Combustible Dust. Understanding, Assessing, and Mitigating. Combustible Dust Hazards Ben Peetz, ASP CFPS February 18, 2014

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1 Understanding, Assessing, and Mitigating Combustible Dust Hazards Ben Peetz, ASP CFPS Senior Loss Prevention Specialist, Lumbermen s Underwriting Alliance Lieutenant, Napoleon (IN) Volunteer Fire Department Indiana Safety and Health 2014 Indianapolis, Indiana Combustible Dust What is com dust? How much com dust is dangerous? Fire vs. explosion Prevention / Mitigation / Engineering Primer on dust management systems Emergency response considerations 2 1

2 What do we tend to think of first when we hear the term COMBUSTIBLE DUST????????? 4 2

3 CSB Video Excerpt 5 What about other materials? Sawdust / Wood Coal Grain / Foods Sugar Flour Rubber Chemicals Plastics Nylon Polymers Pharmaceuticals Metals Aluminum Magnesium Zinc 6 3

4 If it didn t start out as a rock it can likely cause a dust fire or explosion. Hazardous amounts? Now that we know which dusts How much dust does it take to be hazardous? 8 4

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6 11 1/32 is enough Less than 1/32 combustible dust needed in suspension to be explosive. The thickness of a dime (less that 1/16 ) is twice the amount of fuel needed to be deadly. 12 6

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10 19 CSB - Shawn Boone Story 20 10

11 New problem? 1785 First recorded flour mill explosion, Italy 1803 Coal dust explosion in mine, England dead Coal dust explosion, Utah Jan 3, dead, Pekin IL corn starch Sept 7, dead, Brach s candy, Chicago 21 Responses? Late 1800s Studies of flour mill explosions begin in the United States 1896 NFPA formed Early 1900s Studies of coal dust explosions begin in the United States 1911 NFPA create Explosive Dust Cmte. NFPA 61, 484, 654, 664; 652 coming 22 11

12 NFPA 652 Technical committee started the draft with four main chapters Based on basic concepts in each current standard hazard identification hazard assessment hazard management management systems Due for publication as 2015 standard 23 Regulations? Codes? NO specific combustible dust REGULATION Is OSHA avoiding issue? has begun the rulemaking process to develop a combustible dust standard for general industry. but no established timeline. CPL Combustible Dust N.E.P. Using other standards to enforce 24 12

13 OSHA applicable to dust Housekeeping Exit Routes EAP Ventilation Electrical / Equipment HAZCOM 25 Existing standards 29 CFR (a)(1) All places of employment, passageways, storerooms, and service rooms shall be kept clean and orderly and in a sanitary condition. Used where layers of combustible dust allowed to accumulate to depths considered viable for a fire or explosion hazard to workers

14 GDC to enforce NFPA Compressed air cleaning of dust (b) enforcement of 30 PSI as the universal limit for compressed air exposure NFPA 664 (2012) Prevention of Fires and Explosion in Wood Processing and Woodworking Facilities Defines 15 PSI as the limit for safe blow pressure 27 Some states use fire codes Some jurisdictions have adopted standards and fire codes for combustible dust. E.g, both California and Georgia have adopted state occupational regulations governing combustible dust Other states fire marshals have established specific codes relating to the hazard

15 NFPA definitions Combustible Particulate Solid Any solid material composed of distinct particles or pieces, regardless of size, shape, or chemical composition that presents a fire hazard. (NFPA ) Consider the forest products industry Dust? Chips? Shavings? Fibers? 29 Combustible Dust Combustible dust is one particular type of CPS. presents a flash fire hazard or explosion hazard when suspended in air or the process-specific oxidizing medium over a range of concentrations. (NFPA ) 30 15

16 Combustible Dust Fine particles that will burn rapidly and present an explosion hazard under certain conditions. Often organic in nature Also can include metals 31 Where do we find ComDust? OSHA considers dust generation to be a normal condition during certain processes: Abrasive blasting Cutting Grinding Polishing / sanding Crushing of materials Conveying, mixing, sifting or screening dry materials Buildup of dried residue from processing wet materials

17 Particle Size Generally under 500 microns, or 0.5 millimeters Anything that will fit through a U.S. #35 testing sieve is considered a deflagrable dust Changed in NFPA 664 (2012) from # What does that mean? Based on industry standards, regular granulated table sugar typically has a grain size about.5 mm, or 500 microns. Thus any product that produces any amount of dust particles smaller than common sugar would constitute a combustible dust

18 More comparison Table salt generally is less than 500 microns, typically at.3-.4 mm in size. Excellent example of a material where most particles would pass through a 500 micron (0.5 mm) sieve. 35 Size doesn t always matter Shape will determine the volatility Flatter or elongated particle (more surface area to amount of volume) will burn at a faster rate. Flatter or rod-shaped particles may not pass a #35 sieve, but still pose a deflagration hazard

19 Explosibility Minimum ignition energy (MIE) Ease / likelihood of igniting a dispersed cloud Minimum explosible concentration (MEC) Minimum amount dispersed in air to explode. Dust deflagration index (Kst) Relative explosion severity compared to others Larger Kst value = more severe explosion. 37 Explosive testing for Kst Dust expl. class Kst Characteristic Typical material St 0 0 No explosion Silica St 1 >0 and 00 Weak explosion Powdered milk, charcoal, sulfur, sugar, zinc St 2 >200 and 200 Strong explosion Cellulose, wood flour St 3 >300 Very strong explosion Aluminum, magnesium OSHA Hazard Communication Guidance for Combustible Dusts 38 19

20 Example Kst values Product Kst Characteristic Activated carbon 44 Weak Explosion Aluminum grit 100 Weak Explosion Aluminum powder 400 Very Strong Explosion Asphalt 117 Weak Explosion Barley grain dust 240 Strong Explosion Magnesium 508 Very Strong Explosion Polyethylene 134 Weak Explosion Starch, corn 202 Strong Explosion Sugar 138 Weak Explosion Toner 145 Weak Explosion Wood dust 102 Weak Explosion Wood Flour 205 Strong Explosion 39 Deflagration Burning material heats the next layer of cold material and ignites it This process moves from the point of ignition to a point where an ignitable fuel supply ends. Think of an expanding fireball that consumes suspended dust as it grows

21 Sawdust cannon video 41 Required for deflagration Small enough particle to initiate deflagration Particles suspended in air High enough concentration of particles Ignition source The entire sample does not need to be <420 microns to pose a deflagration hazard 42 21

22 Deflagration hazard Only need a small percentage in com dust range for deflagration to occur. Degree of deflagration hazard can vary Characteristics of the material Volume of the dust Processing methods used. 43 Deflagration damage Damage to buildings, equipment and people Primarily a function of: total amount of fuel burned in the event (= total amount of energy released) maximum flame velocity that is achieved manner in which the expansion of the combustion gases is contained. Deflagration is different from detonation Confinement to an area causes explosions 44 22

23 CSB video - Dust explosions 45 Combustible Dust Explosions Dust explosion pentagon takes fire triangle and adds: Dispersion / suspension of particles Confinement of the cloud If one part of the pentagon is missing, a combustible dust explosion will not occur

24 Let s look at a deflagration Start with a cloud of suspended dust: 47 Anatomy of a deflagration Provide an ignition source: 48 24

25 Anatomy of a deflagration Suspended particles ignite in one area: 49 Anatomy of a deflagration Flame front moves through fuel supply: 50 25

26 Anatomy of a deflagration Gases of combustion expand rapidly while igniting adjacent fuel: 51 Anatomy of a deflagration The large quantity of heat generated causes the gases of combustion to expand beyond that space initially occupied by the suspended dust in air

27 Deflagration Combustible dust piled on the floor = low risk of deflagration 53 Deflagration Combustible dust blown into the air = high risk of deflagration 54 27

28 NFPA 664 (2012) Removal of Dust Surfaces shall be cleaned in a manner that minimizes the generation of dust clouds. Blowing down with steam or compressed air or even vigorous sweeping shall be permitted only if the following requirements are met: (1) The floor area and equipment shall be vacuumed prior to blowdown. (2) Electrical power and other sources of ignition shall be shut down, removed from the area, or classified for use in dusty areas per NFPA 70, National Electrical Code. (3) Only a low gauge pressure of 103 kpa (15 psi) steam or compressed air shall be used. (4) No open flames, sparks from spark-producing equipment, or hot surfaces capable of igniting a dust cloud or layer shall exist. (5) All fire protection equipment shall be in service. 55 NFPA 664 (Appx ) Sweeping and/or vacuuming are the preferred methods to be utilized. Facilities should not be operating during blowdown. Blowdown should be done in individual sections of the building, starting near the center and working out, in order to prevent filling the entire building with dustladen air. Blowdown should be frequent enough that large amounts of dust are not blown into suspension

29 Location may affect volatility Smallest particles most easily carried up Greatest concentrations often in the highest elevations. Overhead fugitive dust is usually the lightest and the finest and consequently most hazardous

30 Deflagration Dust often accumulates in overhead areas. An acoustic event causes the dispersal of dust into a suspended cloud. = high risk of deflagration 59 GREAT BALLS OF FIRE! Open environment = flash fires rather than explosions With no confinement, little to no pressure that builds up. Still very dangerous! 60 30

31 Ignition sources Equipment or tool could strike metal and generate sparks. Machine failure throws a hot piece of metal from a machine. A bearing could get hot and ignite material that contacts it. Electrical deficiency Tramp metal in dust system piping, creating sparks as it bounces through

32 Tactical Considerations for Manufacturing Operations March 24, Tactical Considerations for Manufacturing Operations March 24,

33 Tactical Considerations for Manufacturing Operations March 24, Heat within equipment Tactical Considerations for Manufacturing Operations March 24,

34 Tactical Considerations for Manufacturing Operations March 24,

35 69 Explosion What will happen when the deflagration is contained within a limited compartment? Bin Silo Dust filtration unit A room or building 70 35

36 Big bang? Similar to popcorn pop except popcorn pressure increase is from expansion of water into steam, rather than combustion. A rapid increase of pressure within an enclosed space causes the container to rupture. 71 FM Global Dust Exp Video 72 36

37 Deflagration & Explosion Low-speed deflagration within a closed vessel or structure Pressure effects produce damage due to expansion of gases. Heat released by the deflagration causes combustion gases and excess air to expand thermally. 73 Deflagration in a compartment = EXPLOSION The rapid expansion increases to pressure that exceeds a compartment s ability to contain that pressure

38 Anatomy of an explosion Flame front moves through a fuel supply that is within a compartment: 75 Anatomy of an explosion Gases expand rapidly and the volume within the compartment fills

39 Anatomy of an explosion The expansion creates a pressure that can exceed the compartment s strength. 77 Anatomy of an explosion This is known as an EXPLOSION. If the compartment is not designed to release this over-pressurization, the compartment itself fails catastrophically

40 Silo explosion video 79 Explosion venting This emphasizes the importance of adequate explosion venting. Designed to provide a means of releasing energy in the event of an explosion Equipment or structural 80 40

41 Explosion venting video 81 West Pharmaceuticals video 82 41

42 83 Prevention vs. Mitigation High fuel loads will result in high-energy explosions, which are impossible to vent. West Pharmaceuticals explosion resulted from extraordinary energy release that could never have been vented. Make sure prevention is a priority! Housekeeping is the #1 practice for the prevention of catastrophic explosions

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44 Lakeland Mills Prince George, BC 87 Lakeland Mills Prince George, BC Sawmill ball of flame kills 1, injures 24 Workers say building exploded around them Second explosion in B.C. in 4 months A January explosion near Burns Lake B.C., killed two and destroyed the mill

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46 Primary vs. Secondary Initial energy that begins the sequence is called the primary event. Not necessarily a deflagration or explosion A primary event dislodges fugitive dust by vibrating or shaking the equipment and structure. Fuel laden air seeks an ignition source. 91 Primary / Secondary In a primary explosion or deflagration, the air movement and pressure concussion may be enough to suspend additional fuel. As this dust becomes suspended in air, ignites and produces a secondary explosion. Additional secondary explosions may result

47 Dust Explosion Simulator By Dordt College Agriculture Dept., Sioux City, IA 93 Simulator video 94 47

48 Primary vs. Secondary Often the secondary explosions are more destructive than the primary, causing more damage and/or injuries than the first. It may also damage a dust-containment system which releases dust into the air, providing more fuel for additional secondary involvement

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50 99 Dust management systems These present the most potential for an explosion. Three basic components: Blower / collection system Extraction / separation Storage / area of use

51 101 A giant shop-vac Filter bags work as dirty air is forced through the bags by pressure (typically up from the bottom). Clean air exits the house, and the dust collects on the bags

52 Dangers of filtration units Primary concern with a pressurized filter house is the potential for an explosion. Cleaning process in a filtration unit -- known as the blowdown or shakedown sequence Constant instances where the interior air of the bag house can be completely filled with finite dust. This means only an ignition source is needed to complete the explosion pentagon. 103 Dust system configurations

53 105 Cyclones = no bags Cyclones are not equipped with bags, so not pressurized. Dust is removed by the physics of the air and the dust s motion. Air enters the cyclone and dust drops out

54 No pressure = less danger Because cyclones are not pressurized, there is much less risk of an explosion. Fire could still result in the storage area. Cyclones may be used in conjunction with filtration units. 107 Storage Dust is then blown from the bags or shaken into the base of the cone, where it exits the unit and is moved into a storage bin, silo, etc. Stored dust may then be used as boiler fuel or perhaps sold to outside customers

55 109 Storage methods Storage systems may be as extensive as massive steel or concrete silos May be as simple as portable dumpsters, or even barrels

56 Positive vs. Negative Positive systems are designed with the blower fan pushing dirty air into and through the dust filtration unit. Negative systems are designed with the fan on the clean air piping, to pull air through the bag house 111 Dangers of positive systems Dirty air is pulled through fan blades. A malfunction in the blower fan itself could present an ignition source. Any spark or heat generated by the fan will enter the house

57 FIRE: Don t make it worse If we do not fully understand and consider the implications of every action taken in an emergency situation, we exponentially increase the risk of injuries or deaths. We MUST understand how a fire should be addressed without increased danger to firefighters

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60 Silo explosion video 119 It s happened before October 1, 2003 New Knoxville, OH Initial reports stated, A silo at a lumber company in western Ohio exploded injuring seven firefighters and an undetermined number of lumber yard employees, the fire chief said. The explosion killed two firefighters - one firefighter was standing on top of the silo, while another was in an aerial basket

61 Two deaths plus: The explosion blew the top off of the burning silo, sending chunks of the 75-foothigh concrete structure flying to areas over 100 yards away. Another firefighter atop the silo and eight people on the ground - six firefighters and two of the plant's owners - were injured in the explosion. 121 How? Why? Incident reports repeatedly show that such fires can result in dust explosions whenever the product is agitated. This explosion occurred well after firefighting efforts had been initiated. The explosion is believed to have been caused by air rushing into a cavity as wood chips burned, thus igniting gases and dust

62 One a lot vs. another? News reports stated that, according to the fire chief, firefighters couldn't allow the silo fire to burn itself out because that would have endangered the lumber company's buildings and workers. Sparks could have been emitted from the opening at the top, said the fire chief, according to news reports. 123 That s just one example December 21, 1997 Iredell County, North Carolina Three firefighters injured when silo filled with sawdust exploded 2½ hours into suppression. Blast occurred when panels removed for overhaul after contents were thought to be extinguished. Explosion s force blew the top off the silo. Injured firefighters were wearing class III harnesses, but the catwalk to which they were anchored was blown apart

63 More examples May 4, 2002 Sacramento, California Firefighters were just arriving at a woodworking plant when a blast occurred in its three-story-tall sawdust hopper, throwing a worker from an eightfoot-high catwalk to the ground. Automatic sprinklers already had controlled the fire when a worker dumped the smoldering contents, shaking up the contents and allowing oxygen to enter. 125 More examples In another incident in Ohio, firefighters were burned when they opened an overhead duct containing burning sawdust; the spilling of the contents resulted in a large fireball. Lack of compartmentation

64 Each of these examples started out simply as burning sawdust. In each one of these actual events, burning sawdust turned DEADLY. Not complex or complicated scenarios In responses that obviously endangered or killed firefighters or civilians, was any of the risk really reduced or lives / property saved? 127 Photo courtesy of : John Larew

65 Pre-planning Facility knows what to do FD knows what to expect FD understands the dangers FD considers spread potential Methods of applying water / other agent Consider how to unload / purge storage Equipment to move purged materials 129 Carris Reels video

66 Safe distances This means NO ONE climbs or attempts to manually open any hatches or panels. Ground crews are kept minimal and at a safe distance from thrown debris. Consider deck guns or monitor nozzles May require letting a unit burn Options for safe isolation (pull down ducts?) 131 Photo courtesy of : John Larew

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68 135 Silo explosion video

69 Combustible Dust Hazards Ben Peetz, CFPS February Photo 18, courtesy 2014 of : John Larew137 February 18, 2014 Combustible Dust Hazards Ben Peetz, CFPS 138 Photo courtesy of : John Larew 69

70 139 Photo courtesy of : John Larew February 18, 2014 Combustible Dust Hazards Ben Peetz, CFPS 140 Photo courtesy of : John Larew 70

71 141 Unmanned aerial devices Never put anyone on a ladder in close proximity of a potential explosion vent. Engineered explosion vents Man-doors / maintenance access Seams or weak points in construction where rupture could occur

72 Photo courtesy of : Kirk A. Neidermyer 143 Photo courtesy of : Kirk A. Neidermyer

73 Photo courtesy of : Kirk A. Neidermyer 145 Always expect an explosion The safest approach is to never have anyone in position where you wouldn t want them if there was an explosion. Any attempt at removing fuel could cause dust to shift and disperse. Just the burning of the fuel could create voids that cause settling and dispersal

74 Harvestore Silo 147 Safest approach is to have automatic equipment in place that will respond in the event of a fire. Automatic sprinkler heads to the interior of the dust containment unit Open heads tied to electronic heat detection and solenoidactivated deluge valve

75 Interior Automatic Sprinklers 149 Dry-pipe or antifreeze loops Where freezing temp s may occur, units are to be protected by a dry-pipe system or an auxiliary anti-freeze loop

76 FDC & standpipe to heads As an alternative where water supplies are inadequate, a pre-installed fire department connection on a standpipe to open deluge heads may be recommended as an option. This prevents the need for firefighters to climb on or open the unit to get water inside. 151 Additives / alternatives Consider adding Class A Foam to any water supplies used on fibrous materials. Have been some attempts at using nitrogen gas for silos

77 Prevent / divert explosions Best protection afforded by spark detection and suppression system These systems monitor for sparks and work to extinguish them prior to reaching the dust unit. Spark detection systems are commonly referred to by their brand name, such as GreCon or Flamex. 153 Spark detection Detectors watch for sparks

78 Spark suppression If a spark is detected, a spray nozzle is activated downstream that is timed to extinguish the spark as air flow carries it through the system. 155 GreCon video

79 Detect, suppress, detect, abort A second set of detectors is often installed to ensure the first zone was successful. If a spark is detected again, the system may activate a second spray along with a high-speed abort gate. 157 High-speed abort gates Designed to re-direct an explosion s heat and pressure to a safe area The gate is activated instantly by the detection system to divert all return air to outside atmosphere

80 Isolate and limit spread Options for isolation include dampers in the pneumatic ductwork. This includes both the dirtyair intake piping, as well as any clean air re-entering the facility Protects the interior of the building and any occupants 159 Gravity dampers on infeed

81 Gravity swing-dampers Often indicated by a pivot bearing where the gravity-damper swings Usually equipped with a counterweight arm to assist with operation 161 Fusible-link fire dampers Protects only against a smoldering fire within the dust unit Activated by the melting of a fusiblelink, which allows the release of an accordion-type damper to close off the duct. Fusible-link dampers are often indicated by raised segment on return air line

82 Fusible-link drop dampers Several types exist, such as accordion or drop-gate dampers: All work to prevent fire spread to unaffected areas 163 Rotary air lock Inside the air lock chamber is a rotating baffle, similar in design to a revolving door This allows the dust to enter from the top, and as the baffle rotates around, the dust falls out without air flow Also ensures an explosion follows a preferred route

83 Know your dust! Evaluate the potential Must have a strict dust management plan Housekeeping must be stressed! Know what you need to do to prevent incidents to reduce effects of an incident to assist you in response to an incident 165 Combustible dust situations don t always have to end poorly. Prevention is of the utmost importance. Housekeeping is the most critical point. Maintenance must prevent leaks and ignition Operators and supervisors must be trained Proper engineering and equipment Trained, knowledgeable responders

84 For more information Benjamin Peetz, ASP CFPS Senior Loss Prevention Specialist Lumbermen's Underwriting Alliance N Meridian Street, Suite 230 Indianapolis, IN Cell: (812) benjamin.peetz@ins-lua.com