Safety Instrumented System Functional Safety Certification Study

Safety Instrument System plays an important role in the area of process industry. It can be a state of emergency and take measures to avoid expansion of the loss rapidly when there is a danger in production process. For safety instrumented systems, its function is to ensure the safety of production, if its own problems arise, there could lead to no response when it's dangerous, but also arbitrary safety measures be taken when it's safe, and cause a greater loss. The problems of Safety Instrument System are usually caused by the fault of hardware and software and the environment effects, so it is the solution by tracing the root and working out the method to avoid the fault and effects. In the year of 2000 and 2003, International Electrotechnical Commission has published IEC61508 and IEC61511, providing a basis for the research on the functional safety of Safety Instrument System. A regulation called China's compulsory certification (3C) for safety-related products has enacted in china, but there is no Safety Instrument System listed in the "3C" catalogue. This paper will go through the following several aspects of research on functional safety certification of Safety Instrument System on the basis of IEC61508 and IEC61511, and combining with the requirement of "3C":1. Introducing the background and necessity of functional safety certification, and analyzing the current situation both at home and abroad, and pointing out the gap in this field between us and the advanced country.2. Discussing the component parts and the workflow of Safety Instrument System, analyzing the meaning of safety integrity, safety integrity level and risk, pointing out that safety integrity level is the measure of functional safety, highlighting the importance of functional safety.3. Analyzing the meaning of functional safety certification, safety life cycle, mode of operation, failure and fault, studying on the connection between probability of failure and safety integrity level, and developing some premises for the functional safety certification.4. Studying on the auditing methods of the safety integrity of hardware and software, the method of "Proven In Use" and the testing method of electromagnetic stamina. A qualitative analysis of constructional constraints and a quantitative analysis of Average probability of failure on demand are utilized in the auditing on the safety integrity of hardware, and a qualitative analysis with the techniques and measures recommended by IEC61508 and IEC61511 is utilized in the auditing on the safety integrity of software.