Research On Assessment Of Safety Integrity Level For Multi-temperature Coupled Safety Control System

Along with improving the reliability of electrical and electronic equipment, many areas began to use the system consisted of the electrical and electronic devices to implement security controls or security protection function. These systems are used to reduce the probability of occurrence of hazardous events, or to mitigate the consequences of hazardous events, eventually achieve the required security objectives. However, because of failure on these security-related system, when in the need for the implementation of security features, which can't correctly perform the operation, leading to disaster. To ensure that E/E/PE safety-related system functions are really performed, resulting in research on functional safety-related.This paper focuses on the reliability of temperature control system with the coupling of multi-zone object to illustrate the functional safety assessment method and implementation of major effect. When analyzed the hardware configuration of PCC temperature control system, hardware manuals data sheets and the working principle, function security of temperature control loop is identificated, used HAZOP and LOPA qualitative analysis to determine temperature gauge/low security performance indicators of the system. Used FMDEA hardware analysis techniques, and combined with typical industrial database failure mode and effect analysis and the dangerous consequences analysis, access to obtain each failure rate of each component failure mode, but also a detailed analysis of diagnostic capability.The most difficulty of this paper is based on the Markov reliability modeling, adding several factors of hardware reliability,for example structural redundancy,common cause failure,diagnostic coverage et,which can made the Markov model process more scientific and reasonable. Markov model of the three subsystems are established, given a specific theoretical derivation and programming to achieve the fast computation of large matrices in MATLAB.To easily achieve the reliability analysis of safety instrumented system based on the Markov model,fault tree model,reliability block diagram methods, we developed the hardware security integrity level evaluation software under Matlab7.6 environment. This software can effectively achieve the reliability of safety instrumented system such as the 1oo1, 1oo2, 2oo2, 2oo3, 1oo2D voting structure, and calculate failure probability parameters of the average probability of dangerous failure, PFS and SIL. It can be used for the design and assessment stages for SIS, with user-friendly, flexible-modeling and easy-to-handle characters. The software's effectiveness and good accuracy can take some reference effect on the subsequent modeling design of safety instrumented systems.