Within the IEC 61508 / 61511 standards, the SIL is a fundamental means of specifying the safety integrity requirements of a SIF.
SIL Determination is an assessment of the risk reduction required from SIFs to give a sufficiently low level of risk in relation to a specific hazardous event. ABB has a highly structured approach to SIL determination that is recorded on ABB’s TRAC software tool.
ABB recommends the use of Layer of Protection Analysis (LOPA) for SIL Determination. A calibrated risk graph can also be used for initial screening of simple low consequence scenarios where the required risk reduction is likely to be in the ‘unclassified’ range or even not required at all.
For complex scenarios or those potentially involving high levels of instrumented risk reduction, a quantified hazard analysis would be the approach of choice, and ABB can provide this support when required.