Office of Safety & Health Consultation
presents
Combustible Dust
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Goal
To improve the safety of workers in
environments where combustible dusts may be
encountered by increasing employee awareness
of this hazard and by demonstrating how the
hazard can be recognized and addressed in
their workplace.
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Objectives
• Identify the elements necessary for
dust to explode.
• Explain how to prevent dust from
reaching combustible levels.
• Describe the difference between
primary and secondary dust
explosions.
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Introduction
• A Chemical Safety Board Study Shows:
– From 1996 to 2005, a total of 106 explosions
resulted in 16 fatalities and 126 injuries, at an
estimated cost of $162.8 million in damages to
the facilities.
– In 2005, there were 13 grain dust explosions
reported in the US.
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Organic Dust Fires & Explosions
• Organic Dust Fires
and Explosions:
– Massachusetts
(3 killed, 9 injured)
– North Carolina
(6 killed, 38 injured)
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Massachusetts Incident
Fire in a foundry shell molding machine
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North Carolina Incident
• Combustible
polyethylene dust
accumulated above
suspended ceilings at
pharmaceutical plant
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Grain Handling Industry Experience
In the late 1970s, grain dust explosions
left 59 people dead and 49 injured.
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Grain Handling Industry Experience
In 1987, OSHA promulgated the Grain Handling
Facilities standard (29 CFR 1910.272) still in effect
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Combustible Dust Explosions
Imperial Sugar 2008
Dust
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Malden Mills 2004
Kansas 2011
What’s so bad about a little dust?
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It’s Only Dust
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It’s Only Sugar!
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A Chronology of Past Events
• February 7, 2008 – Imperial Sugar Plant explodes
• February 11, 2008 – Fire still burning in parts of plant
• February 24,2008 – 11th worker dies from injuries
• July 2008 – OSHA fines Imperial Sugar Co. $8.8 million For
violations in Georgia and Louisiana
• August 2008 – 14th worker dies from injuries
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What’s so bad.
• For the employer the millions of dollars in
OSHA fines and insurance payments not to
mention the cost of rebuilding the plant .
• For the workers and their families – the cost,
heartbreak and pain – That 14th worker spent 6
months in a burn unit fighting for his life. A
total of 40 other workers were injured with
severe burns.
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Between 1980 and 2005 the Chemical Safety Board has
knowledge of over 280 dust explosions resulting in 119 deaths and
718 injuries
That averages to more than 10 explosions per year
Despite the time since the Port Wentworth explosion brought this
issue to the national forefront the explosions continue.
10/30/2011 6 killed, 2 injured Kansas
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Important Points Regarding the CSB Data
According to the CSB, “The combustible dust incidents the CSB lists…from
1980 to 2005 are likely only a small sampling, as no federal or state
agency keeps specific statistics on combustible dust incidents, nor does any
single data source provide a comprehensive collection of these incidents.
Information about small combustible dust incidents and near-misses is also
generally unavailable.
Incidents that cause no fatalities, significant injuries or major fires may not be
recorded in the OSHA and fire incident databases
The true extent of the problem is likely understated.
Due to these limitations, the CSB does not represent the incident data as
complete or error free and other compilations of dust explosion data are
available.”
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Dust Incidents, Injuries & Fatalities 1980 - 2005
(Not even close to being a complete summary of incidents)
Fatalities
Incidents
Injuries / Fatalities
Injuries
Incidents
Figure 11. Dust incidents, injuries & fatalities, 1980-2005
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Source: Chemical Safety Board
Types of Industries Involved in Dust Incidents
Equipment
Manufact'g.
7%
Furniture &
Fixtures
4%
Other
7%
Fabricated
Metal Products
7%
Electric
Services
8%
Food Products
24%
Lumber/
Wood
Products
15%
Rubber &
Plastic
Products
8%
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Primary Metal
Industries
8%
Chemical
Manufact'g.
12%
Types of Dust Involved in incidents
Inorganic
4%
Coal
8%
Plastic
14%
Metal
20%
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Other
7%
Food
23%
Wood
24%
Combustible Dust Explosions History
Malden Mills
Methuen, MA
December 11, 1995
37 Injured
Nylon Fiber
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Combustible Dust Explosions History
Jahn Foundry
Springfield, MA
February 26, 1999
3 dead
9 Injured
Phenolic resin dust
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Combustible Dust Explosions History
•Ford River Rouge:
•Secondary
•Coal Dust Explosion
•February 1, 1999
•Killed six workers and
injured 36
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Combustible Dust Explosions History
May 16, 2002
Rouse Polymerics
Vicksburg, MS
5 dead, 7 injured
Rubber Dust
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Combustible Dust Explosions History
•January 29, 2003 West Pharmaceutical
Services, Kinston, NC
–Six deaths, dozens of
injuries
–Facility produced rubber
stoppers and other
products for medical use
–Plastic powder
accumulated above
suspended ceiling ignited
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West Pharmaceutical facility destroyed by polyethylene dust
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Combustible Dust Explosions History
• February 20, 2003 – CTA Acoustics
Corbin, KY
– Seven Workers died
– Facility produced
fiberglass insulation
for automotive
industry
– Resin accumulated
in production area
and was ignited
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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
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Combustible Dust Explosions History
• October 30, 2011
• Bartlett Grain Elevator
Atchison Kansas
- 6 Workers killed
- 2 Workers injured
Workers were loading
corn onto a train
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The Dust Explosion Pentagon
Ignition Source
Ignition
Source
Dispersion
Deflagration
Confinement
Explosion
FIRE
Combustible Dust
Oxygen in Air/Oxidizers
To prevent an explosion – remove one corner of the pentagon
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The primary explosion is rarely the end of the story.
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Secondary Explosions
• Occur when the blast wave from the initial
explosion causes accumulated dust in other
areas (which may be remote and unrelated to
original explosion) to become airborne and
explode
• Anecdotally many investigators discover that “puffs” (small
unreported explosions) had been observed for some time prior
to the reported incident.
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So How Do I Prevent a Dust Explosion?
If one of the five elements of the Pentagon is
missing a catastrophic explosion cannot occur.
= No Explosion
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Ignition
Source
Ignition Source
Dispersion
Deflagration
Confinement
Explosion
FIRE
Combustible Dust
Oxygen
FIRE
I in Air/Oxidizers
FIRE
Two elements are difficult to eliminate:
1) Oxygen in Air
2) Confinement within processes or buildings
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Ignition
Source
Ignition Source
Dispersion
Confinement
Deflagration
Explosion
Combustible Dust
FIRE
Oxygen in Air/Oxidizers
FIRE
I
But my process doesn’t include dust!
Are you sure?
FIRE
If you work with any solid combustible material, ingredients or
intermediate products or by-products, handling, conveying, or otherwise
manipulating these materials can create combustible dust.
Even materials typically handled and stored wet can become dry.
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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.
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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
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• Different dusts of the same chemical material may
have different ignitability and explosibility
characteristics depending on variables of particle size,
shape, and moisture content.
• Good housekeeping might seem like an easy answer.
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But housekeeping is only part of the
answer!
• As much as is practical, containment and dust
collection systems are important.
• But they must be installed and maintained in a
manner that keeps them from becoming an
ignition source
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NFPA 654, Standard for the Prevention of Fire and
Dust Explosions from the Manufacturing, Processing
of Combustible Particulate Solids
Recommends:
1.
2.
3.
4.
5.
6.
7.
8.
9.
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;
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);
Only use vacuum cleaners approved for dust collection;
Locate relief valves away from dust hazard areas; and
Develop and implement a hazardous dust inspection, testing,
housekeeping, and control program.
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Use dust collection systems and filters
Dust Control
•Design of facility & process
equipment
•Contain combustible dust
•Clean fugitive dust
•Regular program
•Access to hidden areas
•Safe cleaning methods
•Maintenance
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Inspect for dust residues in open and hidden areas
(at regular intervals);
Like most pharmaceutical manufacturers this was a “clean” facility.
West Pharmaceutical facility destroyed by polyethylene dust
Which accumulated above the tiles in a dropped ceiling
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NFPA 654, Standard for the Prevention of Fire and
Dust Explosions form the Manufacturing, Processing
of Combustible Particulate Solids
Contains comprehensive guidance on the control of ignition sources:
1.
Use appropriate electrical equipment and wiring methods;
2.
Control static electricity, including bonding of equipment to ground;
3.
Control smoking, open flames, and sparks;
4.
Control mechanical sparks and friction;
5.
Use separator devices to remove foreign materials capable of igniting
combustibles from process;
6.
Separate heated surfaces from dusts;
7.
Separate heating systems from dusts;
8.
Proper use and type of industrial trucks;
9.
Proper use of cartridge activated tools; and
10. Adequately maintain all the above equipment.
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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
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Ignition Source Control
Electrical equipment
Class II, Division 1 and 2
Class I and Class III may also be an issue
Consider equipment both inside dust
handling equipment and outside
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Ignition Source Control
Mechanical sparks & friction
Rotating equipment bearing failure can
lead to very hot surfaces (above the MIT)
Sliding surfaces can develop charges
Steel tools dropping onto concrete or steel
A good mechanical integrity
management system/vibration analysis
system is needed to detect problems in
advance with bearings and other
surfaces
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Ignition Source Control
Mechanical sparks & friction
Open flame control
Use of tools & vehicles
Maintenance
All require effective control of Hot Work
Look for permit systems
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Ignition Source Control
Design of heating systems & heated
surfaces
Know your materials
Minimum Ignition Temperature (MIT)
Maintain temperature controls
Moisture content may be critical
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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 Hazards
61 Agriculture
68 Deflagration Venting Systems
69 Explosion Prevention Systems
70 National Electric Code
77 Static Electricity
85 Boiler and Combustion
Systems
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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Viewing NFPA Standards
www.nfpa.org
Point to “Codes and Standards”
Click “Document List”
Click on standard desired, NFPA XXX
On bottom, click “Preview this Document”
Below disclaimer, click “I Agree”
Click “Open NFPA XXX”
After standard opens, the “1-2-3” button
gives you the Table of Contents
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So What Should I Do?
1) Evaluate your workplace for the 5 points of
the explosion Pentagon:
a)
Combustible Dust
b)
Ignition Source
c)
Confinement
d)
Dispersion
e)
Oxygen in Air/Oxidizers
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How?
• a) Combustible Dust – Do you see “dust” in your
workplace that is used in your process or is a by
product of your process
• (i.e. At a sawmill sawdust is a by product of the
cutting of logs/boards into product)
• b) Ignition Source -eliminate any possible sources of
ignition, from electricity to static electricity - a
minimum of Class II electrical features
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How?
• c) Confinement – This will depend on the
configuration of the workplace and can be difficult to
eliminate
• d) Dispersion - keep dust from suspension in air
– Use dust collectors
– When cleaning do not re-suspend accumulated
dust in air (DO NOT use air to “clean” surfaces)
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How?
• e) Oxygen in Air/Oxidizers
• Oxygen in the air cannot be eliminated (unless
workers are in SCBs)
• Oxidizers, if present for process, should be isolated or
replaced
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So What Should I Do?
If you find that you do have the five elements
or you know you have four and may not be quite sure about number 5
DO NOT DELAY
Seek assistance
We don’t want your site
to look like this!
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–
If you have questions about this presentation call the Delaware Office
of Safety and Health Consultation at 302-761-8219.
If you have questions about our free Safety and Health Consultations
Please call us at 302-761-8219.
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Post Script -Five weeks later at another Imperial
Sugar plant:
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So sometimes it’s not
just a little dust
It’s a really fast way to demo a building
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