A Major Hazard Difficult to identify Invisible to the naked eye - - PowerPoint PPT Presentation

A Major Hazard

• Difficult to identify
• Invisible to the naked eye
• Often goes unnoticed

• Georgia, 2008.
• Sugar Dust Explosions.
• 14 killed, 38 injured.
• WV, 2010.
• Metal Dust Explosion.
• 3 killed, 1 injured.

Combustible Dust Explosions

• Wisconsin, 2017.
• Grain Dust Explosion.
• 5 killed, 12 injured.
• USA, 2018.
• 194 Dust Explosions and Fires
• +25% from 2017

Combustible Dust Explosions

What Do These Events Have in Common?

They can be prevented.

What is Combustible Dust?

A collection of fine, solid particles which, either from a single source or in a mixture with other materials, are liable to catch fire

• r explode upon ignition when dispersed in the air.

Volatility

• Some can be ignited unexpectedly

(iron dust & water)

• Measured by ‘Kst’ value
• The higher the Kst value, the more

severe of an explosion

• hsonline.com

The 5 Elements of a Dust Explosion

• 1. Fuel – The combustible dust
• 2. Oxidant – Typically the oxygen in the air
• 3. Ignition Source – Depends on the dust type
• 4. Dispersion – The accumulation and spread of particles
• 5. Confinement – Leads to rising pressure and vessel rupture

Deflagration

• Term used for flash fires and explosions
• Flash Fires are Unconfined Deflagration
• Explosions are Confined Deflagration

Combustion which propagates through a gas or across the surface of an explosive at subsonic speeds, driven by the transfer of heat.

The Two Explosions

• The initial explosion after ignition
• Dislodges surrounding dust particles

Primary Explosion Secondary Explosion

• Occurs when dust goes airborne and ignites
• This explosion is often more destructive

Prevention & Mitigation

• Prevention refers to stopping an incident from occurring

prior to its incipient stages

• Mitigation refers to protecting workers, equipment or the

environment from an incident after the incipient stages

Prevention & Mitigation

• Remove Combustible Dust
• Concentration Reduction
• Oxidizer Reduction
• Spark Detection & Control
• Proper Hot Work Systems
• Avoid Self-Ignition
• Ignition Source Control

Prevention & Mitigation

• Containment
• Venting
• Flameless Venting
• Suppression Systems

Consider Testing Your Facility

A Dust Hazard Analysis (DHA) will not only determine if there is a significant amount

• f dust in your facility, but will systematically review and identify the potential for a

fire, flash fire and explosion hazards associated with the presence of one or more combustible particulate solids arising from processes in your facilities.

Components of a DHA

• Methodology & Scope
• Material Characterization
• Process Characterization
• Hard Analysis & Recommendations
• Administrative Controls &

Recommendations

Methodology & Scope

• No single process works for every

situation

• One of the most common is Node-Based

Node

An environment that has both oxygen and a combustible dust present. A site may have only one such node or it may have nodes reaching into the hundreds.

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Material Characterization

• Listing materials by maximal pressure
• Material source and delivery method must

be included in the list

• Samples may be taken and tested from

materials with multiple or unknown components

Process Characterization

• Utilizing the documentation, testing

results and a site visit to determine risk factors

• Credible ignition sources must be

inspected

Hard Analysis & Recommendations

• A strategy is formulated to offer mitigation
• r consistent control of dust in the facility
• Information must be clear, concise and be

visible to all workers

• The report should have the goal to unite

everyone in a team effort to make the facility safe

Administrative Controls & Recommendations

• The final report should include preventative

maintenance recommendations

• Includes an emergency planning response

procedure for such events

Recap