Preventing Dust Explosions and Fires in the Die Casting Industry(-122)

1、Combustible Dust Course for Die Casting Industry Employees Preventing Dust Explosions and FiresProtecting Employees from the Effects of Dust Explosions and FiresNADCA North American Die Casting AssociationNADCA North American Die Casting AssociationUnit 1 Preventing Dust Explosions and Fires in the

2、Die Casting IndustryUnit 2 Protecting Employees from the Effects of Dust Explosions and Fires in the Die Casting IndustryUnit 3 Unit 4 Introductions Class Schedule InstructionsTerminal objectives for this CourseUpon completion of this course students should be able to:1. Explain how the materials us

3、ed in die casting facilities may cause dust explosions and fires, the consequences of these events and how they may be prevented and mitigated.2. Implement the work practices and procedures that will keep employees in the die casting industry safe from the hazards of dust explosions and fire.Alloy d

4、usts explode!Preventing Dust Explosions and Fires in the Die Casting IndustryUnit 1NADCA North American Die Casting AssociationEnabling Objectivesconsequences to employees themselves and to the die casting plant; and, Identify the materials used in die casting that may cause dust explosions and/or f

5、ires and how they may be prevented or reduced in severity if they occur.Students should be able to:Discuss dust explosions and fires as a significant safety problem that may affect them; Explain how these events occur and how they may have catastrophic Metal Dust Collector -Exploded and CollapsedThi

6、s presentation is based on “Combustible Dust in Industry. . .” - OSHA Safety and Health Information Bulletin (SHIB 07-31-2005) (download at :/ )NFPA 484 “Standard for Combustible Metals”, 2009 Ed. (on-line free viewing at )Combustible Dust ExplosionsBackgroundThis section describes a series of horri

7、fic dust explosions that have occurred recently. The US Chemical Safety and Accident Investigation Board (CSB) and OSHA have identified these explosions as representative of a national safety problem. The list includes a spectacular metal dust explosion and fire in Indiana that killed one and injure

8、d one employee. BackgroundBackgroundMetal Dust Fire and Explosion: Indiana (1 killed,1 injured)Recent Sugar Dust ExplosionOrganic Dust Fires and Explosions: Massachusetts (3 killed, 9 injured) North Carolina (6 killed, 38 injured) Kentucky (7 killed, 37 injuredCommon Causal Factors Housekeeping to c

9、ontrol dust accumulations unacceptable; Ventilation system design flaws; Lack of Hazard Assessment; Lack of explosion prevention and mitigation.Phenol Phenol formaldehyde resinformaldehyde resinpolyethylene dustpolyethylene dustImperial Sugar CompanyPort Wentworth GA Explosion and FireFebruary 7, 20

10、0814 Deaths and Numerous serious injuriesUS Chemical Safety and Hazard Investigation Board PhotoUS Chemical Safety and Hazard Investigation Board PhotoUS Chemical Safety and Hazard Investigation Board PhotoUS Chemical Safety and Hazard Investigation Board PhotoUS Chemical Safety and Hazard Investiga

11、tion Board PhotoUS Chemical Safety Board Found a pattern of catastrophic dust explosions Recommended that OSHA take action MSDS sheets often fail to provide dust explosion informationU.S. DEPARTMENT OF LABOROccupational Safety and Health AdministrationDIRECTIVE NUMBER: CPL 03-00-008EFFECTIVE DATE: M

12、arch 11, 2008SUBJECT: Combustible Dust National Emphasis ProgramOSHA inspectors are to go out and inspect facilities across the US.With confinement there is an explosionDust Explosion RequirementsDust is combustible.It must be dispersed in air or another oxidant, and The concentration is at or above

13、 the minimum explosible concentration (MEC).There is an ignition source, such as an electrostatic discharge, - spark, - glowing ember, - hot surface, - friction heat, or - a flame that can ignite the dispersed combustible mixture Some event disturbs the settled dust into a cloudDust cloud is ignited

14、 and explodesDust explosion in a work areaDust settles on flat surfacesDustAdapted from CSBDust collector venting flame jetDust explosion in equipmentDust explosion in equipmentWith dispersal and ignition of 2 kg dust by the flame jetDustCollectorDust explosion in equipmentDust explosions damage a c

15、ontainment system (such as a duct, vessel, or collector). The additional dust dispersed into the air may cause one or more secondary explosions. These can be far more destructive than a primary explosion.An initial (primary) explosion in processing equipment or in an area where fugitive dust has acc

16、umulated: may shake loose more accumulated dust; or,Time, msec. (Timing of actual events may vary)0 25 50 75 100 125 150 175 200 225 250 300 325 Primary deflagration inside process equipmentShock wave causedby primary deflagrationTime, msec.0 25 50 75 100 125 150 175 200 225 250 300 325 Time, msec.0

17、 25 50 75 100 125 150 175 200 225 250 300 325 Shock waves reflected by surfaces within the building cause accumulated dust to go into suspensionTime, msec.0 25 50 75 100 125 150 175 200 225 250 300 325 Dust clouds thrown in the air by the shock wavesTime, msec.0 25 50 75 100 125 150 175 200 225 250

18、300 325 Primary deflagration breaks out of the equipment enclosure - creating a source of ignitionTime, msec.0 25 50 75 100 125 150 175 200 225 250 300 325 Secondary deflagration ignitedTime, msec.0 25 50 75 100 125 150 175 200 225 250 300 325 Secondary Deflagration is propagated through the dust cl

19、oudsTime, msec.0 25 50 75 100 125 150 175 200 225 250 300 325 Secondary deflagration bursts from the buildingTime, msec.0 25 50 75 100 125 150 175 200 225 250 300 325 Collapsed building with remaining firesAdapted from OSHA diagrams prepared byJohn M. Cholin, P.E., FSFPE, J.M. Cholin Consultants, In

20、c.Combustible dust explosion hazard may exist in a variety of industries dyes, coal, metals (e.g., aluminum, chromium, iron, magnesium, and zinc), and fossil fuel power generation. food (e.g., candy, starch, flour, feed), plastics, wood, rubber, furniture, textiles, pesticides, pharmaceuticals, Dust

21、 Explosion Hazard Dust Explosion Hazard “. . .any industrial process that reduces a combustible material and some normally noncombustible materials to a finely divided state presents a potential for a serious fire or explosion.” (NFPAs Industrial Fire Hazards Handbook)Combustible Dust ExplosionsPrac

22、tice Quiz1. A combustible dust explosion or deflagration may occur when combustible dust, an ignition source, air or other oxidant, _ are present. Dispersion of the dustB. ConfinementC. A. and B. aboveD. None of the above2. Combustible dust explosion hazards frequently exist in which of the followin

23、g industrial activities?A. Collecting beach and lake bottom sandB. Mixing cement C. Manufacturing and finishing magnesium and aluminum alloy castings.D. All of the aboveCombustible Dust ExplosionsPractice Quiz3. A combustible dust explosion in a piece of equipment or area where dust has accumulated:

24、 May shake loose more accumulated dustB. Damage a containment systemC. Cause one or more destructive secondary explosionsD. All of the aboveCombustible Dust ExplosionsPractice Quiz1. A combustible dust explosion or deflagration may occur when combustible dust, an ignition source, air or other oxidan

25、t, _ are present. Dispersion of the dustB. ConfinementC. A. and B. aboveD. None of the above2. Combustible dust explosion hazards frequently exist in which of the following industrial activities?A. Collecting beach and lake bottom sandB. Mixing cement C. Manufacturing and finishing magnesium and alu

26、minum alloy castings.D. All of the aboveCombustible Dust ExplosionsPractice Quiz3. A combustible dust explosion in a piece of equipment or area where dust has accumulated: May shake loose more accumulated dustB. Damage a containment systemC. Cause one or more destructive secondary explosionsD. All o

27、f the aboveCombustible Dust ExplosionsIn this section, we described a series of horrific dust explosions that have occurred recently. Common causes were identified How the explosions occurred was outlined The factors needed to produce an explosion and the explosion process was discussed in detail. P

28、articles In this section, particles that participate in the explosion process are discussed. Their characteristics are identified. How they form in an industrial process is outlinedMetal Dust ParticlesParticlesSize Pellets 2mm diameter Granules0.42mm - 2mm dust particles Minimum Explosible Concentra

29、tionDust CombustibilityWhat bulb?25 watts2 metersGlass40 g/m3 concentration of comb. dust suspended in airGlassWhat is wrong here?Dust CombustibilityInformation sources Best to rely on “As used” test dataChemical supplier test dataMSDS sheets Published tablesVariables Particle size, Shape Changes in

30、 the material produced by process equipment. Many othersDust from Die Casting AlloysChipsProduced DustResulting inFacility Analysis ComponentsDust CombustibilityPractice Quiz1. The primary factor in an assessment of a materials dust explosion hazard is to: Determine whether the dust is in fact combu

31、stibleB. Measure the size of the particlesC. Determine if the dust will pass through a #40 USG screenD. None of the above2. A deflagration is a combustion event that:A. Burns at a rate slower than the speed of soundB. Provides a “pushing force” C. Is the mechanism of destruction in most industrial d

32、ust explosions.D. All of the aboveFacility Analysis ComponentsDust CombustibilityPractice Quiz3. Dust produced in die casting plants is almost always combustible when dispersed in air at the correct concentration:A. TrueB. FalseFacility Analysis ComponentsDust CombustibilityPractice Quiz1. The prima

33、ry factor in an assessment of a materials dust explosion hazard is to: Determine whether the dust is in fact combustibleB. Measure the size of the particlesC. Determine if the dust will pass through a #40 USG screenD. None of the aboveFacility Analysis ComponentsDust CombustibilityPractice Quiz2. A

34、deflagration is a combustion event that:A. Burns at a rate slower than the speed of soundB. Provides a “pushing force” C. Is the mechanism of destruction in most industrial dust explosions.D. All of the above3. Dust produced in die casting plants is almost always combustible when dispersed in air at

35、 the correct concentration:A. TrueB. FalseOther Hazard Analysis ConsiderationsElectrical equipment and facilities at the plant Magnesium Alloys Aluminum Alloys Zinc-Aluminum and Zinc Alloys (For Zinc alloys utilize “as used” test data or treat as Class II)Dust AreasNEC Class II Group E Electrical cl

36、assification OSHA Electrical standard (29 CFR Part 1910 Subpart S) NFPA 70, the National Electrical Code. (NEC) NFPA 499, . . . Classification of Combustible Dusts and of Hazardous (classified) Locations for Electrical Installations in Chemical Process Areas.ElectricalEquipmentClassIIDivision1Group

37、EF GEElectrical Classification and CleaningIf Clean-up is constant and Dust layer is not apparent; Surface color is discernible; e.g.: Storage area with bags, drums, or closed hoppers; No dust around.Ordinary Electrical EquipmentSee NFPA 499 Figure 5.8(e)Ledge Dust Surface color obscured with Group

38、E metal dustA hazard and NEC Class II locationFire Codes* speak plainlyGroup E dusts . . . could cause a short in the electrical equipment . . . . . (electricity may find) the path of least resistance through a dust layer, heating up the dust particles in it path and thus providing a source of ignit

39、ion. The resulting electric arc could ignite a dust layer or dust cloud.Fire Codes* speak plainlyDusts containing magnesium or aluminum are particularly hazardous, and the use of extreme precaution is necessary to avoid ignition and explosion.Group E. Atmospheres (contain) combustible metal dusts, i

40、ncluding aluminum, magnesium, and their commercial alloys, or other combustible dusts whose particle size, abrasiveness, and conductivity present similar hazards. . .*NFPA 70 National Electrical Code (2005) Article 500Indoor unrestricted areaOpen or semi-enclosed equipmentSourceModerate or Dense Dus

41、t CloudDust LayerNEC Electrical ClassificationClass II Group E Metal Dust AreasClass II Group E Metal Dust AreasPlan/TopViewElevation/SideViewDust SourceModerate or Dense Dust Cloud or Layer 1/8 inchDust Layer 1/32 Inch Structural members Conduit and pipe racks Cable trays Floors Above ceiling Equip

42、ment (leaks around dust collectors and ductwork.)Other Hazard Analysis ConsiderationsDust ControlPractice Quiz1. One of the most important factors for the prevention of dust explosions in the die casting industry is: Removal of any fugitive dust through systematic, effective housekeeping.B. Excellen

43、t housekeeping.C. Planned, thorough and frequent regular housekeeping activities.D. All of the above.Other Hazard Analysis ConsiderationsDust ControlPractice Quiz2. An important component of any good housekeeping program involves:A. Allowing waste and scrap from machining operations to accumulate ar

44、ound equipment.B. Inspect for dust residues in hidden areas, at regular intervals and, if necessary, removal of any dust.C. Blowing down, or aggressively knocking, or sweeping down any dust.D. All of the above.2. OSHA inspectors have been instructed that a combustible dust layer of 1/32-inch thickne

45、ss exceeding 5% or 1000 sq. ft. or room area may indicate that the employer has violated the housekeeping regulations.A. True B. FalseOther Hazard Analysis ConsiderationsDust ControlPractice Quiz1. One of the most important factors for the prevention of dust explosions in the die casting industry is

46、: Removal of any fugitive dust through systematic, effective housekeeping.B. Excellent housekeeping.C. Planned, thorough and frequent regular housekeeping activities.D. All of the above.Other Hazard Analysis ConsiderationsDust ControlPractice Quiz2. An important component of any good housekeeping pr

47、ogram involves:A. Allowing waste and scrap from machining operations to accumulate around equipment.B. Inspect for dust residues in hidden areas, at B. Inspect for dust residues in hidden areas, at regular intervals and, if necessary, removal of any regular intervals and, if necessary, removal of an

48、y dust.dust.C. Blowing down, or aggressively knocking, or sweeping down any dust.D. All of the above.2. OSHA inspectors have been instructed that a combustible dust layer of 1/32-inch thickness exceeding 5% or 1000 sq. ft. or room area may indicate that the employer has violated the housekeeping reg

49、ulations.A. TrueA. True B. FalseIgnition ControlIgnition ControlNFPA 484 Use appropriate electrical equipment and wiring methods; Control static electricity, including bonding of equipment to ground; Control smoking, open flames, and sparks;No!Ignition Control Separate heating systems from dusts; Pr

50、oper use of cartridge activated tools; and Adequately maintain equipment.Hot work permit_GrinderKaboom!Ignition ControlOther ignition sourcesOSHA regulates powered industrial trucks 29 CFR 1910.178 (c): Does not permit powered industrial trucks where combustible metal dust is present in hazardous co

51、ncentrations; e.g.: Heavy dust concentrations, or Thick dust layer; See NFPA 505.Other Hazard Analysis ConsiderationsIgnition ControlPractice Quiz1. Many activities that must occasionally be done in dusty areas produce arcs, sparks and hot surfaces: They must be done, so do them as fast as possible.

52、B. Implementing a hot work permit system and following it will control any of these hazards.C. Uncontrolled these ignition sources may cause an explosion.D. A. and B. above.Other Hazard Analysis ConsiderationsIgnition ControlPractice Quiz1. Many activities that must occasionally be done in dusty are

53、as produce arcs, sparks and hot surfaces: They must be done, so do them as fast as possible.B. Implementing a hot work permit system and following it will control these hazards.C. Uncontrolled, these ignition sources may cause an explosion.D. A. and B. above.Damage ControlMethods controlling and red

54、ucing hazard SeparationSeparation of the hazard (isolate with distance); SegregationSegregation of the hazard (isolate with a barrier);MetalDustHazardNot 8 ft3 Outside location Engineered containment Venting to outside SuppressionIn general dry dust collectors greater than 8 cubic feet in volume loc

55、ated must be located outside.Damage ControlOSHA has fined facilities where Dry dust collectors located inside the building (some exceptions) and/ordust collectors returning air back inside the building Ductwork not grounded not constructed of metal Outside wallDamage Control1068 meters/ /minuteDust

56、built upDust flowingE.G.: Ontario Fire Code (0) requires velocity to exceed 1068 meters/ /minute1068 meters/ /minute18m/sec3560ft/minDucts must be designed to maintain sufficient velocity to ensure the transport of both coarse and fine particles?Facility Analysis ComponentsIn this section, t

57、he various components of facility analysis were discussed.Several factors were identified as critical to the analysis: Material combustibility; Electrical classification; Dust control; Ignition control; and, Damage control.Gentle sweeping onlyPractice Quiz The following dry filter type dust collecto

58、rs larger than 8 cu. ft. in volume may be located inside the plant: Cyclone and bag house collectors. Collectors that exhaust inside the plant. Collectors with explosion relief panels venting inside the work area. None of the above.The following dust properly engineered dust collectors may be locate

59、d inside the plant: Wet collectors. Dry collectors venting outside to a safe area. Dust collectors protected by an explosion suppression system.1. All of the above.Facility Analysis ComponentsDamage ControlPractice Quiz 3. It is sometimes not possible to suppress a deflagration in combustible metal

60、dust because: Flame speed is too fast and too much heat is produced by the expanding fire ball after ignition. Not enough heat is produced. Flame speed is to slow and the suppression system activates too quickly.A. None of the aboveFacility Analysis ComponentsDamage ControlPractice Quiz The followin