Risks Associated to Combustible Dust Handling
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Risks Associated to Combustible Dust Handling by OSHA
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Risks Associated to Combustible Dust Handling
- 2. SponsorshipSponsorship Department of Labor Occupational Health and Safety Administration (OSHA) Susan Harwood Training Grant This material was produced under Susan Harwood grant number 19480-09-60-F-72 Occupational Safety and Health Administration, U.S. Department of Labor. The contents in this presentation do not necessarily reflect the views or policies of the U.S. Department of Labor, nor does the mention of trade names, commercial products, or organizations imply endorsement by the U.S. Government.
- 3. Work TeamWork Team UNIVERSITY OF PUERTO RICO Río Piedras Campus Division of Continued Education and Professional Studies (DECEP) Migdalia Ruiz, MS – Project Director Lymari Orellana, MS, Trainer Adaliz López, MS, Trainer Carmen Vázquez, BSSI, CIHT, Trainer
- 4. PurposePurpose The purpose of this presentation is to compile within one document the hazards present while handling combustible dusts in industrial processes. The following will be discussed: • Hazard characteristics and behavior of Combustible dusts. • How to perform risk assessments to recognize hazards associated with combustible dusts, and • Suggested Control Methods.
- 5. ObjectivesObjectives • Define combustible dust and its impact on industry • Mention loss statistics due to dust explosions • Identify risk areas • Discuss available controls • Identify applicable associated standards • Briefly introduce the proposed regulation
- 6. Topics to be discussedTopics to be discussed 1. Historical background 2. Definitions 3. Related risks 4. Facility evaluation 5. Controls – Prevention – Mitigation 6. Training 7. Proposed Rule 8. References
- 7. HISTORICAL BACKGROUNDHISTORICAL BACKGROUND Industrial Explosions
- 8. Are These Materials Explosive?Are These Materials Explosive? sugar metal plastic wood coal medicines
- 9. Imperial Sugar CompanyImperial Sugar Company February 7, 2008 •Port Wentworth, Georgia •14 deaths and numerous injured persons •A spark started the fire and explosion of the sugar cloud
- 10. 10 Fire and Explosion by Metal Powder :Fire and Explosion by Metal Powder : IndianaIndiana October 23, 2003 • Huntington Indiana • 1 dead, 6 injured • Aluminum powder caught fire in a dust collector, from there the flame spreads generating the explosion
- 11. February 20, 2003 •Corbin, Kentucky, •7deaths, several injured •An poorly worked oven lit a cloud of phenolic resin dust, causing the explosion. Fire and Explosion in “CTA Acoustics”Fire and Explosion in “CTA Acoustics” 11
- 12. West PharmaceuticalWest Pharmaceutical January 29, 2003 • Kingston, North Carolina • 6 deaths, 38 injured • Phenolic resin dust accumulation enabling false ceiling fire and dust explosion 12
- 13. Fire and Explosion in Malden MillsFire and Explosion in Malden Mills December 11, 1995 • Methuen, Massachusetts • 37 workers injured • Destruction of the polar fabric manufacturing company (nylon fibers)
- 14. Grain HandlingGrain Handling During the 70s there were several explosions in grain silos. This led to implement a specific standard 1910.172, for that industry, which has significantly reduced the explosions in this industry. 14
- 16. DefinitionsDefinitions • Combustible dust: Very small particles (<420 microns) that when dispersed in air have the ability to ignite under certain conditions. • The NFPA 654 (2006) defines combustible dust as a particulate solid that presents a fire hazard or deflagration when suspended in air (or other oxidant) at various concentrations independent of size or shape.
- 17. Combustible Solid ParticulateCombustible Solid Particulate Dust Fines (coal dust) fibers Flakes Fragments Bits Mixture of any of the foregoing 17 Any combustible solid material composed of particles or different pieces independent of the size, shape or chemical composition Includes: pellet
- 18. Particle Size of Common MaterialsParticle Size of Common Materials Common Material Size (microns) Salt 100 Granulated white sugar 450 - 600 Sand 50+ Talc, Dust (baby) 10 Mold Spores 10 – 30 Human Hair 40 - 300 Fluor 1 - 100 18 Source: OSHA y Filtercorp International Ltd.
- 19. Combustible Dust Fires and ExplosionsCombustible Dust Fires and Explosions Fire Triangle
- 20. Fires and Explosions of Combustible DustFires and Explosions of Combustible Dust For a combustible dust explosion to happen, it requires the presence of all these factors Ignition Source Fuel (dust)Oxidant Confinement Dispersion
- 21. DispersionDispersion • It is the effect of moving the cloud of dust from one place to another, may it be by mechanical processes (transport, ventilation, vibration, improper cleaning) or as the result of a primary explosion.
- 22. ConfinementConfinement • Occurs when the fire occurs in a confined space, where the rapid change in temperature causes a rapid change in pressure. • This change in pressure or shock wave can be more or less destructive depending on the magnitude of the explosion and how the structure is closed
- 23. DeflagrationDeflagration In the deflagration the flame advances as the material is consumed creating a fire front, with pressure changes
- 24. DetonationDetonation • The combustion speed advances faster than the speed of sound generating an audible event. • Dificult to control once it has begun
- 25. 25 The minimum amount of dust suspended in air that will support deflagration. It is estiamted that this concentration (MEC) can reduce the visibility of a 25 wat bulb in a room to only 6 feet of distance Minimum ExplosiveMinimum Explosive Concentration (MEC)Concentration (MEC) 25 watts 6 feet = 2 meters Combustible dust concentration suspended in air > MEC Source: Course 7120 OSHA Training Center
- 26. ExplosionExplosion Results from the combination of these factors: • fire • dispersion of solid particulate material • in a more or less enclosed space + + =fire dispersion ExplosionExplosion confinement
- 27. 27 Fuente: Curso 7120 OSHA Training Center Primary Explosion from dust in equipment Dust Colector
- 28. Secondary Explosion Mechanism 1. Dust accumulates on work surfaces 2. An event disperses dust creating a cloud 3. The cloud ignites and explodes
- 29. 29 Fuente: Curso 7120 OSHA Training Center Secondary Explosión from dust in area Dust Colector Dust Accumulation (on floor and surfaces) Expansive wave
- 30. ¿WHO IS AT RISK?¿WHO IS AT RISK? Industries
- 31. Industries that Generate or HandleIndustries that Generate or Handle Combustible DustsCombustible Dusts – Textiles – Forest Products – Wastewater Treatment (used) – Recycling of metal, paper, plastic – Coal • Metalworking • Pharmaceutical products • Food • Paper products • Wood products • Agriculture • Chemical Manufacturing
- 32. Metal PowdersMetal Powders • Aluminum • Iron Carbonile • Zinc • Bronze • Magnesium
- 33. Plastic Powder/ rubberPlastic Powder/ rubber • Molded Cellulose • Polyethylene • Melamine and its resin • Polypropylene • Polyacrylamide • Epoxy or phenolic resin
- 34. FoodFood • Cotton • Rice starch, corn, wheat • Sugar • Coffee • Cocoa Powder • Coconut shell • Spice powder • Potato starch
- 35. FoodFood • Rice flour, oats, corn, potato, wheat • Lime • Walnut powder • Soybean powder • Seeds of raw cassava • Sunflower SeedsTomatoe • Carrot
- 36. ChemicalsChemicals • Sodium stearate • Ascorbic Acid • Carboxymethyl Cellulose • Lactose • Calcium Acetate • Methylcellulose • Dextrin
- 37. Powders Containing CarbonPowders Containing Carbon (Carbonaceous powders)(Carbonaceous powders) • Cellulose paste • Activated charcoal • Black charcoal • Bituminous coal • Petroleum coke • Wood charcoal • Pine soot • Petroleum • Celullose • Lignin • Dry chemical
- 38. Agricultural ProductsAgricultural Products • Rice starch • Celullose • Dry powdered milk • Wheat starch • Egg white • Barley • Lactose
- 39. RISK ANALYSISRISK ANALYSIS Area Assessment
- 40. RisksRisks FactorsFactors ¿ What factors should I consider for preventing explosion? Major Factors: • Dust Combustibility • The accumulation of dust in areas and work surfaces • Presence of ignition sources.
- 41. Combustibility DeterminationCombustibility Determination The first step in the risk analysis should be to determine if the powder is combustible 41
- 42. Powder CombustibilityPowder Combustibility • Verifiy if the presence of dust increases the risk of fire, explosion and / or a detonation within the workspace. In some cases it will be determined by an specific flammability test. • Consider: – Particle size and shape – relative humidity and oxygen present in the environment – Minimum explosive dust concentration (MEC).
- 46. Other Considerations in Risk AnalysisOther Considerations in Risk Analysis • Must assess the electrical ratings of the areas • Consider the scenario in which dust may be generated as a result of equipment failure or operating procedures 46 Fuente: Curso 7120 OSHA Training Center
- 47. Hazards AnalysisHazards Analysis • Determine if a combustible dust is potentially dangerous in a work area • Look for accumulations of fine dust • Find ways in which the powders are dispersed in the air • Possible sources of ignition • Consider dust collectors, hoppers and other equipment that can confine a cloud of dust. • Investigate possible ignition sources
- 48. Principal Methods of ControlPrincipal Methods of Control Prevention & Mitigation
- 49. Principal Methods of ControlPrincipal Methods of Control Both OSHA and NFPA established that the best way to prevent the combustible dust hazard is using engineering controls such as; – Design of pipes and equipment capable of containing the dust or a dust explosion safely – Reduction of work surfaces where dust can accumulate – Control of ignition sources
- 50. Principal Methods of ControlPrincipal Methods of Control Control methods are devided: Prevention of fire and / or explosion, this mean, to prevent it from happening either of these situations by; Dust accumulation control – Ignition sources control – Reduction in the concentration of oxidant (NFPA 69 Chap.7)
- 51. Principal Methods of ControlPrincipal Methods of Control Mitigation of damage, once the fire or explosion process occurs or explosion, keep damages to a minimum by: • Systems of ignition detection and control • Containment pressure deflagration • Deflagration Suppression • Isolation
- 52. Principal Methods of ControlPrincipal Methods of Control Administratives – Establish a cleaning program with regular frequencies – Good work practices Personal Protective Equipment – Equipment classified as fire resistant (FR)
- 53. Prevention – Dust ControlPrevention – Dust Control NFPA 654 recommends: • Minimize the relelease of fugitive dust that comes from process equipment or ventilation systems • Use dust collection systems • Use work surfaces that reduce dust accumulation and facilitate cleaning 53 The spots are traces of dust Fuente: Curso 7120 OSHA Training Center
- 54. Prevention – Dust controlPrevention – Dust control NFPA Code 654 – • Inspect and clean dust residues at regular intervals in open and hidden areas • Hidden areas should have access for inspection, if not must be sealed 54
- 55. Prevention – Dust ControlPrevention – Dust Control NFPA code 654 • Use cleaning methods that do not generate dust clouds; • Only use vacuum cleaners approved for combustible dust collection
- 56. Prevention – Ignition ControlPrevention – Ignition Control NFPA Code 654 Consider all sources of ignition from : • Electrical systems and lighting equipment • Static electricity, including grounding connection of equipment; • Flame and sparks control; 56 No! Fuente: Curso 7120 OSHA Training Center
- 57. Prevention – Ignition ControlPrevention – Ignition Control NFPA Code 654 • Sparks and friction mechanical control to remove foreign materials that can cause fires in combustible materials of the process; • Separate combustible dust from hot surfaces and equipment that generate heat • Have hot work permits available
- 58. 58 Magnetic Separator Hopper Magnets operating position Fuente: Curso 7120 OSHA Training Center
- 59. Prevention – Ignition ControlPrevention – Ignition Control Other ignition sources • OSHA 29 CFR 1910.178 (c) regulates powered industrial trucks on dust areas • The coal handling operations must meet the electrical requirements specified in OSHA 29 CFR 1910.269 59 Class II Group E,F,G
- 60. Prevention – Ignition ControlPrevention – Ignition Control NFPA Code 654 The manual loading of material from intermediate bulk containers is not allowed, when the movement of dust may cause a flammable atmosphere. Tank with flammable mixture No! Fuente: Curso 7120 OSHA Training Center
- 61. Mitigation – Damage ControlMitigation – Damage Control 61 Are methods used to control and reduce the severity of an explosion or fire.
- 62. Mitigation – Damage ControlMitigation – Damage Control 62 Are methods used to control and reduce the severity of an explosion or fire.
- 64. 64 TrainingTraining Personnel working in areas at risk of explosion or fire from combustible dust must be trained at least: • Hazard Communication on combustible dusts • Engineering control methods such as detection, suppression and extinguishing
- 65. 65 TrainingTraining Workers must be trained on: • Equipment and systems preventive maintenance • Considerations as the electrical classification of the area • Emergency plans
- 66. NEW PROPOSED RULENEW PROPOSED RULE Standard Combustible Dust
- 67. 67 The U.S. Chemical SafetyThe U.S. Chemical Safety BoardBoard Conducted a comprehensive study of dust explosions and found A pattern of catastrophic explosions. • The MSDS often fail to provide information on dust explosion • Recommended that OSHA develop a standard. OSHA responded by establishing its National Emphasis Program (NEP) for combustible dust
- 68. Industries Inspected Under the NEPIndustries Inspected Under the NEP 164 123 103 86 80 69 55 40 34 30 050100150200 WoodMat. Food ChemicalInd. Prod.Metal Rubber/Plastic Metales Elec.Serv. Mobiliario Equip.Transp. Otros
- 69. Combustible Dust ViolationsCombustible Dust Violations • General Duty Clause Violations • Housekeeping Violations • Electrical Violations 130 167 36 133 206 48 151 35 0 50 100 150 200 250 5(a)(1) HazCom Extintores Elec.(Loc Peligrosa) Limpieza Aire Comprimido EPP Primeros Auxilios
- 70. Other ViolationsOther Violations • Industrial Trucks (Forklifts) • Hazard Communication • Personal Protective Equipment • Lockout/tagout • Machine Guarding • Exit Routes
- 71. Common Findings - HousekeepingCommon Findings - Housekeeping • Hazardous levels of dust in the workplace due to poor cleaning • Process equipment, such as windmills, air ducts, mixers and dust collectors are not designed or maintained to keep dust out of nearby areas • Horizontal surfaces not minimized
- 72. Common Findings - ElectricalCommon Findings - Electrical • Using electrical equipment and vacuum cleaners not approved for locations in areas with combustible dust. • Management of motor vehicles (forklifts) not authorized in areas with combustible dust
- 73. Common Findings - Fire ProtectionCommon Findings - Fire Protection • Heating equipment with open flames used in areas that generates or handle dust. • Lack of preventive maintenance of mechanical equipment - creating heat and friction • Perform hot work in areas where dust is handled without hot work procedures
- 74. Common Findings - Explosion ControlCommon Findings - Explosion Control • Lack of ventilation or explosion supression systems in work areas where combustible dust is present • Isolation deflagration systems not provided. • Operating rooms without delivery systems for explosion
- 75. Common Findings– Explosion ControlCommon Findings– Explosion Control • Lack of ventilation and supression systems on hoppers, silos, bucket elevators, and dust collectors. • Equipments with dust bag located inside the buildings without appropriate systems for explosion protection. • Explosion releasing directly to work areas instead of outwards
- 76. Proposed RuleProposed Rule • These findings and the studies conducted by the Chemical Safety Board have resulted in OSHA decision to start the process to adopt a rule for the handling of combustible dust in the General Industry • Originally known as the Congress project HR5522.
- 77. Proposed RuleProposed Rule • Standard is expected to discuss issues such as : – Definitions – Methods of hazard evaluation – Methods of hazard control – Interaction with the Hazard Communication Standard – Trainings – Emergency rescue plan, etc. • Currently at the public hearings stage (Jun 2010).
- 79. Applicable StandardsApplicable Standards Existing OSHA Standards: – 1910.22 – Housekeeping – 1910.38 – Emergency Action Plans – 1910.94 – Ventilation – 1910.119 – Process Safety Management – 1910.269 – Generation of Electrical Energy – 1910.272 - Grain Handling Facilities
- 80. Applicable StandardsApplicable Standards • Existing OSHA Standards (cont.) 1910.307 - Hazardous locations, 1910.1200 Hazard Communication • Section 5 (a) (1) – General Duty Clause • ANSI and NFPA Applicable standards
- 81. ReferencesReferences • OSHA 29 CFR 1910 – Applicable standards • NFPA 654 – Prevention of Fire and Dust Explosions from Manufacturing, Processing and Handling of Solid Combustible Particle. • NFPA 499 – Combustible Dust Classification, and Hazardous Locations. • NFPA 61 – Agricultural and Food Processing Facilities • NFPA 69 – Explosion Prevention Systems • CSB – Chemical Safety Board, publications
Editor's Notes
- Since 1980 there have been over 280 combustible dust explosions, according to a study by The Chemical Safety Board (CSB). The result has been a total of 133 deaths and more than 730 wounded. Most of the workers or their employers do not recognize the hidden dangers of combustible dust in general industry operations.
- All these materials have the potential to become combustible dust if reduced to a very fine size and if the other conditions necessary to create an explosion are present (see p. 29)
- The sugar processing plant, 91 years old, was located near the city of Savannah, and processed granulated and powdered sugar. Investigation of the Chemical Safety Board revealed that the initial explosion occurred in a bucket elevator. It is assumed that the silo operations created a buildup of combustible sugar dust suspended on horizontal work surfaces generating the first explosion. The primary explosion generated a fire, caused the partial collapse of the four floor building, and also spread more dust into the atmosphere. The airborne dust generated a series of secondary explosions that advanced rapidly throughout the gallery of the silo and the tunnel. The fire of secondary explosions in turn affect the packing facility, and the inside of adjacent buildings.
- A disastrous explosion and fire occurred in a cast aluminum automotive parts in Indiana with the consequence one dead and six wounded. The investigation determined that the event&apos;s primary explosion occurred because of dust in or near a smelter of aluminum pieces. This was followed by a secondary explosion in the dust collection equipment, causing a fire of great proportions.
- A common work practice in this plant was to use compressed air, electric fans and brooms to remove dust from the day&apos;s operations. This generated a dust cloud in the vicinity of the furnace of the production line. It was also common to see small fires ignite by the accumulation of combustible dust near the oven, which operators put out with fire extinguishers or hoses. The day of the accident the furnace was not working properly, the door was open, allowing contact with dust and there were no employees on hand to contain the fire. The first blast of dust and fire triggered secondary explosions in several production lines, which destroyed much of the production area.
- The investigation of this case identified the false ceiling spaces as hazardous areas where dust can accumulate and usually pass undetected. Phenolic resins are commonly used as finishes for materials such as paper, fiberglass or cotton, which will be used to create molds or work surfaces for applications in art, electronics, textiles and others.
- According to the research, the first event was probably an explosion of powder containing polar nylon fibers. Although there had been minor incidents of fire with nylon fibers, managers and employees in general did not know that the fibers were a risk of explosion, before this event.
- The experience of the grain handling industry helps to illustrate the nature of the combustible dust problem and some possible solutions.
- Combustible dusts with a particle size less than 420 microns are considered by most reference sources as explosives. For example, the particle size of flour is around 100 microns. Size Pellets (wood)&gt; 2mm diameter Granules between0.42mm - 2mm Dust Particulate&lt; 0.42mm (420ųm) Pellet is commonly used to designate a solid material compacted as a small cylinder of approximately 2 mm of diameter. A solid particulate of .42 mm o 420 microns (cubic or spherical) is believed to be big enough to remain suspended in air for a considerable amount of time. This particulate size can pass through a #40 standard sieve. IMPORTANT: solid particulate or oblong flakes not passing though a #40 standard sieve can still be considered a hazard if they behave like a spherical solid particulate
- The easiness of ignition and the seriousness of the combustible dust explosion are usually influenced by particle size. Finer particles tend to be more explosive because they have more superficial area in relation to their mass, which permits a rapid reaction with oxygen when dispersed in air, helping spread the explosion.
- The table shows the different size of common particles.
- Fire is a chemical reaction that generates energy as light and heat. For fire to ignite it requires three elements: fuel (combustible dust), ignition source (spark), and the oxidant agent (oxygen, air ).
- An explosion can occur after the initial fire, for this to happen two additional elements, besides those of fire, need to be present : dust dispersion (movement of enough solid particulate to create a dust cloud) and confinement (enclose within a space or equipment). Adding these two elements to the fire triangle creates what is known as the dust explosion pentagon. Be sure to define the following:1. EXPLOSION – The burst or rupture of an enclosure or container due to pressure buildup caused by a deflagration. Explosions within work areas are produced as the result of dust accumulation in areas generating fine dust when combustible solid particulates are produced, processed, handled or transported . it should be expected that all combustible solid particulates generate o contain combustible dust.
- The confinement does not necessarily mean that the space or equipment is completely closed, but it rather refers to the resistance or barrier provided to the free movement of the pressure wave.
- It occurs when the combustion zone advances a velocity slower than the speed of sound, quickly producing great amounts of heat. The generated heat induces quick expansion of air and other gases freeing a great amount of pressure which can result in structural damages or injuries to workers.
- The speed of sound is the speed by which sound travels in an elastic medium (air, fluid). In dry air @ 20 °C (68 °F), the speed of sound is 343 meters per second (1,125 ft/s).
- There are factors that determine dust explosivity: solid particulate size, humidity content of the solid particulate, ambient humidity, available oxygen for combustion, solid particulate shape and concentration (minimum explosive concentration, “MEC”). This dust concentration level is usually found in ducts, dusts collectors or process equipment. That concentration will be present when the material accumulated in work surfaces is dispersed in air due to an explosion. Thus, housekeeping is a critical factor in explosion prevention.
- If one of the elements of the Pentagon is eliminated the explosion will not occur. Two of the elements in the pentagon are dificult to eliminate: the oxidant agent (air), and the confinement of the dust cloud (inside processes or buildings). Nevertheless, the other three elements of the pentagon, dust, dispersion and ignition sources, can be controlled. An initial or primary dust explosion can lead to one or more secondary dust explosions. This can happen when the initial dust explosion occurring inside process or emission control equipment ignites combustible dust in nearby areas. A secondary explosion occurs when accumulated dust on work surfaces or floors is ignited as the result of the first explosion. The expansive wave from this explosion can cause the ignition of fugitive dust from nearby areas
- This slide illustrates a dust explosion inside the equipment. The dust collector is essentially constructed to conatian a pressurizationo event until it can be vented safely to a relief point or through an engineering ventialtion control. It is designed and calculated for the type of event tahas might occur inside. The result wil be a falme front like a stream that will vent through the dust collector relief point . The worker shown here is out of the danger zone.
- This slide illustrates a dust explosion inside the equipment. The dust collector is essentially constructed to contain a pressurization event until it can be vented safely. Nevertheless, nearby areas to the vent relief point, have significant amounts of fugitive dust accumulation, allowing the flame front to reach more dust and generating a secondary explosion.
- Plastics and rubber have their base on large (poly)specific molecules chains of specific molecules (ethylene, propylene, etc. Polyethylene) Polyethylene - plastic most commonly used, has several formulations and their uses range from hip replacements to covered elastic. HDPE (high density) - used for packaging juice, milk and other foods, also in toys. LDPE (low density) used in plastic bags and rigid containers Melamina y su resina – usado en la producción de textiles, adhesivos y fibras resistentes a fuego Polipropileno – algunas aplicaciones incluyen empaque, textiles (sogas, ropa termal, alfombras), papelería, piezas plásticas y envases reusables, equipo de laboratorio, componentes de automóviles y otros. Poliacrilamida – coagulante en el tratamiento de aguas usadas y en la industria de papel. También usado en la producción de lentes de contacto
- They are used as raw material for everyday products Ascorbic acid is known as vitamin C Methylcellulose gives consistency to shampoos, toothpaste and food products (ice cream) The sodium stearate is the basis of solid deodorants, some rubber, latex paints and inks. Dextrin has many uses, if it is yellow is used for adhesives / glues. If it is white as a food additive, textile treatment, medicines and binding agent in paper.
- The majority of natural and synthetic organic materials and some metals, can form combustible dust.
- To determine whether an explosion may occur in a facility, we must conduct a risk analysis for the powder. The main thing to determine in this analysis is whether the dust is actually combustible. To do this you need to know if a cloud of dust studied detonated, deflagrate, or if you have any fire hazard. This information can be located in the data provided by the manufacturer or by a specific flammability test (see ASTM)
- It is believed that fine particles or smaller can play an important role in the ignition of dust clouds and hence, on the spread of the explosion. As more small particles there are in a determine space, larger surface area will be available for combustion. The smaller the particle, the easier it is warming up to the ignition temperature of the substance.
- Dust accumulation may occur in open areas such as work surfaces or floors or hidden areas on beams and false ceilings where is not possible to observe the build-up easily. Dust dispersion rarely occurs as a result of natural ventilation in most cases using a mechanical device or cleaning equipment caused the movement of dust
- Any potential ignition source present in the work area can supply the energy needed to start the fire and / or explosion. Vehicles - forklift must be rated for use in Class II areas, typically are electric or of internal gas with specials covers on the engine or emission to prevent sparks. Process equipment - should be grounded or have the appropriate device driver or dissipate static charges. They should not have any mechanical sparks hot surfaces without proper protection systems. The lamp must meet electrical code requirements (NEC, NEMA). The mechanical equipment such as vacuum cleaning has to be type approved for use in Class II electrical classification.
- Actually there are several elements to take into account when assessing an installation to determine if there is a fire hazard or combustible dust explosion. This chart summarizes these factors: Materials that can be combustible when particle size is reduce Processes that: use (cleaning processes) consumed (as part of its raw material) or produce combustible dusts Equipments on which dust can concentrate or are not appropriate for the electrical rating of the area: Open areas where combustible dust may accumulate Hidden areas where combustible dust may accumulate Means by which dust can be dispersed in the air, and Potential sources of ignition.
- Risk analysis should include evaluation of the electrical classifications. A detailed analysis that considers all possible scenarios that can generate dust is recommended, taking as reference the corresponding electrical code. They have tried to use some subjective rules to establish a relationship between the electrical rating and frequency of cleaning is recommended that you begin cleaning immediately: When you can write on the dust. If dust obscures the surface color - provided by the metal powder. If dust accumulation reaches the dimensions given in Table A.6.6.2 of NFPA 654 Quantity Accumulation frequency Cleaning frequencyelect. Classification. NegligibleAlmost noneN/A None – gen. use Up to 1/32”Less frequent, Less during None – gen useno more than 2-3 times per year -per shift - Up to 1/32”Frequent(&gt;3 time/year) Clean as neededNone – covered Continuous – &lt; a 1/32” /24 hr to mantain 1/64” NEMA12, sealed From 1/32” a 1/8” Less frequent clean during None – covered (2 coins) per shift NEMA 12, sealed From 1/32” a 1/8”Frequent to continousClean as necessaryClass III to keep 1/64”division 2 Greater at 1/8” Les frequent Stop and clean Class II immediatelydivision 2 Greater than ¼”Continue to frequentClass II, Division 1
- Look for: processes that use, consume or produce fine powders. accumulations of fine dust, even in hidden areas (such as inside air conditioning ducts or suspended ceilings (acoustic)).
- We must establish a program of regular cleaning frequencies for floors and horizontal surfaces, such as ducts, pipes, hoods, attic and rafters to minimize dust accumulation within areas of operation. Work surfaces should be designed to minimize dust accumulation and facilitate cleaning.
- NFPA 654 - provides general recommendations for prevention and damage control that can be adapted to any industry
- Only use vacuum cleaners approved for dust collection in areas classified as Class II
- Use the following ignition controls; Using methods of wiring and electrical equipment suitable for the area. Control of static electricity, including grounding the equipment. Smoking Control, flames and sparks
- You can use permanent magnets or electromagnets with failure indicators to warn of unwanted material. This slide illustrates the need for periodic inspection and cleaning.
- The 1910.178 establishes the recommended powered industrial trucks categories for areas classified as Class II The 1910.269 is more properly directed to the requirements in distribution or electrical generation areas from different sources in this case coal.
- The transfer of combustible dust from intermediate bulk containers (IBC) can cause static ignition hazard. NFPA 654 discusses the various types of IBC and the risk of ignition of the powder for each type of IBC. As more conductivity is associated with a IBC, reduces the risk of ignition. Manual additions through a hatch or lid to a container containing flammable vapors are allowed in batches of 50 lbs. or less. The lower amount of product reduces the risk of a fireball that involves workers.
- Some methods of control and risk reduction involves the separation of the hazard (isolation distance) or segregation of the hazard (isolate with a barrier). These and / or other methods listed on this slide can fit into engineering solutions carefully planned.
- In 2006, the CSB issued a report recommending that OSHA regulate powders for industry in general, according to the provisions of the NFPA standards. Since that recommendation OSHA established a national emphasis program. He also began the steps to create a regulation for dust.