SIL-based Yucheng Gas Stations Functional Safety Evaluation Instrument

The gas station is an important part of the entire natural gas pipeline system. Safety instrumented system can effectively reduce the risk of the station and It is the necessary measures to ensure the safety and efficient operation of the gas station. However, the safety function of the safety instrumented system itself is not absolutely safe, inevitably there are security issues. The safety instrumented function evaluation of the gas station is to measure the reliability of the safety instrumented system, improve the level of functional safety of safety instrumented systems.Firstly, the gas station’s safety instrumented system is defined. By detailed investigating the25gas station’s safety instrumented system on the East Gas Transmission, found that emergency shutdown system’s failure is the most serious one in the safety instrumented systems of gas station. For the emergency shutdown system of the gas station, establish a fault tree and analysis the fault tree’s minimal cut sets, identified the actuator as the weak link in the emergency shutdown system.Secondly, the paper researched the two aspects methods from SIL grading and SIL verify. SIL classification, compared two methods of SIL classification:the corrected risk graphs and the Layer of Protection Analysis, analysis of the Layer of Protection Analysis’s advantage in the quantitative grading, determine use the Layer of Protection Analysis to classified emergency shutdown system’SIL in gas station, at the same time, according to the characteristics of the Layer of Protection Analysis, proposed the Layer of Protection Analysis which combination with hazard and operability analysis, and then developed a gas station SIL classification process. SIL verification, SIL verification of two methods:the fault tree and the Markov method. By way of example, summed up the advantages of the Markov method in the calculation of thinking and programming with intuitive and scalability, determined using Markov method to checking failure probability, then based on Markov modeling methods, the use of the Visual Basic6.0environment to write the program to calculate the SIL level, supporting computing.Third, using the methods of SIL classification and verification, take the actual gas station for example, evaluate the emergency shutdown system of of Yucheng gas station. Determined5safety instrumented function’s SIL of emergency shutdown system in Yucheng station, only2safety instrumented functions meet the requirements, the remaining three safety instrumented function does not meet the expectations, in which the impact of the security of the whole system. Finally, summarized the method of improving safety instrumented function’s SIL.The conclusions of this study has a certain sense to reduce the gas station safety instrumented system failure and improve the reliability of the gas station, and provide some reference for the design of the gas station security instrument.