Evaluation And Application Of Safety Integrity Level Of Safety Instrumented System In Natural Gas Station

With the large-scale and modernization of production,storage and transportation equipment or equipment in natural gas station,the high concentration of energy and the potential accident risk are further increased.As an important protection measure of natural gas industry,the Safety Instrumented System(SIS)mainly performs appropriate adjustments or alarms or shutdown controls on the results of the basic control system monitoring of the plant to ensure the smooth operation of the process.Although safety instrumented system can be widely used in different process units of natural gas station,many enterprises lack pertinence,effectiveness and rationality in the setting of safety instrumented system.Therefore,in order to avoid the occurrence of equipment over interlock or under interlock,and make the safety instrumented system achieve the protection function of stable operation of process units,this paper takes Shanxi natural gas liquefaction peak shaving station as an example to carry out functional safety assessment on the safety instrumented system of the process unit,which is of great significance for reducing the severity of accident consequences and ensuring the reliable operation of equipment.In this paper,the following aspects of SIL assessment of peak shaving stations are studied(1)Based on the detailed investigation of the liquefaction peak shaving station,combined with the configuration of the station control system,the risk factors of the process unit in the liquefaction peak shaving station are analyzed,and the work content of the functional safety assessment is clarified,which mainly includes the SIL grading and SIL verification of the safety instrumented system.(2)After analyzing the advantages and disadvantages of the risk chart method and LOPA analysis method,this paper selects LOPA analysis method as the main method to determine the safety integrity level of safety instrumented system in peak shaving station.The risk control objective of SIL grading is obtained through relevant industry standards and engineering experience,and then the SIL grading analysis of each process unit of liquefaction peak shaving station is carried out by using LOPA analysis method.(3)Combined with the SIL grading results of peak shaving station,after analyzing the redundant structure of interlocking system,according to the relevant data of field instruments,using fault tree model and Markov model to verify and calculate the SIL level of storage tank in peak shaving station,and determine the SIL level of current SIS.Through comparative analysis,it can be found that the fault tree model is convenient for modeling,but the calculation error is large,Although the modeling process of Markov model is complex,the calculation results are more accurate.Finally,the influence of periodic strategy on the verification results is analyzed,and suggestions are put forward for the interlocking loop which does not meet the requirements of the target SIL level.