Research On LNG Carrier Safety System Design

LNG is short for Liquefied natural gas, which is the cleanest resource in the world. It's an important application form of natural gas resources. It's firstly produced by natural gas purification treatment field, and then liquefied under ultra-low temperature, finally transported by LNG Carriers. China has abundant natural gas resources, so it has important and far-reaching strategic significance to accelerate the development of China's natural gas industry, to ease China's energy supply and demand, optimize energy structure, improve the ecological environment and accelerate the urbanization and improve people's quality of life.LNG Carrier was a special ship which carried liquefied natural gas under -163℃,due to the ultra-low temperature boiling point, flammable and explosive, and 1:600 proportion of high risk characteristic of the gasification, so the design of LNG Carrier safety system is particularly important for the safe operation of LNG Carrier.LNG Carrier safety system included Emergency Shutdown system (ESD) and Fire and Gas Detection system (F&G).There is no specific standard guiding for LNG Carrier safety system design, this article focused on the LNG Carrier safety system design, including following contents:1. Study on the development of Safety system; understand the development trend of safety system. By analyzing the risk of LNG Carrier, illustrate the necessity of LNG Safety system.2. Discuss the characteristics of Safety Instrumented system and the distinction to basic process control system. Researching on design way of SIS, including the methods of risk analysis, confirmation and validation of safety integrated level, in order to provide theoretical guidance for the LNG Carrier Safety system design.3. Analyze LNG Carrier safety system, including Emergency Shutdown system (ESD) and Fire and Gas Detection system (F&G).Then chose LNG Carrier separator as an example to design its Level Safety Instrumented System. This article gave the detail design for separator level safety system, and result showed that the design of it meet the safety integrated level requirement.4. Markov method is an effective method applied to system reliability analysis. This Article used this method to analyze reliability of LNG Carrier Cargo Tank level control system. By using Markov method to establish state transition matrix of system, then calculate the reliability probability of the system. This experience lays foundation for further scientific reliability analysis for LNG cargo system.