The Research On Design And Improvement Of Safety Instrumentations System For A Benzol Hydrorefining Process

With the development and increase of safety manufacture and safetymind, the uses of safety instrumented system in the dangerous process of oiland petrochemical industry and chemical field are more and more. Comparingof basic process control system, the SIS has some special technical functionsand features like as: functional safety, multiple redundancy structure, safetyintegrity level, reliability and probability of failure.This thesis proceeds from the reality with introducing the concept of SIS,and background knowledge and current situation as well. Researching theinternational standards and basic theory includes IEC61508&IEC61511, thetechnology of redundancy and fault-tolerance, the voting structure of SIS, andthe protection level model of safety and the lifecycle period of safety system.Meanwhile explaining the differences with safety instrumented system andbasic process control system.Then this thesis states the design methods of SIS based on the theoryresearch. Including the design of field sensor, terminal actual element andlogic server, with the three ones are the critical components of a whole safetyinstrumented system. After stating the typical system structure with differentSIL, this thesis researches the analysis method of SIS. Although the functionsimplemented of SIS won’t very complicate, the demand of system reliabilityare very high because the safety is very important for process manufacture. Sothe thesis studies the technical index about reliability like failure rate andpattern. The probability of failure with dangerous and probability of failurewith safety are important. And how to analysis and compare with model methods of reliability block diagram, fault tree analysis and Markov model.In the fourth chapter, this thesis design a factual safety instrumentedsystem project based on hydride sulfurization with stating the necessity ofsetting up SIS in such a dangerous process industry. Then it designs the safetyfunction of the safety system according to the process demands, anddesigning the detail network structure, hardware configuration and softwareprogramming as well. In fact the SIS runs very well until now.Because of the cost consideration and some other reasons, the system haslots of probabilities to improve. So the thesis considers a better method withcomparing the redundancy structure between1oo2,2oo3and1oo2D, whosestructure represents three typical SIS from three leading automation suppliers.The conclusion is that the structure of1oo2D is much better and with highcost performances as well. It has a strong competitiveness. Based on theconclusion it design a new model safety instrumented system with some newadvanced functions like smart system, intelligent diagnostic of field deviceswhich can provide a more effective maintenances work for engineers andlower complicated programming and structure with functional block.In a word, the purpose of the thesis is researching how to design anadvanced and reliable safety instrumented system based on theory study.Simultaneously, hoping it will provide some references and enlightenments inthe future research and design of SIS.