Combustible Dust CAN HURT YOU

Transcription

1 Michael A. Serpe CSP SafetyFirstna, Inc Joseph P. Howicz CSP, CFPS Combustible Dust CAN HURT YOU In this presentation we will discuss: the latest hazard assessment strategies for combustible dust identified in Combustible Dust the new edition of NFPA 654; the OSHA GHS standard s rules on combustible dust; and how the OSHA combustible dust questions can be used to prevent or control dust hazards 1

2 NFPA 654 (2013) Implements major changes to requirements for combustible dust hazard assessment and housekeeping emphasizing Amount of dust deposited outside equipment Testing and analysis of dust Housekeeping related to hazard assessment 3 NFPA 654 (2013) Changes the Rules for Dust Hazard Assessment Allows any one of four performance options to be used to determine if a dust explosion and/or flash fire hazard area is present Based on plant site data Emphasizes total mass of dust on surfaces outside equipment and available to create a dust cloud Relates housekeeping requirements to hazard assessment more detailed guidance 4 2

3 Revisions Set New Limits on Amount of Dust Standard introduces the term criterion Describes a permitted mass of dust A threshold Any additional dust is hazardous More dust requires greater precautions 5 Revisions Set New Limits Amount of Dust Focus is on the amount (mass) of fuel available to create a dust explosion or flash fire. Each of the hazard assessment methods is deemed provide roughly equivalent safety 6 3

4 Hazard Assessment Protection from the effects of dust deflagration and/or fire is required where a dust explosion or fire hazard Flash fire exists 6.1 Dust accumulations with sufficient depth to prevent discerning the underlying surface color are to be evaluated to determine if a hazard... exists, i.e.: A Hazard Assessment is 7 required Hazard Assessment Dust layers that do not obscure surface colors and can be ignored in calculating the mass of combustible dust It s Gone! 8 4

5 A visible cloud is close to or exceeds the lower flammable limit 9 Combustible Dust Flash Fire A high speed combustible dust fire (deflagration) in the process area. Requirements Ignition Source Combustible dust particles Dispersion in air or = Concentration > LFL 5

6 Primary deflagration breaks out of equipment Dust clouds are thrown into the air and ignite Dust explosions Initial (primary) explosion in processing equipment or in an area where fugitive dust has accumulated: may shake loose more accumulated dust This may cause one or more secondary explosions. Burst an equipment item or the building May be far more destructive than a primary explosion. 6

7 Dust Combustibility The primary factor in any assessment is whether the dust is in fact combustible. Lab Testing is necessary if there are questions NFPA 654 lays out detailed procedure for sampling dust accumulations outside equipment Requires an estimate of amount of accumulated dust Performance Methods for Determining the Mass of Dust and the Dust Hazard Layer Depth Criterion Method Compares calculations of the amount of dust present to an amount determined by a standard layer depth and density Two Mass Methods ( A and/or B ) Formulas are used to calculate a maximum permissible quantity of dust. Based in part on NFPA 68 deflagration/ explosion calculations. Risk Evaluation Method a documented study of material properties and inherent design features is necessary to determine the hazards 14 7

8 NFPA Revisions Set New Limits on Amount of Dust Standard introduces the term criterion Describes a permitted mass of dust accumulated outside equipment A threshold: Any additional dust is hazardous More dust requires greater precautions 15 Hazard Assessment Only the outer footprint area is used for area calculations. Amount of dust on ledges, mezzanines, tops of equipment, etc. is added to the total for dust only. Room or building area defines the enclosure for any explosion Areas of the ledges themselves are not added to footprint area of the room or building. 16 8

9 Hazard Assessment Personnel exposed to a dust flash fire hazard are to be protected with flameresistant garments Requires operating and maintenance procedures to address PPE Training and Planning Required Refers to NFPA 2113 (2012)... Flame resistant Garments for Protection of Industrial Personnel Against Flash Fire 17 Layer Depth Criterion Method The first method of Hazard Assessment involves a criterion of 1/32 inch (0.8 mm) of dust covering 5% of area, up to 1000 ft 2 Based on dust bulk density of 75 lb/ft 3 ~1/16 inch (1.6 mm) May be increased for dusts that are not as dense often to 1/16 inch (1.6 mm) These dusts provide less fuel (mass) for dust explosion or deflagration 18 9

10 Layer Depth Criterion Method /32 inch (thickness of a paper clip wire) for 75 lb/ft 3 dust About 0.2 lbs of dust for each square foot 0.2 lb/ft 2 limit applies with any dust (regardless of dust density) 1/32 inch 19 Layer Depth Criterion Method Criterion of 1/32 inch for 75 lb/ft 3 dust Roughly 2½ ft 3 for 1000 dusty square feet or about 190 to 200 lbs more or less About 5 ft 3 for an approximately 38 lb/ft 3 dust or about 190 to 200 lbs +/ _ Some rubber compound dusts Some prepared food mixes Polyethylene powder Dusty feet 2½ ft 3 75 lb/ft 3 dust 5 ft 3 38 lb/ft 3 dust 20 10

11 Layer Depth Criterion Method Permitted Layer Depth Criterion (in.) = (1/32 in.) X (75 lb./ft3 ) Bulk density of facility dust (lb./ft 3) Determine the permitted mass or amount of dust within the room or building. Bulk density of the dust at the plant is inserted into the formula to calculate the criterion. Compare with the actual (estimated) mass or amount present. 21 Layer Depth Criterion Method Layer Depth (inches) 1/4 1/8 1/16 1/ Bulk Density (lb/ft 3 ) Roughly equal to 0.2 lbs/ft 2 11

12 Hazard Assessment Mass Methods A and B and.5 The two Mass Methods may be used to calculate the maximum quantity of dust permitted to accumulate outside of equipment. Building explosion and collapse Based in part on NFPA 68 deflagration/ explosion calculations, both are intended to be conservative and protective. They provide a way to determine if precautions must be taken to protect employees and the building or to provide safeguards for Flash fire workers in the immediate area 23 Hazard Assessment Mass Methods A and B and.5 Mass Method A requires the total room or building floor area and the general height of the room. Mass Method B requires dust combustibility properties and information about the building strength against explosions All mass method calculations are performed using the metric system, e.g.: Method A limit for the area of a dust accumulation = 2000 m 2 Dusty 12

13 Mass Method A Building Damage Floor area and ceiling height are multiplied by a factor (0.004). It is an engineering estimate that summarizes the performance of typical dusts and buildings in dust deflagration events The multiplier represents: Dynamic strength of weak buildings Worst case dust concentration Maximum dust explosion pressure Entrainment fraction of the dust Hazard Assessment Mass Method A - building damage Enter values for floor area (m 2 ) and ceiling height (m) M basicexp = X X H M basicexp A floor = Threshold dust mass(kg) for building damage A floor = Lesser of enclosure floor area (m 2 ) or 2000 m 2 H = Lesser of enclosure ceiling height (m) or 12 m

14 Mass Method A Flash Fire A conservative multiplier (0.02) is used to relate: The volume of the burnt dust cloud after expansion against unconfined (atmospheric) pressure; and, The likelihood of personnel being burned or killed by the burning cloud is multiplied X building area, but not > 2000 m 2, similar to the calculation for explosion. In method A, the amount of dust allowed vs. flash fire will always be less than the amount for building explosion. 27 Mass Method A flash fire Section provides the following equation: Where: This amount of dust provides enough fuel to be a serious flash fire hazard to personnel - other than a person involved with the ignition of the event 28 14

15 Hazard Assessment Mass Method B Very Specific Information and complex formulas are used Design strength of room or enclosure for building damage calculations Combustible properties of the dust at the plant must be tested per ASTM E 1226 Room area and height must be known May result in somewhat larger permitted accumulations, particularly for Larger particle size and/or lesser bulk density dusts Hard to ignite dusts with low Kst values 29 Hazard Assessment Mass Method B flash fire A formula is used to estimate the size of a fireball of burning Dust Fireball dust The height of a person multiplied by the area is used as the volume of the space. The worst case concentration of plant dust is used A probability not exceeding 0.05 (5%) is used to approximate an occupant being in the same location as the deflagration flame. There is some residual risk to personnel

16 Hazard Assessment Risk Evaluation Method Detailed examination of dusts and materials, facility and equipment, processes and operations employee exposures to determine if dust explosions and/or flash fires are prevented, suppressed, controlled. Studies often performed by a fire protection engineer Rigorous, thorough analysis, intended to address all combustible dust scenarios 31 NFPA 654 Hazard Assessment Regardless of method Areas of dust accumulation are measured and estimated All areas not separated, segregated or detached are considered as one Depths are determined Dust accumulation areas are computed Result is compared to the threshold criterion 10,000 ft 2 building Dust bulk density +/- 38 lbs/ft 3 Location Est. ft 2 Est. depth Floor 100 ft 2 1/16 in. Pipes, beams, fixtures 1000 ft 2 1/8 in. Top of Eq. 200 ft 2 1/16 in. 3-5 times threshold for most dusts Action is taken to assure that prevention, protection and maintenance controls are correct 32 16

17 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 airmaterial Continuous Suction? separators Cleaning frequency, methods and portable vacuum cleaner requirements are RETROACTIVE for all facilities 33 17

18 Cleaning Frequency 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 35 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 RETROACTIVE 36 18

19 Timing of Unscheduled Cleaning Accumulation on the worst single square meter of surface 1 to 2 times threshold dust mass/accumulation limit (TDM/AL) Longest Time to Complete Unscheduled Local Cleaning Accessible Surface Remote Surface 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 (a) 37 Cleaning Frequency For facilities operated with MORE THAN the chosen criterion for threshold dust mass/ accumulation per 6.1: It is permitted to prepare a documented risk assessment to determine the level of housekeeping consistent with protection requirements Additional protective measures are necessary per A FR clothing and properly installed explosion venting would be included Chapter 4 identifies some general safety requirements DUST 38 19

20 Cleaning Methods Surfaces shall be cleaned in a manner that minimizes the risk of generating a fire or explosion hazard. Vacuuming shall be Forceful the preferred method Sweeping of cleaning. Where vacuuming is impractical, permitted RETROACTIVE cleaning methods shall include sweeping and water wash-down. Cleaning Methods 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 washdown are not to exceed the threshold dust accumulation. RETROACTIVE 40 20

21 Cleaning Methods 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 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 RETROACTIVE 41 Housekeeping Procedures 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 Housekeeping program is BIG Flame-resistant garments 42 per NFPA 2113 RETROACTIVE 21

22 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. 43 Portable Vacuum cleaners They are to meet the following: Generally non-combustible construction and meet requirements for construction and static electrical hazard controls per and 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 Conductive or Dust-laden air must not pass through the fan or blower Static-dissipative Hose 44 22

23 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 45 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 46 23

24 Monday March 26, CFR part OSHA Hazard Communication Standard 29 CRF part 1910,1915, 1926 Hazard Communication Hazardous chemical definition now includes combustible dust as a physical hazard Requirements are gradually coming into effect for Training Labeling Safety data Sheets (SDSs) Hazard Communication and Combustible Dust Rules now apply to combustible dust, e.g.: Particulates Dusts generated by the normal conditions of use, e.g.: cutting, sawing, grinding of products and shapes Continue to apply to dusts that meet definition of Flammable Solids 24

25 COMPLETION DATES REQUIREMENT(S) Dec 1, 2013 Employers (ERs) June 1, 2015 Chemical mfrs, importers, employers distributors Train employees on the new label elements and SDS format. Compliance with all modified provisions of new rule, except: Dec 1, 2015 GHS label required on shipments of containers June 1, 2016 Employers Transition Period to the above dates Update workplace labeling and the hazcom program, and provide addl. employee training for newly identified hazards. Comply with 29 CFR final standard, current standard, or both Combustible Dust Labels, Signs and Placards Labeling is required once the chemical is brought into the work area where it will be processed in a way to create the hazard Dust Containers p_table=interpretations&p_id=28880 December 27, 2013 MEMORANDUM on classification 25

26 Combustible Dust Label and Safety Data Sheet Content Hazard category: Combustible Dust Signal word: Hazard statement: Pictogram: Precautionary Statement: Warning May form combustible dust concentrations in air. Not required or specified Not required OSHA implements its Combustible Dust National Emphasis Program (NEP) Unannounced dust inspections required of each OSHA office and (indirectly) each OSHA state plan Inspector guidance Sample questions on the hazard Policy guidelines Housekeeping PPE Similar issues DIRECTIVE NUMBER: CPL

27 OSHA Enforcement and Outreach 500 +/- targeted inspections each year About 5 to 10 violations per inspection 80% serious Housekeeping General Duty clause [5(a)(1)] violations Hazard Communication Electrical Training Courses Compliance Officers OSHA Ed Center Courses Meetings, Publications The OSHA inspection plan for combustible dust Appendix B of the dust inspection program identifies a number of questions to be asked by the OSHA inspector during an inspection focused on combustible dust. Any inquiry into combustible dust hazards must utilize Recognized and Generally Accepted Good Engineering Practices (RAGAGEP), e.g.: NFPA 654, and any number of additional questions suggested by the facility operations, activities and environment. 27

28 1.What types of combustible dust does the facility have? OSHA will test the dust at the OSHA lab Additional (Less Reliable) Sources: MSDS Sheets Supplier data sheets and advice Table of NFPA 499 Table 1 in NMAB L sphere Hartman 2. Does the facility have a housekeeping program with regular cleaning frequencies...? Is it established for floors and horizontal surfaces, such as ducts, pipes, hoods, ledges, and beams, to minimize dust accumulations...? Is the dust on floors, structural members, and other surfaces removed concurrently with operations? Is there dust accumulation of 1/32 inch thick, or greater? What are the dimensions of the room and the area covered with the dust? 28

29 6. Are the dust-containing systems (ducts and dust collectors) designed (so) that fugitive dusts are not allowed to accumulate in the work area? 7. Are (dry) dust collectors greater than 8 cubic feet in volume located inside of buildings? >8 ft 3 Outside location Engineered containment Venting to outside Suppression 29

30 11. Is there an ignition control program (grounding and bonding and other methods of dissipating electrostatic charge for ductwork)...? Ground clip When Compression Fitting Interrupts Continuity Duct 13. Are electrically- powered cleaning devices approved for the hazard classification...? such as sweepers or vacuum cleaners used in dusty areas (see) HAZ LOC 30

31 17. Does the dust collector system have spark detection and explosion/deflagration suppression systems? (There are alternative measures.) Spark/ember Detectors Water spray extinguishment Dusty air Detectors and Suppressors 25. Does the company use methods to dissipate static electricity, such as by bonding and grounding? For static generating dusts Small particle size What to do? bonding and grounding bonding and grounding bonding and grounding bonding and grounding bonding and grounding bonding and grounding bonding and grounding bonding and grounding bonding and grounding bonding and grounding bonding and grounding bonding and grounding 31

32 18. Are all components of the dust collection system constructed of noncombustible materials? Big: PVC or other similar duct materials are powerful static accumulators and combustible as well Transparent view ports may Disrupt electrical continuity Generate static Temporary expedients can be a hazard Note: Dust collector bags are typically combustible Duct sections bonded and grounded 19. Are ducts designed to maintain sufficient velocity to ensure the transport of both coarse and fine particles? E.G.: Ontario Fire Code ( ) requires velocity to exceed 1068 meters/minute Dust flowing >1068 meters/minute 18m/sec 3560 ft/min Dust built up <1068 meters/minute 32

33 26. Are employees who are involved in operating, maintaining, and supervising facilities that handle combustible dust OSHA Inspector s Questions CPL , Appendix B 1. What types of combustible dust does the facility have? 2. Does the facility have a housekeeping program with regular cleaning frequencies established for floors and horizontal surfaces, such as ducts, pipes, hoods, ledges, and beams, to minimize dust accumulations within operating areas of the facility? 3. Under the housekeeping program, is the dust on floors, structural members, and other surfaces removed concurrently with operations? 4. Is there dust accumulation of 1/32 inch thick, or greater? 5. For housekeeping violations, what are the dimensions of the room and the dimensions of the area covered with the dust? 6. Are the dust-containing systems (ducts and dust collectors) designed in a manner that fugitive dusts are not allowed to accumulate in the work area? Handout 33

34 OSHA Inspector s Questions CPL , Appendix B 7. Are dust collectors greater than 8 cubic feet in volume located inside of buildings? 8. If dust explosion hazards exist in rooms, buildings, or other enclosures, do such areas have explosion relief venting distributed over the exterior walls of buildings and enclosures? 9. Is such venting directed to a safe location away from employees? 10. Does the facility have isolation devices to prevent deflagration propagation between pieces of equipment connected by ductwork? 11. Does the facility have an ignition control program, such as grounding and bonding and other methods, for dissipating any electrostatic charge that could be generated while transporting the dust through the ductwork? 12. Does the facility have separator devices to remove foreign materials capable of igniting combustible dusts? 13. Are electrically- powered cleaning devices, such as sweepers or vacuum cleaners used in dusty areas, approved for the hazard classification, as required under (b)? Handout OSHA Inspector s Questions CPL , Appendix B 14. Is smoking permitted only in safe designated areas? 15. Are areas where smoking is prohibited posted with No Smoking signs? 16. Is the exhaust from the dust collectors recycled? 17. Does the dust collector system have spark detection and explosion/deflagration suppression systems? (There are other alternative measures.) 18. Are all components of the dust collection system constructed of noncombustible materials? 19. Are ducts designed to maintain sufficient velocity to ensure the transport of both coarse and fine particles? 20. Are duct systems, dust collectors, and dust-producing machinery bonded and grounded to minimize accumulation of static electrical charge? 21. Is metal ductwork used? Handout 34

35 OSHA Inspector s Questions CPL , Appendix B 22. In areas where a hazardous quantity of dust accumulates or is present in suspension in the air, does all electrical wiring and equipment comply with (b) requirements? 23. Does the facility allow hot work only in safe, designated areas? 24. Are bulk storage containers constructed of noncombustible materials? 25. Does the company use methods to dissipate static electricity, such as by bonding and grounding? 26. Are employees who are involved in operating, maintaining, and supervising facilities that handle combustible dust trained in the hazards of the combustible dust? 27. Are MSDSs for the chemicals which could become combustible dust under normal operations available to employees? Combustible Dust CAN HURT YOU In this session, we discussed: the latest hazard assessment strategies for dust identified in the new edition of NFPA 654; the OSHA GHS standard s rules on combustible dust; and how the OSHA combustible dust questions can be used to prevent or control dust hazards Michael A. Serpe CSP SafetyFirstna, Inc. michael_a_serpe@yahoo.com Joseph P. Howicz CSP, CFPS jphowicz@sbcglobal.net