Wet scrubbers are used in dust collection for a variety of reasons. One of the reasons is to help prevent fires and explosions.

Wetting Particles Using Wet Scrubber

Since wet scrubbers use water to help with dust removal their environments usually have a very high humidity. In this environment dust particles become wet and this can often prevent them from catching fire and/or exploding. Material such as wood has a much different fire danger when it is wet compared to dry.

As we see on the news, when there is a draught there are more forest fires around the country. This also applies to wet scrubbers. Spraying water on a solid can often prevent an explosion or fire. This is done by wetting the particles thereby making it harder for them to combust but also by wetting down any spark or fire that could cause an explosion.

Material Used vs. Wet Scrubber

If you are using a wet scrubber there are some thing you should keep in mind. Some material, such as alkali metals, will react with water and potentially explode. Other metals like magnesium can also cause fires and explode with water. Keep in mind that controls need to monitor the water in the wet scrubber system, because if it loses water, an explosive situation could quickly develop. 

So when looking at an explosive application, wet scrubbing can often provide dust removal for you, but not always. There are certain disadvantages of wet scrubbing that should be reviewed before determining if it is the right solution for you.

To learn more about which dust collector, please contact our experts at 440-543-7400 or visit our website: www.dustcollectorhq.com.

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Dust collectors have multiple accessories that can be used to help optimize the system. Some are used to protect the system, some are used to monitor the system, and some are used to make the system operate smoothly. The following blog is a quick description of a few of them.

Meters

• Airflow meters – allow you to measure the airflow through the system. Effective to know if your system is operating correctly.
• Differential pressure gage – used to monitor the pressure drop through the dust collector. Often can warn you if your dust collector is having an issue (sudden change in pressure drop) or when maintenance is required (high or low pressure drops).
• Level meter – allows you to monitor the amount of material in your hopper. This will tell you if you’ve bridged the hopper, your airlock stopped, etc.
• Temperature gage – allows you to monitor the temperature of your system and prevent damage to components such as filters, seals, instrumentation, etc.

Valves and Tools

• Vibrators – allow you to shake material in the hopper, preventing bridging.
• Air nozzles – blow compressed air into the hopper preventing dust from settling and bridging
• Airlocks – allows material to leave the dust collector hopper and prevent air from passing through (entering or leaving the system)
• Zero speed switch – used to monitor the airlock to make sure it is operating and inform the operators when it stops.
• VFD – perhaps the most useful of all this allows you to increase or decrease the airflow in the system by adjusting the operating speed of the exhaust fan.

Explosive Applications

• Explosion vent – mounted on the dust collector, it allows an explosive overpressure to relieve in a controlled fashion preventing destruction of the dust collector and surrounding areas.
• Flameless explosion vent – similar to the above but designed to cool down the release so no flame is vented out. Can be used indoors.
• Chemical suppression – used to inject an inert material into the dust collector which will prevent the dust in the vessel from exploding.
• Thermal sensor – monitors the heat in the dust collector and is used to activate chemical suppression.
• Pressure sensor – monitors the pressure in the dust collector and is used to activate chemical suppression when over pressure is measured.
• Isolation gate – installed before the dust collector, this prevents an explosion in the dust collector from moving back into the building and the rest of the process.

To learn more about which dust collector, please contact our experts at 440-543-7400 or visit our website: www.dustcollectorhq.com.

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When you are designing your ductwork, there are two ways you can do it. 1) You can use dampers to control the airflow at each pickup and balance the system or 2) You can balance by design which means the ductwork is designed so that the proper airflow goes through each pickup without the need to install dampers. There are positives and negatives with both. The following will go over them.

Balance by Dampers

Using dampers to balance your system provides much more flexibility but is much harder to achieve. This design has dampers at each pickup point which allows you to dial in the design airflow. It will allow you to add and remove pickup point (within reason). Of course, the duct needs to be designed so the minimum air velocity is maintained to keep any dust in suspension.   The major issue with using dampers is that you have to balance the whole system, and every change affects every other damper. This means it takes skill and a lot of patience to balance the system. And any change, whether it is adding or removing a pickup point, the accidental (or deliberate) adjustment of the damper will affect the rest of the system. This could mean a total rebalancing of the whole system.

Basically, what this means is that if you require a versatile system which allows you to bring areas online or take offline while keeping the system as small as possible then using dampers is best for you. Just remember that every time you change the damper location you will need to rebalance the system. If you are not experienced this can be a very frustrating and time consuming job.

Balance by Design

The balance by design ductwork is designed so that the resistance throughout the system is such that the correct amount of air is being picked up at each pickup point. This has a few benefits, the first being it is an install and forget design. (Please note we don’t actually mean forget). Once the ductwork is designed and installed, it will naturally pick up the designed amount of air until something changes. A properly designed system will have enough air velocity in each area to keep dust from falling out. So this means you won’t need to adjust anything. We would recommend periodic checking of airflows to be sure the system is operating at the right airflow. If you find that it isn’t then the ductwork has been damaged, changed, or material has built up in it.

The negative of this design is that once it is installed you can’t change it easily. If you are adding or removing any pickup points then you may need to modify the ductwork to be sure you keep the design airflows. You will have to pay special attention that your airflow remains high enough to keep any dust in suspension. The other negative is that it will pull the airflow from all pickup points all the time. And if you are looking to use only one pickup point at a time, then the system will be bigger than might otherwise be needed.

To learn more about which dust collector, please contact our experts at 440-543-7400 or visit our website: www.dustcollectorhq.com.

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This is one of the most important questions you can ask. The answer to this question can require you to invest in expensive protection equipment or not, but that is much better than the loss of thousands of dollars in equipment, production time, and most importantly, employee safety. There are a few ways to answer this question. Some of which are safer than others. The main question you will need to ask yourself, is the dust combustible?

Is My Dust Explosive?

If the material can react with oxygen then there is a chance it can be explosive. However, just because it is combustible, doesn’t mean it is explosive. Generally if a dust is greater than 500 micron in size, it is not explosive. However, what if the dust is smaller than 500 microns?

The safest course is to send your sample into a test facility for a simple Explosibility Screening (Go/ No Go) test. This test will take a small sample and try to ignite it to see if the sample will explode. If it explodes then an explosion severity test should be performed, which provides data on the speed of the explosion (K_st) and strength of the explosion (P_max). This data is very important to designing equipment that will prevent, contain, or divert explosions safely.

Some dust might be generated from material you got from a vendor, and they might have already done explosion testing on the material. You might be able to use this data for the design of your equipment depending on the process. The main thing being, what are you doing with your process? If you are sorting, grinding, drying, etc. the material then you can be changing the explosibility of the dust. If there has been a change, then the material should be tested again or you can assume it to be explosive and use the suitable published data.

The Explosibility of Dust

The explosibility of dust is highly dependent on the material size and humidity. A few examples would be aluminum. Spirals of aluminum from trimming wouldn’t be explosive, but a fine aluminum powder would be. Another example is wood dust. Dry wood dust is very explosive, while wood with a high water content is not.

You should not depend on your history working with the dust, because dust explosions are fickle. You might be working with dust for 20 years and have no issues and then suddenly there is an explosion. Or it might be the 1^st time you work with a dust that an explosion happens. One thing is for sure, if you have had flash fires with the dust, you definitely should have it test for explosibility. A flash fire is a sign that you have an issue with your process and should do further investigation to make sure you won’t have an explosion and to prevent more flash fires.

Dust Hazard Analysis (DHA)

If your dust is explosive, you will then need to have a Dust Hazard Analysis (DHA) done on your process/ building, etc. The DHA reviews your process, operational and maintenance procedures, equipment, etc.   It then provides procedures, equipment changes, etc. to address the issues and provide for a safe process. OSHA will request a copy of your DHA during any inspection. So it is important that you have an answer to the question “Is my dust explosive?” and have something to back up the answer in case you are asked by OSHA, your insurance company, local fire inspector, etc.

To learn more about which dust collector, please contact our experts at 440-543-7400 or visit our website: www.dustcollectorhq.com.

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As maintenance staffs become smaller and have less time to do preventative maintenance, technology needs to step in and help. 

Level Switches

That is where level switches in dust collector hoppers fit in.  An airlock works by allowing dust from the dust collector to leave the vessel while preventing air from leaking in or out of the system.  Some airlocks operate by emptying the hopper as soon as dust falls and some require a buildup above them to help seal the valve and provide motive force. 

The main thing is, that dust often times will not constantly be falling through the valve.  This means that walking next to a vessel won’t always tell you if the airlock is operating correctly. 

Installing a level switch in the hopper will help.  The level switch measures the amount of material in the hopper and if too much is in the hopper it will provide a signal (alarm).  This will tell maintenance that the airlock is not operating correctly and it needs to be investigated.  Depending on the system’s controls, the alarm can be a local alarm (light and/or horn) or feed into the central computer.

Dust collection systems can range from being fairly simple to extremely complex. 

It’s important to know that you have the proper system for your application. Some questions always come up when looking at dust collection systems.

To make life easier, we have put together some common questions we get asked along with answers and explanations. Have a look.

Volume 1:  

Volume 2:

To learn more about which dust collector, please contact our experts at 440-543-7400 or visit our website: www.dustcollectorhq.com.

To improve efficiency and safety, there is no substitute for an on-site inspection by an experienced expert. Click below to start with a free 20-minute phone consultation by clicking the button.

Heavy dust loading in the dust collector leads to high maintenance dust collectors.  Since most dust collectors are fabric filters (baghouse, cartridge collectors, shakers, etc.), heavy dust loading will cause/require high frequency of cleaning of the filters.  Most filters are cleaned by injecting high pressure air into the clean side, causing the filters to expand a bit.  This causes dust to fall off the filters.  Filters wear out due to the frequent expanding and contracting.  So the more often you have to clean a filter, the faster the filters will wear out.

Pleated Filters

This is made even worse if the filters are pleated.  Pleated filters have valleys and ridges which increase the surface area available for air to diffuse through the filter.  However, high dust loading can cause the pleated filter valleys to fill up and not properly clean during a cleaning cycle.  This will severely restrict the surface area available for airflow, which will lead to higher velocities through the filters.  A higher velocity increases the chances of dust getting through the filters.  This can cause holes to develop in the filter.  It can also cause dust to plug a pathway through the filter, thereby further restricting airflow.  It can also cause a decrease in removal efficiency.

So if you have high dust loading in your dust collector, it might be beneficial to install a pre-filter to increase filter life and make maintenance much less of a hassle.

Pre-filtering may reduce operating and maintenance costs by extending bag or filter life and improving removal efficiencies. This video discusses five warning signs that your dust collection system needs a pre-filter.

If you prefer this valuable information in white paper form, get our whitepaper, Top 5 Reasons to Use a Cyclone as a Pre-filter.

To learn more about which dust collector, please contact our experts at 440-543-7400 or visit our website: www.dustcollectorhq.com.

To improve efficiency and safety, there is no substitute for an on-site inspection by an experienced expert. Click below to start with a free 20-minute phone consultation by clicking the button.

To help answer this question, NFPA has released NFPA-652 and 654. A combustible dust is defined as a finely divided combustible particulate solid that presents a flash fire or explosion hazard when suspended in air or the process-specific oxidizing medium over a range of concentrations. Basically, what this means is when the dust is in the air and its concentration is enough to cause a flash fire or propagate a deflagration or explosion if exposed to a spark or heat source, then it’s considered combustible.

Combustible Dust Testing

Unless you know for sure that your dust isn’t combustible, you should send the dust sample to a lab for testing. The lab will provide one of three responses – no reaction, combustible but not propagating, or propagating. 

Usually the lab will initially do a Go/ No-Go test. If the dust doesn’t exhibit combustion, the testing will stop. If it does exhibit combustion, they will then do further tests and provide explosion properties ( Kst and Pmax) of the dust. The Kst tells you how quickly the explosion will propagate, while Pmax tells you the power behind the event.

Common Knowledge about Combustible Dust

1. A combustible dust mixed with non-combustible dust may or may not pass the go / no-go test; therefore, if you have both in a mixture, get a test.
2. Material that may not burn can still be combustible as a dust, unless you know for sure, getting a test is the safe bet.
3. If you have made a process change that changes the composition, relative concentrations, etc. of the dust, then the combustibility of the dust may have changed and a new test should be done.
4. If you have combustible dust in your facility, then a hazard analysis of the area must be done every five years.

Dust Collector FAQ Volume 1

To make life easier, we have put together some common questions we get asked along with answers and explanations. Have a look.

To learn more about which dust collector, please contact our experts at 440-543-7400 or visit our website: www.dustcollectorhq.com.

To improve efficiency and safety, there is no substitute for an on-site inspection by an experienced expert. Click below to start with a free 20-minute phone consultation by clicking the button.

When it is time to add a dust collector to your application, you have to find a place for the dust collector.  This isn’t always easy.  New facilities are usually designed around the equipment that is being installed.  However when a system in an existing facility is modified or installed, you will have limited space to install the dust collector system.  There are four factors that you should take into account when finding a place for your dust collector. (Part 1 of 4)

Explosive dust

One of the most important factors to take into account is the explosibility of the dust.  If the dust is explosive you will have to make sure the location of the dust collector conforms with the appropriate NFPA specification.

The NFPA specifications require dust collectors to be located outdoors if they have explosive dust, unless specific explosion venting or mitigation equipment is being used.  Even if your dust collector is located outdoors, it should still have venting, because you don’t want your collector to create shrapnel during and incident.

Explosive Vent

One of the most common and least expensive explosion protection methods is the installation of explosion vents on the dust collector.  The explosion vent directs the pressure wave out of the vessel through an area, thereby controlling the explosion.  This protects the dust collector from the worst of the damage.

When using explosion vents, it does matter if your dust collector is indoors out outside.  When located indoors, the explosion is required to be vented outside.  The vent is connected to ductwork to an opening in an outside wall or roof.  When this is used, the dust collector should usually be within 5 feet of the wall.

When the dust collector is outdoors it should be orientated so that the explosion vents are directed away from the building and any other equipment.  The vents should also be directed away from any walkways, roadways, and areas where employees would be. (Ex. Rally points, picnic tables, etc.)

Flameless Vent

A flameless vent can be used instead, which allows the dust collector to be installed inside without venting it outdoors.  The flameless vent directs and vents the explosion as a standard vent, but it has metal fins mounted on the vent so the explosive wave travels past the fins.  The metals fins rapidly cool the wave, stopping the flame, so only a hot pressure wave is left.  Enough room must be left around the flameless vent so that adjacent equipment isn’t damaged.  The vent area should not be an area where workers are or a walkway.

Chemical Suppression

Chemical suppression is another technology that is used to protect dust collectors from explosions.  The technology uses non-explosive chemicals to flood the dust collector and prevent an explosion.  Sensors located in the dust collector and the ductwork measure the temperature and pressure to monitor for an explosion.  When they detect an explosion the chemical suppression system is activated.

Chemical suppression systems require yearly maintenance to make sure the system is still protected.  So the sensors and chemical canisters need to be accessible for the maintenance checkups.  This means platforms or open spaces for portable lifts should be located around the equipment.

To learn more about which dust collector, please contact our experts at 440-543-7400 or visit our website: www.dustcollectorhq.com. 

Click below and watch our Webinar that offers a thorough explanation of the changes in NFPA 68 and how they may affect your existing system design.