Case Study: Buncefield Fire What We Have Learned Amro Kasht, Ariful Azam, Moataz Nour & Solayman Kawsher Mary Kay O’Connor Process Safety Center Extension in Qatar Texas A&M University at Qatar, PO Box 23874, Education City, Doha, Qatar Introduction Incident Analysis b The Buncefield fire was a major conflagration caused by a series of explosions on 11 December 2005 at the Hertfordshire Oil Storage depot near the M1 motorway in Hertfordshire, England. Buncefield Oil Storage depot was used to receive petrol, aviation fuel, diesel and other fuels by pipelines, where they were stored and later distributed via pipelines or road tankers to other facilities like petrol stations and airports. The general mechanism of ‘confined explosion’ does not explain the type of explosion that occurred at Buncefield as the majority of the cloud was not confined. There are two known mechanisms for generating an explosion in a relatively unconfined vapor cloud. One is a deflagration and the other is detonation. Buncefield accident that cannot be simply explained by deflagration and some of the fact that suggest deflagration to detonation (DDT) mechanism include: a) High overpressures b) Directional Indicators c) Pressure decay outside the cloud Consequences Fig: Vehicles , drums and other enclosures which exhibited damage consistent with overpressure in excess of 200 KPa Fig: Extent of flammable cloud Fig: Direction of net drug impulse across the Buncefield site Sector Cost (£ million) Site operators (compensation claims) 625 Aviation 245 Competent Authority and Government response 15 Emergency response 7 Environmental impact (drinking water) 2 Total 894 Taking the combination of all analysis, following explosion scenario can be suggested: Ignition in the Pump House resulting in a confined explosion venting into the external cloud. The flame propagated into the tree line to the north of the Pump House. The flame accelerated (deflagration) in the tree line Instead of continuing as a deflagration, transition to detonation occurred somewhere near the junction of Buncefield Lane and Three Cherry Trees Lane. Design and Operation Improvements The MIIB Design and Operation recommendations Systematic assessment of safety integrity level requirements Protecting against the loss of primary containment using high-integrity systems Engineering against escalation of loss of primary containment Engineering against escalation of loss of secondary and tertiary containment Operating with high-reliability organizations Delivering high performance through culture and leadership Overfill protection strategies Incident Timeline 10/Dec/05 06:50 pm Tank 912 in bund A started receiving motor fuel from the T/K South pipeline, pumping at about 550 m3/hour. 11/Dec/05 03:05 am ATG system failed to show an increase in levels, despite the tank continuous filling. 11/Dec/05 05:37 am Tank started to overflow (~ 300 tons) and vapor cloud started to form. 11/Dec/05 06:01 am Vapor cloud exploded, registering 2.4 on Richter scale. 11-16/Dec/05 Emergency services took control of the scene. The fire took 5 days to control. Perspective Approach (API RP)  precise solution for an application Functional Approach (IEC) methodology and performance standards Standard Safety Approach in Industry Design Recommendations Remotely operated shut off valve Fuel transfer Management Safety management procedure for fuel transfer is required. Written procedure should be in place and consistent with current practice. During equipment failure, ROSOV can be used to avoid major disaster. The ROSOVs should fit the outlet pipe of the tanks and should be in fail safe mode. . Tank Roofs Vent Rim seal Valve Piping In earthquake prone areas, piping should have step geometry . Pipe supports should have fire protection Double deck floating roof. Anti-rotation device on floating roofs Hydrocarbon detection in drained water with automatic isolation. Storing materials with a flash point below 21°, flame arresters should be provided. Fixed roof tank to be fitted with a gas blanket (N2) Dual rim seal Foam dam should be provided. Valves on atmospheric tanks should be labeled. The isolation valves and actuators should be secured directly to The Tank wall References The Buncefield Incident 11 December 2005, in: The final report of the Major Incident Investigation Board, Buncefield Major Incident Investigation Board, London, 2008, Volume 1 & 2. Special thanks to Dr Luc Véchot.