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Combustible Dust 2015 nfpa 644


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Combustible Wood Dust Safety

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Combustible Dust 2015 nfpa 644

  1. 1. Combustible Wood Dust Safety John Newquist Draft 8 2 2015
  2. 2. History of Dust Explosions • First recorded dust explosion occurred in Turin, Italy back in 1785 • 281 combustible dust incidents in the US from 1980-2005 • Resulted in 119 deaths and 718 injuries
  3. 3. Introduction  Accidents in Industry caused by Combustible Dusts For example, combustible sugar dust was the fuel for a massive explosion and fire that occurred Feb. 7, 2008, at the Imperial Sugar Co. plant in Port Wentworth, GA., resulting in 13 deaths and hospitalization of 40 more workers, some of whom received severe burns. Below is an illustration of the facility after the explosion.
  4. 4. Introduction • Accidents in North Carolina caused by Combustible Dusts Above: Courtesy U.S. Chemical Safety Investigation Board Above: Aerial View of explosion and fire that occurred on Jan 29, 2003, at West Pharmaceutical Services plant in Kinston, N.C
  5. 5. Introduction  What Materials Can Form a Combustible Dust? A combustible dust explosion hazard may exist in a variety of industries, including: food (e.g., candy, sugar, spice, starch, flour, feed), grain, tobacco, plastics, wood, paper, pulp, rubber, furniture, textiles, pesticides, pharmaceuticals, dyes, coal, metals (e.g., aluminum, chromium, iron, magnesium, and zinc), and fossil fuel power generation.  Above: Courtesy U.S. Chemical Safety Investigation Board, November 2003, fatal accident at an automotive parts plant explosion in the U.S. that involved aluminum dust that originated near an aluminum chip melting furnace.
  6. 6. Combustible Dust Events in US: 1980-2005 Food Products 24% Lumber & Wood 15%Chemical Manufacturing 12% Primary Metal Industries 8% Rubber & Plastic Products 8% Electric Services 8% Other 7% Fabricated Metal Products 7% Equipment Manufacturing 7% Furniture & Fixtures 4% Distribution of Dust Events by Industry Food 23% Wood 24%Metal 20% Plastic 14% Coal 8% Inorganic 4% Other 7% Distribution of Dust Events by Material Type Note: Coal mines & grain handling facilities excluded from study (Ref. U.S. Chemical Safety Board Report No. 2006-H-1)
  7. 7. Dust Explosion by Equipment Type Equipment Type % of Incidents Dust Collector 52 Impact Equipment 17 Silos & Bins 13 Dryers & Ovens 9 Processing Equipment 6 Conveyor 3 Source: FM Global Property Loss Prevention Data Sheet 7-76, “Prevention and Mitigation of Combustible Dust Explosion and Fire”, May 2008
  8. 8. NFPA Dust Standards • Keyway Documents Standard Industry Edition NFPA 652 All New NFPA 654 All – General Industry Document 2013 NFPA 61 Food/Agricultural 2013 NFPA 664 Wood 2012 NFPA 484 Metal 2012 NFPA 655 Sulfur 2012
  9. 9. NFPA Dust Standards • How-to Documents Standard Purpose Edition NFPA 68 Explosion Venting 2013 NFPA 69 Suppression/Isolation/Containment/Inerting 2014 NFPA 77 Static Hazards 2014 NFPA 70 National Electric Code 2014 NFPA 499 Practical Electric Classification 2013
  10. 10. April 2014 • Corrigan TX • Four people remain hospitalized, three in critical condition, after an explosion and fire at a Polk County plywood mill • a) dust collector bags impeded the venting area of the dust collector deflagration vents. • b) explosion vents releasing in the dust collector without taking measure to protect employees from the fireball path • c) dust collector vented and the deflagration traveled upstream to the sander. • d) responding to a fire within the sander dust collection system without the main blower remaining in operation. • e) responding to a fire within the sander dust collection system without a choke between the sander dust collector and silo leading to the briquetter.
  11. 11. Chemical Safety Board • From 2008 to 2012, The CSB board documented, 50 combustible dust accidents that led to 29 fatalities and 161 injuries.
  12. 12. Objectives) • Identify the NFPA 654/664 Standards applicable to your dust issues. • Identify three OSHA Standards cited in COMDUST NEP • Identify three questions that a plant would be asked in an OSHA COMDUST NEP inspection.
  13. 13. OSHA • OSHA has regularly stated that NFPA standards that have not been specifically incorporated into OSHA standards or adopted by state or local jurisdictions should be considered by companies as guidance. • At the same time, however, the NEP Compliance Directive instructs OSHA inspectors to consult the NFPA standards to “obtain evidence of hazard recognition and feasible abatement methods” to support a citation under the GDC. • Consequently, companies should consult NFPAs when evaluating and mitigating potential combustible dust hazards at their facilities.
  14. 14. The Long and Winding Road • History of Hazards • OSHA Inspections • Issues • Citations • Trends
  15. 15. Trend 1 – Rare Events but Still Occurring • Two British Columbia sawmills - 2012 • Four dead and 52 injured • Fines of up to $652,000 • These were wood dust explosions
  16. 16. Trend 2 – OSHA NEP continues • Combustible Dust National Emphasis Program (NEP) – revised March 2008 • CSB issues recommendations in 2005 • Advanced Notice of Proposed Rulemaking (ANPRM) – published October 2009 • Expert panel met May 2011
  17. 17. Possible Ignition Sources • Possible ignition sources include: – Open flames and sparks (welding, industrial grinding and cutting, matches, etc.) – Hot Surfaces (dryers, bearings, heaters, etc.) – Heat from Mechanical Impacts – Electrical Discharges (switch and outlet activation) – Electrostatic Discharges (static electricity) – Smoldering or burning dust – Smoking materials (cigarettes, lighters, cigars, etc.)
  18. 18. OSHA Inspections • Over 1000 COMDUST NEP inspections since 2008 • High Violations per inspections (Over 6.0/inspection) Triggers are: • Complaint or referral • Media reports of fires and explosions • Inspection Targeting List ~150-300 inspections in 2014
  19. 19. Sample Accident Jan 2009 • The laminate panels pass on a conveyor underneath a curing UV light. • A panel jammed up underneath the UV light. • The panel heated up to the point where it charred, smoldered and eventually caught fire. • The charred pieces were sucked up into the local exhaust system, where they ignited the dust collector located outside the plant. • The dust collector blew up, sending a shock wave back into/through the plant. Several overhead doors were blown off, and one of these struck 4 employees, injuring them.
  20. 20. COMDUST NEP • Plant history of fires • Employer’s Dust Management System • MSDS’s • Dust Accumulation • Dust Collectors • Ventilation Specifications • One liter of dust sampled • Photos • Interviews – Employees, Employers
  21. 21. Sample OSHA Questions • What is the Plant’s Housekeeping program? • Is there dust accumulation of 1/32 inch thick? • Dust collectors located inside of buildings? • Explosion relief venting distributed over the exterior walls of buildings and enclosures?
  22. 22. NFPA 654 Layer Depth Criterion Method 6.1.3 Hazard is present if dust 1/32 inches thick covers • 5% of room or building area up to 20,000 ft2 • Up to 1000 ft2 in a building 20,000 ft2 or larger 100 feet 200 feet 20,000 sq. ft. Building 5% or 1000 sq. ft. 40 feet 50 ft 1000 sq. ft. Building or Room 5% or 50 sq. ft. 200 feet 200 feet 40,000 sq. ft. Building 1000 sq. ft. 22
  23. 23. How much dust is too much? Fugitive dust outside equipment – Permitted thickness NFPA 654 Particulate Solids 1/32 inch at 75 lbs/ft3 , adjusted for other bulk densities NFPA 664 Wood 1/8 inch assumes 20 lbs/ft3 bulk density NFPA 484 Metals No accumulation – clean daily NFPA 61 Food + Agriculture Remove along with operations – references NFPA 654 OSHA Grain Grain Handling 1/8 inch – program and priority areas listed OSHA NEP General Industry 1/32 inch – Refers to NFPA 654 and FM Data Sheet 7-76 Adapted from: Application of NFPA 654 . . . Samuel A. Rogers, Process Safety, 3 - 2012 23
  24. 24. Sample OSHA Questions • Does the facility have isolation devices to prevent deflagration propagation between pieces of equipment connected by ductwork? • Does the facility have an ignition control program, such as grounding and bonding? Fire through a duct is bad
  25. 25. Sample OSHA Questions • Are Vacuum cleaners used in dusty areas and approved for the hazard classification? • Are separator devices to remove foreign materials used? • Can tramp metal ignite combustible dusts in the dust collection systems? Check the label for Class II
  26. 26. Sample OSHA Questions • Is the exhaust from the dust collectors recycled? • Does the dust collector system have spark detection and explosion/deflagration suppression systems?
  27. 27. Sample OSHA Questions • Are ducts designed to maintain sufficient velocity to ensure the transport of both coarse and fine particles? • What is the design basis for the ventilation? • Are duct systems, dust collectors, and dust-producing machinery bonded and grounded to minimize accumulation of static electrical charge?
  28. 28. Sample OSHA Questions • Is metal ductwork used? • Are bulk storage containers constructed of noncombustible materials? • Are employees trained in the hazards of the combustible dust? • Are MSDSs for the chemicals which could become combustible dust under normal operations available to employees?
  29. 29. NEP Citations • 1910.22, Housekeeping • 1910.38, Emergency action plans • 1910.94, Ventilation • 1910.132, PPE Hazard Analysis • 1910.146, Permit-required confined spaces • 1910.307, Hazardous (classified) locations • 1910.1000 Z table, Toxic and hazardous substances • 1910.1200, Hazard communication • General duty clause 5/16/2002 Vicksburg, MS 5 fatalities, 7 injured 23 serious, 2 unclassified $210,000 Fire in the baghouse, then rubber dust explosion No explosion venting or suppression in baghouse Poor housekeeping 88 fire reports in 13 years
  30. 30. Trend 3 – OSHA will continue to use the General Clause Violation • Dust collectors (Air Material Separator) inside • No proper explosion protection systems such as explosion venting or explosion suppression systems NFPA 654 – 2013 Where an explosion hazard exists, air-material separators with a dirty-side volume of 8 ft3 (0.2 m3) or greater shall be located outside of buildings. There are exceptions.
  31. 31. Typical 5(a)(1) Violations • Systems were not provided to prevent deflagration propagation from dust collectors to other parts of the plant. October 29, 2003 - Hayes Lemmerz Manufacturing Plant, IN Shawn Boone, 33, died in the Aluminum Dust explosion
  32. 32. Typical 5(a)(1) Violations • No explosion relief venting distributed over the exterior walls and roofs of the buildings. CTA Acoustics 2003 – 7 dead Fiberglass fibers and excess phenolic resin powder probably went to the oven while workers were using compressed air and lance to break up a cogged bag house filter
  33. 33. Typical 5(a)(1) Violations • Dust Collector and ducts do not prevent propagation to other parts of the plant From BS&B
  34. 34. Typical 5(a)(1) Violations • Ducts and system were not grounded
  35. 35. Typical 5(a)(1) Violations • Airborne fugitive dust
  36. 36. Typical 5(a)(1) Violations • A means of tramp metal protection was not provided to keep any unwanted metal fragments out of the air-material separators From Duramag
  37. 37. Typical 5(a)(1) Violations • Excessive dust • Not cleaning per the appropriate NFPA Standard
  38. 38. Typical 5(a)(1) Violations • Compressed Air was used for cleaning • Tip: Clean fugitive dust • Regular program • Access to hidden areas • Safe cleaning methods • Maintain dust free as possible • No blow down unless All electrical power and processes have been shutdown and other means cannot work. • See NFPA
  39. 39. Typical 5(a)(1) Violations • No PVC or nonconductive ducts
  40. 40. Typical 5(a)(1) Violations • Not maintaining duct velocity • While conditions can vary, 4000 ft/min is generally accepted as a minimum conveying velocity for wood particulate. • Sec
  41. 41. Strategy for Employers • Test for Combustible Dust • Find Applicable NFPA standards • Implement a Safety Management System • Housekeeping • Electrical Classification • Conduct Process Hazard Analysis for Dust Generation Processes • Control Ignition sources • Develop safety procedures for working on dust collectors • Investigate leaks, hot spots, near misses • Train Employees in hazards of combustible dust • Plan for fires and emergencies
  42. 42. Hazard Assessment & Mitigation • Below Illustrations: Examples of Woodworking Shop area that is kept clean, uses engineering controls (dust collection systems), and is kept free of dust accumulation.
  43. 43. Hazard Assessment & Mitigation • Below Illustration: An example of another Woodworking Shop area that is kept clean and free of dust accumulation.
  44. 44. Hazard Assessment & Mitigation • Below Illustration: An example of an overhead exhaust ducting at Woodworking Shop area that is kept clean and free of dust accumulation.
  45. 45. Where are Dust Sources? • Bag Openers (Slitters) • Blenders/Mixers • Dryers • Dust Collectors • Pneumatic Conveyors • Size Reduction Equipment (Grinders) • Silos and Hoppers • Hoses, Loading Spouts, Flexible Boots
  46. 46. Ignition Source Control Electrical equipment Hot Works Static electricity control Mechanical sparks & friction Open flame control Design of heating systems & heated surfaces Use of tools, & vehicles Maintenance
  47. 47. Mitigation - Venting Venting: • Rupture panels to relieve pressure preventing a vessel failure • Amount of vent area needed is determined using NFPA 68 equations • Explosion vent need to exhaust into a safe area or a quenching device
  48. 48. Mitigation – Suppression Suppression: • Detect a deflagration at early stage and quench the event with chemical suppressant • Cannon/bottle consist of pressurized gas and suppressant chemical • System triggers by pressure or optical sensor • Higher maintenance requirements
  49. 49. Mitigation – Suppression Factors that Impact Suppression • Vessel Volume • Vessel Strength – Reduced Pressure (Pred) • Vessel Geometry – (L/D Ratio) – Filter Bag/Cartridges Factors that Impact Suppression • Initial Pressure (+/-) • Material (Kst) • Activation Pressure (Pstat)
  50. 50. Isolation
  51. 51. Isolation Isolation: • Must be used to prevent propagation of an event in one vessel to interconnected equipment • Usually always needed in conjunction with venting or suppression
  52. 52. Hierarchy of Equipment Use 6.) Containment 7.) Inerting 1.) Free venting a vessel outdoors 2.) Free venting a vessel indoors next to an exterior wall using a duct 3.) Free venting a vessel indoors next to an exterior roof using a duct 4.) Flameless venting 5.) Active Suppression Prevention
  53. 53. Maintenance – It is also important to ensure that all dust-collection systems are operating properly and collected dust is recycled and/or disposed according to the manufacture specifications for the equipment.
  54. 54. Maintenance Check dust collection systems to make sure all leaks are sealed and dust is not accumulating in the ductwork. Check bonding and ground of all components in accordance with the manufacturer instructions.
  55. 55. Hazard Assessment & Mitigation • Below Illustrations: An example of an industrial dust collection system connected to a woodworking shop exhaust ventilation system to capture generated dust.
  56. 56. NFPA 654 - 2013 • Chapters 1 – 3 Administrative • Chapter 4 General Requirements • Chapter 5 Performance- based Design Option • Chapter 6 Facility and Systems Design • Chapter 7 Process Equipment • Chapter 8 Fugitive Dust Control and Housekeeping • Chapter 9 Ignition Sources • Chapter 10 Fire Protection • Chapter 11 Training and Procedures • Chapter 12 Inspection and Maintenance
  57. 57. Seven Key NFPA 654 Changes • 4.2 Process Hazard Analysis (PHA) • TREND 5 – PHA are conducted in less than 10% of companies, but increasing rapidly • OSHA VPP facilities have conducted numerous PHAs • 4.2.1* The design of the fire and explosion safety provisions shall be based on a process hazard analysis of the facility, the process, and the associated fire or explosion hazards.
  58. 58. NFPA 654 PHA • Examine the facility, process, and fire and explosion hazards • Actual test data required to support analysis • Which materials are combustible? • If not known, but suspected, then data are needed • Closed or open processes? • Rate of generation or release of solids to an environment? • Any collection methods in place? • Conclusion: processes generates or handles solids and dusts are formed in process, potential exists
  59. 59. Seven Key NFPA 654 Changes • 4.3 Management of Change. Written procedures to manage change to process materials, technology, equipment, procedures, and facilities shall be established and implemented.
  60. 60. Seven Key NFPA 654 Changes • 4.4.1* Incidents that result in a fire or explosion of a magnitude that causes property damage, production shutdown time, or injury shall be investigated. • 4.4.3* A written report … • 4.4.4* A summary of the incident investigation report shall be shared with affected personnel…
  61. 61. Seven Key NFPA 654 Changes • Those portions of the process and facility interior where dust accumulations exist external to equipment in sufficient depth to prevent discerning the underlying surface color shall be evaluated to determine if a dust explosion hazard or flash fire hazard exists.
  62. 62. Seven Key NFPA 654 Changes •* Dust flash fire or dust explosion hazard areas shall additionally be determined in accordance with any one of the following four methods:  Layer depth criterion method in 6.1.3  Mass method A in 6.1.4  Mass method B in 6.1.5  Risk evaluation method in 6.1.6 The NFPA 2 day course on combustible dust covers these assessment.
  63. 63. Seven Key NFPA 654 Changes • 6.2 Segregation, Separation, or Detachment of Combustible Dust Handling and Processing Areas. • 6.2.1 General. Areas in which combustible dusts are produced, processed, handled, or collected such that combustible dust accumulation on exposed or concealed surfaces, external to equipment or containers, exceeds the threshold as determined in Section 6.1, shall be detached, segregated, or separated from other occupancies to minimize damage from a fire or explosion.
  64. 64. Seven Key NFPA 654 Changes • 7.3.2* Pneumatic Conveying, Dust Collection, and Centralized Vacuum Cleaning Systems. • The design of the system shall be documented, and the documentation shall include the following information:  Data on the range of particulate size  Concentration of combustible dust in the conveyance air stream  Potential for reaction between the transported particulates and the extinguishing media used to protect process equipment  Conductivity of the particulates  Other physical and chemical properties that could affect the fire protection of the process
  65. 65. Mitigation Ignition source control • Electrical equipment • Class II, Division 1 and 2 • Consider equipment both inside dust handling equipment and outside • Static electricity control • Grounding and bonding are key • Inspection of ground and bonding means • Vibrating equipment (e.g., sifters) may cause fatigue failure in straps • Mechanical sparks & friction • Rotating equipment bearing failure can lead to very hot surfaces (above the MIT) • Sliding surfaces can develop charges • Steel tools dropping onto concrete or steel • Mechanical integrity management system/vibration analysis system • Hot work program • Open flames • Design of heating systems & heated surfaces • Use of tools & vehicles • Maintenance • Comfort heating equipment shall obtain combustion air from clean outside source
  66. 66. Damage Control • Detachment (outside or other bldg.) • Separation (distance within same room) • Segregation (barrier) • Pressure resistant construction • Pressure relieving construction • Pressure Venting • Relief valves • Maintenance • Specialized detection systems • Specialized suppression systems • Explosion prevention systems • Maintenance
  67. 67. Dust Collectors
  68. 68. Dust Collectors
  69. 69. Hierarchy of Equipment Use 6.) Containment 7.) Inerting 1.) Free venting a vessel outdoors 2.) Free venting a vessel indoors next to an exterior wall using a duct 3.) Free venting a vessel indoors next to an exterior roof using a duct 4.) Flameless venting 5.) Active Suppression Prevention
  70. 70. Dust Collectors
  71. 71. Dust Collectors
  72. 72. Hierarchy of Equipment Use 6.) Containment 7.) Inerting 1.) Free venting a vessel outdoors 2.) Free venting a vessel indoors next to an exterior wall using a duct 3.) Free venting a vessel indoors next to an exterior roof using a duct 4.) Flameless venting 5.) Active Suppression Prevention
  73. 73. Dust Collectors
  74. 74. Dust Collectors
  75. 75. Hierarchy of Equipment Use 6.) Containment 7.) Inerting 1.) Free venting a vessel outdoors 2.) Free venting a vessel indoors next to an exterior wall using a duct 3.) Free venting a vessel indoors next to an exterior roof using a duct 4.) Flameless venting 5.) Active Suppression Prevention
  76. 76. Dust Collectors
  77. 77. Dust Collectors
  78. 78. Dust Collectors Milton Hershey School Location: Hershey, PA Application: Woodworking Model: CYLK4440 Air Flow: 8,500 CFM
  79. 79. Dust Collectors Lincoln Middle School Location: Passaic, NJ Application: Woodworking Model: DKLD48015 Air Flow: 4,800 CFM
  80. 80. Dust Collectors William Patterson University Location: Wayne, NJ Application: Woodworking Model: DKPD72015 Air Flow: 5,700 CFM
  81. 81. Dust Collectors Gloucester HS Location: Gloucester, MA Application: Woodworking Model: CYLK4450 Air Flow: 10,000 CFM
  82. 82. Dust Collectors New Oxford Middle School Location: New Oxford, PA Application: Woodworking Model: DKLD48015 Air Flow: 8,500 CFM
  83. 83. Hierarchy of Equipment Use 6.) Containment 7.) Inerting 1.) Free venting a vessel outdoors 2.) Free venting a vessel indoors next to an exterior wall using a duct 3.) Free venting a vessel indoors next to an exterior roof using a duct 4.) Flameless venting 5.) Active Suppression Prevention
  84. 84. Multiple tasks involving exposures may involve use of FR as normal work wear. NFPA 2113 (2012) Recommends FR use for combustible dust A.5.2 • Work where dust is present on equipment or structure • Changing dust collector bags For example, FR garments should be required for the following: Per OSHA NEP 84
  85. 85. Dust depth Frequency Hsk’pg Req. Classification Negligible dust (color discernable) N/A N/A Unclassified – general purpose Negligible dust to < 1/32 inch (paper clip) Infrequent – Episodic release, not > 2-3 times yearly Clean up during same shift Unclassified – general purpose Negligible dust to < 1/32 inch Continuous to frequent – Continuous with < 1/32 inch per 24 hours or Episodic release, > 3 times yearly Clean as needed – maintain average < 1/64 inch (puffy little cloud with each step) Unclassified – NEMA 12 dust entry resisting enclosures and /sealed non- heat producing equip. (For existing plants – New to be Class II, Div. 2)Groups F and G Dusts 85
  86. 86. 1/32 to 1/8 inch (Two Quarters stacked) Infrequent Clean up during same shift Unclassified – NEMA 12 dust entry resisting enclosures and /sealed non- heat producing equip. (For existing plants – New to be Class II, Div. 2) 1/32 to 1/8 inch Continuous to frequent Clean as needed – maintain average < 1/16 inch Class II, Division 2 >1/8 inch Infrequent Immediately shut down and clean Class II, Division 2 > 1/8 inch Continuous to frequent Clean frequently – minimize accumulation Class II, Division 1 Groups F and G Dusts 86
  87. 87. NFPA 654 – Housekeeping 8.1,2 Fugitive dust control is to be provided by continuous suction wherever dust is liberated in normal operations The dust is to be conveyed to air- material separators Cleaning frequency, methods and portable vacuum cleaner requirements are RETROACTIVE for all facilities Continuous Suction ? 87
  88. 88. Cleaning Frequency 8.2.1 At facilities operated with LESS than the chosen threshold dust mass/accumulation per 6.1, cleaning frequency must ensure: • Accumulated dust levels do not exceed the chosen amount of dust • There is a planned inspection process that maintains cleaning at the correct rate 89
  89. 89. Cleaning Frequency 8.2 For facilities operated with LESS than the chosen threshold dust mass/accumulation • Set specific time requirements for cleaning local and short term spills • The intent is to remove the excess materials quickly so that such spills do not need to be included in the mass calculations of 6.1 90
  90. 90. Timing of Unscheduled Cleaning Longest Time to Complete Unscheduled Local Cleaning Accumulation on the worst single square meter of surface Accessible Surface Remote Surface 1 to 2 times threshold dust mass/accumulation limit (TDM/AL) 8 Hours 24 Hours 2 to 4 times TDM/AL 4 Hours 12 Hours >4 times TDM/AL 1 Hour 3 Hours Adapted from NFPA 654 Table A. 91
  91. 91. Cleaning Frequency 8.2.1 For facilities operated with MORE THAN the chosen criterion for threshold dust mass/ accumulation per 6.1: DUST • FR clothing and properly installed explosion venting would be included • Chapter 4 identifies some general safety requirements 92 • Additional protective measures are necessary per A. • It is permitted to prepare a documented risk assessment to determine the level of housekeeping consistent with protection requirements
  92. 92. Cleaning Methods 8.2.2 Surfaces shall be cleaned in a manner that minimizes the risk of generating a fire or explosion hazard. Vacuuming shall be the preferred method of cleaning. Where vacuuming is impractical, permitted cleaning methods shall include sweeping and water wash-down. 93
  93. 93. Cleaning Methods 8.2.2 Blow-downs are permitted for cleaning inaccessible surfaces or surfaces where personal safety risk is less than other methods. Use the following precautions: Vacuuming, sweeping, or water wash-down methods are to be used first Dust accumulations in the area after vacuuming, sweeping or water wash-down are not to exceed the threshold dust accumulation. 94
  94. 94. Cleaning Methods 8.2.2 NEMA 12 (resists ingress dust of particles) • All ignition sources and hot surfaces capable of igniting a dust cloud or dust layer must be shut down or removed from the area Additional requirements for dust blow-down • Compressed air hose nozzles must be limited to 30 psi discharge pressure as per OSHA • All electrical equipment potentially exposed to airborne dust in the area is to meet 95
  95. 95. Housekeeping Procedures Housekeeping program is BIG Must be documented (and addressed) in the dust process hazard analysis and management of change procedures Housekeeping procedures should include: • Risk analysis of the dust • Particle size • Moisture content • MEC and MIE • Other safety risks introduced by cleaning methods • Personal safety procedures and fall protection • Flame-resistant garments per NFPA 2113 96
  96. 96. Housekeeping Procedures Procedures should also include: • Cleaning sequence and methods to be used • Equipment including: • lifts, • vacuum systems, • attachments, etc. Safety Note: Large and high velocity fans may be used to prevent dust accumulations. Use of such fans to blow down significant dust accumulations present the same risks as compressed air blow-downs. 97
  97. 97. Portable Vacuum cleaners • Hoses are to be conductive or static- dissipative – both suction and air delivery hoses • All conductive components including wands and attachments must be bonded and grounded • Dust-laden air must not pass through the fan or blower Conductive or Static- dissipative Hose They are to meet the following: • Generally non-combustible construction and meet requirements for construction and static electrical hazard controls per 9.3.2 and 7.13.2 98
  98. 98. Portable Vacuum cleaners Additional requirements • Electrical motors must not be in the dust laden air stream unless listed for Class II, Division 1 locations • No paper filter elements for liquid or wet pick-up • Metal dust vacuums are to be listed for Class II, Division 1, Group E and meet other NFPA 484 requirements for specific metal used 99
  99. 99. Vacuum Cleaners for Use in Hazardous Locations And .3 • Use vacuums listed for the location or • Provide a fixed-pipe suction system with appropriate remotely located exhauster and dust collector. • Where flammable vapors are present, units are to be listed for both Class I and Class II locations HAZ LOC 100
  100. 100. Spills of Large quantities of dust A. In UNCLASSIFIED areas • Bulk material should be collected by sweeping, or shoveling • Listed Class II vacuums may also be used • Vacuum cleaners per (e.g.: compliant air driven units) may be used afterwards for residue Vacuum Truck See also OSHA Fact Sheet DSG FS-3589 10 2012 Vacuum trucks are similar to vacuum cleaners. They require analysis with management of change (MOC) to remove large quantity spills or releases of dust per 4.3 101
  101. 101. Concluding Remarks • No two dust explosions are the same. – No uniform dust laws like there are for gases • Standards are evolving • The dust explosion hazard exists – Be aware of the “I’ve never had a dust explosion before”
  102. 102. Questions?
  103. 103. Safety and Health Information Bulletin Purpose Background Elements of a Dust Explosion Facility Dust Hazard Assessment Dust Control Ignition Control Damage Control Training References
  104. 104. Resources and Questions? • NFPA 2-day Combustible Dust Seminar • Combustible Dust Guidebook - NFPA • OSHA SHIB • • LinkedIn Combustible Dust Forums • Facebook Grain Mill Accident page