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Introduction
Describes combustible dust, methods to control combustible dust, and includes descriptions of vacuum cleaners for combustible dust
You will learn:
What is Combustible Dust?
Types of Combustible Dust
Vacuum Cleaners Used to Control Combustible Dust
How to Identify Combustible Dust
And much more …
Chapter 1: What is Combustible Dust?
Combustible dust is solid material, with particles of varying sizes, shapes, and chemical makeup, that have the potential of causing fires or rapid combustion that moves rapidly through an environment and can cause conflagration, destruction, and significant harm to humans. The greatest danger from combustible dust is when the dust is extremely fine, smaller than 425 micrometers (μ), and is suspended in the air.
The particles from combustible dust originate from materials found in manufacturing, agriculture, and the chemical industry. For a dust to be defined as combustible, it has to have characteristics that make it susceptible to ignition and combustion when suspended in the air. The inclination toward combustion is based on particle size, concentration, and chemical composition.
Due to the recent combustible dust explosions and the concerns of the Occupational Safety and Health Administration (OSHA), there has been an uptick in companies evaluating whether they have a combustible dust problem in their facilities. All manufacturing operations that handle any form of dust are aware of the hazards in relation to handling such materials. In addition, the National Fire Protection Association (NFPA), under provision 654 (2013 edition), has developed a definition of what combustible dust is:
“A finely divided combustible particulate solid that presents a flash fire hazard or explosion hazard when suspended in air or the process-specific oxidizing medium over a range of concentrations.”
Chapter 2: Types of Combustible Dust
As everyone knows, there are specific parameters that have to be present for a fire to occur. Referred to as the fire triangle, the three components that are necessary to initiate a fire are fuel, oxygen, and ignition source. Although the factors relating to fires are present in the combustion of dust, there are two other factors that are added to the fire triangle to create a dust explosion, which are dispersion and confinement. The addition of the two extra parameters expands the fire triangle into the dust explosion pentagon.
The danger of the occurrence of a dust explosion is mainly in regard to the confinement of the dust cloud, which is the concentration of flammable material to form a target mass for the ignition of dust particles. When a dust cloud is dispersed, deflagration occurs causing an unconfined flash fire that is just as dangerous as when the dust cloud is confined but not as explosive. At the heart of any combustible dust explosion is the fuel for the explosion, which is the combustible dust.
Classifications of Combustible Dust
A scientific classification process is used to assess and manage the risks of dust explosions and provides a standardization for an understanding of the explosiveness and hazards related to different types of dust. Each type of dust, wood, sugar, flour, metal, coal, rubber, and plastic, has different characteristics. By studying and understanding the properties of dust, it is possible for companies to alleviate the dangers of dust clouds, the hazards of explosions, and potentially unsafe conditions.
The regulation and monitoring of dust uses dust classifications to guide work sites to help them adhere to safety protocols. Combustible dust is divided into classes St 0, St 1, St 2, and St 3 with each classification having a Kst value that represents their deflagration index based on a dust's explosibility potential and combustion properties. The values represented help to place dust into categories as to the severity of a potential explosion produced by the dust.
Kst: Size-normalized maximum rate of pressure rise under standard testing conditions
Combustible Dust Classifications Table
Explosion
KSt Value
Characteristics
ST 0
KSt = 0
No Explosion
ST 1
KSt > 0 and ≤ 200 (bar-m/s)
Weak Explosion
ST 2
KSt > 200 and ≤ 300 (bar-m/s)
Strong Explosion
ST 3
KSt > 300 (bar-m/s)
Very Strong Explosion
Sugar Dust
Sugar is an organic substance that burns easily and creates dust that is explosive when sugar is in its dry and dusty form. Fine dust from sugar can generate 100 psi pressure when enclosed for 100 milliseconds. Refineries produce the most sugar dust during the last stages of the refining process after the crystals have been poured through a heated dryer. Dust is generated when the refined sugar is loaded into a silo. In addition, sugar dust is generated when sugar is ground into a fine powder to produce confectionary powder. Sugar combustible dust particles have the standard 420 μ or smaller diameter.
Wood Dust
Wood dust is the product of the milling of wood and is found in sawmills and wood shops. Due to the nature of processed wood, dust is found in every part of the environments where wood is processed. Regardless of the size of the materials, all wood dust is combustible and volatile. Unlike large wood chips, fine wood dust has the potential to be hazardous and explosive and presents a greater danger than other forms of dust. While the initial ignition of the dust is damaging during the primary explosion, it is the shockwave from the explosion that disperses wood dust that creates a deflagration.
Flour Dust
Flour is a common ingredient and used for the manufacture of a wide range of food products. In its dust form, flour is combustible and a danger to the food processing industry. As with all forms of combustible dust explosions, flour dust explosions occur when particles of dust are ignited by an ignition source, such as spark, flame, or heating element. All of the ingredients used in the production of food are dormant in their powder state. It is only when they are handled and create a dust cloud that they become dangerous. The factors that lead to the ignition of flour dust are poor ventilation, heat from equipment, improper handling, and poor housekeeping.
Metal Dust
In recent years, there has been rapid growth in the metal manufacturing industry with the addition of laser cutters and manufacturing cells that efficiently and quickly fabricate metals. The difficulty with the new processes is the metal dust that they generate that adds to the hazards of metal work. Metal dust behaves differently than organic dust if it is ignited reaching temperatures of 3500°C (6332°F), which is a 1000° (1832°F) hotter than organic dust. The higher temperature increases flame speed and explosion pressure, factors that make it extremely difficult to control metal dust explosions.
The most explosive types of metal dust are aluminum, bronze, magnesium, silicon, and zinc with aluminum and magnesium being more explosive than flour or sugar dust. A factor that makes metal dust more dangerous than organic dust is the potential reaction that can be created when metals are mixed. Unlike the blending of ingredients for cooking, the mixing of incompatible metals can lead to hazardous and dangerous conditions.
Rubber Dust
Rubber dust is created by grinding, polishing, sawing, cutting, or sanding rubber, which generates fine particles that can be explosive if not properly handled. Rubber products are produced by subjecting a wide range of chemicals to heat, pressure, and catalytic action. While the final product is a necessity, the production process subjects the environment to dust, vapor, gas, fumes, and chemical contamination, which is the reason that workers that assist in the production of rubber wear protective clothing and masks. Exposure to rubber dust, aside from being combustible, can lead to lung disease and breathing problems.
There are two chemicals that are found in rubber dust – organic and inorganic. The organic chemicals in rubber dust are a danger to aquatic animals while inorganic chemicals are potentially combustible metals, such as lead and zinc. The fine particles of rubber dust accumulate in ventilation systems where their concentration increases the risk of ignition from static electricity. As with all forms of combustible dust, very fine and small particles collect on equipment where they are exposed to the friction of mechanical processes, further increasing the dangers of explosion.
Plastic Dust
Plastic molding, extruding, forming, and finishing produces plastic products that are necessary and used all over the world. The final steps in the production of plastic products are the processes of trimming, shaping, and adjusting of plastics, which release dust. Since plastic production is high volume, the result is a high volume of dust. As with all forms of dust, the accumulation of plastic dust creates a hazard for explosions and fires. Of the various types of dust, plastic dust is the most volatile due to the plastic heating up, melting, evaporating, and releasing flammable gas.
The hazards related to plastic dust are the many chemicals that are used to form plastics, which include monomers, epoxies, resins, colorants, surfactants, and plasticizers as well as various additives. The majority of the substances, chemicals, and materials used to produce plastics are deemed to be hazardous to humans and the environment. Plastics that are used the most for the manufacture of plastic products include acrylic (PMMA), acrylonitrile butadiene styrene, (ABS) Delrin/Acetal, nylon, polycarbonate, and polyethylene terephthalate (PET/PETE)
Recycling Dust
One of the major programs that is being supported by industry is the recycling of waste materials such that they can be repurposed and reused. The program is society’s attempt to protect and save the environment for future generations. The unfortunate side effect of recycling is the creation of toxic and volatile dust. The recycling industry has its main focus on paper, plastics, metals, and electronics, which are crushed, shredded, sorted, and separated, processes that create and combine fine particles that become airborne and settle on flat surfaces. As with other forms of dust, the accumulation of recycled dust presents hazards for combustion and explosions.
While it is desirable to clean and collect the dust, the circumstances under which the dust is created are not ideal for cleaning and removal, a factor that compounds the danger. In addition, the conglomeration of materials that are collected for recycling contain a vast and wide array of different substances and chemicals that, in some cases, do not react well together, further exacerbating the potential hazards.
Chapter 3: Methods for Controlling Combustible Dust
The dangers of combustible dust have led to the introduction of a wide assortment of methods that are designed to prevent, diminish, and eliminate the potentialities of dust combustion. On a grand scale, there are dust collectors and dust collection systems that filter the air of an environment and collect hazardous dust using filters and other devices. While these methods are exceptionally effective, they are unable to collect dust that has settled on exposed surfaces.
Of the list of preventative measures that have been emphasized by OSHA and NFPA, the one that is the most widely recommended to control the proliferation of dust is routine proper housekeeping. As with any environment, a certain level of cleanliness and organization is necessary for proper functioning. This is especially true where there is combustible dust. Although the first steps in cleaning an environment involves the use of vacuums, in the case of combustible dust, the typical vacuum is not sophisticated enough or qualified for the process, which requires a specially designed combustible dust vacuum that has non-static elements.
The standard industrial vacuum is a powerful cleaning device capable of collecting a wide range of waste. The problem with the process of an industrial vacuum, when collecting combustible dust, is the static electric charge created in the vacuum’s hose. If a hose becomes charged, the ungrounded hose making contact with grounded material can create static electricity that would arc and trigger an explosion. Vacuum manufacturers, realizing the potential danger, have designed combustible dust vacuums that are capable of collecting and accumulating combustible dust.
Combustible Dust Vacuums
Combustible dust vacuums, known as explosion proof vacuums, are designed to clean up hazardous explosive materials without igniting the materials or causing an explosion. They are made for the chemical industry and manufacturing that produces combustible dust. The basic principle behind combustible dust vacuums is to control ignition sources and provide regularly scheduled preventative maintenance.
Dust ignition proof vacuums are designed such that they do not allow arcs, sparks, or the generation of heat that could cause ignition of dust suspended in the air. For a vacuum to be certified as being dust ignition proof, it must adhere to the specifications published by a Nationally Recognized Testing Lab (NRTL), which are listed by OSHA. In order for a lab to be approved, it must have the required testing and certification equipment listed in OSHA 29 CFR 1910.7.
Combustible Dust Vacuum Components
Housing – The housing is made of anti-static stainless steel or reinforced fiberglass.
Compressed air – As an extra measure of safety, combustible vacuums do not have an electric motor to create suction but use compressed air supplied by a hose.
Compressed air nozzle – The compressed air nozzle forces air into a mixing chamber at high velocity producing suction through negative air pressure. The use of compressed air in the construction of combustible dust vacuums is a necessity to avoid the use of electricity that could spark an explosion.
Filter – The mixture of air and dust passes through a filter, usually a HEPA filter, prior to being released into the dust collection bag. Combustible dust vacuums with peak efficiency have graduated filters, in a series, to trap particulate matter.
Anti-static hoses – All of the hoses for combustible dust vacuums are anti-static, also known as static dissipative hoses, that are securely connected to the vacuum. They have a conductive layer made of a carbon black compound, which allows the hose to conduct and dissipate static electricity.
Venturi Combustible Dust Vacuum
A Venturi combustible dust vacuum uses a Venturi tube to generate suction by using air flow that moves through the tube, which generates a low-pressure area that creates a vacuum. As compressed air is sent through the nozzle of the vacuum into a chamber, it speeds up and then rapidly slows down as it enters the mixing chamber. The fluctuation produces negative air pressure and suction that moves dust and air through a filtration unit into the collection drum.
Pneumatic Combustible Dust Vacuum
As with a Venturi combustible dust vacuum, pneumatic vacuums are powered by compressed air and a Venturi system to generate suction. They operate very quietly, are lightweight, and are easy to use. The concept behind pneumatic combustible dust vacuums is the removal of moving parts to avoid the creation of arcing, friction, or sparking. Pneumatic combustible dust vacuums are specially designed for the cleaning of combustible dust in hazardous locations. They are used for National Electrical Code (NEC) Class I and Class II environments with Class I being for gas and vapor environments while Class II are combustible dust environments.
Centralized Vacuum Systems
Although individual vacuums are used for cleaning combustible dust, many companies rely on centralized systems that have been vetted for the handling of combustible dust. Individual combustible dust vacuums have materials that do not spark or create electrical static. They have a compact design that makes them easy to use.
Centralized vacuum systems are larger and cover a larger area. Their size requires greater preparation for their installation due to the many facets of their construction. The elements of a centralized system include a suction unit, pipes, ducts, a filtration system, and various forms of safety devices. The suction unit draws air from a work area and transports it through the ductwork to the collection unit.
Cleaning provided by centralized combustible vacuums are found in coal plants, grain operations, food production, pharmaceutical companies, chemical facilities, and any industry that produces bulk powders. The wide use of centralized systems is due to easy accessibility, efficient cleaning, and rapid removal of dangerous materials. Although the main features of a centralized system are located throughout a facility, the collection unit is normally located outside and has been designed to meet local regulations.
Combustible Dust Collectors
Combustible dust vacuums are an ideal way for controlling the build up of dust on surfaces in a work area. Combustible dust collectors are a more dynamic method of collecting dust since they are able to filter the air in a work location removing particulate matter in the air that can be ignited and cause a conflagration. Each type of industrial combustible dust collection system is designed to capture, collect, filter, clean, and contain dust particles that are potentially explosive or fire hazards.
Cyclone Separators
Cyclone separators use centrifugal force to remove dust from the air stream. Although dust is the main concern, cyclone separators can capture large particles and have a highly advanced filtration system. The large particle ability of cyclone separators makes them ideal for abrasive dust that stresses other types of dust collectors. In many cases, they are teamed with baghouse collectors and cartridge collectors. Cyclone dust collectors are used for paper dust, chemical processing, and gas cleaning. They use overhead ductwork and suction hoods to move air to the dust collector unit.
In order to create the cyclone centrifugal force, cyclone separators are cylindrically shaped to create the air movement. Dirty air enters in a spiral and clean air exits by a counterflow, clean air outlet. As the whirling centrifugal force is applied to the air, heavier particles are forced against the sides of the cylinder and fall to the bottom of the cylinder into a collection unit.
Baghouse Combustible Dust Collector
Baghouse dust collectors are the most widely used form of dust collector. They are a highly efficient cost-effective dust collection solution. The process of a baghouse dust collector includes a system of fabric filter bags arranged in rows and mounted vertically in a metal housing. Dust filled air is received from a duct system where it passes through the system of filters. The movement of the air is energized by blowers that draw in the dust filled air.
There are three methods used by baghouse dust collectors to remove dust collected by the fabric filters. Each of the methods is gentle and nonaggressive but are efficient in cleaning the filters. The three methods are pulse jet, shaker, and reverse air, which vibrate the filters forcing them to release dust into the collection units located below the filters.
Shaker baghouses shake the filters and are used when compressed air is not available. Pulse jet baghouses use a timed pulse of air that moves along the length of the filters to remove the collected dust. Reverse air baghouses use a fan to generate the air stream to clean the filters. The method is a low-pressure, high-volume cleaning process.
Wet Combustible Dust Collectors
Wet combustible dust collectors are widely used with combustible dust due to their ability to reduce deflagration, fire, and potential explosions. The process of a wet dust collector is designed to capture, scrub, and remove any source of ignition. Wet combustible dust collectors are used with combustible dust that can absorb water and is hygroscopic. Dust that is sticky or becomes sticky in humid conditions are the types of materials that require the use of a wet combustible dust collector.
Typical wet combustible dust collectors have a cyclonic or Venturi design and use a combination of air pressure and water as the collection agents. Dust is pulled from the airstream and passes through a stream or spray of water that scrubs the collected particles. After the water scrubbing treatment, the dust separates due to the force of gravity and falls into the collection tank.
The popularity of wet combustible dust collectors is due to their ability to capture very small dust particles and are useful in production operations that create fine hazardous combustible dust. In addition, the choice of wet combustible dust collectors is closely related to dust particles that can be easily ignited.
Cartridge Combustible Dust Collectors
Cartridge combustible dust collectors draw air in through cylindrical air filters that capture and remove dust from the air stream. The dust collected by the cartridges is removed by compressed air pulses. The cartridges for a cartridge dust collector are pleated filter cartridges that sit in a rack. Air is pulled through the cartridges that capture particulate matter in the pleats of the cartridges. As with wet combustible dust collectors, cartridge combustible dust collectors are ideal for capturing fine particulate dust from welding, plasma cutting, and laser tools. The system is exceptionally efficient and capable of capturing dust as small as 0.3 µ.
Unlike wet combustible dust collectors, cartridge combustible dust collectors are not ideal for capturing tacky, sticky, or damp particles that can clog the pleats of the filters, reducing efficiency, and causing system failures.
The four combustible dust collectors described above are the most common types of dust collectors used to filter combustible dust. There are several variations of the types of dust collectors listed above. Although there is a wide variety of dust collectors, not all dust collectors are capable of filtering and collecting combustible dust. Manufacturers work with customers in selecting a dust collecting system that best fits a customer’s operation and processes.
Combustible Dust Control Fans
One of the problems with combustible dust is its build up in areas that are hard to reach or isolated from other methods of dust control. A method of attacking the situation is the use of high velocity fans that are strategically placed to provide airflow to hard-to-reach areas. The term fan may give a misinterpretation of what high velocity fans are, which are fans that have blades designed to rotate at exceptionally high speeds. The fronts of the fans have grills that protect them from any dust build up and accurately directs the airflow.
The factor that differentiates high velocity fans from ordinary fans is their ability to push a high volume of air in a short period of time. The force created by the rapid rotation of the fans is capable of projecting a rapidly moving air stream over a long distance, as in warehouses, assembly operations, and the overhead interior of buildings. There are a wide variety of uses for high velocity fans with their primary function being the removal of dust. Combustible dust control fans are used for controlling wood dust, paper dust, and dust from plastics production.
Chapter 4: Classification and Regulations Regarding the Handling of Combustible Dust
Combustible dust has been a destructive force in several industries, which has necessitated the development of regulations and standards that outline the proper handling and cleaning of dust filled air. For an air cleaning system to be approved as a combustible dust handler, it has to be approved by testing labs listed by OSHA.
The classification of combustible dust falls into a unique set of parameters that are considered when defining a particular type of dust. The classification system for combustible dust helps in assessing and managing the potential risks of dust in industrial environments. It is a standardized framework for understanding the explosiveness, danger, and hazards related to different forms of dust.
The factors used to classify combustible dust are particle size, particle shape, and the moisture content of the dust. The size and shape of dust particles determine their surface area and reactivity. Fine particles are more reactive and combustible, a factor that leads to rapid combustion or dust explosions. Dust with a high moisture content is less prone to ignition, which affects its classification.
The factor that is the most impactful in determining the combustibility of a dust is its chemical composition, which directly relates to its volatility. Varying levels of substances in dust determine its combustibility and strongly influences how hazardous and explosive a dust may be. In addition to the chemical content of one dust, there is also the factor of the combination of different dusts that may add to their combustibleness.
Pmax and Kst
Pmax and Kst are two common measures of the explosiveness and combustibility of dust. While these two factors are not the total range of parameters that can determine the explosiveness of a dust, they serve as major guidelines. Pmax and Kst are measurements of air pressure and are used to test the volatility of a dust in carefully controlled laboratory conditions.
Pmax – Pmax is the maximum pressure and the maximum amount of damage a dust can cause in a confined space. It provides data as to the pressure that can be generated during a dust explosion.
Kst – Kst is the rate at which pressure increases during a dust explosion and is the value into which a material falls in order to control the hazards of a dust explosion. It is divided into categories that are used to group different types of dust. A high Kst value indicates a potentially violent, volatile, and destructive explosion. The units of Kst are the rate of pressure rise multiplied by the cube root of volume. (Bar/s) x m
National Electrical Code (NEC) Class for Combustible Dust
The NEC classifies hazardous locations as to a location's potential for causing a fire or explosion due to the presence of gases, vapors, liquids, combustible dust, and ignitable fibers. The classification process is divided into Class I, Class II, and Class III, with Class II used to define the dangers of combustible dust. Under each class are divisions or zones that identify the conditions for the occurrence of an explosion. In addition to the divisions or zones are the groups that define the necessary ignition properties that are in the atmosphere.
Class II locations have a sufficient amount of combustible dust capable of creating an explosion and are ignitable. Division 1 under Class II includes areas where combustible dust normally exists and is part of everyday operations. Division II is where combustible dust does not exist or only exists due to an abnormal or uncharacteristic event. The dust from Class II is divided into groups categorized by NEC as E, F, and G, which are grouped according to auto ignition temperature and substance conductivity. Of the two grouping factors, conductivity is the most important in regard to the explosive characteristics of dust.
Group E
Group E includes St 3 dust, which is dust from aluminum, magnesium, and their alloys. Also included are combustible dusts whose particle size, abrasiveness, and conductivity are part of the hazards of using electrical equipment.
Group F
Group F includes St 1 dust that contain combustible carbonaceous dusts that include coal, coke, carbon black, and charcoal dust with 8% entrapped volatiles or dust that has been mixed with other materials to produce an explosive hazard.
Group G
Group G is an all-inclusive classification that includes dusts that have not been covered in Groups E and F. Dusts in this group include agricultural dusts, such as flour, cocoa, starch, grain and wood, thermoplastic resins, molding compounds, pharmaceutical drugs, and chemical powders.
Regulations and Standards Related to Combustible Dust
The American Society for Testing and Materials International (ASTM), NFPA, and OSHA have regulations and standards regarding the identification, handling, and safety conditions for combustible dust. OSHA is a federal government group while ASTM has been accepted as an international set of standards. The focus of the NFPA is on conditions that will lead to fires and explosions and has a long list of regulations regarding combustible dust.
OSHA Regulations
29 CFR 1910.22
A general industry standard that requires companies to maintain clean workplaces as a method for preventing hazards. The regulation stipulates the importance of proper housekeeping and dust removal.
29 CFR 1910.307
This requirement is in regard to the use of equipment in hazardous locations, such as areas where combustible dust exists. It sets the standard for industry safety related to hazardous locations where combustible dust is present and outlines safety measures, equipment requirements, and training.
29 CFR 1910.272
This standard addresses hazards regarding grain handling and mandates the use of dust control measures and safety procedures to protect workers.
American Society for Testing and Materials International
ASTM E1226
Outlines Standard Test Method for determining the Explosibility of Dust Clouds with procedures for performing laboratory tests to evaluate deflagration parameters. The data collected can be used to determine the size of deflagration vents using equations published in
NFPA 68, ISO 6184/1, or VDI 3673. Methods and procedures used are specific to the tested sample.
ASTM E1515
Standard Test Method for Minimum Explosible Concentration of Combustible Dusts provides procedures for performing laboratory tests to evaluate relative deflagration parameters of dusts.
National Fire Protection Association (NFPA)
As may be assumed, the list of standards for the NFPA is very long and specific covering a plethora of potential hazards.
NFPA 61: Standard for the Prevention of Fires and Dust Explosions in Agricultural and Food Processing Facilities
NFPA 68: Standard on Explosion Protection by Deflagration Venting
NFPA 69: Standard on Explosion Prevention Systems
NFPA 70: The National Electrical Code (NEC)
NFPA 499: Recommended Practice for the Classification of Combustible Dusts and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas
NFPA 652: Standard on the Fundamentals of Combustible Dust
NFPA 654: Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids
NFPA 655: Standard for the Prevention of Sulfur Fires and Explosions
NFPA 664: Standard for the Prevention of Fires and Explosions in Wood Processing and Woodworking Facilities
Above and beyond the list of regulations listed above there are several international organizations that have stipulations, standards and regulations regarding combustible dust that include European Committee for Standardization, Verein Deutscher Ingenerie, The International Fire Code (IFC), and the International Organization for Standardization (ISO). Each of these organizations are aware of the dangers and hazards related to combustible dust and have relegated substantial resources to its control and prevention.
Chapter 5: Where Combustible Dust is Found
One of the problems related to combustible dust is in regard to underestimating the dangers it presents and overlooking it until it causes a major problem. As has been evidenced by several companies in the recent past, neglecting combustible dust can lead to devastating and catastrophic disasters and the total and complete destruction of a facility.
Ideological Procedures to be Taken Regarding the Prevention of Combustible Dust Damage
Learn what combustible dust is by studying samples of combustible dust and companies that have suffered from combustible dust explosions. Examples: The West Fraser Mill in Scotland, UK, DeBruce Grain Elevator in Kansas City, and the Imperial Sugar Company in Georgia.
Prepare a management plan for monitoring, cleaning, and controlling combustible dust. Many reputable companies provide advice and guidance regarding ignition sources, cleaning techniques, and collection methods.
Examine the many organizations that provide standards, regulations, procedures, techniques, and methods for dealing with combustible dust. Every industry that generates combustible dust has up to date methods of managing the combustible dust.
Woodworking Industry
Dust in the woodworking industry comes from cutting, sanding, or other methods for processing wood products. The fine wood particles become suspended in the air creating an explosion hazard that can lead to flash fires and explosive conditions if ignited. Places susceptible to such circumstances are sawmills, carpentry shops, furniture manufacturing companies, and lumber processing plants.
Agriculture
Anyone who has ever worked on a farm knows of the many types of dust that are generated through the handling of wheat, corn, hay, and other plants. Grain handling and storage generates a huge volume of dust that is allowed to dissipate into the air. The dust becomes more dangerous when isolated in confined spaces where it can explode if ignited. Aside from activities on the farm, dust from agricultural products can be prevalent in bakeries, flour mills, pasta production facilities, and other forms of food processing.
Chemical Manufacturing
Chemical industries that produce pharmaceuticals, dyes, and pigments create chemical dust that include coal and sulfur, which are flammable in particulate form. Unlike other types of dust, dust from chemical manufacturing has the additional challenge of being reactive with potential toxicity from the combustion of the chemicals. In addition, the interaction between chemical dust can cause a dangerous reaction if not sufficiently controlled. Many of the safety efforts of chemical companies are devoted to controlling and managing the generated dust.
Biosolids
Biosolids come from wastewater treatment facilities and organic processing, which generate explosive combustible dust when there is a buildup of dry residue. The dust that is created is the most explosive type and has extremely fine particles. Stringent safety standards are applied to the handling of biosolids that include adequate ventilation and documented safety protocols.
Metal Dust
Metal dust is generated from the grinding, abrasive blasting, cutting, and polishing of metals. The consistency of metal dust is due to the combustible nature of the metals when reduced to a fine dust. The ignition of metal dust can result in violent explosions with intense destructive fires. The metals that predominantly produce metal dust are aluminum, magnesium, titanium, and steel, which are the most common metals used to produce metal products.
Plastics
The molding, extrusion, and recycling of plastics produces volumes of metal dust that is highly explosive due to the plastic resins used to produce plastic material. As with metal, plastic dust has very fine particles that have a higher potential of exploding.
The few industries described above are a sampling of the many types of combustible dust that are generated from the production and manufacture of popular products. Additional industries that produce combustible dust as part of their manufacturing are power plants, mining operations, and synthetics production that produce polyesters, nylon, and other artificial fibers. The textile industry, that produces fabrics for the manufacture of clothing, produces dust from cotton and synthetic fibers.
The prevalence of dangerous and toxic dust is a major concern of modern manufacturing that has developed methods for controlling and monitoring the presence of dust in their facilities. Although certain segments of society may overlook the need to prevent the accumulation of dust, companies that produce products that generate dust are dedicated to preventing combustible dust from becoming a major problem and use every method available to manage the situation.
Conclusion
Combustible dusts are particles and pieces of solid materials that present a danger of combustion, fire, and deflagration that can destroy and damage property and people.
If not contained, combustible dust can cause catastrophic damage to facilities, structures, equipment, and people.
There are several methods used to contain and control combustible dust that include regular house cleaning, proper ventilation, and air flow systems.
For a dust to be classified as combustible, it must possess specific characteristics that make it likely to ignite and combust when suspended in air. The key attributes of combustible dust are particle size, concentration, and chemical composition.
Combustible dust is the most dangerous when it has particles that are smaller than 420 μ due to their increased surface area.
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Jet Dust Collectors
A jet dust collector is a suction filtration unit that pulls dust ladened air into a filtration system that collects particulate matter and releases clean air. The filters of jet dust collectors are cleaned by compressed air that uses...
Types of Dust Collectors
During the Industrial Revolution, when companies began producing high volumes of industrial waste like fine dust, wood dust, and other particles, an American, in 1852, S.T. Jones, applied for the first dust collector patents, a single bag filter...