Safety Integrity Level (SIL)

Safety Integrity Level ( SIL )

      Safety instrumented system SIS ( Safety Instrumented System ) is also called an instrumented safety-related system or an instrumented system that performs safety functions. It has been widely used in petroleum, natural gas and chemical industries, such as safety interlocking systems for system units, PLCs Emergency stop system, fire alarm system, etc. The failure of these systems can lead to huge losses in safety, environment and property. The safety integrity level ( SIL ) is the requirement for the safety integrity of the safety instrumented system, expressed in discrete data.

 Detailed introduction

►       2000 Nian 5 months, the International Electrotechnical Commission officially launched the IEC61508 standard, entitled "Electrical / electronic / functional safety of programmable electronic safety systems", below that is the view of the safety lifecycle defined in the standard. The selection of SIL is based on the fourth step of the first three steps. The first three steps mainly solve the problem of determining the scope of protection, that is, determining the scope of EUC ; identifying hazards; assessing the risks of hazards; and determining the allowable risks of hazards. The fourth step is to determine the safety function and the safety integrity level of the safety function, that is, SIL . The fifth step is to assign safety functions to specific safety-related systems, and at the same time assign safety integrity levels to each safety-related system, that is, to determine the SIL of each safety-related system .

IEC61511 "Functional Safety of Safety Instrumented Systems in the Industrial Field" was launched by the International Electrotechnical Commission following the basic functional safety standard IEC61508 . For instrument safety systems based on the use of electrical / electronic / programmable electronics ( E/E/PE ) technology, the IEC61511 standard specifies the basic principles to be adopted in the design and use of logic solvers, as well as the components of the instrument safety system. The minimum standards that sensors and final components should meet, and the methods of safety life cycle activities that meet these minimum standards are proposed, that is, the requirements for the specification, design, installation, operation and maintenance of safety instrumented systems in the process industry are standardized ; Put forward requirements for the system, hardware, and software of the safety instrumented system. The following figure shows the SIS safety life cycle phase and functional safety assessment phase specified by the standard .