Safety Integrity Level Design Method Research Of Residual Oil Hydrogenation Unit

Safety instrument system (SIS) is a kind of safety control system which is often used in process industry. SIS system can prevent accidents from happening and reduce consequences of accidents effectively. However, failure action and spurious tip of SIS often happened which could make the SIS system lose its security function.To avoid failure action and spurious trip of SIS, a design method of safety integrity level has been put forward in this paper to prevent failure action and spurious trip of SIS based on the SIS system design data of common petrochemical plants equipment at home and abroad. The method is consisted of two aspects:SIL design based on experience and SIL design based on risk quantitative calculation. In the SIL design based on the experience, SIL design is done based on SIS database information from the SIS design package of mature used SIS design systems and the corresponding SIF information database in petrochemical plant. In the SIL design based on quantitative calculation, SIL design is done based on initial event failure database and protective layer failure database of common petrochemical plants in CCPS or Oracal database, layers of protection analysis (LOPA) method is used to calculate and determine the SIL level. The above method has divided into four parts:(1) The unit of risk identification, HAZOP analysis method is used in this part to identify high risk level unit as well as it’s cause, consequence, risk level, existing measures and suggestions of risk, etc.(2) The SIL design based on experience, the commonly used SIS and SIF information can be find out according to the type name and equipment name of high risk unit, so does the SIL level, and then, the fault tree model, the reliability block diagram (RBD) model and markov model analysis method (Markov) could be used to verify the SIL level. (3) In the SIL design based on risk quantitative calculation, HAZOP and LOPA analysis could be used, and the risk matrix analysis and the ALARP principle was combined to calculate the SIL level, the validation method in part (2) is used for SIL level validation either. (4) Comparing and summarizing the SIL design results of part (2) and (3), the finally SIL level and SIS design can be finally done.The development the safety integrity level design software called SIL-ASSIST has been developed based on Foxtable software platform according to the above method, the importance of design database was highlighted, the existing design experience of SIL can be introduced which will make the design results more relevant to the engineering application.Finally, the SIL design method and the software have been used in the SIL design of residual oil hydrogenation unit in a petrochemical plant equipment, and the SIL design of stripper (C-3001) and fractionating column feed heating furnace (F-3001) system have been taken as examples to illustrate the application of methods and software process. The application shows that the SIL design method and the software can avoid the failure action and spurious trip of SIS to a certain extent.