotary valve often involves removing the drive assembly, end plate, and finally the rotor. This process can take hours to perform. Rotary valves are also expensive to operate. Typically, these valves are left running continuously, even when there is no dust present in the hopper. This not only wastes electricity but puts undo wear on the valve. Repair and replacement parts for rotary airlock valves can be quite costly as well. Even with these shortcomings, the rotary airlock remains the industry standard for most dust discharge applications.

One alternative which has been gaining popularity is a non-powered automatic dust discharge valve. These valves, like the Armadillo and Platypus Vacu-Valves from Aerodyne, rely on the negative pressure (max -18" W.C.) of a dust collector to hold a rubber sleeve closed to maintain an airlock. As the weight of the dust in the hopper builds up, the sleeve is forced open and dust is discharged from the valve. Leaf springs inserted into the valves sleeve also help to counterbalance the vacuum. A video demonstration of how this works is available here. The valves are available with a variety of sleeve materials for different applications. While these valves can not be used in every dust collection system they are a very economical alternative to expensive rotary valves.

The Vacu-Valves from Aerodyne are priced at a fraction of the cost of standard rotary airlock valves and require no electricity to operate. These valves have no controls and require no lubrication. They easily handle abrasive materials that would jam or wear out a rotary valve.

To learn more about which dust collector valve is right for you, please contact our experts at 440-543-7400 or click on the button below to get our infographic, Vacu-Valve is a Simpler Solution.

At one time mechanical dust collectors were the industry standard in dust collection and air pollution control. However, with an ever increasing focus on air quality, EPA regulations regarding dust collection have steered the manufacturing world toward the higher efficiency capabilities of fabric filter baghouses, cartridge filters, and other dust collection equipment utilizing filter media. This change has undoubtedly helped to reduce the amount of harmful emissions released into the atmosphere in manufacturing processes. Unfortunately, the use of these fabric filter baghouse collectors is not without cost. The limitations of filter media such as moisture, heat, and high particulate volumes have added to the challenges of successful dust collection. Additionally, the high cost of bag or cartridge replacement, maintenance issues, and expensive pulse-jet controls to clean filter media can add up. The solution to these headaches for many has been the use of mechanical dust collectors before final-stage filtration.

Mechanical dust collectors use a cyclonic air flow to separate particulate from an air stream. The centrifugal force created by the rotary flow throws the dust out of the air stream and toward the walls of the collector. In a typical cyclone, the particulate strikes the wall of the collector and falls to a hopper below for collection. Cleaned air is then vented through the top of the collector. While this form of collection can be highly efficient in dealing with large, dense particulate, extremely fine dust lacks the inertia to escape the air stream and is subsequently carried out with the cleaned air. Some high efficiency cyclones like the Aerodyne 'S' Series, use two air streams, to more efficiently separate the dust. The Aerodyne's powerful secondary air stream intercepts the particulate before it contacts the side wall, reducing wear when handling abrasive materials. This secondary air stream also helps to sustain the cyclonic action inside the collector, thereby increasing its efficiency.

Filter media dust collectors such as baghouses and cartridge filters use a fine filter media to remove dust from an air stream. The dust-laden air is drawn into the collector where it passes through the filter media and particulate is intercepted. Dust builds up on the filter until it is cleaned or replaced. Cleaned air is then vented out of the collector.

Many manufacturing processes involve circumstances that make it very difficult to rely completely on a baghouse. Heavy dust loading can be a maintenance nightmare for a filter media collector. A rock crushing operation based out of Minnesota realized the benefits of placing a cyclonic dust collector before its baghouse. The enormous amount of rock dust generated in the crushing operation was blinding the bags and causing frequent shutdowns. The decision was made to install a cyclonic dust collector to receive the dust before being sent through the bag house. The cyclone captured the vast majority of the rock dust, leaving only a small amount of fine particulate for the bag house to handle. The cost of the additional equipment was quickly recovered through fewer shutdowns and less frequent bag replacement.

Processes involving high temperature exhaust gas also plague filter media collectors. The hot air temperatures exhausted from foundries, glass making plants, and power plants can burn the filter media used by most baghouses. While high temperature filter bags and cartridge filters are available, they can be an expensive addition and are still not completely immune to the heat. Used as a spark arrestor, a cyclonic dust collector can be placed before a bag house to both reduce the temperature of the air stream and the particulate loading before it enters a final stage filter.

While a mechanical dust collector may not be necessary in every application, the benefits that can be gained from this proven technology are evident. As emission standards become more stringent and process costs continue to rise, any advantage that can be taken should be considered. By comparing process costs such as materials, labor, and downtime with the expense of a cyclone, a decision can be made as to the need for such equipment.

To learn more about the different types of Dust Collection methods,  please contact our experts at 440-543-7400 or click on the button below to get our whitepaper, Not Your Grandfather's Cyclone. 

Dust collection system design can be a very complicated process. Beyond determining variables such as air volumes, drop sizes, and capture velocities, there is perhaps no more important design consideration than fire prevention. This is especially true in systems that are used in hot work applications, such as sawing, grinding, or sanding, where sparks can potentially be generated. If a spark is drawn into a system’s ductwork, it has the possibility of travelling all the way to the system filters which are typically constructed of combustible materials. If this happens, the filters can catch on fire, which can lead to catastrophic destruction of the dust collection system, the entire building, or result in serious injury or loss of life.

Any well thought out system will take this scenario into consideration and incorporate preventive measures to reduce the likelihood of this happening. Installing a spark arrestor in the duct work before the baghouse is a method that is commonly used to reduce fire risk. Spark arrestors vary in design, but most of them are designed with the intent of slowing the spark down, allowing it to cool down and burn out before it can do any damage to the baghouse or cartridge collector.

Another option is incorporating a pre-filter cyclone before the fabric filters. A cyclone works on the same principle when it comes to spark arresting, using centrifugal force to direct any sparks to the cylindrical surface of the cyclone, spinning them along the metal walls of the cyclone where they are drained of their energy via conduction. The cyclone has the added benefit of removing the majority of heavier particulate before it reaches the filters, which alleviates overall system loading.

The ongoing emphasis by OSHA and NFPA on combustible dusts and dust collection systems in general means that regulatory compliance will become increasingly important for any facility that uses dust collectors.  Prevention and suppression devices such as sprinklers in the ductwork, explosion vents, chemical suppression systems, and pre-filter cyclones can all be used to reduce and possibly eliminate the risk of fire. The type of dust being collected, the combustibility of the dust, dust particle size, and filter construction are among the factors that must be considered when selecting the appropriate fire protection for your system.

Which prevention or suppression system does your dust collection system need? Asking that question is the first step in protecting your system, your facility, and the people who work in your facility.

To learn more about how Aerodyne can help you keep your dust collection filter cleaning system operating efficiently,  please contact our experts at 440-543-7400 or click on the button below to get our whitepaper, Top 5 Reasons to Use a Cyclone as a Pre-filter.

For dust collection systems to operate as they are designed, baghouse and cartridge collector filters need to be regularly cleaned.  Many systems employ compressed air for this purpose, periodically sending blasts of air through the filters which effectively removes particulate matter from them. The frequency of these cleaning cycles can be controlled by various methods, such as a pressure drop monitor that allows for detection of a filter that is beginning to clog, or with a simple timer. Air flow is typically controlled with the use of a solenoid operated diaphragm valve.

These valves are the critical component in keeping a system operating at peak efficiency. A valve that is stuck in the closed position or does not open when required will not allow the filters to be cleaned, which will result in an overloaded system that could potentially allow higher than expected levels of particulate to be discharged into the atmosphere or lead to premature system failure due to increased loading.  Conversely, a valve that gets stuck in the open position will result in costly compressed air being constantly sent through the filters.

Maintaining the health of these valves is obviously an essential factor in promoting the long term effectiveness of a dust collection system. The simplest way to achieve this is by making sure that the valves are included in a preventive or predictive maintenance program, so that any issues can be addressed before they become major problems. More advanced systems provide continuous monitoring of valve operation, which can alert maintenance personnel to any problems with the valves or the system in general.

To learn more about how Aerodyne can help you keep your dust collection filter cleaning system operating efficiently,  please contact our experts at 440-543-7400 or click on the button below to watch Dust Collection System Maintenance Video.