SIL selection is the process of assiging a SIL (Safety Integrity Level) to a safety function in order to close the gap between residual risk (evaluated in HAZOP) and tolerable risk (as per Client Risk Matrix).
SIL (or its inverse – Risk Reduction Factor RRF) is defined in IEC 61508/61511 for low demand operation, as follows:
SIL | PFD (avg) | PFD (power) | RRF |
1 | 0.1–0.01 | 10−1 – 10−2 | 10–100 |
2 | 0.01–0.001 | 10−2 – 10−3 | 100–1000 |
3 | 0.001–0.0001 | 10−3 – 10−4 | 1000–10,000 |
4 | 0.0001–0.00001 | 10−4 – 10−5 | 10,000–100,000 |
Kategorie:
SIL Selection / LOPA