Combustible Dust Hazards and Control Wes Hofmann Safety Engineer OSHA - St. Louis Area Office Sept....
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Transcript of Combustible Dust Hazards and Control Wes Hofmann Safety Engineer OSHA - St. Louis Area Office Sept....
Combustible Dust Hazards and Control
Wes Hofmann
Safety Engineer
OSHA - St. Louis Area Office
Sept. 2008
Why are we here??
To prevent and/or reduce the following:
Catastrophic Combustible Dust Incidents
Malden Mills
Methuen, MA
December 11, 1995
37 Injured
Nylon Fiber
Combustible Dust Explosions History
Firefighting efforts following the explosion at Malden Mills (Methuen, Massachusetts, December 11, 1995).
Combustible Dust Explosions History
Jahn Foundry
Springfield, MA
February 26, 1999
3 dead9 Injured
Phenolic resin dust
Combustible Dust Explosions History
• Ford River Rouge: • Secondary • Coal Dust Explosion• February 1, 1999• Killed 6 workers and
injured 36
Combustible Dust Explosions History
May 16, 2002Rouse PolymericsVicksburg, MS5 dead, 7 injuredRubber Dust
Combustible Dust Explosions History
• January 29, 2003 - West Pharmaceutical Services, Kinston, NC– 6 deaths, dozens of
injuries– Facility produced rubber
stoppers and other products for medical use
– Plastic powder accumulated above suspended ceiling ignited
West Pharmaceutical facility destroyed by polyethylene dust
Combustible Dust Explosions History
• February 20, 2003 • CTA Acoustics • Corbin, KY
– 7 Workers died– Facility produced
fiberglass insulation for automotive industry
– Resin accumulated in production area and was ignited
Combustible Dust Explosions History
• October 29, 2003• Hayes Lemmerz
Manufacturing Plant– Two severely
burned (one of the victims died)
– Accumulated aluminum dust
– Facility manufactured cast aluminum automotive wheels
Chemical Safety Board (CSB) Report Notes
• Notes from the CSB - US Dust Incidents 1980 to 2005*:
- “Dust incidents are a significant industry safety problem”
- On average “10 dust explosions per year”
- Nearly 5 fatalities and 29 injuries per year
- The annual rate is increasing
Dust Incidents, Injuries, Fatalities 1980-2005 [CSB Report]
FatalitiesInjuriesIncidents
Inju
ries
/ F
atal
itie
s
Inci
den
ts
Chemical Safety Board (CSB) Report Notes
• Notes from the CSB - US Dust Incidents 1980 to 2005*:
- 281 incidents recorded
- 119 fatalities
- 718 injuries
- 14 fatalities in three incidents in 2003.
Chemical Safety Board (CSB) Report Notes
• Notes from the CSB - US Dust Incidents 1980 to 2005*:
*CSB Investigative Report: Combustible Dust Hazard Study Nov. 9, 2006 (Database excluded grain, coal, transportation and non-manufacturing).
Types of Combustible Dusts
• Metal dust such as aluminum and magnesium
• Wood dust• Coal and other carbon dusts.• Plastic dust• Biosolids• Organic dust such as sugar,
paper, soap, and dried blood.• Certain textile materials• Candy, sugar, spice, flour, grain• Rubber• Fertilizer
Industries: Dust Explosion Hazards
Industries with potential dust explosion hazards:• Agriculture• Chemical • Textile • Forest and furniture products • Metal Processing • Paper products • Pharmaceuticals • Recycling operations (metal, paper, and plastic recycling
operations.)• Food
Fire Triangle - Dust Explosion Pentagon
FIRE TRIANGLE: DUST EXPLOSION PENTAGON:
Combustible Dust Oxygen in Air
Ignition Source (Heat)
Dispersion Confinement
Explosion
(Fuel)
Combustible Dust Explosion Pentagon: Five Elements – ALL Necessary
1. Combustible Dust (Fuel)
2. Oxygen in Air
3. Ignition Source
4. Dispersion
5. Confinement
1. Combustible Dust (Fuel)
2. Oxygen in Air
5. Confinement
3. Ignition Source
4. Dispersion
Explosion
IMPORTANTNO DUST EXPLOSION OCCURS
if one or more elements are missing
Element 1: Combustible Dust
Agricultural Products such as:• Corn Starch, Dry Milk, Sugar,
Wood Flour, Powered MilkAgricultural Dusts such as:• Cocoa Powder, Hops (malted),
Rice Flour, Wheat grain dustCarbonaceous Dusts such as: • Petroleum Coke, Pine Soot,
Bituminous Coal, Wood Charcoal.
Chemical Dusts such as:• Lactose, Sulfur, Calcium
Acetate, Methyl-CellulosePlastic Dusts such as:• Phenolic Resin,
(poly)Propylene, (poly)Vinyl Chloride, Melamine Resin
Metal Dusts such as:• Aluminum, Magnesium, Zinc,
Bronze
Fuel Source: Combustible Dust
Elements 1, 2, and 3 are part of the Fire Triangle
Element 2: Oxygen in Air
• The Oxygen content in air is all that is necessary to support an explosion.
Elements 1, 2, and 3 are part of the Fire Triangle
Element 3: Ignition Source
Can be Electrical • Static• Lighting or • Generated
Can be Mechanical• Match/lighter• Spark
Elements 1, 2, and 3 are part of the Fire Triangle
Element 4: Dispersion
Dispersion in the right concentration• Dust needs to be dispersed in the air
NOTE:
Elements 1, 2, 3, and 4 will cause a deflagration
Element 5: ConfinementExplosion
• Confinement can be provided by process equipment, ducting, piping, dust collection equipment, and the building (itself).
All 5 Elements = EXPLOSIONExplosion
Propagation of a Dust Explosion:2 Stages
Deflagration
Propagation of a Combustion Zone at a speed that is less than the speed of sound in the unreacted medium.
ExplosionThe bursting or rupture of an
enclosure or a container due to the development of internal pressure from deflagration.
(Remembering: The container could be the building structure itself.)
Secondary Explosions
As this animation illustrates, secondary explosions can be far more destructive than primary explosions due to the increased quantity and concentration of dispersed combustible dust.
The “Typical” Explosion Event
ProcessEquipment
InitialInternal Deflagration
Time, msec.0 25 50 75 100 125 150 175 200 225 250 300 325
Latent Dust throughout the facility
The “Typical” Explosion Event
ProcessEquipment
InitialInternal Deflagration
Shock Waves
Time, msec.
0 25 50 75 100 125 150 175 200 225 250 300 325
The “Typical” Explosion Event
ProcessEquipment
InitialInternal Deflagration
Elastic ReboundShock Waves
Time, msec.0 25 50 75 100 125 150 175 200 225 250 300 325
The “Typical” Explosion Event
Time, msec.0 25 50 75 100 125 150 175 200 225 250 300 325
ProcessEquipment
InitialInternal Deflagration
Dust clouds causedby Elastic Rebound
The “Typical” Explosion Event
ProcessEquipment
Containment Failure from InitialDeflagration
Dust Clouds Causedby Elastic Rebound
Time, msec.0 25 50 75 100 125 150 175 200 225 250 300 325
The “Typical” Explosion Event
ProcessEquipment
Secondary DeflagrationInitiated
Dust Clouds Causedby Elastic Rebound
Time, msec.0 25 50 75 100 125 150 175 200 225 250 300 325
The “Typical” Explosion Event
ProcessEquipment
Secondary DeflagrationPropagates through Interior
Time, msec.0 25 50 75 100 125 150 175 200 225 250 300 325
The “Typical” Explosion Event
ProcessEquipment
Secondary DeflagrationVents from Structure
Time, msec.0 25 50 75 100 125 150 175 200 225 250 300 325
The “Typical” Explosion Event
Secondary DeflagrationCauses Collapse and Residual Fires
Time, msec.0 25 50 75 100 125 150 175 200 225 250 300 325
Diagrams Courtesy of John M. Cholin, P.E., FSFPE, J.M. Cholin Consultants, Inc.
Definitions and Terminology What is Combustible Dust?
NFPA’s, NEP, & General Info.: • Definitions• Data (Particle size)• Electrical• Explosion Event• General Information
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.
Definitions and Terminology 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
Common Material Size (microns)
Table salt 100
White granulated sugar 450 - 600
Sand 50+
Talcum (baby) powder 10
Mold spores 10 – 30
Human hair 40 - 300
Flour 1 - 100
Source: Filtercorp International Ltd.
Increase of Surface Area
• Finer the particle > surface area = more explosive a dust is likely to be
• Dust made up of particle sizes from fine to coarse; fines play a more prominent role in explosion
• Presence of dusts should be anticipated in the process stream-regardless of starting particle size
Definitions and Terminology
• Class II Locations– Locations 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.
Definitions and Terminology
– Group F. Atmospheres containing combustible carbonaceous dusts that have more than 8 percent total entrapped volatiles as per ASTM D 3175 *, OR• Those 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.
• ASTM D 3175: Standard Test Method for Volatile Matter in the Analysis Sample of Coal and Coke (used for coal and coke dusts)
Definitions and Terminology Deflagration Vs. Explosion
• Deflagration: Propagation of a combustion zone at a velocity 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.
Explosion
Deflagration
Detonation
Employer’s Responsibilities
• Facility Components Analysis• Assess Workplace Conditions• Prevention Methods (Electrical)• Control Methods• Corrective Actions• Facility Changes• Employee Training
Facility Components Analysis
• 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.
Assess Workplace Conditions
Determine if any of the Combustible Dust are Produced or Processed, if so:
- All areas of the facility need to be checked for any locations where there are dust deposits.
- Sample the dust to identify the type of material it is and to determine if it is combustible.
- Check high areas above false ceiling, on ledges, top of beams, top of joists and on the top of and around any process equipment.
Prevention Methods forExplosions by Electrical Equipment
Dust-Ignition Proof • Equipment enclosed in a
manner that excludes dusts and does not permit arcs, sparks, or heat otherwise generated or liberated inside of the enclosure to cause ignition of exterior accumulations or atmospheric suspension of a specified dust on or in the vicinity of the enclosure.
Dust Tight• Enclosures constructed
so that dust will not enter under specified test conditions
Control Methods
Deflagration Isolation• A method employing
equipment and procedures that interrupts the propagation of a deflagration of a flame front, past a predetermined point.
Deflagration Suppression• The technique of
detecting and arresting combustion in a confined space while the combustion is still in its incipient stage, thus preventing the development of pressure that could result in an explosion.
Corrective Actions
If combustible dust conditions are found, corrective action is needed. Such action(s) should include but are not limited to:
- Repair of any leaks in process equipment.
- Establishment of Housekeeping Plan and Schedule to control dust present out side of process equipment.
Determine Facility Changes
Determine if:- Flame Detectors are needed on Process
Equipment.- Fire Extinguisher operated by Flame Detectors
are needed on Process Equipment.- Blow Out Venting is needed on Process
Equipment.- Any present or new Blow Out Venting needs to
be vent to the outside of the building
Possible Facility Changes or Method Controls
Screw Conveyor Chokes
Possible Facility Changes or Method Controls
Screw Conveyor Chokes
Possible Facility Changes or Method Controls
Rotary Valves
Possible Facility Changes or Method Controls
Flame Front Diversion
Possible Facility Changes or Method Controls
Mechanical Isolation
Possible Facility Changes or Method Controls
Chemical Isolation
Employee Training and Operational Changes
Employee Training• Necessary Training of
Employees on handling Combustible Dust Hazards.
• Retraining of Present Employee.
• Establish Training Program for New Employees.
Operational Changes• Establish a reporting
system for employees to report dust accumulation conditions that are occurring.
Combustible DustEnforcement
per National Office Stats:
Richard Fairfax, CIH
Director
Enforcement Programs
November 1, 2007 – June 30, 2008(8 mos. Period)
Inspections Conducted
258
68
0
50
100
150
200
250
300
350
400
Federal 18(b) State
326 Total Inspections
Total Violations Issued
746
441
0
100
200
300
400
500
600
700
800
900
Federal 18(b) State
1,187 Total Violations
% Total Violations Cited As Serious
74%
28%
0%
20%
40%
60%
80%
100%
Federal 18(b) State
% Total Violations Cited As S,W,R,FTA, Unclass
75%
30%
0%
20%
40%
60%
80%
100%
Federal 18(b) State
Avg. Number Violations Issued Per Initial Inspection
6
7.8
0123456789
10
Federal 18(b) State
Avg. Penalty Per Serious Violation
$850$764
$0
$200
$400
$600
$800
$1,000
Federal 18(b) State
% Inspections In-Compliance(Insps W/O Violations & Closed)
12% 9%
0%
20%
40%
60%
80%
100%
Federal 18(b) State
Combustible Dust Violations
• (5)(a)(1) Violations – 29• Housekeeping Violations – 42• Electrical Violations – 14
Typical 5(a)(1) Violations
1. Baghouse dust collectors (at several facilities) were located inside a building without proper explosion protection systems, such as explosion venting or explosion suppression systems.
2. Deflagration isolation systems were not provided to prevent deflagration propagation from dust collectors to other parts of the plant.
3. The rooms with excessive dust accumulations were not equipped with explosion relief venting distributed over the exterior walls and roofs of the buildings.
Typical 5(a)(1) Violations
4. The horizontal surfaces such as beams, ledges and screw conveyors at elevated surfaces were not minimized to prevent accumulation of dust on surfaces.
5. Air from the dust collector was recycled through ductwork back into the work area. This was found at several facilities.
6. Legs of bucket elevators were not equipped with explosion relief venting.
Typical 5(a)(1) Violations
7. Explosion vent on bucket elevator(s) were directed into work areas and not vented to a safe, outside location away from platforms, means of egress, or other potentially occupied areas.
8. Equipment (such as grinders and shakers) were not maintained to ensure that they were dust tight, thus combustible dust would leak into the surrounding area.
9. Pulvirizers were not provided with explosion venting or deflagration suppression systems.
Typical 5(a)(1) Violations
10. Ductwork from the dust collection system to other areas of the plant were not constructed of metal.
11. Employees were using electric grinder(s) on a duct entering a baghouse style dust collector without a hot work permit system.
12. Open flames from a propane heater for comfort heating were in an area where agricultural products were ground.
Other Primary Applicable OSHA Standards
1910.22 General – Housekeeping
1910.307 Electrical Hazardous (Classified) Locations
1910.178 Powered Industrial Trucks
1910.263 Bakery Equipment
1910.265 Sawmills
1910.272 Grain Handling
Housekeeping: Possibility of Secondary Explosion?
Dust Layer Thickness Guidelines
1/8” in grain standard
Rule of thumb in NFPA 654
1/32” over 5% of area – Floor area max. 20,000 SFFloor area exceeds 20,000 SF – 1,000 SF Upper Limit for dustThese facts are an idealized approach (Reference Annex D – NFPA 654)
1/32” approximately equals the thickness of a typical paper clip.
Dust Layer Thickness Guidelines
Rough calculations show that the available surface of bar joists is approximately 5% of the floor area;
The equivalent surface for steel beams can be as high as 10%.
OSHA Contact Information:
NEED TECHNICAL and/or
SAMPLING INFORMATION:
The following personnelmay be of assistance:
OSHA Contact Information:
TECHNICAL INFORMATION:
Sanji Kanth – OSHA National Office
200 Constitution Ave. NW
Room 3119
Washington, DC 20210
(202) 693-1850
OSHA Contact Information:
OSHA SAMPLING INFORMATION:
Jon Rima – Salt Lake Technical Center
8660 S. Sandy Parkway
Sandy, Utah 84070
(801) 233-4966
That’s All Folks!!
Thank You For Your Time!!