Com dust 7125 seminar 2017

Combustible Dust
Safety
John Newquist
Draft 12 24 2017

Scope
•This course covers the hazards posed by
combustible dust within general industry.
•The seminar format is a shortened version of
the OSHA #7120 Introduction to Combustible
Dust Hazards and omits discussions on
National Fire Protection Association (NFPA)
Standards, combustible dust definitions, and
workshops.

Terminal Learning Objective
Program participants will understand:
• Combustible dust danger in their industry.
• The Dust, Fire, and Explosive Pentagon.
• The methods to prevent or mitigate the effects of
combustible dust explosion and resulting fire.
3

Are These Materials Explosive?
sugar
metal
plastic
wood
coal
medicines
Combustible dust in a jar
video

Safety Origins
•1884 Pennsylvania
Mine Safety Act
(PMSA) was passed
into law.

Corn Products Explosion
•Jan 3 1924
•42 died
•Starch Dust
•Pekin IL
•Explosion in starch packing
house.
•Dumping buggies of starch
•Low moisture due to cold.

Texas City
•April 16, 1947
•Cargo Ship of
Ammonium Nitrate
Exploded
•Neighboring Monsanto
plant caught fire
•561 died

Brach’s Candy
•Sep 7, 1948
•18 died
•Spark from electrical
equipment ignited
suspended starch dust
•Open storage of starch.

Continental Grain Elevator - 1977
•Westwego, LA
•Grain Elevator
Explosion
•Dec 1977
• Spark ignited grain dust
• The explosion killed 36
people

Farmer’s Export
Company
•December 28, 1977-
Galveston, TX
•Spark near grain
elevator caused
explosion
•18 died, 35 injured

11
Dust Incidents, Injuries & Fatalities 1980 - 2005
Source: CSB
Injuries/Fatalities
Figure 11. Dust incidents, injuries & fatalities, 1980-2005
Incidents
Fatalities
Injuries
Incidents

12
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.
•Incidents that cause no fatalities, significant injuries or major
fires may not be recorded in the OSHA and fire incident
databases
CSB VIDEO

Coal Dust
• Throughout a twenty‐five year
(1980‐2005) study of PRB
coal‐fired power plants, there
were an average of 11 fires or
explosions, 29 injuries, and 5
deaths per year.
• Another study conducted by the
United States Department of
Labor during the 1996‐2009
time period noted 437
workplace coal power‐related
deaths, averaging 33 deaths per
year in the United States..
Will County Power Plant Crusher Building Explosion

Buffalo Rock
•1988
•4 dead
•Bullet filling machine
misfires.
•Housekeeping
•Electrical

15
Catastrophic Combustible Dust Incidents since
1995

16
Malden Mills
Methuen, MA
December 11, 1995
37 Injured
Nylon Fiber
1995

17
Firefighting efforts following the explosion at
Malden Mills (Methuen, Massachusetts, December
11, 1995).

Ford River Rouge Power Plant
•2/1/1999
•Dearborn , MI
•MIOSHA General Duty
egregious
•$1,500,000 penalty
•Natural gas boiler explosion
triggered secondary coal
dust explosion that had
accumulated on building
and equipment surfaces
•No flame sensing interlock
for the gas lines
Killed six workers and injured 36

19
Combustible Dust Explosions History
Jahn Foundry
Springfield, MA
February 26, 1999
3 dead
9 Injured
Phenolic resin dust

20
May 16, 2002
Rouse Polymerics
Vicksburg, MS
5 dead, 7 injured
Rubber Dust

21
• 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

22
West Pharmaceutical facility destroyed by polyethylene dust

23
• 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
CSB VIDEO

24
• October 29, 2003
• Hayes Lemmerz
Manufacturing Plant
–Two severely
burned (one of the
victims died)
–Accumulated
aluminum
dust
–Facility manufactured
cast aluminum
automotive wheels
CBS Video Hayes Lemmerz

Chemical Safety Board
• From 2008 to 2012, our board documented,
50 combustible dust accidents that led to 29
fatalities and 161 injuries.

Imperial Sugar - 2008
• Feb 7, 2008
• 14 died
• 60 injured
• $180-220 million dollar est. loss
• $7,700,000 Fine – OSHA
Csb video

2008
•Transfer of metal dust
into mixer
•What questions would
you ask?

Jan 2009
• The laminate panels pass on a conveyor
underneath a curing UV light.
• A panel jammed up underneath the UV
light.
• The panel heated up to the point where
it charred, smoldered and eventually
caught fire.
• The charred pieces were sucked up into
the local exhaust system, where they
ignited the dust collector located
outside the plant.
• The dust collector blew up, sending a
shock wave back into/through the
plant. Several overhead doors were blown off,
and one of these struck 4 employees,
injuring them.

Metal Dust - 2011
• Hoeganaes plant TN
• Four dead, two explosions
• The plant manufactures metal
powder used in the automotive
industry
• CSB and OSHA investigations
• The company issued a
statement saying it has begun
a review “to ensure that we
fully understand the cause of
the fire and have
implemented appropriate
measures to prevent a
recurrence of this incident.”
• “We have already made
significant progress on some
of the issues raised by the CSB
and we won't resume
production until we are
confident that all issues have
been addressed.”

Grain Dust Explosion - 2011
•Oct 29, 2011
•Six dead, 2 injured
•Five Willful, 8 serious
•$400,000 penalty
•Settled for $182,000
•Unclassified
•Lawsuit by families

August 2012
• WESTON, Mo. -- More than 200
people were briefly evacuated
after a small explosion and fire at
Kansas City Power & Light's Iatan
power plant in Weston.
• Coal bunker.
• Platte County fire crews were
dispatched to the coal-fired
power plant and quickly
contained the blaze.

2012
•Two British Columbia
sawmills in 2012
•Four dead and 52
injured
•Fines of up to $652,000
•These were wood dust
explosions

July 2013
• Springdale, MO
• 1 dead, 3 burned.
• “The dust associated
with the type of process
goes on here resulted in
some type of a flash fire
that encapsulated three
of the employees,”
McDonald said.

Feb 2014• Federal inspectors
determined excessive
accumulation of grain
dust in the hammer mill
area ignited and the
explosion killed one
worker and sent five
others to area
hospitals.
• The blast caused
excessive damage to
the building and closed
the feed mill.

April 2014
Corrigan TX
Four people remain hospitalized, three in critical condition, after an explosion
and fire at a Polk County plywood mill
• a) dust collector bags impeded the venting area of the dust collector
deflagration vents.
• b) explosion vents releasing in the dust collector without taking measure
to protect employees from the fireball path
• c) dust collector vented and the deflagration traveled upstream to the
sander.
• d) responding to a fire within the sander dust collection system without
the main blower remaining in operation.
• e) responding to a fire within the sander dust collection system without a
choke between the sander dust collector and silo leading to the
briquetter.

May 2014
• Hartford CT
• A workbench in the
finishing room of the facility
caught fire on May 19,
2014, while an employee
cleaned titanium aircraft
parts.
• The room's dust collection
system lacked adequate fire
and explosion controls.
• Flammable titanium dust
had also settled on
electrical equipment.
Titanium Dust Collector fire
photo

August 2014
• 75 people were killed
and 185 others injured
after an explosion
ripped through a metal
products factory in
China’s eastern Jiangsu
Province

January 2015
• Farmington Hills, MI
• An employee was prepping the
north sand hopper interior walls.
• A fire started when a spark,
radiant heat and/or conductive
heat, likely ignited the fire
retardant insulation.
• One employee died (37/M) and
three were hospitalized from
smoke and soot inhalation with
complications.

January 2015
• Ticonderoga, NY
• An employee was climbing a fixed ladder to change filter bags
on the bag house.
• While changing, fly ash was released from the bagger or silo.
• The employee caught on fire and died as a result of extensive
burns.
• 57/M

February 2016
• Rockmart, GA
• An employee was scooping
feed pellets off the floor with
a shovel.
• There was an explosion when
the dust ignited and the
employee was killed.
• 25/M

September 2016
• Francesville, IN
• An employee was operating the
north leg of a grain elevator.
• Grain was being emptied from a
semi-trailer into the north pit
and then being sent to the wet
holding bin when a grain
explosion occurred.
• The employee received burns to
his body resulting in his death.
• 67/M

Apr 2017
• Dust collection systems
must be installed which will
safely capture potentially
explosive aluminum fines.
Metallic dusts from grinding, sawing or
cutting should be picked up by one
collection system, while dusts from
buffing and polishing should be picked up
by a different system.
This will prevent the mixing of explosive
and flammable dusts.

Apr 2017
• If maintenance is planned and
welding or cutting is required, all
machinery, ductwork and
collectors must be shut down,
emptied and cleaned, and all
aluminum dust removed from the
area and properly disposed of.
• The interior surfaces of all
equipment must be carefully
inspected to check for possible
accumulations of fine powder,
particularly at elbows, welded
joints, etc. These surfaces must
be wiped clean.

May 2017
NFPA requires that an explosion isolation
device be installed on all suction side
ducts that transport material with a KST
value above zero.
KST values are used to measure the speed
at which pressure rises during a standard
explosion severity test.
EcoMAXX™ No Return Valve

May 2017
•On May 31 at approximately 11 p.m., an explosion occurred at
our milling operations located in Cambria, Wisconsin.
•The cause of the explosion is not known
•Corn milling
•$1.8 million citation

Nov 2017
• New York cosmetics factory left
30 to 35 people injured, including
seven firefighters caught in the
second blast, officials said
Monday.
• "A deceased male employee was
recovered from the plant fire at
approximately 7:40 p.m
• Police said the first explosion
occurred around 10:15 a.m.
Monday at the Verla
International cosmetics factory in
New Windsor, about an hour's
drive from New York City.
Firefighters who responded were
inside when the second explosion
occurred around 10:40 a.m.

Required Conditions for an Explosion
•The dust must be combustible and fine enough to be
airborne.
•There must be sufficient oxygen in the atmosphere to support
and sustain combustion.
•There must be a source of ignition.
•The dust must be confined.
•The dust must be dry.
Dust Particle
4
9

50
Types of Dust Involved in incidents
Metal
20%
Wood
24%
Food
23%
Other
7%
Plastic
14%
Coal
8%
Inorganic
4%

51
Types of Industries Involved in Dust Incidents
Other
7%
Food Products
24%
Lumber/
Wood
Products
15%
Chemical
Manufact'g.
12%Primary Metal
Industries
8%
Rubber &
Plastic
Products
8%
Electric
Services
8%
Furniture &
Fixtures
4%
Equipment
Manufact'g.
7%
Fabricated
Metal Products
7%

52
Equipment Involved in Dust Explosions
Source: Guidelines for Safe Handling of Powders and Bulk Solids, CCPS, AICHE
Material
US (1985 – 1995) UK (1979 – 1988) Germany (1965 – 1980)
Number of
Incidents
% Number of
Incidents
% Number of
Incidents
%
Dust Collectors 156 42 55 18 73 17
Grinders 35 9 51 17 56 13
Silos/Bunkers 27 7 19 6 86 13
Conveying
Systems
32 9 33 11 43 10
Dryer/Oven 22 6 43 14 34 8
Mixers/Blenders >12 >3 7 2 20 5
Other or
Unknown
84 23 95 31 114 27
Total 372 100 303 100 426 100

58
The “Typical” Explosion Event
Process
Equipment
Initial
Internal
Deflagration
Time, msec.
0 25 50 75 100 125 150 175 200 225 250 300 325

59
Process
Equipment
Initial
Internal
Deflagration
Shock Wave
Time, msec.
0 25 50 75 100 125 150 175 200 225 250 300 325

60
Process
Equipment
Initial
Internal
Deflagration
Elastic Rebound
Shock Waves
Time, msec.
0 25 50 75 100 125 150 175 200 225 250 300 325

61
Time, msec.
0 25 50 75 100 125 150 175 200 225 250 300 325
Process
Equipment
Initial
Internal
Deflagration
Dust clouds caused
by Elastic Rebound

62
Process
Equipment
Containment
Failure from Initial
Deflagration
Dust Clouds Caused
by Elastic Rebound
Time, msec.
0 25 50 75 100 125 150 175 200 225 250 300 325

63
Process
Equipment
Secondary Deflagration
Initiated
Dust Clouds Caused
by Elastic Rebound
Time, msec.
0 25 50 75 100 125 150 175 200 225 250 300 325

64
Process
Equipment
Propagates through Interior
Time, msec.
0 25 50 75 100 125 150 175 200 225 250 300 325

65
Process
Equipment
Vents from Structure
Time, msec.
0 25 50 75 100 125 150 175 200 225 250 300 325

66
Causes 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.

Safety and Health
Information Bulletin
Elements of a Dust Explosion
Facility Dust Hazard Assessment
Dust Control
Ignition Control
Damage Control
Training
References

Dust Hazard 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
July 2014

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.”
• 2017 Edition – A combustible
particulate solid that presents a
flash fire or deflagration hazard
when suspended in air or some
other oxidizing medium over a
range of concentrations.
69

Explosive Limits
• The Minimum Explosive
Concentration (MEC) for grain
dust, grain flour, or ground feed
ingredients varies according to
the particle size and energy:
•Smaller particles are more
powerful
•Caloric value of the product
• Corn starch is considered one of
the more volatile and powerful
grain products.
• As the size of the particle
decreases the risk of a
deflagration or explosion
increases.7
0

Electrical Classification
• The facility analysis must identify areas requiring special electrical equipment
classification due to the presence (or potential presence) of combustible dust.
• 1910.307(c) - Electrical installations. Equipment, wiring methods, and
installations of equipment in hazardous (classified) locations shall be
intrinsically safe, approved for the hazardous (classified) location, or safe for
the hazardous (classified) location.

• All Equipment should be check to see if rated for Class II locations.

Dust Control
Minimize the escape of dust from process equipment or ventilation
systems;

Dust Control
• Use dust collection systems and filters;

Dust Control
• Utilize surfaces that minimize dust accumulation and facilitate cleaning;
Good Not good

Dust Control
• Provide access to all hidden areas to permit inspection;

Dust Control
• Inspect for dust residues in open and hidden areas, at regular intervals;

Dust Control
• Clean dust residues at regular intervals;

Dust Control
• Use cleaning methods that do not generate dust clouds, if ignition
sources are present;

Dust Control
• Only use vacuum cleaners approved for dust collection
• Typically sold as “Explosion Proof Industrial Vacuum Cleaners”

Dust Control
• Locate relief valves away from dust hazard areas; and
Vent in a safe location

Dust Control
• Develop and implement a hazardous dust inspection, testing,
housekeeping, and control program (preferably in writing with established
frequency and methods).

Accumulation
• Production
• Packaging
• Process
• Horizontal surfaces
• Floors

Hidden Areas
Beams
False Ceilings
Ducts
Piping

Dispersion
Mechanical
Vibration
Ventilation

Ignition Control
• Use appropriate electrical equipment and wiring methods;
Housekeeping
needs to be kept up

Ignition Control
• Control static electricity, including bonding of equipment to ground;

Ignition Control
• Control smoking, open flames, and sparks;

Ignition Control
• Control mechanical sparks and friction;
Firefly spark
detection
video

Ignition Control
• Use separator devices to remove foreign materials capable of igniting
combustibles from process materials;
Mag separator video

Ignition Control
• Separate heated surfaces from dusts;

Ignition Control
• Separate heating systems from dusts;

Ignition Control
• Proper use and type of industrial trucks;

Damage Control
• Separation of the hazard (isolate with distance);
Put dust collector outside if possible

Damage Control
• Segregation of the hazard (isolate with a barrier);
Separate room
Cavity Barriers to prevent
flame spread

Damage Control
• Deflagration venting of a building, room, or area;

Damage Control
• Pressure relief venting for equipment;
Flameless venting

Damage Control
• Provision of spark/ember detection and extinguishing systems;

Damage Control
• Explosion protection systems (also refer to NFPA 69, Standard on
Explosion Prevention Systems);

Damage Control
• Sprinkler systems;

Management
• Prevention through design
• Trade Shows
• Facility analysis
• Periodic Audits
• Prevention and protection
program.
• Plant dust housekeeping
• Ignition control
• Monetary resources
• Training for Employees

Training
• Employees need to be trained:
• To recognize and prevent hazards
associated with combustible
dust:
• Safe Work Practices for cleaning
• In taking preventative action;
and/or,
• How to alert management.

OSHA• Continental Grain
• GRAIN SEP
• Initial Class
• Access to Codes
• General Duty
• Hazardous Material Class –
Howicz
• CSB – 2006 - OSHA Inspectors
not trained on combustible
dust hazard recognition and
prevention
• Nationwide Training - 2007
• Imperial Sugar - 2008
• NEP Combustible Dust
• Slideshare.net

OSHA Inspections
• Over 5000 COMDUST NEP
inspections since 2008
• High Violations per
inspections (Over
6.0/inspection)
Triggers are:
• Complaint or referral
• Media reports of fires and
explosions
• Inspection Targeting List
~150-300 inspections in 2016
#1 General Duty in Region V is
combustible dust

COMDUST Inspection
• Plant history of fires
• Employer’s Dust
Management System
• MSDS’s
• Dust Accumulation
• Dust Collectors
• Ventilation Specifications
• One liter of dust sampled
• Photos
• Interviews – Employees,
Employers

OSHA NEP
The purpose of this NEP is to inspect
facilities that generate or handle
combustible dusts which pose a
deflagration or other fire hazard when
suspended in air or some other oxidizing
medium over a range of concentrations,
regardless of particle size or shape;
deflagrations can lead to explosions.

OSHA NEP
Types of dusts include, but are not limited to: metal dust, such as aluminum
and magnesium; wood dust; plastic dust; biosolids; organic dust, such as
sugar, paper, soap, and dried blood; and dusts from
certain textiles.

OSHA NEP
If a nonformal complaint is received related to a facility handling combustible
dust, and if an inspection is conducted to investigate the complaint based on
the criteria contained in OSHA Instruction CPL 02- 00-140, then an inspection
as required by this NEP should be conducted if the Area Director determines
that the facility has not already been inspected under this instruction and
resources are available to conduct the NEP inspection.

Combustibility Determination
Presence of dust increases the risk
of fire, explosion and / or a
detonation within the workspace.
The first step in the risk analysis
should be to determine if the
powder is combustible
110

Sample OSHA Questions
• What is the Plant’s
Housekeeping program?
• Is there dust accumulation
of 1/32 inch thick?
• Dust collectors located
inside of buildings?
• Explosion relief venting
distributed over the
exterior walls of buildings
and enclosures?

• Does the facility have
isolation devices to prevent
deflagration propagation
between pieces of
equipment connected by
ductwork?
• Does the facility have an
ignition control program,
such as grounding and
bonding?
Fire through a duct is bad

• Are Vacuum cleaners
used in dusty areas and
approved for the hazard
classification?
• Are separator devices
to remove foreign
materials used?
• Can tramp metal ignite
combustible dusts in
the dust collection
systems? Check the label for Class II

• Is the exhaust from the
dust collectors
recycled?
• Does the dust collector
system have spark
detection and
explosion/deflagration
suppression systems?

• Are ducts designed to maintain
sufficient velocity to ensure the
transport of both coarse and fine
particles?
• What is the design basis for the
ventilation?
• Are duct systems, dust collectors,
and dust-producing machinery
bonded and grounded to minimize
accumulation of static electrical
charge?

• Is metal ductwork used?
• Are bulk storage containers
constructed of
noncombustible materials?
• Are employees trained in
the hazards of the
combustible dust?
• Are MSDSs for the
chemicals which could
become combustible dust
under normal operations
available to employees?

Standards Cited
• Combustible dusts found in grain
handling facilities are covered by 29
CFR 1910.272.
• For workplaces not covered by
1910.272, but where combustible
dust hazards exist within dust
control systems or other containers,
citations under section 5(a)(1) of the
OSH Act (the General Duty Clause)
may generally be issued for
deflagration, other fire, or explosion
hazards.

NEP Citations
• 1910.22, Housekeeping
• 1910.38, Emergency action plans
• 1910.94, Ventilation
• 1910.132, PPE Hazard Analysis
• 1910.146, Permit-required confined
spaces
• 1910.272, Grain handling facilities
• 1910.307, Hazardous (classified)
locations
• 1910.1000 Z table, Toxic and
hazardous substances
• 1910.1200, Hazard communication
• General duty clause
5/16/2002 Vicksburg, MS
5 fatalities, 7 injured
23 serious, 2 unclassified
$210,000
Fire in the baghouse, then rubber
dust explosion
No explosion venting or
suppression in baghouse
Poor housekeeping
88 fire reports in 13 years

121
Hazard Communication
• SDSs do not adequately convey combustible dust hazards

123
Housekeeping
• OSHA
1910.22(a)(1) - All places of employment, passageways, storerooms, service rooms, and
walking-working surfaces are kept in a clean, orderly, and sanitary condition.

126
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
equals about 5% of floor area
–Max 20,000 SF
–Idealized

127

128

129

130

131

132

133

134

• “if the workplace has a Class II location, then citations under 29 CFR
1910.307 may be issued to those employers having electrical equipment
not meeting the standard’s requirements. “
Class 2 HVAC

Flame Resistant Clothing
Citations under 1910.132(a) (the general requirement to provide and assure the use
of protective equipment, including protective clothing) may be issued, if an
employee exposure to potential burn injuries can be documented.

Forklifts
• Forklifts can be an ignition
source in dusty
environments

Training
• 1910.272(e)(1)(i) General safety precautions associated with the facility,
including recognition and preventive measures for the hazards related to
dust accumulations and common ignition sources such as smoking; and,
• 1910.272(e)(1)(ii) Specific procedures and safety practices applicable to
their job tasks including but not limited to, cleaning procedures for
grinding equipment, clearing procedures for choked legs, housekeeping
procedures, hot work procedures, preventive maintenance procedures
and lock-out/tag-out procedures.

Training
• July 7 2010 Imperial Sugar Settlement agreed to 5 training points
• 1. The physical hazards and hazardous properties including, but not
limited to, combustibility and explosivity of sugar, powdered sugar,
cornstarch and coal dusts
• 2. The prevention and mitigation of combustible dust hazards including,
but not limited to, dust accumulation, ignition sources, and housekeeping
• 3. The specification, ordering, development of electrical classification
drawings, installation, maintenance and control of change of electrical
equipment, with an emphasis on approved electrical equipment for
hazardous classified areas designated in OSHA’s standards at Subpart S –
Electrical
• 4. The hazard recognition and reporting of electrical equipment which is
not properly installed or maintained, e.g., unapproved extension cords or
box fans in hazardous locations, frayed electrical conductors on a product
machine, the addition of an “ordinary” light fixture in a hazardous
classified area, etc.
• 5. Reasons for wearing fire retardant clothing

Written Programs
$6160
Potential ignition sources

Hot Works
• Around collection points and
ductwork or in areas where
hazardous levels of dust
accumulations may occur
• In section 5(a)(1) cases a hot
work permit system may be
noted as a feasible abatement
method.

Hot Works
• Use Alternatives
• Analyze the Hazards
• Monitor the Atmosphere
• Test the Area
• Use Written Permits
• Train Thoroughly
• Supervise Contractors

Typical 5(a)(1) Violations
• Ducts and system were
not grounded

Grounding
All equipment used in the
dust generating process
must be thoroughly
grounded to remove static
electricity.
“Recommended Practice on
Static Electricity,” NFPA 77,
should be followed.
Inspection and cleaning of all electrical equipment must be done regularly and
frequently (at least weekly).
Ground connections should be checked visually on a daily basis by the
operators.

• Compressed Air was
used for cleaning
• Tip: Clean fugitive dust
• Regular program
• Access to hidden areas
• Safe cleaning methods
• Maintain dust free as possible
• No blow down unless All
electrical power and
processes have been
shutdown and other means
cannot work.
• See NFPA

•Dust collectors inside

• Explosion Vents in bad
locations

• No Spark detection

• Systems were not
provided to prevent
deflagration
propagation from
dust collectors to
other parts of the
plant.
October 29, 2003 - Hayes Lemmerz
Manufacturing Plant, IN
Shawn Boone, 33, died in the
Aluminum Dust explosion

• Not maintaining duct
velocity
• Aluminum Conveyor
velocity might be 4500
ft/min for pneumatic
conveyors

• No explosion relief
venting distributed
over the exterior
walls and roofs of the
buildings.
CTA Acoustics 2003 – 7 dead
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

• Airborne fugitive dust

• A means of tramp metal
protection was not
provided to keep any
unwanted metal
fragments out of the
air-material separators
From Duramag

• Excessive dust
• Not cleaning per the
appropriate NFPA
Standard

Strategy for Employers
• Test for Combustible
Dust
• Find Applicable NFPA
standards
• Implement a Safety
Management System
• Housekeeping
• Electrical Classification
• Conduct Process Hazard
Analysis for Dust
Generation Processes
• Control Ignition sources
• Develop safety
procedures for working
on dust collectors
• Investigate leaks, hot
spots, near misses
• Train Employees in
hazards of combustible
dust
• Plan for fires and
emergencies

Thank You
• Combustible dust.
• Wood pellet mfg.
• A hammer mill equipped
with outside dust collector,
spark detection,
extinguishment in case of
fire, and airlocks.
• All grounded and dust
emissions not noticeable.

168
Older Information for
Reference

Aluminum Dry Dust Collector 484
• 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

Wood Dust Collectors 664
• Pneumatics per NFPA 654
• No spark producing connected in wood dust collection
• Dust collector located either
• -Outside (Not on roofs)
• - Indoor w deflagration system
• - Indoor w Fire protection
• - Indoor w designed relief vents to the outside
• - Indoor w restrictions (Only for wood processing no grinders/sanders,
max air handling of 5000 cfm, fan motor totally enclosed and fan
cooled, daily dust removal, collector 20 ft from means of egress, dust
collectors separated 20 feet)

Sugar/Grains Dust Collectors 61
•Located outside w 2 exceptions
•- Collector located close to an exterior wall, vented to
outside via straight ducts, and design w explosion
resistant vents and collectors
•- Inside w explosion prevention system
•Separators may be inside
•Does not apply to bin vent dust collectors
•Alarm if dust collector shuts down

Dust Collectors 654
•Located outside w 3 exceptions (7.13)
•- Under 8 cuft
•- Collector protected – suppression, oxidant
reduction, deflagration venting, pressure
containment, or vent with flame arresting
device
•- Collection equipped with deflagration ducts
that vent to the outside,

NFPA References
• 654 General
• 664 Wood
• 61 Agriculture
• 484 Metal
• 850 Coal Power
Plants
• 70 National Electric Code
• 499 Classification of
Combustible Dust
• 68 Deflagration Venting
Systems
• 69 Explosion Prevention
Systems
• 91 Exhaust Systems
• 2113 Flame Resistant
Clothing

Where are Dust Sources?
• Bag Openers (Slitters)
• Blenders/Mixers
• Dryers
• Dust Collectors
• Pneumatic Conveyors
• Size Reduction Equipment (Grinders)
• Silos and Hoppers
• Hoses, Loading Spouts, Flexible Boots

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

Seven Key NFPA 654 Changes
• 4.2 Process Hazard
Analysis (PHA)
• TREND 5 – PHA are
conducted in less than
10% of companies, but
increasing rapidly
• OSHA VPP facilities
have conducted
numerous PHAs
• 4.2.1* The design of the
fire and explosion
safety provisions shall
be based on a process
hazard analysis of the
facility, the process, and
the associated fire or
explosion hazards.

NFPA 654 PHA
• Examine the facility,
process, and fire and
explosion hazards
• Actual test data required
to support analysis
• Which materials are
combustible?
• If not known, but
suspected, then data are
needed
• Closed or open processes?
• Rate of generation or
release of solids to an
environment?
• Any collection methods in
place?
• Conclusion: processes
generates or handles solids
and dusts are formed in
process, potential exists

• 4.3 Management of
Change. Written
procedures to manage
change to process
materials, technology,
equipment, procedures,
and facilities shall be
established and
implemented.

• 4.4.1* Incidents
that result in a fire
or explosion of a
magnitude that
causes property
damage,
production
shutdown time, or
injury shall be
investigated.
• 4.4.3* A written report
…
• 4.4.4* A summary of
the incident
investigation report
shall be shared with
affected personnel…

• 6.1.1.1 Those portions of
the process and facility
interior where dust
accumulations exist
external to equipment in
sufficient depth to
prevent discerning the
underlying surface color
shall be evaluated to
determine if a dust
explosion hazard or flash
fire hazard exists.

• 6.1.1.3* Dust flash fire or
dust explosion hazard
areas shall additionally be
determined in accordance
with any one of the
following four methods:
• Layer depth criterion
method in 6.1.3
• Mass method A in 6.1.4
• Mass method B in 6.1.5
• Risk evaluation method in
6.1.6
The NFPA 2 day course on combustible
dust covers these assessment.

• 6.2 Segregation, Separation, or
Detachment of Combustible Dust
Handling and Processing Areas.
• 6.2.1 General. Areas in which
combustible dusts are produced,
processed, handled, or collected such
that combustible dust accumulation
on exposed or concealed surfaces,
external to equipment or containers,
exceeds the threshold as determined
in Section 6.1, shall be detached,
segregated, or separated from other
occupancies to minimize damage
from a fire or explosion.

• 7.3.2* Pneumatic Conveying,
Dust Collection, and Centralized
Vacuum Cleaning Systems.
• 7.3.2.1 The design of the system
shall be documented, and the
documentation shall include the
following information:
• Data on the range of particulate
size
• Concentration of combustible
dust in the conveyance air stream
• Potential for reaction between
the transported particulates and
the extinguishing media used to
protect process equipment
• Conductivity of the particulates
• Other physical and chemical
properties that could affect the
fire protection of the process

Mitigation Ignition source control
• Electrical equipment
• Class II, Division 1 and 2
• Consider equipment both inside dust handling equipment and outside
• Static electricity control
• Grounding and bonding are key
• Inspection of ground and bonding means
• Vibrating equipment (e.g., sifters) may cause fatigue failure in straps
• 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
• Mechanical integrity management system/vibration analysis system
• Hot work program
• Open flames
• Design of heating systems & heated surfaces
• Use of tools & vehicles
• Maintenance
• Comfort heating equipment shall obtain combustion air from clean outside source

Damage Control
• Detachment (outside or other bldg.)
• Separation (distance within same room)
• Segregation (barrier)
• Pressure resistant construction
• Pressure relieving construction
• Pressure Venting
• Relief valves
• Maintenance
• Specialized detection systems
• Specialized suppression systems
• Explosion prevention systems
• Maintenance

Safety and Health Information Bulletin
• Purpose
• Background
• Elements of a Dust Explosion
• Facility Dust Hazard Assessment
• Dust Control
• Ignition Control
• Damage Control
• Training
• References

Resources and Questions?
• NFPA 2-day
Combustible Dust
Seminar
• Combustible Dust
Guidebook - NFPA
• OSHA SHIB
• www.csb.gov
• LinkedIn
Combustible Dust
Forums
• Facebook Grain Mill
Accident page

189
NFPA Definitions and Terminology
• Air-Material Separator (AMS). A device designed to separate the conveying air
from the material being conveyed.
• Combustible Dust. A finely divided combustible particulate solid that presents a
flash fire hazard or explosion hazard when suspended in air or the process-specific
oxidizing medium over a range of concentrations.
• Minimum Explosible Concentration (MEC). The minimum concentration of a combustible dust
suspended in air, measured in mass per unit volume, that will support a deflagration.
• Minimum Ignition Energy (MIE). The lowest capacitive spark energy capable of
igniting the most ignition-sensitive concentration of a flammable vapor-air mixture
or a combustible dust-air mixture as determined by a standard test procedure.

Grain Definitions
• 1910.272(c) Definitions.
• "Choked leg" means a condition of material buildup in the bucket elevator that results in the stoppage of material flow and
bucket movement. A bucket elevator is not considered choked that has the up-leg partially or fully loaded and has the boot
and discharge cleared allowing bucket movement.
• "Flat storage structure" means a grain storage building or structure that will not empty completely by gravity, has an
unrestricted ground level opening for entry, and must be entered to reclaim the residual grain using powered equipment or
manual means.
• "Fugitive grain dust" means combustible dust particles, emitted from the stock handling system, of such size as will pass
through a U.S. Standard 40 mesh sieve (425 microns or less).
• "Grain elevator" means a facility engaged in the receipt, handling, storage, and shipment of bulk raw agricultural
commodities such as corn, wheat, oats, barley, sunflower seeds, and soybeans.
• "Hot work" means work involving electric or gas welding, cutting, brazing, or similar flame producing operations.
• "Inside bucket elevator" means a bucket elevator that has the boot and more than 20 percent of the total leg height (above
grade or ground level) inside the grain elevator structure. Bucket elevators with leg casings that are inside (and pass through
the roofs) of rail or truck dump sheds with the remainder of the leg outside of the grain elevator structure, are not
considered inside bucket elevators.
• "Jogging" means repeated starting and stopping of drive motors in an attempt to clear choked legs.
• "Lagging" means a covering on drive pulleys used to increase the coefficient of friction between the pulley and the belt.
• "Permit" means the written certification by the employer authorizing employees to perform identified work operations
subject to specified precautions.

191
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.

• Class II, Division 1: One of the following three situations must exist in order for an area
to be considered a Class II, Division 1 location:
• Where combustible dust is present in the air under normal operating conditions in such
a quantity as to produce explosive or ignitable mixtures. This could be on a continuous,
intermittent or periodic basis.
• Where an ignitable and/or explosive mixture could be produced if a mechanical failure
or abnormal machinery operation occurs.
• Where electrically conductive dusts in hazardous concentrations are present.

• Class II, Division 2: One of following two situations must exist in order for an area to be
considered a Class II, Division 2 location:
• Combustible dust will not normally be in suspension in the air in quantities sufficient to
produce explosive or ignitable mixtures, and dust accumulations will normally be
insufficient to interfere with the normal operation of electric equipment or other
apparatus, but combustible dust may be in suspension in the air as a result of infrequent
malfunctioning of handling or processing equipment.
• Resulting combustible dust accumulations on, in or in the vicinity of the electric
equipment may be sufficient to interfere with the safe dissipation of heat from electric
equipment or may be ignitable by abnormal operation or failure of electric equipment.

Particle Size of Common Materials
Common Material Size (microns)
Salt 100
Granulated
white sugar
450 - 600
Sand 50+
Talc, Dust (baby) 10
Mold Spores 10 – 30
Human Hair 40 - 300
Fluor 1 - 100
194Source: OSHA y Filtercorp International Ltd.

195
Source: Dust Explosions in the Process Industries, Second Edition, Rolf K Eckhoff
Explosible Range
Dust
Deposit
Explosible
Range
IH
Range
10-3
10-2
10-1
1 10 101
102
103
104
105
106
MASS OF POWDER/DUST PER UNIT VOLUME [g/m3
]

196
Definitions and Terminology
•Minimum Ignition Temperature (MIT). The lowest
temperature at which ignition occurs.
–the Smaller the particle size – the Lower the MIT
–the Lower the moisture content - the 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

197
Definitions and Terminology
•Deflagration Index, Kst – Maximum rate of
pressure rise (dP/dt) normalized to 1.0 m3
volume.
•Pmax – The maximum pressure reached during
the course of a deflagration.

198
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 0 No explosion
St 1 >0 and
<=200
Weak
explosion
St 2 >200 and
<=300
Strong
explosion
St 3 >300 Very strong
explosion

NEP OSHA References
• References.
• A. OSHA Regional Notice (Region III), Directive Number: 2006
- 556 (CPL 04), Local Emphasis Program for Dust Explosion
Prevention, October 1, 2006.
• B. OSHA Instruction CPL 02-00-103, Field Inspection
Reference Manual, September 26, 1994.
• C. OSHA Instruction CPL 02-01-004, Inspection of Grain
Handling Facilities, 29 CFR 1910.272, November 8, 1996.
• D. OSHA Instruction CPL 02-01-038, Enforcement of the
Electric Power Generation, Transmission, and Distribution
Standard, June 18, 2003.2
• E. Safety and Health Information Bulletin (SHIB)--Improper
Installation of Wood Dust Collectors in the Woodworking
Industry—May 2, 1997.
• K. NFPA 70, National Electrical Code (2005).
• L. NFPA 77, Recommended Practice on Static Electricity.
• M. NFPA 86, Standard for Ovens and Furnaces.
• N. NFPA 120, Standard for Fire Prevention and Control in Coal
Mines.
• O. NFPA 91, Standard for Exhaust Systems for Air Conveying
of Vapors, Gases, Mists, and Noncombustible Particulate
Solids (2004 Edition).
• P. NFPA 484, Standard for Combustible Metals (2006 Edition).
• Q. NFPA 499, Recommended Practice for the Classification of
Combustible Dusts and of Hazardous (Classified) Locations for
Electrical Installations in Chemicals Process Areas (2004
Edition).
• R. NFPA 654, Standard for the Prevention of Fires and Dust
Explosions from the Manufacturing, Processing, and Handling
of Combustible Particulate Solids (2006 Edition).

References
• S. NFPA 664, Standard for the Prevention of Fires and
Explosions in Wood Processing and Woodworking Facilities
(2007 Edition).
• T. NFPA 2113, Standard on Selection, Care, Use and
Maintenance of Flame Resistant Garments for Protection of
Industrial Personnel Against Flash Fire.
• U. ASTM E1226 – 05, Standard Test Method for Pressure and
Rate of Pressure Rise for Combustible Dusts.
• V. ASTM E1515, Standard Test Method for Minimum
Explosible Concentration of Combustible Dusts.
• W. FM Global, Data Sheet No. 7-76, Prevention and
Mitigation of Combustible Dust
• Explosions and Fire (2006 Edition).
• X. National Materials Advisory Board (NMAB) 353-3-80,
Classification of Combustible Dusts in Accordance with the
National Electrical Code.
• Y. NFPA 85, Boiler and Combustion Systems Hazards Code
(2007 Edition)

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