Buncefield Presentation CI

The Buncefield Oil Depot Explosions

11th December 2005

Dougal Drysdale, University of Edinburgh

Independent Member of the Board of Investigation

Combustion Institute British Section: Spring Meetin g 2010

www.buncefieldinvestigation.gov.uk

1

●

Hemel Hempstead


2

M1

Direction from which next image is taken

Buncefield Oil Storage and Transfer Depot


Bund A

Northgate Building

Tank 912

Buncefield Lane

M1

Fuji Building


Bund A

Northgate Building

Tank 912

Buncefield Lane

M1

~200 m


• On Sunday 11 December 2005, a number of explosions occurred.

• A main explosion of massive proportions occurred at 06:01:32.

• There was a large fire, which engulfed over 20 larg e fuel storage tanks over a high proportion of the site.

• 43 people injured in the incident, none seriously. No fatalities.

• Significant damage occurred to both commercial and residential properties.

• About 2,000 people were evacuated.

• Sections of the M1 motorway were closed.

• The fire burned for five days, destroying most of t he site and emitting large plume of smoke into the atmosphere, dispersing over southern England and beyond.

• Fuel supplies to SE England were seriously disrupte d

The Incident


From W

Northgate Building


From N

Classic example of an inversion layer


Fire in Northgate Building


From S

Canary Wharf

City of London


Agencies involved:• Hertfordshire Police (co-ordinating)• Hertfordshire Fire and Rescue Service (HFRS)• Hertfordshire County Council• Dacorum Borough Council• Environment Agency• Health Protection Agency

• HFRS supported by 32 other brigades in some capacity

• At the peak of the fire on 12 December, 180 fire figh ters wereinvolved on site

• More than 750 000 litres of foam concentrate were used, together with 55 million litres of water and 30 km of high-vol ume hose.

The Response



BPA Tank 12


912

12

910915

From WWater tank

Remains of the pumphouse



Tank 12

912

The pumphouse

From N

912

12

910915

From WWater tank

Remains of the pumphouse


Tank 912

Buncefield Lane


Three Cherry Trees Lane

Bund A

Northgate Building

Tank 912

Buncefield Lane

M1

~200 m



Fuji Building

Northgate Building


Fuji Building


Damaged car found between the Northgate and Fuji Bu ildings

Tyres deflated – forced off their seals


Damaged van in the Northgate Building Car Park

Fuji Building


Line of damaged cars in Three Cherry Trees Lane (north of the Car Park)

Tank 12



24

• Joint Competent Authority of HSE and the Environment Agency under Control of Major Accident Hazard (COMAH) Regulations 1 999

• Investigation established by the Health and Safety Commissionunder Section 14.2a of the Health and Safety at Work etc. Act 1974

• Decision taken NOT to have a Public Inquiry

• Lord Newton invited to Chair an Independent Investiga tion Board of six, including two members external to the joint Competent Authority

• Eight Terms of Reference laid down

The Investigation


Eight Terms of Reference laid down

The Board


Eight Terms of Reference

1. To ensure the thorough investigation of the inciden t, the factors leading up to it, its impact both on and off site, and to establish its causation including root causes;

2. To identify and transmit without delay to duty hold ers and other appropriate recipients any information requiring immediate action to further safety and/or environmental protection in relation to storage and distribution of hydrocarbon fuels;

3. To examine the Health and Safety Executive’s and th e Environment Agency’s role in regulating the activities on this site under the COMAH regulations, considering relevant policy guidance and intervention activity;

4. To work closely with all relevant stakeholders , both to keep them informed of progress with the investigation and to contribute relevant expertise to other inquiries that may be established;

5. To make recommendations for future action to ensure the effective management and regulation of major accident risk at COMAH sites. This should include consideration of offsite as well as onsite risks and consider prevention of incidents, preparations for response to incidents, and mitigation of their effects;

6. To produce an initial report for the Health & Safet y Commission and the Environment Agencyas soon as the main facts have been established. Subject to legal considerations, this report will be made public;

7. To ensure that the relevant notifications are made to the European Commission ; and

8. To make the final report public .

to establish its causation including root causes


6. To produce an initial report for the Health & Safet y Commission and the Environment Agencyas soon as the main facts have been established. Subject to legal considerations, this report will be made public;

27

First Term of Reference:

1. To ensure the thorough investigation of the inciden t, the factors leading up to it, its impact both on and off site, and to establish its causation including root causes.

Clearly, there was loss of primary containment which led to the formation of a vapour cloud


Tank 912 contained winter grade Gasoline

Winter grade gasoline:

Actual composition unknown, but a likely composition (by weight) was deduced to be (Atkinson et al.):

n-butane (as surrogate for all C4) 9.6%

n-pentane (as surrogate for all C5) 17.2%

n-hexane (as surrogate for all C6) 16%

n-decane (as surrogate for all low-volatility hydrocarbons) 57.2%


Loss of tertiary containment


First Term of Reference:

1. To ensure the thorough investigation of the inciden t, the factors leading up to it, its impact both on and off site, and to establish its causation including root causes.

Clearly, there was loss of primary containment which led to the formation of a vapour cloud

The vapour cloud found a source of ignition, but why was the explosion so violent?


The vapour cloud found a source of ignition, but why was the explosion so violent?

Published: 21st February, 2006

Three Progress Reports


Published: 11th April, 2006Published: 9th May, 2006


Timeline of events (3 rd Progress Report)10th December 2005

19.00 hrs Transfer of fuel to Tank 912 commences (550 m3/hour)

11th December 2005

01.30 hrs Stock check – everything OK

03.00 hrs Level gauge of Tank 912 no longer changes (not detected)

05.20 hrs Calculation indicates that Tank 912 would have been full

05.38 hrs Vapour seen coming from NW corner of Bund A (CCTV)

05.46 hrs Vapour cloud 2 m deep (CCTV)

by 05.50 hrs Vapour cloud flowing off-site on to car park (CCTV)

after 05.50 hrs Pumping rate (to Tank 912) increases to 890 m3/s

06.01 hrs First explosion


C C T V Camera

White mist first seen in this locality (05:38 hrs)

Water tank

Tank 912

Also – extent of the vapour cloud


Clock incorrect -10 minutes fast


Meteorological conditions11th December 2005

At 06.30 hrs

Low windspeed (0 m/s 25 miles due south, < 3 m/s 12 miles due north*)

Temperature ~ 0oC (-1 oC 25 miles south, 1 oC 12 miles north*)

Relative humidity 99%

Atmospheric stability Pasquill Category “F” (inversion)

Consequently, the heavier-than-air vapour/air mixtu re is not dispersed, but “slumps” to form a pancake-shaped clo ud

* 25 miles south – RAF Northolt (“no air movement”)12 miles north – Luton Airport (“light westerly wind”)


Pancake-shaped cloud*:

Area at ignition – 120,000 m 2

Maximum extent – 200 m off-site to the West

Maximum depth – perhaps 4 m along Three Cherry Trees Lane to the North

(sloping site – depth < 1m to the South near the filling gantries)

Average depth taken to be 2 m ( for modelling)

Atkinson et al. estimated initial composition of the vapour/air mixture to be 6% n-butane, 6.1% n-pentane, 2.06% n-hexane in air. (Total, 14.16% hydrocarbon in air)



Northgate Building

Videocamera viewpoint

Northgate Building

05:30:29 05:45:39

05:53:43

Extent of burn damage


200 m

39


Annular deflector plate

Ullage vent

“Wind girder”


Fuel spills over deflector plate

Fuel is diverted toward the tank wall by

deflector plate

Droplet formation enhanced by intersection of

liquid sprays and vapour

Air loaded with fuel vapour

driven rapidly downward by

liquid spray

Increased surface area allows volatile fuel

fractions to evaporate and vapour gathers in

bund


Atkinson et al: Initial vapour/air mixture will be 14.2% hydrocarbon)

15m


Demonstration carried out at HSL, Buxton



Red line indicates the extent of the

burn damage and is assumed to

correspond with the limit of the vapour cloud


Telegraph pole in Buncefield Lane showing heavy sooting

Tree trunk in Northgate car park showing abrasion


47

Candidate ignition sources?

Pumphouse

Emergency Generator Cabin


Remains of the pumphouse (there was evidence of an i nternal explosion)


Candidate ignition sources?

Pumphouse

Emergency generator cabin


Location of the Emergency Generator Cabin beside th e Northgate Building


Emergency generator cabin, near the south-east corn er of the Northgate buildingClear evidence for an internal explosion


Steel post in the west car park of theNorthgate building. The post shows abrasion marks on its south face

Abrasions to the base of a tree in the Northgate building west car park, viewed from the south


Approximate location of the “directional indicators”


• Restated summary of the incident

• Set out Board’s 4 areas of concern:• Design and Operation of sites• Emergency Preparedness• Land Use Planning• CA’s policies & procedures

• Established primary containment as a key area for regulator and industry focus

• Asked the HSE to review approach to planning, with a view to taking risk further into account

• Re-stated interest in research into explosion mechanism

• Extensive appendices

Published: 13th July, 2006

Initial Report of the Board

● Re-stated interest in research into explosion mechanism



Other reports from the MIIB

Recommendations on the design and operation of fuel storage sitesPublished 29 March 2007

Recommendations on the emergency preparedness for, response to and recovery from incidentsPublished 17 July 2007

Explosion Mechanism Advisory Group reportPublished 16 August 2007

Recommendations on land use planning and the control of societalrisk around major hazard sitesPublished 15 July 2008

Policy and Procedures Review(To be published)

Explosion Mechanism Advisory Group reportPublished 16 August 2007


Appointment of Explosion Mechanism Advisory Group

Membership:

Professor Derek Bradley (Leeds University)

Professor Geoff Chamberlain (Shell Global Solutions)

Dr Laurence Cucso (Health and Safety Laboratory, Buxton)

Professor Dougal Drysdale (Edinburgh University) (Chair)

Dr Mike Johnson (Adventica)

Professor Hans Michels (Imperial College, London)

Professor Vincent Tam (BP Exploration)

The group met four times between December 2006 and Marc h 2007 – their report was submitted to the MIIB in April 2007 and published in August 2007


EMAG

Term of reference : to advise if further research was necessary to explain the violence of the explosion

All forensic evidence was made available to the Group

Modus Operandi: open discussions at each meeting, with intense activity between each one

Conclusions :

Recommendations :


EMAG

Conclusions :

Directional markers (deflection of trees, lamp post s, etc.) likely to have been caused by reverse flow in the rarefaction wave, i.e. NOT by air movement ahead of the propagating flame

High overpressures indicated high flame speeds –possibly detonation

Magnitude and distribution of overpressures difficu lt to assess


EMAG

Recommendations :

A 2-Phase Joint Industry Project should be initiate d.

Phase 1 should complete the assessment started by EMAG and, on the basis of this, define a programme of further research – if deemed necessary (Phase 2).

Guidance to industry and HSE should be a primary deliverable of the work.

The project should be initiated as soon as possible , with Phase 1 completed in early 2008*. * Phase 1 report published in June 2009


Buncefield Explosion Mechanism Phase 1

Steering Committee

Chair: HSE Chief Scientist Dr Patrick McDonald

Members: Stakeholders who funded Phase 1

Technical Committee

Chair: HSE Chief Scientist Dr Patrick McDonald

Members: EMAG members (without Bradley and Michels)Ian Barnes (MoD)Bassam Burgan (SCI) (Programme Manager)Paul Uijt de Haag (RIVM)Jens Holen (StatoilHydro)Pol Hoorelbeke (Total) David Painter (HSE)Niall Ramsden (Energy Institute)Clark Shepard (ExxonMobil)



OBJECTIVES OF THIS PROJECT

To provide as definitive a record as possible of the characteristics of the Buncefield incident relevant to the formation and dispersion of the vapour and to the explosion, including the distribution of damage to nearby items and structures;

Where possible, to provide industry and the regulator with guidance for the operation of oil fuel storage sites based on this record of information and current knowledge of vapour cloud formation, dispersion and explosions;

To define the research that would be required in Phase 2 to confirm in greater detail the explosion mechanism involved in the Buncefield accident and to provide improved guidance for both oil storage facilities and facilities storing other flammable liquids.

To provide as definitive a record as possible of the characteristics of the Buncefield incident

Where possible, to provide industry and the regulator with guidance for the operation of oil fuel storage sites

To define the research that would be required in Phase 2 to confirm in greater detail the explosion mechanism involved in the Buncefield accident


WHY WAS THE EXPLOSION SO VIOLENT?

Buncefield Explosion Mechanism: HSE Research Repor t RR718


Work packages :

Assessment of the Observations and OverpressuresAssessment of Witness StatementsExamination of CCTV recordsAssessment of damage to objects (other than buildin gs)Overall assessment of damage to buildingsDetailed assessment of damage to buildingsCharacterisation of the Buncefield Explosion

(including characteristics of the cloud, ignition l ocation, timing of the explosion phases, magnitude and distribution of the overpressures, explosion propagation, and how Buncefield compares with previousincidents)

Comparison of potential scenarios with the Buncefie ld Explosion(deflagration or detonation?)

Alternative explosion mechanismsProposals for Phase 2




Characterisation of the Buncefield Explosion

Characteristics of the cloud

Ignition location

Timing of the explosion phases

Magnitude and distribution of the overpressures

Explosion propagation

How Buncefield compares with previous incidents


Extent of burn damage – also roughly the extent of the

pancake-shaped vapour cloud


65

Direction of net drag impulse across the Buncefield siteOutside the cloud, the impulse was outwards (yellow a rrows)


Pump house

Direction of drag within the footprint of the vapour cloud is towards the origin of the explosion




Assessment of damage to objects (other than buildin gs)

Crushed hydraulic switch box

Crushed electrical connection box

Crushed car

Experiments were carried out to try to replicate this type of damage

Conclusion? Within the cloud, overpressures were above 200 mb, but there is evidence for > 1 bar (perhaps much more?) locally




Assessment of damage to buildings

A combination of experience and numerical calculations suggest that this degree of damage indicates overpressures of 150 – 200 mb

Conclusion? Need to know much more about the source term which requires greater knowledge of the explosion mecanism

Northgate Building Fuji Building





Characteristics of the cloud

Ignition location

Timing of the explosion phases


Explosion propagation

How Buncefield compares with previous incidents



Remains of pumphouse

Propagation of flame radially outwards from the pumphouse




Evidence for location of the ignition source

06:03:28 06:03:29


Buncefield Explosion Mechanism: HSE Research Report RR718



Ignition location – the emergency pumphouse

Explosion propagation –

Internal explosion destroys the Pump House (first e xplosion) andthe flame propagates outwards through the cloud, pa rts of which are in the hedgerows

EXSIM used to model the process (CFD Code developed for explosions in process plant – uses sub-grid turbulence generation)




EXSIM – CFD Model developed by ShellVerified against full scale tests carried out ( inter alia) by British Gas/Adventica

“Bang box” Array of horizontal pipes enclosed with plastic sheeting


Enclosure filled with a stoichiometric methane/air mixture



EXSIM – CFD Model developed by ShellVerified against full scale tests carried out ( inter alia) by British Gas/Adventica


Array of pipes fills < 50% of the bang box



EXSIM – CFD Model developed by Shell(note that EXSIM cannot model the transition from D eflagration to Detonation)


Array of pipes fills 100% of the bang box




Ignition location – the emergency pumphouse

Explosion propagation –

Internal explosion destroys the Pump House (first e xplosion) andthe flame propagates outwards through the cloud, pa rts of which are in the hedgerows

EXSIM used to model the process (CFD Code developed for explosions in process plant – uses sub-grid turbulence generation)

Assumptions – the fuel is propane

the vapour cloud is stoichiometric

the trees and undergrowth can be modelled as if the y consisted of rigid pipes in a Cartesian array



Representation of vegetation in Buncefield Lane



Final simulation gas cloud and wooded lanes

Buncefield Lane


912



Fuel cloud 214 ms after combustion initiated within pump house



Overpressure plane scaled to red = 300 mbar (peak = 660 mbar)



Reverse flow behind flame front – high velocity but low density (red is > 300 m/s)



Unburnt fuel vapour (shown in red) as flame front enters Buncefield Lane (366 ms after ignition)

Unburnt fuel vapour as combustion follows Buncefield Lane (454 ms after ignition)

Fuel cloud 214 ms after combustion initiated within pump house



Overpressure as flame-front enters Buncefield Lane (366 ms, red = 200 kPa (c. 2 bar))

Overpressure as combustion follows Buncefield Lane(454 ms, red = 1 bar)



More finely resolved congestion



Pressure at 239 ms after ignition, red = 3 bar overpress ure


Explosion pressure increasing along the lane



Modelling the Buncefield Explosion

EXSIM predicts very high flame speeds (up to 600 m/s ) but does not model DDT (Deflagration to Detonation Transition)

Almost certainly, a flame travelling at 600 m/s woul d undergo the transition to detonation

Detonation probably occurred in the hedgerow near the in tersection of Three Cherry Trees Lane and Buncefield Lane and wou ld have propagated through the rest of the cloud wherever the mixture was within the detonable limits

Propagation velocity? 2000 m/s

Combustion Institute British Section: Spring Meetin g 2010Combustion Institute British Section: Spring Meetin g 2010

Damaged car found between the Northgate and Fuji Bu ildings

Tyres deflated – forced off their seals


Did a detonation propagate across the car park?




Implications:

Do we have to consider fuel storage depots as high ha zard sites?

Essential that the mechanism is properly resolved s o that correct decisions can be made regarding land u se

planning, etc.





Given that loss of primary containment is a recognised problem (we can reduce its probability), how can we guarantee that a Buncefield-type explosion cannot occur in the future?

Was the mode of release of the gasoline a critical fa ctor?

Do we have to re-design the storage tanks?

What were the critical characteristics of the hedgerows that most contributed to the development of the explosion ?

Do we have to remove all hedgerows adjacent to storage facilities, or would control of the undergrowth be sufficient?





Complacency is not an option!

26th October 2009 – major explosion and fire in Puerto Rico, 2.8 on Richter scale. (Understood to be gasoli ne release)

http://www.cnn.com/2009/WORLD/americas/10/26/puerto .rico.fire/

30th October 2009 – major explosion and fire in Jaipur, India, 2.3 on Richter scale. Involved failure of p ipeline valve, gasoline released.

http://timesofindia.indiatimes.com/city/jaipur/12-k illed-in-Jaipur-IOC-depot-fire-Army-called/articleshow/5178346.cms



Acknowledgements

Part of this presentation is based on the original ppt used by Taf Powell at the 5 th International Seminar on Fire and Explosion Hazards, Edinburgh, 2007

The rest is drawn freely from the Final Report of the MIIB*, the Phase 1 Report published as HSE Research Report RR718**, and a paper to be presented next week at the 5th International Seminar on Fire and Explosion Hazards, Leeds (Bradley, Chamberlain and Drysdale)


* www.buncefieldinvestigation.gov.uk** www.hse.gov.uk/research/rrpdf/rr718.pdf

Thank you for your attention

Any Questions?



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