UK HSE prosecution following 2011 fatal explosion in oil refinery

What happened?

The UK HSE has prosecuted two companies after an explosion killed four workers and seriously injured another at an oil refinery in Pembrokeshire in 2011.  Five workers were emptying a tank using a vacuum tanker when the explosion and subsequent fire took place.  The explosion resulted in a fireball which severed the 5-tonne tank roof, and this was projected 55 metres to impact against a butane storage sphere.  The roof narrowly missed a pipe track where a range of flammable materials were carried.

Investigation found the explosion was most likely to have been initiated by the ignition of a highly flammable atmosphere within the tank, during what should have been a routine emptying operation [IMCA emphasis] in preparation for further cleaning and maintenance.  The investigation also found there had been longstanding failures within the refinery safety management systems (SMS) and as a result the risks posed by flammable atmospheres …were not understood or controlled. [IMCA emphasis]

Please see here for the full UK HSE press release.