SIL 3 Safety Rating

SIL stands for Safety Integrity Level and Cowan Dynamics has a range of SIL 3 safety certified actuators to meet Safety Integrity Level requirements for flow control equipment and valve automation.  The concept of safety integrity levels (SILs) is now prevalent in the field of safety-critical systems, and a number of standards advocate its use in the design and development of such systems. This rating is designed to provide customers with reliable actuation solutions in critical applications without compromising their Safety Instrumented Systems (SIS – compliant with IEC 61511/ISA 84). Meeting various national and worldwide standards, SIL has four levels used for rating. The higher the level, the better the system performance. 

Assignment of SIL is an exercise in risk analysis where the risk associated with a specific hazard, that is intended to be protected against by a SIF, is calculated without the beneficial risk reduction effect of the SIF. That unmitigated risk is then compared against a tolerable risk target. The difference between the unmitigated risk and the tolerable risk, if the unmitigated risk is higher than tolerable, must be addressed through risk reduction of the SIF. This amount of required risk reduction is correlated with the SIL target. In essence, each order of magnitude of risk reduction that is required correlates with an increase in one of the required SIL numbers.


Written by Cowan Dynamics

February 24, 2020

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