National Emphasis Program

National Emphasis Program
Combustible Dust National Emphasis Program Combustible Dust Oxygen in Air Ignition Source Dispersion Confinement Explosion FIRE Deflagration Combustible Dust

Background History of Combustible Dust Incidents
Overview of Combustible Dust NEP Hazard Mitigation Techniques Resources

Select Catastrophic Combustible Dust Incidents since 1995

Combustible Dust Explosions History
Malden Mills

Malden Mills 12/11/1995 Lawrence , MA 13 hospitalized No citations
Made nylon fibers and suspected the static electricity ignited the fibers that were glues to make fibers stand on end in the fleece making process. The employer manufacturers various types of textile products for upholstery and clothing. One production process for an upholstery product is known as flocking. During this process, small chemically-treated nylon fibers are applied to a fabric backing using an electrical field. Three of the company's five flock lines are located on the first through third floors and were in operation. A sudden explosion/deflagration occurred on the first floor, originating at the beginning of the production lines where some employees were cleaning. The explosion/deflagration moved throughout the entire first floor of the building with great force, leaving only small incidental fires. Employees #1 through #13 were injured. Employees located closest to the explosion suffered multiple burns. Employees further away sustained less severe burns. Some injured employees were located on the second floor directly above the explosion point. They sustained minor injuries, smoke inhalation, bruise and contusions. Some of the employees who helped with a search and rescue were treated for smoke inhalation. The explosion was caused by an electrical spark which ignited a combustible nylon fiber dust cloud in the hopper room at the beginning of a production line. The hopper room is where the nylon fibers are applied to the cloth backing. 37 people were injured in an explosion of nylon fibers. Even though the facility was completely destroyed, the owner of the company kept the employees on the payroll long after the explosion. The Malden Mills explosion was likely ignited by the static electricity used to make the fibers stand on end, where they could be glued to fabric to make fleece.

Firefighting efforts following the explosion at Malden Mills (Methuen, Massachusetts, December 11, 1995).

Jahn foundry A

Jahn Foundry 2/25/1999 Springfield, MA 3 fatalities, 9 hospitalized
General duty, electrical and housekeeping. $115k Secondary explosion ignited phenol formaldehyde resin. Initial cause is not sure. Heavy deposits of resin dust were found in the flexible exhaust ducts serving the ovens in the shell molding stations Employees #1 through #12 were in the shell mold department when there was a large explosion. All twelve sustained burns, from which Employees #6, #8, and #12 died. Employees #1 through #5, #7, and #9 through #11 were hospitalized. OSHA and fire investigators determined that the damage was caused by secondary explosions of accumulated resin within exhaust ductwork throughout the building. He noted that the investigation determined that an initiating fire event in one of the Shell Mold stations in the Shell Mold Building was pulled into the exhaust ventilation system. The interior of the ductwork of that system was heavily loaded with deposits of phenol formaldehyde resin, an explosive organic dust. The ignition of this dust caused a turbulent fire and explosion(s) which traveled through the interior ductwork and in turn shook down explosive concentrations of combustible resin dust that had collected on surfaces throughout the Shell Mold Building. When the fire exploded out from the ductwork, it ignited these airborne concentrations of combustible dust, causing a catastrophic dust explosion which lifted the building's roof and blew out its walls. The report notes that, although it was not possible to conclusively determine the initiating event which caused the resultant dust explosion, a number of plausible scenarios were developed from the physical and testimonial evidence. Of these, the following two were determined to be the most probable: Dust Scenario: Heavy deposits of resin dust were found in the flexible exhaust ducts serving the ovens in the shell molding stations. The open ends of the ducts were placed adjacent to the ovens, at approximately head level, and in an area where employees must present themselves to deal with the ovens. Jarring of the duct readily dislodged the deposits of dust. In this scenario, jarring of the duct caused dust to fall down onto the oven and be ignited. The resulting fireball was then pulled back into the flexible duct where it started the turbulent fire and explosions in the exhaust ventilation system. Gas Scenario: The fuel trains to the ovens in the shell molding stations were found to be in very bad condition. The internal mechanisms of the valves controlling the flow of combustion air and natural gas to the ovens were found to be massively contaminated with resin and sand. The proper functioning of these valves was critical for providing air and gas to the ovens in the correct ratio to support combustion. Oven flameouts were a recurrent problem. The ovens were not provided with a flame-sensing device to prevent the flow of gas to the oven in the absence of main flame. Although a switch and thermocouple prevented the flow of gas to the oven in the absence of a pilot flame, the pilot flame was not able to light the burners. Thus, in the absence of a main flame, gas could continue to flow to the oven. In this scenario, gas was flowing to an oven that was not lit. The unburned gas collected in sufficient quantities to finally be ignited by the pilot or other ignition source, and the resulting fireball was pulled into the flexible duct where it started the turbulent fire and explosions in the exhaust ventilation system. The report found that inadequate housekeeping, ventilation, maintenance practices and equipment were all causal factors for the initiating and catastrophic events.

Ford River Rouge: Killed six workers and injured 36

Ford River Rouge Power Plant
2/1/1999 Dearborn , MI General Duty egregious, 1.5M Natural gas boiler explosion triggered secondary coal dust explosion that had accumulated on building and equipment surfaces On February 1, 1999 a natural gas explosion at the power plant for the Ford River Rouge facility near Dearborn, Michigan, triggered subsequent secondary explosions of coal dust that had accumulated on surfaces in the plant. Six people died and another 30 were injured. The power plant had to be completely rebuilt. Six employees were taking a boiler off-line for maintenance. A natural gas valve was inadvertently left open. When a secondary butterfly valve was opened for purging, gas entered the unfired boiler which was still hot. This resulted in an explosion in the boiler and that explosion caused secondary explosions from coal dust that had accumulated on building and equipment surfaces. All six employees were killed in the explosion.

Rouse Polymerics

Rouse Polymerics 5/16/2002 Vicksburg, MS 5 fatalities, 7 injured
23 serious, 2 unclassified 210K to 187k Fire in the baghouse, then rubber dust explosion

January 29, West Pharmaceutical Services, Kinston, NC Six deaths, dozens of injuries Facility produced rubber stoppers and other products for medical use Combustible dust was ignited by some ignition source causing an initial explosion in the Milling Room, which dislodged ceiling tiles, steel beams, and wall panels, and also putting a large quantity of combustible dust from these areas into suspension, which was added fuel to the blast wave from the first explosion, creating a second and larger explosion, that exited through the roof of the Northeast tower section of the building, in the ACS area. Three workers were killed from this explosion on 1/29/03 and three other workers died later (1/31/03 to 3/03/03), in the UNC Burn Center in Chapel Hill, NC. 85/86 Citations were deleted. $602K to $100k was the final serious penalty for a single general duty violation.

West Pharmaceutical facility destroyed by polyethylene dust
Another photo of the virtual destruction of the plant West Pharmaceutical facility destroyed by polyethylene dust

West Pharmaceutical Services
Combustible dust was ignited by some ignition source causing an initial explosion in the Milling Room, which dislodged ceiling tiles, steel beams, and wall panels, and also putting a large quantity of combustible dust from these areas into suspension, which was added fuel to the blast wave from the first explosion, creating a second and larger explosion.

CTA Acoustics 02/20/2003 Corbin , KY 7 fatalities, 37 injured
4 serious including b, 28k 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. Only three weeks after the explosion in North Carolina, another deadly blast occurred in Corbin, Kentucky, at the CTA Acoustics facility. Thirty-seven people were injured, and seven workers died, some weeks after the explosion from severe burn injuries. This photo shows one of the many production areas where workers were caught in secondary dust explosions that traveled from one production line to the next. On February 20, 2003, at approximately 7:30am an explosion occurred at CTA Acoustics, Inc. in Corbin, KY. The explosion and subsequent fires resulted in the injury of 45 employees, 18 of which were hospitalized. Of the 18 employees hospitalized, six later succumbed to their injuries. Most injuries consisted of 1st, 2nd and 3rd degree burns. Other injuries included lacerations, smoke inhalation, and one knee fracture. The explosion occurred in the area of the facility's production lines known as Lines 405, 403, 402 and 401, which produce a fiberglass/resin blend automotive insulation. The explosion damaged all lines with the most significant damage on Lines 405 and 403. Damage to the facility included blown out roof decking, fire and blast damage to the dust collection system on the equipment. At the time of the explosion, employees were beginning their shift and the four lines were being prepared to run product. All of the seriously injured were working on or near the four lines when the explosion occurred as supervisors, machine or oven operators, or product inspectors. two of the injured line employees were working on the roof performing maintenance duties on the dust collection system for line 405.

October 29, Hayes Lemmerz Manufacturing Plant Two severely burned (one of the victims died) Accumulated aluminum dust Facility manufactured cast aluminum automotive wheels

Hayes Lemmerz International
10/29/2003 Huntington IN One fatality, one injured 6 serious, 42k General duty and b cited A dust collector attached to the recycling equipment exploded. The explosion propagated through piping to a furnace where the burned employees were working Hayes Lemmerz aluminum foundry in Huntington, Indiana. Two workers were engulfed in flames from an aluminum dust explosion. One of those workers died later that evening; another spent weeks in the burn unit. Hayes remelted scrap aluminum in their automotive wheel casting plant. A dust collector attached to the recycling equipment exploded. The explosion propagated through piping to a furnace where the burned employees were working. On at about 8:25 PM the facility experienced a major explosion and fire in the number 5 furnace area that killed one employee and severely burned another. 5 others were transported to emergency care facilities and released after treatment, these included 3 Hayes Lemmerz employees and two contract employees doing foundry stack testing. The day of the explosion at about 3:00 P M a fire was reported in the number 5 furnace chip melt side well exhaust duct. The maintenance department was sent to evaluated the fire and shut the exhaust ventilation system down to allow the fire in the pipe to self extinguish as this was the plant policy for aluminum dust fires in the pipe. About 8:10 or 8:15 the employees started the system up after the pipe had cooled and been cleaned out by the employees. An employee who was working in the area that evening states in his statement in part the night of the event we had to wait for a smoldering in the multi clone pipe to go out then we cleaned the ash out of the pipe started multiclone blower checked for proper operation turned on the dry chip blower #3 then the auger checked multiclone for proper operation we were starting to leave when a big flash came out of the well where the chips feed in this moved the dust off of the ceiling & ignited it causing a ball of fire to move through the room it also destroyed equipment outside the building & started many small fires inside the building in that area.

Types of Dust Involved in incidents
Coal Food Plastic Wood Metal

Types of Industries Involved in Dust Incidents

Dust Incidents, Injuries, and Fatalities

What Combustible Dusts are explosible?
Some Metal dust Wood dust Coal and other carbon dusts. Plastic dust Biosolids Organic dust such as sugar, paper, soap, and dried blood. Certain textile materials

What metal dusts are explosive?
B – 110 MEC g/m3 Mg – 15.7 AL – Si – 200 S – 100 Ti – 70 Cr – undetermined Fe – Ni - NF Zn – 300 to NF Nb – 420 to undetermined Mo – NF Sn – 450 Hf – 180 Ta – 400 W – 700-undetermined Pb - NF

Which Industries have Potential Dust Explosion Hazards?
Agriculture Chemical Textile Forest and furniture products Metal Processing Paper products Pharmaceuticals Recycling operations (metal, paper, and plastic recycling operations.) Coal Power plants and coal processing facilities

CSB Recommendations To OSHA
1) Issue a standard designed to prevent combustible dust fires and explosions in general industry 2) Revise the Hazard Communication Standard (HCS) ( ) to clarify that the HCS covers combustible dusts Communicate to the United Nations Economic Commission (UNECE) the need to amend the Globally Harmonized System (GHS) to address combustible dust hazards Provide training through the OSHA Training Institute (OTI) on recognizing and preventing combustible dust explosions. While a standard is being developed, implement a National Special Emphasis Program (SEP) on combustible dust hazards in general industry

Definitions and Terminology
What is Combustible Dust? NFPA 654 (2006) Definitions Combustible dust. A combustible particulate solid that presents a fire or deflagration hazard when suspended in air or some other oxidizing medium over a range of concentrations, regardless of particle size or shape. Combustible Particulate Solid. Any combustible solid material composed of distinct particles or pieces, regardless of size, shape, or chemical composition. Hybrid Mixture. A mixture of a flammable gas with either a combustible dust or a combustible mist.

What is Combustible Dust? NFPA 69 (2002), and 499 (2004) Definitions Combustible Dust. Any finely divided solid material 420 microns or less in diameter (i.e., material passing through a U.S. No 40 Standard Sieve) that presents a fire or explosion hazard when dispersed 1 micron (µ) = 1.0 x 10-6 m = 1.0 x 10-4 cm = 1.0 x 10-3 mm 420 µ = 420 x 10-4 cm = .042 cm = 0.4mm A typical paper thickness is approximately 0.1mm

Particle Size of Common Materials

Class II Locations Class II locations are those that are hazardous because of the presence of combustible dust. The following are Class II locations where the combustible dust atmospheres are present: Group E. Atmospheres containing combustible metal dusts, including aluminum, magnesium, and their commercial alloys, and other combustible dusts whose particle size, abrasiveness, and conductivity present similar hazards in the use of electrical equipment. Group F. Atmospheres containing combustible carbonaceous dusts that have more than 8 percent total entrapped volatiles (see ASTM D 3175, Standard Test Method for Volatile Matter in the Analysis Sample of Coal and Coke, for coal and coke dusts) or that have been sensitized by other materials so that they present an explosion hazard. Coal, carbon black, charcoal, and coke dusts are examples of carbonaceous dusts. Group G. Atmospheres containing other combustible dusts, including flour, grain, wood flour, plastic and chemicals.

Deflagration Vs. Explosion
Definitions and Terminology Deflagration Vs. Explosion Deflagration. Propagation of a combustion zone at a speed that is less than the speed of sound in the unreacted medium. Detonation. Propagation of a combustion zone at a velocity that is greater than the speed of sound in the unreacted medium. Explosion. The bursting or rupture of an enclosure or a container due to the development of internal pressure from deflagration. Deflagration Explosion Detonation

How are MEC and LFL Different?
Definitions and Terminology How are MEC and LFL Different? Minimum Explosible Concentration (MEC) The minimum concentration of combustible dust suspended in air, measured in mass per unit volume that will support a deflagration. The lower flammable limit is the lowest concentration of a combustible substance in an oxidizing medium Lower Flammable Limit (LFL) Upper Flammable Limit (UFL) The upper flammable limits is the highest concentration of a combustible substance in an oxidizing medium that will propagate a flame.

Explosible Range Source: Dust Explosions in the Process Industries, Second Edition, Rolf K Eckhoff

Minimum Ignition Temperature (MIT). The lowest temperature at which ignition occurs. Lower the particle size – Lower the MIT Lower the moisture content - Lower the MIT Minimum Ignition Energy (MIE). The lowest electrostatic spark energy that is capable of igniting a dust cloud. Energy Units (millijoules) Decrease in particle size and moisture content – decreases MIE An increase in temperature in dust cloud atmosphere - decreases MIE Deflagration Index, Kst – Maximum dp/dt normalized to 1.0 m3 volume. Pmax – The maximum pressure reached during the course of a deflagration.

Deflagration Index - Kst
Kst = (dP/dt)max V1/3 (bar m/s) where: (dP/dt) max = the maximum rate of pressure rise (bar/s) V = the volume of the testing chamber (m3) Dust explosion class Kst (bar.m/s) Characteristic St 0 No explosion St 1 >0 and <=200 Weak explosion St 2 >200 and <=300 Strong explosion St 3 >300 Very strong explosion

The “Typical” Explosion Event
Process Equipment Initial Internal Deflagration Time, msec.

Process Equipment Initial Internal Deflagration Shock Wave Time, msec.

Process Equipment Initial Internal Deflagration Elastic Rebound Shock Waves Time, msec.

Process Equipment Initial Internal Deflagration Dust clouds caused by Elastic Rebound Time, msec.

Process Equipment Containment Failure from Initial Deflagration Dust Clouds Caused by Elastic Rebound Time, msec.

Process Equipment Secondary Deflagration Initiated Dust Clouds Caused by Elastic Rebound Time, msec.

Process Equipment Secondary Deflagration Propagates through Interior Time, msec.

Secondary Deflagration Vents from Structure Process Equipment Time, msec.

Secondary Deflagration Causes Collapse and Residual Fires Time, msec. Diagrams Courtesy of John M. Cholin, P.E., FSFPE, J.M. Cholin Consultants, Inc.

Dust Handling Equipment

Types of Equipment Used in Dust Handling
Bag Openers (Slitters) Blenders/Mixers Dryers Dust Collectors Pneumatic Conveyors Size Reduction Equipment (Grinders) Silos and Hoppers Hoses, Loading Spouts, Flexible Boots

USA 42% Equipment Involved in Dust Explosions
Source: Guidelines for Safe Handling of Powders and Bulk Solids, CCPS, AICHE

Blenders/Mixers Heat Generation due to
Rubbing of Solids Rubbing of internal parts Electrostatic Charging of the Solids Dust Formation inside of the equipment Source:

Dust Collectors 42% Fabric Filters (Baghouses)
Presence of easily ignitable fine dust atmosphere and high turbulence Experienced many fires over the years due to broken bags. Ignition source is electrostatic spark discharges Another ignition source is entrance of hot, glowing particles into the baghouse from upstream equipment

Aluminum Dry Dust Collector
Dry Type collectors located outside Explosive Dust Warning sign on collector Collectors or cyclone have temperature alarms No recycling of air from powder collectors Collector ductwork blanked before repairs Filter cannot be synthetic Dust removed AT LEAST once a day Dust put in sealed tight metal containers

Pneumatic conveying system
Downstream equipment have high rate of risk for fires and explosion Static electricity is generated from particle to particle contact or from particle to duct wall contact. Heated particles which are created during grinding or drying may be carried into the pneumatic conveying system and fanned to a glow by high gas velocity. Tramp metal in the pneumatic system may also cause frictional heating. Charged powder may leak from joints to the atmosphere and electrostatic sparking can occur resulting in an explosion. Figure source:

Aluminum Bonding between containers transferring powder aluminum
Explosive vents (if provided) vent to the outside Conveyor velocity 4500 ft/min for pneumatic conveyor

Duct Velocity? Significant dust and chip accumulation.

Pneumatic conveying systems (Cont.)
Prevention and Protection systems Venting Suppression Pressure Containment Deflagration Isolation Spark detection and extinguishing system Use of inert conveying gas

Silos and Hoppers No inter-silo Venting
Silos and hoppers shall be located outside the buildings with some exceptions Air cannons not to be used to break bridges in silos Detection of smoldering fires in silos and hoppers can be achieved with methane and carbon monoxide detectors Pressure containment, inerting, and suppression systems to protect against explosions Venting is the most widely used protection against explosions

Hazard Mitigation

Hazard Mitigation Dust control Ignition source control Damage control

Dust Control Design of facility & process equipment
Contain combustible dust Clean fugitive dust Regular program Access to hidden areas Safe cleaning methods Maintenance

Aluminum Machining operations provided with dust collection
Daily removal of turnings and chips Grinding operation dust collection separate from buffing/polishing operations Vacuum Cleaners only used that are approved for aluminum dust No compressed air cleaning unless no other method available.

Dust Layer Thickness Guidelines
1/8” in grain standard Rule of thumb in NFPA 654 1/32” over 5% of area Bar joist surface area ~ 5% Max 20,000 SF Idealized Consider point in cleaning cycle

Housekeeping Maintain dust free as possible
No blow down unless All electrical power and processes have been shutdown. No welding, cutting or grinding unless under hot-work permit Comfort heating equipment shall obtain combustion air from clean outside source.

Aluminum Building noncombustible
Surfaces where dust can collect have 55 degrees sloping design Explosion venting for aluminum powder processing building Note: For example, a 1/8 inch thick layer of dust, once disturbed, can easily form a dangerous cloud that could explode.

Ignition Source Control
Electrical equipment Static electricity control Mechanical sparks & friction Open flame control Design of heating systems & heated surfaces Use of tools, & vehicles Maintenance

Damage Control Construction
Detachment (outside or other bldg.) Separation (distance with in same room) Segregation (barrier) Pressure resistant construction Pressure relieving construction Pressure Venting Relief valves Maintenance

Explosion Venting The vent opening must be sized to allow the expanding gases to be vented at a rapid rate so that the internal pressures developed by the explosion do not compromise the structural integrity of the protected equipment The volume of the equipment to be protected The maximum pressure during venting (Pred) The KSt of the dust (or fundamental burning velocity of a gas) The burst pressure of the explosion

Explosion Venting NFPA 68
It is the discharge of heat and flame that make indoor application of explosion venting undesirable Vented flame igniting dusts or vapors indoors creates a secondary explosion hazard.

Damage Control Systems
Specialized detection systems Specialized suppression systems Explosion prevention systems Maintenance

NEP/ Industry Application
Agriculture Chemicals Textiles Forest and furniture products Metal processing Tire and rubber manufacturing plants Paper products Pharmaceuticals Wastewater treatment Recycling operations (metal, paper, and plastic.) Coal dust in coal handling and processing facilities.

Employee Training Extensive Employee training required
Hazards of the process Emergency Procedures Location of Electrical switches and alarms Fire fighting for incipient fires Evacuation Equipment operation, start up and shutdown, and response to upset conditions. Fan housing is eroded, which is typically caused by dust leaking through or past the filters.

Other Programs State plan participation in this national emphasis effort is strongly encouraged but is not required. does not replace the grain handling facility directive, OSHA Instruction CPL , Inspection of Grain Handling Facilities, 29 CFR not intended for inspections of explosives and pyrotechnics manufacturing facilities covered by the Process Safety Management (PSM) standard ( ) does not exclude facilities that manufacture or handle other types of combustible dusts (such as ammonium perchlorate) covered under the PSM standard.

CSHOs Safety and Health
PPE and Nonspark Producing Clothing Use of Cameras Use of Safe Practices when collecting dust samples

Primary Applicable OSHA Standards
General – Housekeeping Hazardous (Classified) Locations Powered Industrial Trucks Bakery Equipment Sawmills Grain Handling General Duty Clause General and industry-specific

Resources

Safety and Health Information Bulletin
Purpose Background Elements of a Dust Explosion Facility Dust Hazard Assessment Dust Control Ignition Control Damage Control Training References Purpose: hazard information & mitigation

NFPA Standards – Dust Hazards
654 General 664 Wood 61 Agriculture 484 Metal 480 Magnesium 481 Titanium 482 Zirconium 485 Lithium CSB advocated specifically for NFPA 654 & 484 General Duty Clause

NFPA Standards – Electrical & Systems
70 National Electric Code 499 Classification of Combustible Dust 68 Deflagration Venting Systems 69 Explosion Prevention Systems 91 Exhaust Systems

Combustible Dust NEP Any Questions?
The draft directive has been reviewed by both National and Regional Offices. Comments received during the review process have been addressed. Additionally, OSHA received extensive input from the Office of the Solicitors , along with their final concurrence. The directive was reviewed by the PPB and we received Secretarial approval in the last week of September and It was approved on October 18th.

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