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SIL stands for "safety integrity level."
An SIS has to be evaluated and certified to a certain safety level. SILs are defined by the IEC 61508 and 61511 international safety standards, and indicate the plant risk factor that can be achieved through the introduction of specific safety measures.
For example, by installing an SIL3 SIS in a plant, the risk factor can be reduced to between 10-3 and 10-4. The risk factors for specific SILs are given below:
SIL4: ≥ 10-5 to <10-4
SIL3: ≥ 10-4 to <10-3
SIL2: ≥ 10-3 to <10-2
SIL1: ≥ 10-2 to <10-1
In this way, it is possible to quantitatively and objectively evaluate the safety level when planning to introduce an SIS at a plant. ProSafe-RS is SIL3 certified, and this is the maximum SIL that can be achieved by a programmable logic solver.
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