Application Of SIS And SIL Assessment In Disproportionation Unit

Safety Instrumented System (SIS) has played a pivotal role in the petrochemical production. Implementation of safety instrumented systems through appropriate safety function, can effectively prevent the occurrence of a hazardous event and it will reduce the risk of the production process to an acceptable level. But the safety function of SIS is not absolutely safe because of its own failure, loss its safety instrumented functions, may also lead to dangerous events. Chemical production process at greater risk for harm event should set reasonable and reliable safety instrumented system for protection to reduce risk, reduce the risk of personal events, equipment, and environmental harm. In order to ensure the safety instrumented system achieving the desired level of security, companies should be in accordance with the relevant provisions IEC61508/IEC61511to choose reasonable safety integrity level (SIL) and do reliability assessment for SIS through modeling and calculation to make sure that the design of SIS meeting the safety integrity levels, thereby helping companies develop preventive maintenance strategies to minimize the economic loss.Through the study and research of SIS configuration and hardware design in Shanghai petrochemical co., LTD, using the quantitative calculation method as the core method with the qualitative analysis as the complementary method to do the SIL assessment. In the qualitative analysis level, we find out the high risk points of safety instrument system based on HAZOP analysis report and using Markov model method as the quantitatively method to calculate the SIL level of safety instrument function to determine whether the security instrument settings comply with relevant regulations of IEC61508/IEC61511.We should optimize the design if they do not meet the requirements to help the enterprise saving cost and bringing good economic benefits.