Transcript Dust Explosion(21-25) - UCSB College of Engineering

Dust Explosion
- Mallika Gharpure
Ravikumar gogar
Trupti Gawai
Gokul Gopal
Samyak Gayakwad
Introduction
What it is?
 Dispersion of powders in air
 Form of cloud
 Suitable concentration
 Presence of effective ignition source
Where it can occur?
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Combustible powders
Fine materials
Foods, pharmaceuticals
wood, plastics
Metals, rubber
How it can occur?
Explosible Dust
 Particle size distribution for propagation of
flame
 Presence of oxidant in atmosphere
 Dust cloud concentration within explosion
range
 Ignition source
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What are the associated factors?
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Dust and explosion violence : pressure,
speed
Composition of Dust
Particle Size
Concentration of dispersed dust : LEL,UEL
T, P, moisture content, scale of vessel
Case Study
Process :
 equipment used to pulverize aluminumalloy
 air recycled through a grinder, cyclone
product separator, blower
 a side stream to extract undesired dust to
a dust collector
Batch To Continuous
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a much higher rate of dust generation
high concentrations of very fine dust in the
recycle stream
accumulation of heat in the recycle stream.
installer of the recycle system with no
experience with combustible powders
no explosion prevention or protection devices or
systems provided.
The Accident
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concentration of dust in the circulating air stream above
LEL in most of the recycle system
relatively high temperature of the circulating air
exothermic oxidation of accumulated combustible dust in
the return-air ductwork
an access door on the grinder forcibly ejected, the door
struck the LPG cylinder on a nearby forklift truck.
Escaping LPG vapors – ignited by the dust fireball from
the open grinder door – resulted in a flash fire
fatal burn injuries to the forklift driver
lessons learned from this incident
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Every significant change in a process should be
subjected to a Management of Change analysis
Producers of hazardous materials (and
particularly small-company producers) need to
follow Codes and Standards that apply to their
processes
Code-enforcing authorities should become
more familiar with Codes and Standards that
apply to dust-explosion hazards
Dust-explosion characteristics need to be
included in Material Safety Data Sheets.
Dust Control
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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
Use cleaning methods that do not generate dust clouds,
if ignition sources are present
Locate relief valves away from dust hazard areas
Develop and implement a hazardous dust inspection,
testing, housekeeping, and control program (preferably
in writing with established frequency and methods).
Ignition Control
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Use appropriate electrical equipment and wiring
methods
Control smoking, open flames, and sparks
Control mechanical sparks and friction
Use separator devices to remove foreign
materials capable of igniting combustibles from
process materials
Separate heated surfaces from dusts
Separate heating systems from dusts
Proper use and type of industrial trucks
Adequately maintain all the above equipment.
Damage Control
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Separation of the hazard (isolate with distance)
Segregation of the hazard (isolate with a barrier)
Deflagration venting of a building, room, or area
Pressure relief venting for equipment
Provision of spark/ember detection and
extinguishing systems
Explosion protection systems
Sprinkler systems
References
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‘Dust Explosion Prevention and Protection’ By John Barton
Process safety progress 2007, vol. 26, no4, pp. 324-329
NFPA 654, Standard for the Prevention of Fire and Dust Explosions
from the Manufacturing, Processing, and Handling of Combustible
Particulate Solids
Occupational Safety and Health Administration (OSHA), the
Massachusetts Office of the State Fire
Marshall, and the Springfield Arson and Bomb Squad. "Joint Foundry
Explosion Investigation Team Report." OSHA, Springfield
Thank You….