Techniques for modelling the frequency of explosions on offshore platforms

AbstractThis paper describes a scheme by which the explosion frequencies and resulting overpressures can be predicted for modules on an offshore platform. Given a leak of gas, the success and failure of the isolation, blow-down and deluge systems, which are designed to activate following a leak to mitigate the consequences, are considered. The frequency of each possible response to the leak is predicted using a conventional event tree and fault tree approach. Each scenario has a potential escape inventory, which together with the hole size distribution provides the escaping mass flowrate. Once the flowrate into the module is established, the wind conditions are used to determine the gas in air concentration build-up. The concentration profile with respect to time is linked to the ignition source probabilities, from which calculations can be made to assess the likelihood that an explosion will occur within a specific concentration range.The initial models assume that the gas concentration at any specific t...