There are many things that can affect the hazard that your combustible dust presents. It’s possible for dust that is very safe under most circumstances to cause a dangerous explosion if something goes wrong. Here we’ll talk about some of the kinds of information that you may need to know about your dust to make sure you are protected.
Many engineers will recommend that you test your dust professionally before finalizing your system design. There are a variety of companies that do this; check with your systems engineer to find out who they prefer to work with. This will require you to send in a sample of your dust. If you have more than one type of dust (for example, fine dust from welding and heavier rough dust from grinding), you will want to send samples of all of them to make sure your system can be designed for maximum safety. Combustible dust explosions kill people every year and cause massive damage to property, and it’s worth controlling the problem safely in your facility.
Dust Test Measurements
PARTICLE SIZE (microns):
Some materials are very inert as large pieces, but will burn rapidly in small particulate. Particle size measurement is usually in microns. This is also important for filter efficiency. Particle size is also very important for health purposes: larger particles may be trapped in the nose and throat where they are easy for the body to get rid of, while fine particles (under 30 microns) travel deep into the lungs.
MINIMUM IGNITION ENERGY (MIE):
This is a measurement of how much energy your dust requires to ignite. Some dust requires a lot of energy to ignite (in some explosions, the source of ignition has been an overheating bearing or an open flame). Other dust can ignite with much less energy. Static charges can ignite many types of dust. MIE is how much energy the dust needs to make it ignite.
MINIMUM EXPLOSIVE CONCENTRATION (MEC):
This measures how much dust must be present to cause an explosion. This measurement is usually with airborne dust. It tells you how much dust in the air will ignite if there is a heat source around. This is important because it explains how much dust needs to be floating around in the air to cause an explosion. A secondary explosion, which happens when dust that accumulates in the area lofts into the air by the first explosion, can involve a lot more dust and be a lot more dangerous.
MINIMUM AND MAXIMUM EXPLOSION PRESSURE (PMINand PMAX):
The minimum and maximum explosion pressure. Personnel conduct tests on dust inside a container that can measure pressure. Pminis the smallest amount of pressure that ignition of the dust can produce. Then there’s Pmax, which is more important. It is the maximum amount of pressure that explosive ignition can produce.
Pmaxis measured by increasing the concentration of dust inside the closed chamber and measuring the pressure of the explosion until the maximum is reached (until the greatest possible amount of damage has been determined). This is an important calculation because it allows you to calculate how much damage your dust is capable of doing inside a closed container (like ductwork or a dust collector).
MAXIMUM RATE OF PRESSURE RISE/DEFLAGRATION INDEX ( KST):
This measurement is done in a similar way to Pmax. A mathematical formula converts Pmax to KST, taking the volume (size of the chamber) out of the measurement.
KSTis an extremely important test! The Pmaxmeasures the maximum pressure that the dust could exert exploding in a closed space, but KST is a general measurement of explosiveness. It is a standard measurement for dust collection system design purposes.
The Importance of KST
KST is a measurement of explosion pressure, NOT of combustibility. A low KSTdoes NOT mean that your dust cannot burn and cause catastrophic damage. KSTonly tells you how strong the potential explosive force, not how flammable the dust is.
A KSTof 0 means that dust is not combustible; its Pmin and Pmax are 0 and in a testing chamber it cannot produce any explosion.
A KSTof greater than 0 means the dust is combustible; testing Pmax can create an explosion in the testing chamber. From 0 to 200 (which includes many metal dusts) the explosion class is 1; a weak explosion. NOTE: a “weak explosion” does not mean “no damage”! The catastrophic Imperial Sugar explosion that destroyed a building and killed over a dozen people was caused by sugar with a KST of 1.
A KSTfrom 200 to 300 is a strong explosion (Class 2), and could include things like cellulose dust, other organic fine dust, and some metals and plastics.
A KST over 300 is a very strong explosion (Class 3). Aluminum and magnesium dust are in this category.
Any dust with any Kst above zero is potentially combustible and can cause an explosion. Your system will require appropriate fire and explosion prevention. Fire prevention is key to keep ignition sources out of the dust collector, including spark traps, abort gates, and water or chemical suppression systems. Explosion vent panels are also critical to make sure that an explosion does not cause serious damage if it does occur.
Dust Testing: Putting the Pieces Together
As you can see, all of these pieces of information are important when testing your dust.
– The KST (which is calculated from PMax) tells you how strong an explosion is likely to be.
– The size of the dust is important in determining whether it is combustible.
– The MIE tells you how much or how little energy it will take to ignite your dust
– The MEC tells you how much dust in the air will risk an explosion
A dust with a low KST (sugar, as an example, but also many metals) has a low but not zero KST. It is not going to cause a strong explosion. However, in one facility that had a lot of accumulated sugar dust, an overheating piece of equipment exceeded the dust’s MIE value and ignited it. With so much sugar in the air, the MEC was also exceeded and the dust in the air ignited explosively.
To review: in this instance, a dust with a LOW KST(sugar) was in contact with a heat source that exceeded the MIE and ignited the dust. Because there was a large amount of dust in the air, the MEC was too high and the dust exploded. Secondary explosions caused even more damage because the explosions blew dust into the air and raised the MEC even more. For more information on this incident, see the Chemical Safety Board’s report of the Imperial Sugar Explosions.
While this explosion did not have a high pressure, it did create multiple large low-pressure explosions that blew apart the building and caused numerous deaths. A low KST does not mean your facility is safe from combustible dust explosions.
There are many trades and business operations associated with respiratory illnesses. For example, construction workers are a high-risk group for occupational lung diseases, a study by the National Library of Medicine concluded. There is exposure to high concentrations of dusts in closed spaces and they breathe high levels of crystalline silica. Inhaling free crystalline silica causes a lung disease named Silicosis. Processes like brickmaking, quarrying, and foundry work for making building materials are also high risk to workers. Lung function impairment is the most common respiratory problem among workers with exposure to dusts.
Occupational lung diseases also affect the mining, agriculture, and manufacturing industries. Johns Hopkins Medicine reports that crystalline silica is found in the air of mines, foundries, blasting operations, and stone, clay, and glass manufacturing facilities. Further, people at higher risk for occupational asthma often work in manufacturing and processing operations, farming, animal care, food processing, cotton and textile industries, and refining operations.
Warning Signs and Best Prevention
Common symptoms include fever, recurrent respiratory infections, an abundance of mucus, coughing up blood, chest pain, muscle weakness, and shortness of breath. However, occupational lung diseases can be prevented. Avoiding the inhalation of dust and fumes that cause lung diseases is the best thing you can do. Small particles have an easier time reaching the alveoli and settling into the lungs. Trouble begins when this happens in large quantities.
The infographic below illustrates the lung diseases found in various industries and denotes their warning signs in the body. It also presents how an Imperial Systems CMAXX dust and fume collector with DeltaMAXX filters can help save your life.
Contact Imperial Systems today for a review of your dust and fume collection challenges. We will design a system to help keep your employees safe from occupational lung diseases.
Creative Pultrusions manufactures fiber reinforced plastic for the infrastructure, marine, and other corrosion-resistant markets. Fiber reinforced plastic is durable, resistant to corrosion and damage over time, and makes an excellent support material for many projects.
The company not only manufactures large pieces of fiber reinforced plastic, but they also do many kinds of secondary work, including drilling, sanding, cutting, and CNC machining, which produce large amounts of dust. Testing identified this dust as weakly combustible.
When Creative Pultrusions ran into OSHA’s increased interest in combustible dust management, they considered upgrading their current system of vacuums and slide gates, but discovered that a new system from Imperial Systems was just as cost-effective as trying to rebuilt the old one.
Working with Creative Pultrusions, Imperial Systems was able to design for them a turnkey CMAXX Dust & Fume Collection system that met all of their needs. Once main concerns was air flow to the very large CNC machines that the company uses on large pieces of material. With specially engineered and placed fans, the CNC machines got all the airflow they needed, and the rest of the facility got the dust protection that it needed.
In a large facility where there are so many different stations for grinding, sanding, drilling, and machining, there are many locations for dust to be produced. Imperial Systems was able to design a system where dust was safely captured at all of these check points and removed from the work area.
One important aspect of the system designed by Imperial Systems was the complete fire and explosion prevention equipment that helped them meet NFPA standards on combustible dust. The system even allowed them to increase safety and dust control in areas that hadn’t had sufficient dust collection before the new system.
The company feels safer from combustible dust risks, and they feel confident that they are meeting all NFPA standards and they are prepared for any of OSHA’s expectations. Because Imperial Systems products are built to last, the company remains just as happy with their system today as they were the day it was installed, and confident that they made the right decision in choosing to go with Imperial Systems.
At the time, as a company still building our reputation in the dust collection field, the opportunity to work with a local Pennsylvania company to showcase our skills was a great chance to prove everything we are capable of, and the system we designed was, and continues to be, a showcase of the quality of work that we provide to our customers every day.
We continue to provide as-needed maintenance and support to Creative Pultrusions as their needs grow and adapt. Customer service is a hallmark of Imperial Systems and our field service teams are second to none in their level of expertise and skills.
If you are looking for a new dust collection system, please take a few minutes to watch the video and hear the people from Creative Pultrusions describe in their own words how this system has changed their facility and provided them with exactly what they were looking for.
A fire or an explosion can destroy expensive equipment, damage, or even wreck your building. It can certainly cause injury or death to workers. Dust and fume collection systems are often collecting some type of combustible material. So, these systems often require fire or explosion control systems as well as other types of safety systems.
Difference Between Fire and Explosion Control
It’s important to understand how a fire and an explosion are different. Fire is caused is when a substance rapidly consumes oxygen to produce heat and light. An explosion is an event where energy rapidly expands outward from the source, often creating a damaging shock wave. A fire may not cause an explosion, and explosions can happen without fire. For example, logs in a fireplace can slowly burn for a long time, producing flames and heat. Also, a pressurized tank of gas can explode if the material inside expands.
Is Combustible Dust Flammable or Explosive?
The answer is often both, depending on the conditions. If you try to light a block of metal on fire, not enough of the titanium is exposed to the air to start a fire. However, if you grind up that metal or turn it into gas with a welder, those tiny particles are exposed to plenty of air, and if there is an ignition source, they can catch on fire. Some metals, like titanium, burn so hot that once they are ignited, they can actually use water to burn even more, so using water to put them out just makes it worse.
Another example is sugar. Most of us use sugar all the time without realizing that it’s even flammable. However, an airborne cloud of sugar can combine with oxygen so quickly that it causes a violent explosion. Many other materials behave like sugar: once they become airborne, they can cause dangerous explosions because a fire can ignite the material so quickly.
A dust collector can be a perfect environment for a fire or explosion. Lots of dust inside an enclosed space can be very dangerous if it starts to burn, and it can be explosive. So how do you protect your dust collection system from fire or explosions?
Dust Fire and Explosion Control Devices
Spark detectors, spark trap, and abort gates can all act as fire prevention devices. One common choice for fire prevention is a spark detector. A spark detector will sense a spark before it gets into the dust collector, and it can activate other devices.
The spark detector might activate an abort gate. This will drop and deflect any sparks, fire, or smoke away from the facility and divert it safely. A spark trap installed in the ductwork and purposefully creates turbulence in the airflow. This knocks a spark around until it loses so much heat that it can’t start a fire.
These are devices that protect you and your facility from a fire. There are also chemical suppression systems that can be activated by the spark detector and extinguish a spark before it can start a fire. These systems can also put out a fire once it has started to keep it from spreading and prevent damage.
An in-line deflagration arrestor (IDA) is a type of system design. It protects your facility from explosions by stopping a flame front and preventing it from traveling back into the facility. IDA dust collectors include special filters that help extinguish a flame front and prevent it from going any further.
Explosion isolation valves are triggered by pressure to close off and prevent the explosion from traveling any further. A fast-acting slide gate can also be triggered to contain the explosion inside the dust collector. Once an explosion has occurred, there’s one, primary safety concern. That’s preventing it from getting back into the building or from causing damage or injury.
Devices like explosion vent panels or flameless explosion venting do not prevent explosions. But they do vent the explosion safely if one does occur.
Let’s Figure It Out
Sometimes a dust collector upgrade makes the most sense to protect a facility from fire damage. Contact us here at Imperial Systems to help determine your best options.
With the exploding popularity of 3D printing, it’s inevitable that combustible dust hazards would become part of the process. After all, 3D printing uses materials from plastics and nylon to aluminum and titanium. Almost all of them are combustible and can form explosive airborne dust around the work area.
3D printing is also called additive manufacturing, and it works by fusing layers and layers of extremely fine dust to create the final shape. When using metals, plastics, or ceramics, the layers are often fused by a laser that has the precision to carry out computer-guided designs.
The term “additive manufacturing” is most often found in applications like metalworking, where it is used as an opposite of manufacturing that involves removal of material, like cutting or grinding. 3D printing is a much broader term and can apply to a wide variety of processes.
If the combination of combustible dusts and high-powered ignition sources doesn’t sound like an explosion hazard, consider the fact that this is still a new technology, and many dust collection systems on the market aren’t equipped to handle this kind of hazard. OSHA has already cited at least one company for an explosion that occurred when combustible aluminum and titanium metal powers from their 3D printing process ignited, causing serious injuries.
Besides the risks of a combustible dust explosion, the extremely fine powders needed for 3D printing or additive manufacturing are often hazardous to human health. In other blog posts we’ve discussed the health risks of inhaling these particles, which can be as fine as welding fume dust. With the materials being fused by lasers or other high-heat techniques, harmful particulates are being released into the air along with the dust from the manufacturing process.
These harmful particles can include plastic particles, known toxins like hexavalent chromium, or even byproducts of high-tech aircraft alloys like beryllium. Many of them are health hazards and almost all of them are explosive if the conditions are right. Additive manufacturing or 3D printing often creates perfect conditions for a combustible dust explosion.
How do you mitigate the risk of combustible dust in your 3D printing operation? Proper dust collection will remove all excess dusk from the work area, preventing an explosive situation from occurring. With the CMAXX dust and fume collector, the most efficient filtration and best explosion protection are on your side to make sure your 3D printing areas, expensive pieces of equipment, and workers all stay safe.
Imperial Systems is ahead of the game in designing custom solutions for 3D printing and additive manufacturing applications. If you’re looking for a solution for the combustible dust problem that your application creates, contact the company that’s already designing systems to handle exactly these kinds of problems.
With the best design and quality on the market along with unbeatable fire and explosion protection options, the Imperial Systems CMAXX is the solution 3D printers need to keep their process efficient and safe. High efficiency filters allow for the capture and reuse of expensive powders and keep your work area clean of combustible dust. They also keep your air clear of dangerous byproducts and toxic substances your process might use or produce.
Imperial Systems Newsletter Issue 6 is the second quarter issue of the year. Make sure to check out all of the articles and interviews. Some of the articles include dealing with cement dust, giving a Vo-tech student some real world experience, Charlie back with one of his Good Luck With That stories and more. If you would like a Printed Hard Copy of this issue of our newsletter please contact your Imperial Sales Rep.
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That can be a very hard concept to accept. However, I am constantly amazed that people who work at Imperial Systems live and breathe this selfless idea without even knowing they are doing it. People focus on the good of the company, the community, fellow individuals, our customers and vendors. They have found when they humbly accept this there is no height they cannot achieve.
I have seen Imperial Systems grow from a small operation to seemingly unachievable heights over the years and it continues to exceed any preconceived ideas or plans we may have dreamed up. There is no doubt that this happens because of the people. When completing our recent move, we have been blessed to retain our great employees while adding many new faces. We have guys in the fabrication shop from local vocational schools learning from our experienced fabricators. We also have amazing interns this summer in our Engineering, Marketing and Software departments, furthering their education while providing much needed support on outstanding new projects Imperial is working to complete.
With this growth there will be obstacles and we will make mistakes as we progress. We will overcome these issues and grow as a result of experiencing them. It is through our people and our attitude that we will work to be the best we can be for each other, for the good of the company and all of those affected by the company.
I ask you to be part of what is going on here. We have a newly updated website describing our company, products and services. Please visit it. I encourage you to call and talk with Imperial employees and representatives to find out what we are all about and get to know some of our family. Please don’t just believe my words but come visit us and see for yourself. Our door is always open.
![Occupational Lung Diseases From Dust & Fumes [Infographic]](https://www.isystemsweb.com/wp-content/uploads/2018/08/health-risk-infographic1-1080x675.jpg)
That can be a very hard concept to accept. However, I am constantly amazed that people who work at Imperial Systems live and breathe this selfless idea without even knowing they are doing it. People focus on the good of the company, the community, fellow individuals, our customers and vendors. They have found when they humbly accept this there is no height they cannot achieve.