Preventing_Dust_Explosions.pdf

� Share current events that involve dust related explosions

� Share knowledge, with effective safety training relevant to:- explosive properties of the materials used in your operation- conditions to avoid for mitigation and control of accumulating

dust

� Perform routine inspection and monitor potential ignition sources via safetyhazard inspection and preventative maintenance activities

� Emphasize Safe Work Practices by strictly enforcing and adhering tosafety procedures aimed at dust prevention and control.

SUMMARY

Preventing Dust Explosions

Safe Work Practices Reduce Risk

"Preventing Dust Explosions - What You Need to Know"

PNEAC, PNEAC Forum, Gary Jones’ Health & Safety Alerts, Dust Safety Fact Sheet

Ignition Control

Loss Control (administrative) Measures:

� When non-routine work is performed ensure pre-job planning is completed to identify hazards and mitigate/control all potential ignition sources

BEFORE THE WORK BEGINS!

� Provide employee safety training and guidance in safe work practices that emphasize ignition control




Ignition Control

Loss Control (administrative) Measures:

� Ensure safety procedures are in place and actively enforced to address ignition control

� Ensure a hazard assessment has been performed for the operation

� Periodically review the hazard assessment to make certain it isup-to-date and current with existing operations & processes




Ignition Control

� Avoid contact between heated surfaces and dusts

� Separate heating systems from dusts

� Ensure the proper Type of industrial trucks are in use

� Ensure the proper Type of cartridge-activated tools are in use




Ignition Control

� Use approved electrical equipment and wiring methods

� Keep static electricity under control; this includes bonding of equipment to

ground

� Prevent smoking, open flames, and sparks, mechanical sparks and friction

� Use separator devices to remove foreign materials capable of ignitingcombustibles from process materials




Dust Control

� Use cleaning methods that do not generate dust clouds, vacuum ratherthan blow or dry sweep

� Only use vacuum cleaners approved for dust collection

� Locate relief valves away from dust hazard areas

� Develop and implement a program for hazardous dust inspection,testing, housekeeping, and control program that establishes, in writing,

the method and frequency of these steps




Dust Control

� Minimize the escape of dust from process equipment or ventilation systems

� Use dust collection systems and filters

� Try to use surfaces that minimize dust accumulation and are easy to clean

� Inspect for dust residues in open and hidden areas, and clean them atregular intervals

Safe Work PracticesReduce Your Risk


Preventing/Controlling Dust Explosions


www.OSHA.Gov

Chapter 2: Preventing Dust Formation

Example Control Techniques

Many More

@




Transfer Chutes:

� The chute should be big enough to avoid jamming of material.

� The chute should be designed so the material falls on the sloping bottom of the chute and not on the succeeding equipment.

Source: http://www.osha.gov/SLTC/silicacrystalline/dust/chapter_2.html



Belt Conveyor:

� The amount of dust generated at belt conveyor transfer points depends on the way the material is loaded onto the belt.

� To reduce dust generation the material should be loaded onto the center

of the belt.

Impact at Loading Point:

� A momentary deflection of the belt between two adjacent idlers may resultwhen ore strikes the belt. Tighten center to center spacing between idler rollers to reduce dust.

Source: http://www.osha.gov/SLTC/silicacrystalline/dust/chapter_2.html




� Direct Spouting - Pile Loading:

Dust control is achieved by minimizing point-to-point product transfer



� Direct Spouting Container Loading:

Dust control is attained by way of point-to-point transfer.



� Enclosed Conveyor:

Dust control is achieved and sustained by the enclosure itself.



� Pneumatic Dust Control:

Conveyance air is removed (vacuum) from the product streamand filtered to the atmosphere without the use of movingparts or electricity. Simple installation, efficient operation,

and portability result in a clean and safe working environment.

� Liquid Additives:

Addition of small quantities of mineral oil, vegetable oil or lecithin

is a common practice for grain dust control. The method has other applications with use of liquids compatible with the base material.



Common Engineering Strategies For Dust Concentration Reduction

Are Aimed At Elimination of ……… FUEL!

� Pneumatic Dust Control

� Liquid Additives

� Enclosed Conveyors

� Direct Spouting



Fuel

OxygenConfinement

Dispersion

Ignition

!!Destruction!!

Dust explosion prevention relies on elimination of one or

more of the conditions (ingredients), other than oxygen,

associated with such an event.



Other Unplanned Events


Choked Leg : Possible Causes….Auger Design or Maintenance???

+

= FATALITY

Possible Causes…Unassigned Work Practice (method)

or Unsafe Act



Factors That Lead to Removal of The Floor Guard

Possible Explanations!

� Grain fed too fast it piled up on the floor which required extra cleaning

� Kernels bounced off the floor guard making it necessary to sweep

� Moisture of the corn is high and the grating may cause clogging

� A small amount of residue corn may be impacted at the U-joint area of the augers,which may need to be cleaned by reaching in to this area.



Iowa Farmer/Grain Elevator Operator

Lost A Large Amount of Blood, This Lead To A Fatality

Source: public-health.uiowa.edu/FACE/Reports/REPORT-016.html

CASE IN POINT

Ignition Sources


A CHOKED CONVEYENCE LEG MAY LEAD

TO FIRE, OR AN EXPLOSION CAUSED BY FRICTION/HEAT INGNITION

HOWEVER , IT CAN LEAD TO OTHER UNPLANNED

NON-EXPLOSIVE EVENTS!

Ignition Sources


Fire At Missouri Diamond Pet Food Plant

Saturday, October 11, 2008 at 6:51 p.m.

Fire Fighter Statement:

"It got clogged up and basically with the heat and pressure, there was kind

of a smoldering fire in there,” said Meta firefighter JD Schroeder. “That we kind of had to tear things apart and get into and basically knock it all out, clean it

up, make sure it didn't expand any further than it did."

Source: KRCG-TV Jefferson City, MO Colleen Hogan

Yes !And Not Always in Grain Applications!

Ignition Sources


Choked Leg Friction Is A Grain Transfer Term

� Conveyors, grain augers, and bucket legs move grain

� When a feed valve drops too much grain into a conveyance systemthen…

� Material will “choke” the leg

Choked Leg Friction, CAN IT OCCUR IN OTHER

SECTORS or INDUSTRIES?

Ignition Sources


Georgia, Imperial Sugar PlantHindenburg Burning

Similarities ?

Ignition Sources


The Hindenburg disaster has been attributed to spark discharge igniting

flammable panels which led to the ignition of hydrogen gas held in orleaking from the airship at the time.

The ship had just passed through a thunderstorm and probablypicked up a large charge. Discharge occurred when mooring ropes

were dropped as it came in to land in New Jersey in 1937.

Ignition Sources


Types of ESD:

� The most spectacular form of ESD is the spark which occurs whena strong electric field creates an ionized conductive channel in air.

� This can cause minor discomfort to people and fires and explosions

if the air contains combustible gases or particles.

� Sparks can cause serious explosions because of the high temperaturesreached in a spark. Dust and grain dust explosions are suspected

as being caused by electrostatic discharges.

Ignition Sources


Electrostatic Discharge (ESD)

� The sudden and momentary electric current that flows between two objectsat different electrical potentials.

� The term is usually used in the electronics and other industries to describe

momentary unwanted currents that may cause damage to electronic equipment.

Common Ignition Sources Include

Company XYZ

Electrostatic DischargeWelding

ElectricalFailure

Tramp

Metal

Fire Besides

Welding

Foreign Object Debris

Choked

Leg Friction

Hot Bearings/

Surfaces

Ignition Sources

Sparks from machinery

Ignition Sources



Conditions For Dust Explosions



Dynamics of a DOUBLE WHAMMY…….

1) A dust explosion occurs within the equipment.

2) Internal dust is dispersed into the air.

3) The additional dust ignites due to primary explosion.



The worst dust explosion is known as a:

DOUBLE WHAMMY !



Fuel

OxygenConfinement

Dispersion Ignition

!!Destruction!!



Concentration:

� Below a certain value, the lower explosive limit (LEL), there is simply insufficient dust to support the combustion at the rate required for an explosion. A concentration 20% lower than the LEL is

considered safe.

� Similarly, if the fuel/air ratio increases above the upper explosive limit

there is insufficient oxidant to permit combustion to continue at the necessary rate.



Dispersion

Grain Dust Minimum Explosion Concentration Characteristics:

� Most experts use 50 grams/m³ as the minimum explosion concentration for grain dust

� A person standing in a 50 (g/m³) cubed of grain dust will not be able to see their fingers one foot away.

� Even if all conditions are present for a dust explosion, concentrations below 50 (g/m³) of grain dust at a transfer point generally speaking will not lead to ignition

� Note other dusts have their own MEC



What Factors Are Present For A Dust Explosion To Occur?

1) Fuel - Dust has to be combustible

1) Oxygen – Air will work

3) Confinement - Dust may be confined but not always

4) Dispersion – Particles form a cloud exceeding minimum explosion concentrations (MEC)

5) Ignition - Source is present



Dust Explosion Properties


It is small enough to be considered a dust, but it

is chemically noncombustible!

NO



Table Salt as DUST Can It Burn?



The NFPA definition of combustible dust simply means

a solid that can burn, is finely spread out in air, and is ignitable.

COMBUSTIBLE DUST EXAMPLES INCLUDE :

Common Combustible Dusts:�Coal�Sawdust�Magnesium

Mundane Materials:�Grain�Flour

�Sugar

Powdered Metals:�Aluminum�Titanium



Example Deflagration Applied In A

Controlled State……



Can Anyone Give An Example of Deflagration Applied In A

Controlled State That Is Truly Amazing ?

Remember the ingredients, let’s count them down:

Four……Fuel

Three…..Oxygen

Two…….Ignition

One…….Confinement

� An exothermic reaction….. A deflagration can have an explosive effect



What is A Deflagration Hazard?

A deflagration is defined in Section 2702 of

the International Fire Code (IFC) as follows.

An exothermic reaction, such as the extremely rapidoxidation of a flammable dust or vapor in air, in

which the reaction progresses through the unburned

material at a rate less than the velocity ofsound. A deflagration can have an explosive effect.



�The dust must consist of very small particles, where

the surface area is very large, and so will support combustion.

�Dust is defined as powders with particles less than about 500 micrometers

in diameter, but finer dust will present a much greater hazard than coarse particles by virtue of the larger surface area.



NFPA 654 defines combustible dust as….

� A combustible particulate solid that presents a fire or deflagration hazard

� When suspended in air

� Suspended in some other oxidizing medium

� Over a range of concentrations, regardless of particle size or shapes



Dust Explosion Locations & Events


Aerial View of Georgia, Imperial Sugar Plant

Source: Chemical & Engineering News



� February 07, 2008 Georgia, Imperial Sugar Plant - An explosion and fire of

combustible dust at a Georgia sugar refinery killed six workers.�44 workers were injured �20 of them severely enough to merit treatment at burn centers �17 who have been placed in "medically induced comas"

�December 31, 2008 12:00 a.m. Maricopa Arizona, grain supply companyexplosions left three workers severely burned.�hot metal that fell from a tower where welders were working hit a device

used to scoop grain out of the elevator, igniting corn dust and causing an explosion.

Source: Astrid Galvan - Dec. 31, 2008 12:00 AM The Arizona Republic,Source: Chemical & Engineering News



� Over 30% of these incidents are repeats of prior fires and explosions that

fire departments responded to.

� Subsequently, reoccurring incidents go unnoticed by OSHA, unless there are at least three injuries or one fatality.

Source: http://shameonelaine.org/2008/02/19/9-combustible-dust-explosions-so-far-in-2008



�Can you spot your industry?

Source: http://oshaunderground.blogspot.com/2009/03/2008-dust-explosions-and-fires-overview.html



The Combustible Dust Policy Institute Summary of 2008 Occurrences

concluded:

�Over 150+ combustible dust related fires and explosions occurred.

�Manufacturing, non-manufacturing and utility sectors were affected.

Source: http://oshaunderground.blogspot.com/2009/03/2008-dust-explosions-and-fires-overview.html



Nine Combustible Dust Explosion OccurredIn First Two Months of 2008:

�Minnesota�Missouri�Illinois�Ohio

�Virginia�Kansas�North Carolina�Alabama

“So far it hasn’t been thoroughly confirmed that dust caused the fire or explosion

only that dust is present in the work space where the unfortunate events occurred.”

Source: http://shameonelaine.org/2008/02/19/9-combustible-dust-explosions-so-far-in-2008



Agenda

� Locations & Events

� Properties

� Conditions for Dust Explosions

� Ignition Sources

� Prevention and Control

� Safe Work Practices - Reduce Risk


Preventing Dust Explosions

"Preventing Dust Explosions - What

You Need to Know"

Jim Puppan

Senior Loss Prevention Consultant

Accident Fund Insurance Company of America

Michigan Safety Conference

April 7, 2009

Documents

Preventing_Dust_Explosions.pdf