Multi-physics analysis — a method for the design of safe pressurised systems to resist accidental fire

Pressure vessels for on-shore refineries and terminals, and offshore production facilities are often designed in accordance with the API RP 521, which is a Recommended Practice for the design of pressure-relieving and depressurising systems. It is widely recognised that in some aspects the design according to API 521 is inadequate. Recent guidance developments in Norway address this problem and call for the application of design methods where all processes involved in the fire attack and response of pressurised systems are considered. These processes are of a multi-physics nature combining the time-dependent effects of heat transfer from the fire to the vessel, heat conduction through the vessel shell, heat transfer from the vessel shell to the contents of the vessel, thermodynamics of the vessel contents, pressure and stress. This Paper addresses these processes in detail and presents case studies in the application of multi-physics analysis as a method for safe design of pressurised equipment against accidental fires.