Buncefield 'vapour cloud' probed
13 Jul 2012
London - The UK’s Health & Safety Executive (HSE) has issued a report on the formation of the fuel vapour cloud that led to the massive explosion and fires at the Buncefield fuel depot in 2005.
The report examines what happened as the tank was overfilled with unleaded petrol and cascaded from the top of the tank into the bund.
For its research, HSE constructed a full scale replica of a section of top of the tank involved at Buncefield and also a full height section of the tank wall. This enabled it to simulate the development of the vapour cloud.
Roughly half of the liquid released flowed out over the edge of the tank and formed a freely falling spray, the study found. The other liquid was initially deflected by an inclined plate and ran down the tank wall.
Around 9 metres above the bund, liquid running down the wall hit a circumferential stiffening girder (wind girder) and was projected out, away from the tank, passing through the cascade of liquid from above.
The findings also showed that overall liquid flow results in a relatively fine spray, with droplets a few millimetres in diameter.
Analysis of heat, mass and momentum transfer found that the fuel cascade drives a significant downward flow of air, which was contaminated by high concentrations of light hydrocarbons.
“The hydrocarbon mixture entering the vapour cloud that surrounds the tank is fuel rich. The volume flow is sufficient to establish a cloud of depth 1.6 - 2 m deep over the area affected by the vapour cloud explosion,” said HSE.
Read the full HSE report
