Sponsorship 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.
Work 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
Purpose 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.
Objectives • 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
Topics to be discussed 1. 2. 3. 4. 5. Historical background Definitions Related risks Facility evaluation Controls – – Prevention Mitigation 6. Training 7. Proposed Rule 8. References
Industrial Explosions HISTORICAL BACKGROUND
Are These Materials Explosive? coal sugar metal plastic wood medicines
Imperial 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
Fire and Explosion by Metal Powder : Indiana 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 10
Fire and Explosion in “CTA Acoustics” February 20, 2003 • Corbin, Kentucky, • 7 deaths, several injured • An poorly worked oven lit a cloud of phenolic resin dust, causing the explosion. 11
West Pharmaceutical January 29, 2003 • Kingston, North Carolina • 6 deaths, 38 injured • Phenolic resin dust accumulation enabling false ceiling fire and dust explosion 12
Fire and Explosion in Malden Mills December 11, 1995 • Methuen, Massachusetts • 37 workers injured • Destruction of the polar fabric manufacturing company (nylon fibers)
Grain Handling During the 70 s 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
Definitions IMPORTANT CONCEPTS
Definitions • 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.
Combustible Solid Particulate Any combustible solid material composed of particles or different pieces independent of the size, shape or chemical composition Includes: Dust Fines (coal dust) fibers Flakes Fragments Bits Mixture of any of the foregoing pellet 17
Particle Size of Common Materials Common Material Size (microns) Salt 100 Granulated 450 - 600 white sugar Sand 50+ Talc, Dust (baby) 10 Mold Spores 10 – 30 Human Hair 40 - 300 Fluor 1 - 100 Source: OSHA y Filtercorp International Ltd. 18
Combustible Dust Fires and Explosions Fire Triangle
Fires and Explosions of Combustible Dust For a combustible dust explosion to happen, it requires the presence of all these factors Confinement Dispersion Ignition Source Oxidant Fuel (dust)
Dispersion • 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.
Confinement • 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
Deflagration In the deflagration the flame advances as the material is consumed creating a fire front, with pressure changes
Detonation • The combustion speed advances faster than the speed of sound generating an audible event. • Dificult to control once it has begun
Minimum Explosive Concentration (MEC) 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 25 watts 6 feet = 2 meters Combustible dust concentration suspended in air > MEC Source: Course 7120 OSHA Training Center 25
Explosion Results from the combination of these factors: • fire • dispersion of solid particulate material • in a more or less enclosed space Explosion fire + dispersion + confinement =
Dust Colector Primary Explosion from dust in equipment 27 Fuente: Curso 7120 OSHA Training Center
Secondary Explosion Mechanism 1. Dust accumulates on work surfaces 2. An event disperses dust creating a cloud 3. The cloud ignites and explodes
Dust Colector Expansive wave Secondary Explosión from dust in area 7120 OSHA Training Center Fuente: Curso Dust Accumulation 29 (on floor and surfaces)
Industries ¿WHO IS AT RISK?
Industries that Generate or Handle Combustible Dusts • Metalworking • Pharmaceutical products • Food • Paper products • Wood products • Agriculture • Chemical Manufacturing – Textiles – Forest Products – Wastewater Treatment (used) – Recycling of metal, paper, plastic – Coal
Metal Powders • • • Aluminum Iron Carbonile Zinc Bronze Magnesium
Plastic Powder/ rubber • • • Molded Cellulose Polyethylene Melamine and its resin Polypropylene Polyacrylamide Epoxy or phenolic resin
Food • • Cotton Rice starch, corn, wheat Sugar Coffee Cocoa Powder Coconut shell Spice powder Potato starch
Food • Rice flour, oats, corn, potato, wheat • Lime • Walnut powder • Soybean powder • Seeds of raw cassava • Sunflower Seeds. Tomatoe • Carrot
Chemicals • Sodium stearate • Ascorbic Acid • Carboxymethyl Cellulose • Lactose • Calcium Acetate • Methylcellulose • Dextrin
Powders Containing Carbon (Carbonaceous powders) • • • Cellulose paste Activated charcoal Black charcoal Bituminous coal Petroleum coke Wood charcoal • • • Pine soot Petroleum Celullose Lignin Dry chemical
Agricultural Products • • Rice starch Celullose Dry powdered milk Wheat starch Egg white Barley Lactose
Area Assessment RISK ANALYSIS
Risks Factors ¿ 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.
Combustibility Determination The first step in the risk analysis should be to determine if the powder is combustible 41
Powder 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).
Production Packaging Process Horizontal surfaces • Floors • Beams • False Ceilings • Ducts • Piping Powder Dispersion • • Hidden Areas Open Areas Accumulation • • • Mechanic Vibration Ventilation Sweep Cleaning
Ignition Sources Vehicles Process Equipment Hot Surfaces Cleaning Illumination
Contributing Factors Materials (dust type) Equipment (Electrical class) Processes (use, produce, consume) Areas (open, hidden) EXPLOSION Ignition sources (present) Dispersion (dust movement)
Other 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
Hazards 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
Prevention & Mitigation PRINCIPAL METHODS OF CONTROL
Principal 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
Principal Methods of 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)
Principal 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
Principal Methods of Control Administratives – Establish a cleaning program with regular frequencies – Good work practices Personal Protective Equipment – Equipment classified as fire resistant (FR)
Prevention – 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 The spots are traces of dust 53 Fuente: Curso 7120 OSHA Training Center
Prevention – 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
Prevention – Dust Control NFPA code 654 • Use cleaning methods that do not generate dust clouds; • Only use vacuum cleaners approved for combustible dust collection
Prevention – 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; No! 56 Fuente: Curso 7120 OSHA Training Center
Prevention – 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
Magnetic Separator Hopper Magnets operating position Fuente: Curso 7120 OSHA Training Center 58
Prevention – Ignition Control Other ignition sources Class II Group E, F, G • 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
Prevention – 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. Fuente: Curso 7120 OSHA Training Center No! Tank with flammable mixture
Mitigation – Damage Control Are methods used to control and reduce the severity of an explosion or fire. Combustion Detection and ignition control Deflagration Suppression • Spark and ember detection • Gas sensors • Optical sensors • Detects changes in pressure • Activate discharge supressor material to stop the flame propagation 61
Mitigation – Damage Control Are methods used to control and reduce the severity of an explosion or fire. Containment of pressure / deflagration • Provides cover or structure able to contain the pressure generated in the deflagration • Is not useful for detonation Isolation • Separation - isolated by distance • Segregation - isolating chemical or physical barrier 62
Requirements TRAINING
Training 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 64
Training Workers must be trained on: • Equipment and systems preventive maintenance • Considerations as the electrical classification of the area • Emergency plans 65
Standard Combustible Dust NEW PROPOSED RULE
The U. S. Chemical Safety Board 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 67
Industries Inspected Under the NEP
Combustible Dust Violations • General Duty Clause Violations • Housekeeping Violations • Electrical Violations
Other Violations • Industrial Trucks (Forklifts) • Hazard Communication • Personal Protective Equipment • Lockout/tagout • Machine Guarding • Exit Routes
Common 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
Common 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
Common 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
Common 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
Common 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
Proposed 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 HR 5522.
Proposed 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).
Applicable Standards www. cours-prepa. info/tag/health-regulation
Applicable 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
Applicable 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
References • 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
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