presentation 12 xs

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

Deflagration

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)

0 25 50 75 100 125 150 175 200 225 250 300 325

Primary deflagration inside process equipment

Shock wave caused by primary deflagration

Time, msec.

0 25 50 75 100 125 150 175 200 225 250 300 325

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.

0 25 50 75 100 125 150 175 200 225 250 300 325

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