When a ‘Controlled Burn’ Response might be Appropriate

Presentation by Byrne Ó Cléirigh

Shane Malone, BE MIE, Chartered EngineerThomas Leonard, BE MEngSc, Chartered Engineer

Byrne Ó Cléirigh – Who we are

• Independent, knowledge-based company

• Founded in 1981

• Core discipline is engineering

• Areas of expertise:

– Supply & Use of Energy

– Environmental Protection

– Safety & Risk Management

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Where might Fire Fighting Response be Required?• Petroleum bulk storage

– Tank fire, bund fire, unbunded fire

– Explosions, secondary fires

• Warehousing

– Flammable and combustible goods

• Production plant

– High temperature, high pressure reactors

– Potential for flammable / explosive mixtures

(Images from www.hse.gov.uk)

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Source: www.hse.gov.uk

Risk Assessment / All Necessary Measures

• Hazard Identification and Risk Assessment :

– Identify accident scenarios

– Assess Risk associated with each scenario

– Risk is a combination of Likelihood and Severity of Impact

– All necessary measures to protect people and the environment

• Risk is managed by prevention and mitigation measures

• Fire protection systems are an example of risk mitigation

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Fire Fighting Policy

• IP19 identifies two extremes:

– Burn down

– Total Protection

• Arrangements usually fall somewhere between the two

• Appropriate Policy is determined using best judgement

– When to fight a fire and when to allow a fire to burn down

• Various criteria can be used for making this determination

– PPG 28 Controlled Burn (UK Environment Agency)

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Assessment Criteria• Pollution Prevention Guideline (PPG28)

– Risk to people from fire

– Impact of smoke plume (meteorological and topological factors)

– Potential to extinguish the fire successfully

– Risk of fire spreading

– Presence of important buildings in the vicinity

– Ability to retain fire fighting water

– Potential impacts should fire water run off escape

• Business continuity

• Perception of risk / company reputation

• Discussions with competent authorities

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Risk to People from Fire

• People outdoors:

– Potential for direct exposure to thermal radiation

– Thermal dose (heat flux and exposure time): serious burns, lethal effects

• People indoors:

– Shelter in place: building response – materials of construction

– Safe evacuation: exposure levels at exits to building

• Does policy affect the risk to people?

– Extinguishment

– Burn down

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Development of Fire

– Growth / Decay phase: Lower burning rate; lower temperature plume; less buoyant

– Fully Developed phase: Higher burning rate and emission rates; more buoyant plume

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Smoke Plume – Growth / Decay Phase

• May be potential risk to people from smoke

– Lower buoyancy, less plume rise

– Potential for higher concentrations at ground level

– Potential for plume grounding in high winds

– Topography factors

– Type of fire:

• Rapid development for liquid pool

• Slow development for warehouse

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Smoke Plume – Fully Developed Phase

• Higher rate of burning

– Increased smoke generation

• High temperature smoke plume

– Buoyancy / plume rise

– Little or no risk from smoke to people

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Source: www.buncefieldinvestigation.gov.uk

Rate of Development of Fire – Petroleum Storage

• Rapid growth phase

– Velocity of flame front over pool surface

• Characterised by fully developed phase

• Burn down velocities (Yellow Book)

– Kerosene: 0.039 kg/m2.s (2.9 mm per min)

– Gasoline: 0.055 kg/m2.s (4.4 mm per min)

• Depth of liquid

– Tank Fire: 12 m depth – 2 to 3 days

– Bund Fire: 1.5 m depth – 6 to 9 hours

– Unbunded: 50 mm depth – 10 to 15 min

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Source: www.buncefieldinvestigation.gov.uk

Ease of Extinguishment – Calculate Requirements

• Water / Foam Application Rates (IP19, NFPA, etc)

– Size of fire – rates expressed as l/min/m2

– Type of fire – tank fire, pool fire (surface area)

– Manner of application – fixed or mobile systems

• Duration of Application

– Type of product (Class I or Class II)

– Type of fire – tank fire, pool fire

– Manner of application – fixed or mobile systems

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Ease of Extinguishment

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Source: “The Storage of Flammable Liquids in Tanks” (UK HSE)

Escalation / Domino Effects

• Potential risks with either policy

• Consequence modelling

– Protective cooling to exposed tanks

– Heat flux vs. distance

– Duration of fire event

• Fire resistance of bunds

• Logistics of applying protective cooling to tanks

– Safe distance for fire responders

– Range or throw of fire protection equipment

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Retention of Fire Fighting Water / Foam• Bunded Tank Farm – retention capacity of bund

– Total quantities of material released in fire event (bund fire)

– Total quantities of water / foam applied

• If retention capacity is insufficient, what would escape:

– Foam: will float on top of burning petroleum product

– Burning Product: this could be displaced by the application of water

• Environmental Fate

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Source: “Guidance Note on Storage and Transfer of Materials for Scheduled Activities” (EPA)

Example of Hypothetical Terminal

16Source: Google Maps

Example of Hypothetical Terminal – Tank Fire

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• Bottom injection

• Adjacent tank cooling

• Mobile monitors – water available at high pressure

• Impermeable bund

• Policy & plan is to mount attack on fire

– Have the equipment

– Reduces potential consequences

Example of Hypothetical Terminal – Intermediate Bund

Have water & foam

Have mobile equipment

Spill and fire contained

Cool adjacent tanks with

fixed systems

No local populated areas affected

by Smoke Plume

X No bund pourers

X Restricted access

X Access dependant on wind direction

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Example of Hypothetical Terminal – Large Bund Fire

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X Do not have water & foam

X No bund pourers

X Do not have mobile equipment

Spill and fire contained

Cool adjacent tanks with fixed

systems

No local populated areas affected

by smoke plume

Example of Hypothetical Terminal

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Controlled burn might be appropriate Tank Int. Large

1 People are not at risk, or a controlled burn will reduce the risk to people. Yes Yes Yes

2 There is a low success forecast of extinguishing the fire. No ? Yes

3 Fighting the fire with other techniques would pose a significant risk to fire fighters

No ? Yes

4 Property is beyond salvage. Yes Yes Yes

5 Fire conditions, meteorological conditions and the local topography are appropriate for minimising the air quality impacts.

Yes Yes Yes

6 Firewater run‐off would damage an area of high environmental sensitivity. Yes Yes Yes

7 Firewater run‐off would not affect potable supply intakes and other abstractions.

Yes Yes Yes

8 Firewater run‐off could not impair the operation of a sewage treatment plant.

Yes Yes Yes

Conclusions

• Various criteria to be weighed up in Fire Fighting Policy

• Controlled Burn may be appropriate policy in some instances

• Policy must be clearly developed and understood

– In some cases it will be a matter of judgement on the day

• Policy must be agreed between Operator and Emergency Services

– Both have role in implementing emergency response plans

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Source: IP19 - Fire precautions at petroleum refineries and bulk storage installations

When a ‘Controlled Burn’ Response might be Appropriate

Presentation by Byrne Ó Cléirigh

Shane Malone, BE MIE, Chartered EngineerThomas Leonard, BE MEngSc, Chartered Engineer