Research On Reliability Of LNG Terminal System In Rudong Country Of Jiangsu Province

Liquefied natural gas(LNG),as a kind of clean and high-quality energy,has the characteristics of low carbon and high heat value,so LNG develops rapidly in China.LNG is an inflammable,explosive,cryogenic and poisonous liquid.So there exists risks during the operation of LNG terminal system of Rudong Country of Jiangsu Province.However,the reliability model of LNG terminal system has not been established and the weak link in the system cannot be identified.Therefore,it is very important to propose corresponding reliability enhancement measures by the LNG terminal system reliability research which is significant to improve the LNG terminal system of Rudong Country of Jiangsu Province safety management and safe operation level.In the thesis,based on the logical relationship of LNG shipping and LNG terminal of Rudong Country of Jiangsu Province,the reliability model of LNG terminal system was established.Through building the reliability analysis and fault diagnosis software,the reliability of system was obtained and the weak link was identified.The reliability study of LNG terminal system of Rudong Country of Jiangsu Province was carried out from several aspects:(1)Through the field investingtion of LNG shipping of Rudong Country of Jiangsu Province,the type,size and quantity of LNG carriers received by LNG terminal every year and general situation of the engineering were dissertated.All of the global LNG carrier accients from 1964 to 2013 were analyzed statistically in the thesis.The analysis showed that collision in the port area is the most important in the eight kinds of accidents.Besides,the thesis introduced the general situation of LNG terminal station,including process flow and characteristics of main equipment.Because LNG industry is not large enough to have its own failure frequency,generic failure frequency obtained by HCRD,OREDA,API and related literatures can be applied in reliability analysis.(2)LNG carrier collision accident probability calculation mode was built based on IWRAP collision mode and DNV risk analysis method.Computing programs were written to calculate the probability of collision in the port area as 2.034×10-6.Then a simulation model of the reliability of the LNG shipping was establisthded.The LNG shipping reliability was calculated as 0.9990 in VB programming method with the LNG carrier collision accident probability calculation combined with simulation model of the reliability of the LNG shipping.(3)Firstly,based on the technological process and the logic relationship among the facilities,the reliability model,fault tree were established.Polymorphic Bayesian Network was established based on LNG terminal fault tree.Conditional probabilities tables of 27 child nodes were built through triangular fuzzy number approach.Based on fault trees of 8 equipments,the thesis offered quantitative and qualitative analysis.GeNIe was applied to compute accident probability of LNG terminal as 0.9965.(4)Reliability model of system of LNG shipping and terminal of Rudong Country of Jiangsu Province,the reliability analysis and fault diagnosis software was built by Visual Basic language.This software can integrate with the LNG shipping reliability simulation model and several methods of obtaing failure probability of equipment.Firstly,by software computing the reliability of LNG terminal system of Rudong Country of Jiangsu Province is 0.9959.Then,according to the fault diagnosis module,posterior probability of 77 nodes in the BN model were calculated which showed the weakest link of system is the high-pressure pump.Finally,several measurements were adopted to improve the system reliability.When the failure probability of high-pressure pump low-pressure pump and BOG compressor decreased by fifty percent,the reliability of the system would increase from 0.9959 to 0.9964,0.9964 and 0.9963.