| The domino accident was an incident of high-impact low probability,once the consequences are serious.In the daily industrial production,it was more common that the expansion and upgrading of the fire accident cause domino accident and cause serious accident consequences.The economy of our country was developing rapidly.The number of flammable and explosive materials involved in the production process and daily storage of enterprises had increased.The equipment had become more complex,and the number of major sources of danger had sharply increased,in addition.On the other hand,the existing safety barriers with weak response capabilities and lack of effective emergency measures in the event of accidents resulted in frequent domino accidents.The current research on the domino effect of accidents focused on quantitative assessment of the consequences of domino accidents.However,there was a lack of research on the mechanism of accident prevention,especially the prevention of accident expansion from the occurrence and development process of domino accident.In order to realize the goal of cutting off the accident chain,preventing the accident from escalating,and reducing the accident loss,this paper combined practical cases to solve the optimal layout of safety barriers based on the premise that the accident was prevented from escalation.In this paper,enterprises were the subjects of research.The fire accidents with high frequency in historical accidents were the initial accidents.The probability of occurrence of domino accidents was calculated when different safety barriers acted on the hazard sources.We could solve the optimal safety barrier layout,with a constant budget for the company's existing safety barriers.First of all,the heat radiation intensity of the risk source to the nearby unit was calculated by using the risk material type,physical and chemical properties,device location and other relevant information of the company's hazard source.Then based on the comparison of the thermal radiation intensity value and the thermal radiation threshold,the hazard sources that may lead to an accident escalation after an accident were identified and the corresponding expansion probabilities were calculated.Secondly,according to the different types and roles of safety barriers,after substituting the failure probability on demand of different safety barriers,and the physical effects of the initial accidents that were affected by the safety barriers,the probability of a domino scenario when considering the effect of safety barriers through the calculation model could be calculated.Finally,a "Knapsack Problem" decision model was constructed.Combining the calculation results of the previous two parts and the costs of different safety barriers,the optimal layout of the safety barriers under restricted cost was solved through the computer language.Finally,the paper used a methionine production chemical company as an example.The company had a large stock of dangerous sources and a congested layout.Once a fire accident occurred,it would most likely evolve into a domino accident.The risk sources in the enterprise include seven carbon disulfide storage tanks,two liquid ammonia tanks,one methanol storage tanks,three methyl-mercaptan tanks and one propanol tanks.Without considering the safety barrier,except for methanol and propanol tanks,the remaining twelve tanks in the fourteen tanks exceeded the threshold of thermal radiation produced by the nearby tanks after the fire,which could lead to domino accident.The twelve risk sources might still bring about escalation after replacing the existing enterprise safety barriers,but the maximum expansion probability was reduced compared with the values without considering the safety barrier.The maximum value is 0.8354.After optimization calculation,the maximum probability of the hazard source expansion was 0.696981,under the optimal scheme,which was reduced by 16.6%relative to the actual situation that the enterprise had not optimized.The possible goal of reducing the occurrence of domino accidents had been realized.It was the expansion probability of two largest carbon disulfide tanks,No.1 and 2,when equipped with fire cannons.In the optimal scheme combination,there were only two schemes including foam sprinkle system and water deluge system(fire cannon).The specific configuration was as follows.Two carbon disulfide tanks,No.1 and 2,should use a lower cost fire cannon,which were easy to cause accidents to each other,because of large volume and close range to each other.With the same specifications as those of 1 and 2 tanks,the 3 carbon disulfide storage tank closer to the two target had the highest probability of escalation and escalation without barrier,so the foam sprinkle system with higher cost but best effect was needed.Four small size carbon disulfide tanks,the risk source No.4?7,caused an expansion possibility only next to No.3,and a foam sprinkle system was also required.The expansion probability of the tank 9?13 was obviously less than the seven carbon disulfide storage tanks,and the fire cannon should be used for protection.The results of the study indicate that when the storage tanks storing hazardous chemicals are relatively large in chemical enterprises,it will result in a wide range of accident escalation.The effects of different safety barriers on preventing domino effect are significantly different,and the role of safety barriers is positively related to their costs.The effect of the passive protection system is better than the active protection system.In the active protection system,the effect of the foam sprinkler system to reduce the probability of domino accident is the best,followed by the water deluge system and the automatic water sprinkler system.In practical production,the cost budget is limited,and a reasonable safety barrier setting can reduce the possibility of domino accidents within the scope of research.The research method in this study can solve this optimal setup scheme and provide scientific basis for the enterprise's security barrier setup planning. |
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