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Dust Explosion
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Dust Explosion
Do you know that DUST can
EXPLODE?
‘eh, where can dust explode la’
‘Don’t tipu la..’
‘I got see dust everyday what no explode also what’
‘Yes ah, how come uh?’
And the most common, ‘really?’
‘prove it?’
Many don’t realize
THIS Can give you
THIS
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
The explosion involved a part of the building used to compound rubber
Imperial Sugar Company, Port Wentworth GA. Explosion and Fire Feb. 7, 2008 13 Dead and Numerous serious injuries
PERAI, Nov 8 2006(Bernama) — Eight workers of a motorcycle wheel rim
factory, Excel Rim Sdn Bhd, in Prai industrial area here, were injured when a
DUST COLLECTOR MACHINE at the factory suddenly exploded and led to a
fire that burned the facility to the ground.
Penang Fire and Rescue Department Assistant Director (Operations)
Mohamad Razam Taja Rahim said WORKERS WERE FLUNG BY THE
FORCE OF THE EXPLOSION which occurred at 10.15am.
LOSSES ESTIMATED AT OVER RM1 MILLION and the cause of the
explosion is being investigated, he added.
– BERNAMA
Man, trapped in control room, killed in factory explosion at Seberang
Perai Industrial Park
• Fire is a rapid oxidation process with the evolution of light and heat in varying intensities.
Means to burn down
Subsonic combustion (slower than the speed sound)
It propagates through thermal conductivity (heat transfer)
Hot burning layer heats the next layer and ignites It goes through thermal conductivity of individual layers so it keeps travelling in the material and then ignites it
Dust explosion is a rapid oxidation of the particle surface
Fuel
Dispersion
Oxygen
Confinement
Ignition
Explosive Pentagon
Increasing the surface to mass ratio allows
less heat to dissipate into the mass.
9% 9%
9%
6%
6%
5%
9% 11%
3%
3%
30%
static electricity
friction
fire
hot surface
self ignition
welding
smoulder spots
unknown
electrical equipment
other
mechanical sparks
Minimum ignition energy
Flammable limits
Deflagration Index, KSt.
Maximum Explosion Pressure
Ease of dispersion in air
Expanding gases in the first vessel displaces unburned gases into the second, pre-compressing the mixture and increasing the peak explosion pressure
Ignition Path
Pressure Developed
20m3 to 4m3 Vessel
75.9psi
210.0psi
4m3 to 20m3 Vessel
95.0psi
83.4psi
Example
Combustible dust are considered class 2 dusts
Class 2 Combustible Dusts are divided into
three groups.
Group E : Metal Dusts
Group F : Carbonaceous Dusts
Group G : All the other dusts not found in
Group E and F
In order for a dust explosion to occur it is necessary for the dust to be in suspension, and within its flammable range.
A unique characteristic of dusts is their potential to accumulate on surfaces, and then to be re-suspended, a strong air movement or shock wave.
Time, msec.
(Timing of actual events may vary)
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Primary deflagration inside process equipment
Shock wave caused by primary deflagration
Time, msec.
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Time, msec.
0 25 50 75 100 125 150 175 200 225 250 300 325
Shock waves reflected by surfaces within the building cause accumulated dust to go into suspension
Time, msec.
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Dust clouds thrown in the air by the shock waves
Time, msec.
0 25 50 75 100 125 150 175 200 225 250 300 325
Primary deflagration breaks out of the equipment enclosure - creating a source of ignition
Time, msec.
0 25 50 75 100 125 150 175 200 225 250 300 325
Secondary deflagration ignited
Time, msec.
0 25 50 75 100 125 150 175 200 225 250 300 325
Secondary Deflagration is propagated through the dust clouds
Time, msec.
0 25 50 75 100 125 150 175 200 225 250 300 325
Secondary
deflagration bursts
from the building
Time, msec.
0 25 50 75 100 125 150 175 200 225 250 300 325
Collapsed building with remaining fires
A crucial key to the reduction of fires and explosions is housekeeping.
Housekeeping relates to hazards in addition to fires and explosions.
Research has shown that facilities that are well maintained experience fewer fires, explosions and other accidents
DUST COLLECTORS
Storage Enclosures (e.g., silos, bins, hoppers, etc.)
Pneumatic Conveying Systems
Air-Material Separators
Size Reduction (e.g., hammermills, granulators, grinders, etc.)
Material Feeding Devices (bucket elevators)
Heating Equipment
Deflagration Venting
Suppression
Oxygen Reduction
Deflagration venting through a listed dust retention and flame-arresting device
Isolation (prevent propagation) – chokes, rotary valves, flame front diverters, fast acting valves
Basically, explosion suppression is accomplished in the following steps.
1st •Control
2nd •Detection
3rd •Agent Injection
4th •Suppression
Isolation
Venting
Fike Explosion Venting
Fike Explosion Suppression
Beethoven
