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Combustible Dust: Quick & Dirty

Kristen Butler & Thomas Dean

Georgia Tech Research Institute

404-407-6643 & 404-407-8083

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This Presentation Describes:

• Hazards of combustible dust

• Work practices

• Guidelines

• Training to protect employees

• OSHA’s National Emphasis Program

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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)

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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

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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.

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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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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.

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Organic Dust Fire and Explosion: Georgia

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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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Fire Triangle

Fuel

Oxygen

Ignition

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Dust Explosion Requirements

Adapted from CSB

Fuel Ignition

DispersionConfinement

Oxygen

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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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Thin Dust Layers Can Be Dangerous

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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

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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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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)

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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.

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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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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.

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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

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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

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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.

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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

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*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

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What is wrong here?

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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

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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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Electrical Classification

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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

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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%.”

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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

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?

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;

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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

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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!

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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

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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!

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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

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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.

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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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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

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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.

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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

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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

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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.

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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

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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

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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

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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

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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

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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)

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Citations

• Typical hazards (con’t)

• Cleaning dust with compressed air (electrostatic issue)

• PPE

• Inadequate Ventilation

• HazCom training

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QUESTIONS?