Research On Functional Safety Assessment Of Safety Instrumented System

In the field of industrial process control, in order to prevent the production device in a dangerous condition causing bodily accidents and reduce environmental pollution, as a safety shut down protection system, and being able to carry out potential danger diagnosis, the safety instrumented systems are increasingly being widely used. Safety instrumented System is an important measure of safeguarding production safety, and should be able to correctly implement its safety features in the condition of occurring dangers. However, due to system architecture, hardware, software and the surrounding environment, and other reasons, the safety system will shut down in the wrong parking time, or not take action when needed to shut down, as the result of directly causing casualties and huge property losses. Consequently, the reliability of the safety instrumented system must be high, and can ensure the correct action when must shut down to do the protection. The issuing of international standards IEC61508 and IEC61511 provide effective solution of the above problems, and widely accepted by the process industry, machinery industry, transport and other fields. The standards put forward a new sort of safety principles and methods, as well as provide the guidelines to functional safety assessment of SIS.This paper goes through the following several aspects of study on the basis of functional safety international standards:(1) Discuss the background of functional safety standards and the meaning of functional safety, and analyze the need for functional safety assessment, through the discussion to the status of domestic and foreign functional safety assessment, point out the deficiencies of our functional safety assessment research and application.(2) Analyze the relationship between functional safety assessment and safety evaluation, and bring forward analysis of SIL in the process of safety evaluation, and make it be the objective of assessing the SIL of SIR(3) Discuss the characteristics of SIS and the distinction to basic process control system, highlight the importance of assessment to safety instrumented system.(4) According to the theory of overall safety life-cycle, summarize and analyze the content of functional safety assessment of the three stages, namely: analysis stage, and realization stage and operation stage, to summarize and analyze the content of assessment. Focus on safety assessment methods applicable to process industries in the analysis stage, and the method of confirming the target SIL, analyzing method of SIL of safety instrumented functions in the realization stage. In the operation stage, summarize and analyze the assessment content of overall operation and maintenance and overall amendment and remodel.(5) Focusing on the assessment of hardware random failures and system hardware failure in the realization stage. Bring forward in meeting the safety integrity of objectives, in addition to assessment of the hardware safety integrity, but also analysis the safety integrity of the system.