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SIL Assessment
The assessment of a safety function’s Safety Integrity Level or SIL, (also known as Instrument Protective Function (IPF) Classification) provides a measure of the consequences of its failure on the system or equipment’s safety, implications for the surrounding environment and also the potential financial implications on the operating company (loss of production, replacement of equipment etc). A SIL is one of 4 levels, each corresponding to a range of target likelihood of failures of a safety function, with SIL 1 corresponding to the highest Probability of Failure on Demand (PFD), and SIL 4 the lowest PFD. Functional safety requirements for safety instrumented systems are defined in the standards IEC 61508 (Functional Safety of Electrical / Electronic / Programmable Safety Related Systems) or IEC 61511 (Functional Safety of Safety Instrumented Systems for the Process Industry Sector).
The ARC approach to SIL Assessment
ARC can help you with both qualitative and quantitative SIL assessments of safety instrumented systems and has a wide range of industry experience. Our consultants have developed the SIL assessment tool “ARCSIL”, which makes use of risk graphs, to classify safety functions and identify potential problem areas. In cases where system and equipment design must meet safety integrity levels defined by regulatory or company specifications, “ARCSIL” will assist identifying areas where redesign or modification is necessary to achieve these.
ARC consultants are also experienced in the use of fault and event tree analysis to provide design solutions to achieve SIL ratings and achieve acceptable equipment and system reliabilities.
Experience
Our experience includes the following projects:
SIL assessment of an offshore gas processing complex as part of an ongoing revamp and redevelopment project.
SIL assessment and reliability analysis of a wellhead platform ESD system.
A comparison of the assigned SILs of a new helicopter communications system under IEC 61508 and MoD Defence Standard Def Stan 0056.
SIL assessments of all control and protection systems for a nuclear waste storage facility. |
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