Architecture Design And Safety Research Of Double-triple-channel Redundant And Fault-tolerant System

Safety Instrument System (SIS) is widely used in the industry of petrochemical, machinery, railway, etc. to improve safety. In particular, petrochemical industry demands high safety and availability of SIS, as they are both closely related to economic profits of enterprises. Chinese SIS market is mostly occupied by foreign products, which is not favorable to national strategic security and economic development. Therefore, the study of SIS in the field of petrochemical is of great significance.On the basis of the SIS of petrochemical industry, the author proposes a double-triple-channel redundant and fault-tolerant system(DTRFS) architecture and analyzes its safety performance. First of all, the DTRFS adopts double-triple-channel design and fault-tolerant design to improve its safety and availability. The operation mode of dual active-active is used to eliminate the safety disturbance from traditional redundant and fault-tolerant systems(RFS) with dual hot-standby operation mode. Then, safety modeling methods of RFS are researched. Failure modes and kinds of safety influence factors are considered during safety modeling process. The safety performance index of average Probability of Failure on Demand(PFD), average Probability of Failing Safely(PFS) and average availability are calculated. It greatly simplifies the modeling process and is able to dynamically reflect the system’s safety performance to propose Markov model with transfer status and combine it with the Reliability Block Diagram to model the DTRFS. The concern that it is difficult to model complex system with redundant and fault-tolerant design is resolved by applying the proposed modeling method. Lastly, using the proposed method to model the DTRFS and compare its safety performance of DTRFS with that of typical redundant and fault-tolerant systems. The analysis results show that the DTRFS can achieve the demanded SIL in the field of petrochemical, and it provides higher availability than typical RFS.In this paper, the redundant and fault-tolerant system architecture design balances the safety and availability, which contributes to improving the safety and efficiency of production process of petrochemical. In addition, the safety modeling method proposed in this paper can be used to calculate of reliability data and SIL level of SIS, can provide reference for SIS design and improvement, which is of high value in engineering projects.