Research On Operating Reliability Of Gasification System In LNG Terminal

The LNG industry in China is developing at a high speed,and the reliable operation of LNG station is of great significance to the stable supply of natural gas in natural gas pipe network.Based on reliability theory and LNG station process flow,the reliability of gasification system in LNG terminal is studied.The reliability of key equipments is analyzed,and then the reliability of the system is determined based on the correlation and logical relationship between key equipments.For the lack of failure data in stations,the reliability of the dynamic equipments in gasification system is studied based on performance degradation.The specific fuel consumption is taken as the performance degradation index of gas compressor and efficiency is taken as the performance degradation index of pumps.The performance degradation model of the equipment is established and reliability of the equipment in an overhaul is calculated to optimize equipment maintenance cycle.Taking the gas compressor and pump as the research object,the impacts of different failure thresholds and flow rates on equipment reliability are analyzed,and reliability curves of the equipment are calculated under different failure thresholds and different flow rates.The results show that the pseudo-failure life of the gas compressor increases as the failure threshold increases,and the greater the failure threshold,the faster the reliability decreases during the reliability decline period.As for flow rates,the closer the pump flow rate is to the rated flow,the higher the reliability of the pump will be.The reliability of the pump will decrease when the equipment is operated at a small flow rate for a long time.SCV is divided into igniter and heating coil.The reliability of SCV igniter is analyzed by fault tree analysis method.A fault tree of SCV ignition failure is constructed,and the structural importance and level importance of each basic event are calculated to determine the main reasons for SCV ignition failure.The theory of fuzzy mathematics is adapted to calculate SCV ignition failure probability.The reliability of SCV which runs for four years is 0.9351 based on the correlation and logical relationship between the igniter and the heating coil.The reliability block diagrams and system topology diagrams of Tangshan LNG station gasification system under different operating conditions are established.The reliability of gasification system in LNG terminal is calculated respectively according to different operating conditions.The result shows that the reliability of gasification system is 0.9961 in autumn and 0.9306 in winter.Therefore,the reliability of the gasification system in winter is lower than that in autumn,and more attention should be paid to equipment maintenance in winter.