Flammable Mists from Accidental Hydrocarbon Releases Offshore
The report investigates offshore hydrocarbon releases in an attempt to identify whether mists of hydrocarbon droplets were formed, and if these presented a flammability hazard. Scientific literature has been searched for the present state of knowledge of the physics of two-phase mist generation. An empirical correlation has been used to model the reported hydrocarbon releases for a five year period and estimate whether flammable mists could have been generated.
It was found that ninety-five percent of reported liquid releases (forty-five percent of total reported releases) could have formed flammable mists. It was also noted that there were thirty-five cases of high flash point diesel and machine oils igniting as flash fires in five years.
Having established that flammable mists are being generated, the state of computational modelling and its validity has been reviewed to identify whether industry is able to characterise this risk in order to enact measures to control it. This found that computer programs existed to model both mechanical and flashing mist generation although the ability of these programs to model subsequent dispersion and rainout was limited. Validation studies of jet breakup are continuing but are focused on characterisation of single component flashing releases, not mechanical breakup of multiple component mixtures.
This report and the work it describes were funded by the Health and Safety Executive. Its contents, including any opinions and/or conclusions expressed, are those of the author alone and do not necessarily reflect HSE policy.