| The space of offshore platforms are almost limited leading to equipment concentrated.A large number of flammable and explosive substances,including pipeline,valves and flanges,which is regarded as potential risk,exist in platform.Fire and explosion accidents were regarded as the most dangerous accident not only severe consequence but also high frequency.Offshore platform generally adopt fireproof and explosion-proof walls to lower down the explosive risk.The measure also can protect platforms from suffering large damage when explosion accident happens.The tradition methods of gas explosion,containing TNT and TNO model,have great limitation because they can’t predict the influence of complex structure on near-field Explosion Overpressure precisely.In the guidance procedure of explosive probability of simulation in NORSOKZ-103（2010）,the paper propose a quantitative risk analysis method which consider the effect of environment,frequency of leak and position of combustion source.The middle deck part of the center platform in an offshore gas field was used as model for simulating.Quantitative assessment of explosion in offshore platforms are based on the frequency of gas explosions and the consequences of gas explosions simulated by CFD.The Oil and Gas Leakage Database（HCRD）and Leak software were used for calculating frequency,speed and attenuation of leak.The result were put into UKOOA ignition model for calculating the probability of ignition.We considered many factors synthetically,such as leakage frequency,wind direction,wind speed,leakage rate,leakage direction and ignition probability during the process of probability calculation.The Fluidyn of CFD software was employed for simulating gas diffusion and explosion.The frequency curve of explosion overpressure of the firewall in the middle deck process area was obtained by using weighted average ofβdistribution.By the results analysis,we can obtain a lowest load,whose cumulative overpressure value is 0.93barg when the frequency of explosion overpressure is 7×10-5times per year,as structure design of firewall.The result can provides the basis for the design of the offshore platform firewall. |
