液化天然气加注船安全定量风险分析

摘要

液化天然气（ LNG）加注船是一种为LNG动力船提供燃料的新型船舶，国内目前尚处于起步阶段，缺乏相关安全标准和规范。采用国际定量风险评价（ QRA）的通用理念，研究适用于我国LNG加注船的安全评价方法，提出具体实施步骤和依据准则，并以国内某LNG加注船作为实例分析说明。建立加注船LNG火灾事故树，确定相关火灾事故概率；研究适合加注船火灾事故后果的方形火焰模型，以及LNG火灾热辐射对人体伤害的计算方法；参考国际海事组织（ IMO）的风险准则，确定LNG加注船个人风险和社会风险；最后与按NFPA－59A计算的防火间距作对比分析。通过计算，例中加注船的风险位于须采取相关安全措施的ALARP区域，风险控制区域半径20m。若按NFPA－59A要求计算防火间距，该加注船对外部须划定半径52m区域作为安全区域，且须将船身增长37m以满足内部防火要求，在实际工程中无法实现，相比较QRA方法更适合我国LNG加注船的安全评价工作。%Liquefied natural gas ( LNG) fueling vessel is a new ship used for adding fuel to LNG power ship.At present, the domestic LNG vessel is still in initial stage and lacking of relevant safety standards and specifications. The method being applicable to assess the safety of LNG fueling vessel in China was studied by applying the general idea of QRA ( Quantitative risk assessment ) , the specific implementation procedures and criterions were put for-ward, and the analysis and explanation were conducted by taking a domestic fueling vessel as example.The fault tree of fire accident in fueling vessel was established to estimate the probability of relevant fire accident.The rec-tangle fire model fitted to fire accident consequence of fueling vessel and the calculation method of human body in-jury by thermal radiation of LNG fire were studied.Then the individual and social risk of LNG fueling vessel were determined by referring to the IMO risk criteria.At last, the comparative analysis on fire prevention distance with the calculation result of NFPA-59A was conducted.The results showed that:the risk of LNG fueling vessel in the case is located in the ALARP region, which means some mitigation measure should be taken, and the radius of risk control region is 20m.If calculating the fire prevention distance according to NFPA-59A, the safety region with 52m as radius should be defined outside the fueling vessel, and the length of vessel should be stretched by 37m to meet the requirements of internal fire prevention, which are unrealizable in practical engineering.Comparatively speaking, the QRA method is more fit for the safety evaluation of LNG fueling vessel in our country.