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Pitfalls to avoid in the area of dust

prevention & protection

Sam Clayton, HRL Technology

Dust Explosions Conference

17-18th June 2014

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Presentation Outline

• Common pitfalls in dust prevention and protection

• Relevant case studies / photographs

• Recommended steps to avoid pitfalls

Dust Explosion Conference,

17-18th June 2014

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Safety Depends on a Number of Factors

The variety of factors leads to a wide range of potential pitfalls

Dust Explosion Conference,

17-18th June 2014

SAFETY

Material

Properties

Equipment /

Process

Procedures

Acceptable

residual risk

Human factors

Deviations

Potential Pitfalls (in no particular order)

• Poor housekeeping

• Inadequate or ineffective training

• Lack of understanding

• Workforce complacency

• Lack of hazard analysis

• Change management

• Poor procedures

• Reliance on a risk mitigation

method

• Low probability, high

consequences of events

• Cost of incidents

• Cutting costs

• Risks vary by plant and process

• Deviations in operation - Start-up

and Shutdown

• Air Lancing / Water sprays

• Inadequate earthing

• Spontaneous Combustion

• Many more ………

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Pitfall 1: Low Probability, Severe Consequences

• Risk probability of explosions is often low

• However, consequences can be severe – Loss of lives

– Injuries

– Plant damage

– Loss of production

– Company reputation

• US - A 2006 Chemical Safety Board study identified 281

combustible dust fires and explosions between 1980 and

2005 that killed 119 workers and injured 718, and extensively

damaged industrial facilities.

Dust Explosions are a Major Concern

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Flixborough Cyclohexane

UK 1974

• Gas Explosion

• 28 dead

• $450 million

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Blaye, France, 1997

• Grain storage

facility

• 11 dead

• 1 injured

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Before

After

January 25, 2012 8

Gunnedah Dust Explosion, 2003

• Pet food factory

• Close to home!!

• Cost more than $10 million

• Propane leak: primary explosion

• Dust: Secondary explosion

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Esso Longford Natural Gas 1998

• Massive impact on

the Victorian

community

Pitfall 2: Poor Housekeeping

• Common violation encountered is hazardous levels

of dust accumulation in workplaces

• How much dust is safe

– 0.8 mm layer is considered hazardous

– Rule of thumb: “if an OSHA inspector can run his finger

across a dusty surface or see a footprint, that is considered

a citable condition”

• Clean-up of floors and work surfaces is not enough

– Dust accumulates on elevated surfaces, rafters, etc

10

1 mm dust layer

Explosible Dust

Cloud

5m

high

room

Spillage from equipment

Dust on surfaces

Dust Explosion Conference,

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Secondary Explosion – Domino Effect

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• Often more

severe than

primary explosion

Dust Explosion Conference,

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Steps for Good Housekeeping

• Minimise generation of dust if possible

• Develop procedures and schedule for housekeeping

– Remove accumulations routinely and thoroughly

• Make staff aware of hazards and procedures - training

• Undertake site audits – internal/external

• Use appropriate equipment for dust cleanup

– eg. explosion proof vacuums, soft brooms

– Don’t use pressurised air or water jets for cleaning

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Pitfall 3: Lack of Hazard Analysis

Failure to conduct hazard analysis is a common oversight

• Understanding of dust properties

– Is the dust explosive?

– How explosive?

• Change management

– What are the impacts of a change in feedstock or process or

equipment or staff?

– Understanding of inherent safety features in the plant.

• Analysis is required to assess risk and the level of fire and

explosion protection required

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Explosions for Different Dust Types

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70% of organic

dusts are

explosible

Explosion by Plant Type

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Steps in Hazard Analysis and Risk Assessment

• Understand your dust – Determine explosibility of dust (Kst, Pmax)

– Information required for design of explosion

prevention equipment

• Understand your process

– Conduct hazard analysis and risk assessments

• Internal analysis or by external consultant

• Follow relevant standards for risk assessments and

management (eg. AS/NZS ISO 31000)

• Implement findings

• Effective change management

• Continual improvement

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Pitfall 4: Reliance on Single Mitigation Method

• Failure in primary mitigation method can lead to incidents

• Example is reliance on venting

• Risks should be dealt with in multiple ways

• Therefore require a mitigation strategy in order to

– prevent explosions from occurring and

– limit the effects should an explosion occur.

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Integrated Explosion Protection

• Replace materials, minimise dust, avoid

explosive concentrations, inert processes

• Anticipate and eliminate ignition sources

• Design, earthing, maintenance,

procedures

• Containment, Isolation, Suppression,

Venting, Siting

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Prevent the formation of

explosive atmospheres

Prevent the ignition of

explosive atmospheres

Protect to minimise the

effects of an explosion

1

2

3

Hierarchy of Controls

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Elimination

Substitution

Engineering

Controls

Administrative

Controls

PPE

Isolation

More

Effective

Less

Effective

Pitfall 5: Spontaneous Combustion

• Many combustible materials exhibit self-heating characteristics

(eg. coal, biomass)

• Self-heating in storage occurs due to surface oxidation or

through microbial action (eg composting)

• Given suitable conditions (eg. volume, time, moisture), self-

heating can lead to spontaneous combustion

• Spontaneous combustion can occur for layers on hot surfaces

• Spontaneous combustion is a common ignition source for

explosions

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Example: Coal Plant Explosion and Fire

• $5 - 6M damage bill, 8 months out of service

• 80 people lost jobs

• 2 injuries

• Extensive damage to 2 buildings

• Root Cause: Spontaneous combustion of dried coal on an out of service conveyor

Major contributing factors • Self-heating material • Coal leaks in process • Inadequate housekeeping • Fire doors left open • Insufficient fire protection • Inadequate dust extraction

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Steps to Managing Spontaneous Combustion Risks

• Characterise the self-heating characteristics properties of your

dust

– Storage

– Layers on hot surfaces – Minimum ignition temperature

• Consider self-heating propensity during hazard analysis,

design, etc

• Prevent build-up of dust layers

– Effective housekeeping

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Case Study 1 – Imperial Sugar Refinery

• 2008, Port Wentworth, Georgia, US

• Sugar refining, storage and packaging

• Refinery operated since 1917

• Primary explosion in a conveyor

• Series of secondary dust explosions and fires

• Deaths 14

• Injured 36

• Cost ???

• Deaths most likely due to secondary explosions

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Imperial Sugar Refinery Incident

• Steel belt conveyor below silos fully enclosed

in 2007

– No dust removal system or venting

• Explosion initiated in the conveyor

• Ignition source – unknown

– Most likely heated bearing in conveyor

• Explosion transferred along the enclosed

conveyor

• Series of secondary explosions and fires

– Sugar dust accumulations provided additional fuel

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Factors which led to explosion

• Inadequate design and maintenance of equipment

• Inadequate risk assessment - modifications to plant

– Enclosed conveyor with no venting

• Poor housekeeping practices

• Poor management

• Inadequate procedures for:

– Dust control

– Housekeeping

– Training

– Evacuation

• Highlights range of pitfalls

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Conclusions: Steps for Avoidance of Pitfalls

• Identify and control explosion risks – Understand your process and dust

– Hazard analysis

– Use multiple methods to minimise risk

• Implement effective safety and operations practices – Develop, follow and improve procedures & processes

– Effective housekeeping practices

– Training of staff

– Good communication and safety culture

– Report near misses/hazards

– Undertake auditing

– Complete adequate plant maintenance

• Safety relies on contribution from all staff

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HRL Technology

• Engineering consulting company

• HRL Capabilities

– Dust Explosion Awareness Training

– Dust Handling and Safety Audits

• Walk-through inspection

• Risk assessments

• Review of procedures and documentation

– Characterisation of dust properties

– Process and equipment evaluation

– Transport and stockpiling of dusts

• Characterisation of propensity for spontaneous combustion

• Dangerous Goods Classification

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HRL Technology Pty Ltd ABN 95 062 076 199 www.hrlt.com.au info@hrl.com.au Sam Clayton +61 3 6565 9864

Victoria

Mulgrave (Head Office)

Level 1, Unit 9

677 Springvale Road

Mulgrave 3170 Australia

Tel +61 3 9565 9888

Fax +61 3 9565 9879

Morwell

Tramway Road

Private Bag No. 1

Morwell 3840 Australia

Tel +61 3 5132 1500

Fax +61 3 5132 1580

Queensland

Coopers Plains

Unit 2

33 - 37 Rosedale Street

Coopers Plains 4108 Australia

Tel +61 7 3423 4300

Fax +61 7 3345 5937