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8/13/2010
1
GTRI_B-1
Combustible Dust: Quick & Dirty
Kristen Butler & Thomas Dean
Georgia Tech Research Institute
404-407-6643 & 404-407-8083
GTRI_B-2
This Presentation Describes:
• Hazards of combustible dust
• Work practices
• Guidelines
• Training to protect employees
• OSHA’s National Emphasis Program
GTRI_B-3
BackgroundOrganic Dust Fires and
Explosions:
• North Carolina (polyethylene powder)
(6 killed, 38 injured)
• Kentucky (phenolic resin)
(7 killed, 37 injured)
Georgia (sugar dust)
(14 killed, 36 injured)
8/13/2010
2
GTRI_B-4
Organic Dust Fire and Explosion: North Carolina
• Combustible polyethylene
dust accumulated above
suspended ceilings at
pharmaceutical plant
• A fire at the plant caused
dust to be dispersed and
explode in the ceiling
space
• 6 were killed, 38 injured
• Plant and nearby buildings
were severely damaged
GTRI_B-5
Organic Dust Fire and Explosion: North Carolina
The causes of the incident cited by the Chemical
Safety Board (CSB) included inadequacies in:
• Hazard
assessment;
• Hazard
communication;
• Engineering
management.
GTRI_B-6
Organic Dust Fire and Explosion: Kentucky
• A fire at an unattended oven
ignited a dust cloud created by
cleaning operations at a facility
making fiberglass insulation for
the automotive industry.
• The explosion was fueled by
resin dust accumulated in a
production area,
• The resin involved was a
phenolic binder used in
producing fiberglass mats.
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3
GTRI_B-7
Organic Dust Fire and Explosion: Kentucky
The CSB identified
• ineffective dust control and
• explosion prevention /mitigation
Both of these causes involved
problems relating to
• Hazard assessment;
• Hazard communication;
• Maintenance procedures;
• Building design; and,
• Investigation of previous fires.
GTRI_B-8
Organic Dust Fire and Explosion: Georgia
GTRI_B-9
Organic Dust Fire & Explosion: Georgia
• CSB Identified Key Issues:
• Combustible Dust Hazard Recognition
• Minimizing Combustible Dust Accumulation in the Workplace
• Equipment Design and Maintenance
• The CSB concluded that the secondary dust explosions would have been highly unlikely had Imperial Sugar performed routine maintenance on sugar conveying and packaging equipment to minimize dust releases and sugar spillage, and promptly removed accumulated dust and spilled sugar. When sugar dust and sugar escaped the equipment in the packing buildings, timely housekeeping activities should have been performed to remove accumulations from elevated horizontal surfaces and spilled granulated and powdered sugar on the floors before the sugar accumulated to hazardous levels.
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GTRI_B-10
Fire Triangle
Fuel
Oxygen
Ignition
GTRI_B-11
Dust Explosion Requirements
Adapted from CSB
Fuel Ignition
DispersionConfinement
Oxygen
GTRI_B-12
Some event
disturbs the
settled dust
into a cloud
Dust cloud is
ignited and
explodes
Dust explosion in a work area
Dust settles on flat
surfacesDust
Adapted from CSB
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5
GTRI_B-13
Thin Dust Layers Can Be Dangerous
GTRI_B-14
Dust explosions
An initial (primary) explosion in
• processing equipment or in an area where fugitive dust has accumulated
• may shake loose more accumulated dust, or
• damage a containment 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
GTRI_B-15
Facility Dust Hazard Assessment
• pharmaceuticals,
• dyes,
• coal,
• metals (e.g., aluminum, chromium, iron, magnesium, and zinc), and
• fossil fuel power generation.
Combustible dust explosion hazard may exist in a
variety of industries
• food (e.g., candy, starch, flour, feed),
• plastics,
• wood,
• rubber,
• furniture,
• textiles,
• pesticides,
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GTRI_B-16
Facility Dust Hazard Assessment
“. . .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.”
(NFPA’s Industrial Fire Hazards Handbook)
GTRI_B-17
Particles and Powders*
Size
• Pellets > 2mm diameter
• Granules 0.42mm and 2mm,
• dust particles < 0.42mm (420μm)
Hazard increases as particle size decreases
• Larger surface area for combustion
• Fine particle may have a larger role in dust cloud ignition and explosion propagation.
GTRI_B-18
Particles and Powders*
Dusts may occur in the process stream and cause a hazard, regardless of starting particle size of the material
may
break
into
or
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GTRI_B-19
Facility Analysis Components
Carefully identify:
• Materials that can be combustible when finely divided;
• Processes which use, consume, or produce combustible dusts;
• Open areas where combustible dusts may build up;
• Hidden areas where combustible dusts may accumulate;
• Means by which dust may be dispersed in the air; and
• Potential ignition sources.
GTRI_B-20
Facility Analysis Components
Identify and follow the applicable federal, state, and local laws and regulations. Some commonly applicable mandatory requirements
• OSHA General Duty Clause and Standards
• The International Code Council’s International Fire Code®
• NFPA’s Uniform Fire Code®.
29 CFR 1910
– Local building codes frequently adopt NFPA dust
standards by reference
GTRI_B-21
See
Explosives
Regulations
Dust Combustibility
The primary factor in an assessment of these hazards is whether the dust is in fact combustible.
*Determine if a dust cloud will:
• Detonate
• Deflagrate
• Present a fire hazard
• Or will Not burn or ignite
Testing may be necessary
8/13/2010
8
GTRI_B-22
Dust Combustibility
Combustible dust per NFPA 654
• Prior to 2006 - “Any finely divided solid material that is 420 microns or smaller in diameter (material passing a U.S. No. 40 Standard Sieve) and presents a fire or explosion hazard when dispersed and ignited in air.”
• *2006 Edition – 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.
GTRI_B-23
Dust Combustibility
• *OSHA workplace health Limits (PELs) 2.5 ug/m3
(.0000025g/m3) through 15 mg/m3 (.015 g/m3)
• Explosive range for combustible dusts 15 g/m3
through (Approx.) 1200 g/m3
0 250 500 750 1000 g/m3
Dust cloud concentration
GTRI_B-24
*25 watt light bulb probably can not be seen
through ten feet of a combustible dust mixture
Dust Combustibility
What
bulb
?
25 watts
2 meters
Glass Glass
40 g/m3 concentration of
comb. dust suspended in air
8/13/2010
9
GTRI_B-25
What is wrong here?
GTRI_B-26
Dust Combustibility
Information sources (some better than others)
• “As used” test data
• Chemical supplier test data
• MSDS sheets
• Published tables Variables• Particle size,
• Shape
• Moisture content.
• Changes in the material
produced by process
equipment.
• Many others
GTRI_B-27
Electrical classification
• OSHA Electrical standard (29 CFR Part 1910 Subpart S)
• NFPA 70, the National Electrical Code®.
• NFPA 499, . . . Classification of Combustible Dusts and of Hazardous (classified) Locations for Electrical Installations in Chemical Process Areas.
Electrical
EquipmentClass II
Division 1
Division 2
Group A
B
C
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GTRI_B-28
Electrical Classification
GTRI_B-29
Other Hazard Analysis Considerations
Some subjective (and not always accurate) rules of thumb
*Begin cleaning when dust reaches
• When you can write in it
• When it obscures the color of the surface
• 1/64th inch thick
• 1/32nd inch thick
• 1/16th inch thick
• 1/8th inch thick
• Really no need to clean - if it hasn’t exploded by now, it won’t
GTRI_B-30
CPL 03-00-008 – National Emphasis Program
“immediate cleaning is warranted whenever a dust layer of 1/32-
inch thickness accumulates over a surface area of at least 5% of
the floor area of the facility or any given room. The 5% factor
should not be used if the floor area exceeds 20,000 ft2, in which
case a 1,000 ft2 layer of dust is the upper limit. Accumulations
on overhead beams, joists, ducts, the tops of equipment, and
other surfaces should be included when determining the dust
coverage area. Even vertical surfaces should be included if the
dust is adhering to them. Rough calculations show that the
available surface area of bar joists is approximately 5 % of the
floor area and the equivalent surface area for steel beams can be
as high as 10%.”
8/13/2010
11
GTRI_B-31
Dust Control
NFPA 654 - contains comprehensive guidance
Some of its recommendations:
• Minimize the escape of dust from process equipment or ventilation systems;
• Use dust collection systems and filters;
• Utilize surfaces that minimize dust accumulation and facilitate cleaning;
Spots are
not
raindrops
GTRI_B-32
?
Dust Control
NFPA 654 –guidance
• Provide access to all hidden areas to permit inspection;
• Inspect for dust residues in open and hidden areas, at regular intervals;
• Clean dust residues at regular intervals;
GTRI_B-33
Dust Control
NFPA 654 – guidance
• Use cleaning methods that do not generate dust clouds, if ignition sources are present;
• Only use vacuum cleaners approved for dust collection;
HAZ LOC
8/13/2010
12
GTRI_B-34
Ignition Control
NFPA 654, identifies comprehensive guidance
• Use appropriate electrical equipment and wiring methods;
• Control static electricity, including bonding of equipment to ground;
• Control smoking, open flames, sparks;
No!
GTRI_B-35
Ignition Control
NFPA 654 - guidance
• Control mechanical sparks and friction;
• Use separator devices to remove foreign materials capable of igniting combustibles from process materials;
• Separate heated surfaces from dusts;
Magnetic
Core
Non - Magnetic
rotating drum
GTRI_B-36
Ignition Control
NFPA 654 - guidance
• Separate heating systems from dusts;
• Proper use and type of industrial trucks;
• Proper use of cartridge activated tools; and
• Adequately maintain equipment.
Hot
work
permit_________
_________
_________
_________
Grinder
Kaboom!
8/13/2010
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GTRI_B-37
Ignition Control
Other ignition sources
Use appropriate Class II Electrical equipment and wiring methods where required
OSHA 29 CFR 1910.178 (c) regulates powered industrial trucks in dust areas
Coal handling operations must comply with OSHA 29 CFR 1910.269
Class I & II
Group D & G
GTRI_B-38
Hazardous
vertical surface
accumulation
Training
Employees need to be trained
• To recognize and prevent hazards associated with combustible dust
• In taking preventative action, and/or
• How to alert management.
GTRI_B-39
Training
Employees need to know
• The safe work practices applicable to their job tasks,
• The overall plant programs for dust control and ignition source control.
Training must be
• Before they start work
• Periodically to refresh their knowledge
• When reassigned
• When hazards or processes change
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GTRI_B-40
Training Management Responsibility
• Comply with the Hazard Communication Standard
• Have a qualified team conduct a facility analysis (or have one done by qualified outside persons) prior to the introduction of a hazard and
• Develop a prevention and protection scheme tailored to the operation.
List of
Chemicals
GTRI_B-41
Training
Supervisors and managers should be aware of and support the plant dust and ignition control programs.
Their training should include identifying how they can encourage the reporting of unsafe practices and facilitate abatement actions.
GTRI_B-42
NEP/ Industry Application• Food products
• 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
8/13/2010
15
GTRI_B-43
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 02-01-004, Inspection of Grain Handling Facilities, 29 CFR 1910.272
• Not intended for inspections of explosives and pyrotechnics manufacturing facilities covered by the Process Safety Management (PSM) standard (1910.119)
• Does not exclude facilities that manufacture or handle other types of combustible dusts (such as ammonium perchlorate) covered under the PSM standard
GTRI_B-44
Georgia Regulations –Effective January 1, 2010
Regulations of the Safety Fire Commissioner Chapter 120-3-24-0.12 Rules and Regulations for Loss Prevention Due to Combustible Dust Explosions and Fire.
• Establishes minimum fire safety standards and requirements in all facilities that handle combustible particulate solids.
• Key provisions of the new regulation include
• covered facilities will be required to file an annual registration to the GA Safety Fire Commissioner
• compliance with applicable International Fire Code and NFPA standards addressing combustible dust;
• written safety procedures;
• employee training and periodic refresher training;
• written evacuation plans and periodic drills;
• annual reports on training and evacuation;
• fire alarm systems and other emergency egress design features as provided in NFPA 101, Life Safety Code and the International Fire Code.
GTRI_B-45
Primary Applicable OSHA Standards
1910.22 General – Housekeeping
1910.307 Hazardous (Classified) Locations
1910.178 Powered Industrial Trucks
1910.263 Bakery Equipment
1910.265 Sawmills
1910.272 Grain Handling
General Duty Clause
8/13/2010
16
GTRI_B-46
NFPA Standards – Dust Hazards61 Agriculture
68 Deflagration Venting Systems
69 Explosion Prevention Systems
70 National Electric Code
77 Static Electricity
85 Boiler and CombustionSystems
86 Ovens and Furnaces
91 Exhaust Systems
GTRI_B-47
NFPA Standards Electrical & Systems
484 Combustible Metals
Includes Magnesium, Titanium, Zirconium, Aluminum, Tantalum and other reactive metals
499 Classification of Combustible Dust
654 manufacturing, Processing and Handling of Combustible Particulate Solids
655 Sulfur
664 Wood
and more
GTRI_B-48
Database of Combustible Dust
• BGIA GESTIS-DUST-EX Database of Combustion and Explosion Characteristics of Dusts
• Important characteristics of more than 4000 dust samples from virtually all sectors of industry
• Developed in Germany with the financial support of the EC
48
8/13/2010
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GTRI_B-49
Database of Combustible Dust
• There are limits of applicability of the data
• a wide variation is possible in the nature of the dusts
• e.g., composition, particle size distribution, surface structure, moisture content, etc.
• the numerical value of the characteristics depend on the test methods
• Always be aware that the values listed only serve as a guideline for the design of preventive and protective measures.
http://www.hvbg.de/e/bia/gestis/expl/index.html
49
GTRI_B-50
Citations
• Typical hazards
• Accumulation of combustible dust in areas which have/may have ignition sources
• Lack of, or inadequate, explosion mitigation
• Failure to control ignition sources inside equipment
• Cleaning dust with non-explosion proof equipment (e.g., vacuums)
GTRI_B-51
Citations
• Typical hazards (con’t)
• Cleaning dust with compressed air (electrostatic issue)
• PPE
• Inadequate Ventilation
• HazCom training
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GTRI_B-52
QUESTIONS?