Research On Fire And Explosion Risk Assessment Method For LNG Ship Liquid Cargo Leakage Accidents

Today,under the development conditions of green energy and energy conservation and emission reduction,LNG,as high-quality green energy and high-value transport goods,has gradually become the most eye-catching industry in the ocean engineering field;on the other hand,due to its own volatile,easy to diffuse,flammable and explosive characteristics,the risk research of LNG has also become a research hotspot.As ship transportation is the most important mode of transportation in LNG trade,the risk characteristics and safety analysis of LNG ships in the transportation process has great research significance.This paper mainly conducts a comprehensive analysis and evaluation of the fire and explosion risks of LNG ship leakage.The research object is a 174,000m~3liquefied natural gas ship independently built by Shanghai Hudong Zhonghua.Using the combination of event tree and fault tree,the risk identification and risk frequency of the risk scene of fire and explosion accident caused by natural gas leakage are carried out.Analysis,and the use of software numerical simulation method for risk consequence analysis.The risk assessment analysis is completed on the basis of the frequency analysis and consequence analysis results,and risk reduction measures are given according to the assessment results.The main research works are listed as follows:(1)Based on the analysis of the risk characteristics of LNG,the disaster chain model of LNG ship leakage disaster chain model was established by applying the disaster chain theory,the causes and conditions of the disaster were analyzed,and the fire caused by natural gas leakage was studied.Hazard-causing mechanism of explosion accidents.Using the event tree analysis method to establish an event tree model with natural gas leakage as the initial event,the evolution process of natural gas leakage on LNG ships leading to the occurrence and development of fire and explosion accidents was studied.The settings provide the basis.The fault tree analysis method was introduced into the event tree analysis,and the fault trees of natural gas leakage,ignition source,leakage containment failure and fire detection and alarm failure were respectively established,and the basic events of the fault tree were obtained on the basis of collecting and searching relevant documents and databases The occurrence frequency of the fault tree is completed,and the probability of the event at the top of the fault tree is calculated,and then the frequency of the initial event and subsequent events of the established event tree is obtained,and the quantitative analysis of the event tree is completed.(2)A 174,000m~3liquefied natural gas carrier was selected as a reference ship type,and PHAST software was used to analyze the dangerous concentration in leakage accidents;the thermal radiation flux in pool fires,jet fires and BLEVE fireball fire accidents;the explosion shock wave overpressure in explosion accidents The regional distribution of values and the duration of disaster accidents provide complete conditions for the follow-up evaluation of the severity of leakage and fire consequences according to the indicators.Using the finite element modeling software,the finite element model of the cargo tank section of the hull was constructed,the accuracy of the Euler grid was verified,and the fluid-structure coupling calculation model was set up to analyze the accident conditions of the natural gas meteorological leakage and explosion accident.The LS-DYNA solver performs numerical simulation calculations to obtain structural damage response results such as stress,strain,displacement,and acceleration,which provides reference data for the impact of structural damage in the analysis of the consequences of explosion accidents.(3)Using the method of risk matrix,the risk occurrence probability of the consequences of fire and explosion accidents caused by LNG ship leakage and the risk assessment level of damage consequences were determined,and according to the results of the level evaluation,the risk assessment of LNG ship leakage fire and explosion risk accidents was drawn.matrix.Combined with the results of risk frequency analysis and risk consequence analysis,the occurrence probability level and damage consequence level of LNG ship leakage fire and explosion risk accident consequences are evaluated,and the risk level of different leakage fire and explosion accident consequences is analyzed.Combined with the evaluation and analysis results,measures to reduce the risk of LNG ship leakage,explosion and fire are put forward from three aspects:strengthening safe navigation management,adding hull protection facilities and formulating accident emergency safeguard measures.