SIL Verification (PFD
/ PFH Calculation)
SIL verification is the engineering proof that an as-designed Safety Instrumented Function actually achieves the SIL allocated in the hazard study. The work begins where SIL allocation ends — receiving a SIL Allocation Register from the hazard-study team — and produces the probabilistic, architectural, and systematic-capability evidence that satisfies IEC 61511 Clause 11. Verification is fundamentally about three honest measurements: FMEDA-grade reliability data (λDD, λDU, SFF, DC) from TÜV / exida / SIRA certificates, PFDavg or PFH calculations per IEC 61508-6 Annex B with calibrated common-cause β-factor, and architectural-constraint check per Route 1H or 2H. The audit failures we see in industry cluster on optimistic β-factor scoring, partial-stroke-test coverage claims that exceed manufacturer guidance, and prior-use justifications without statistical evidence — each of which collapses under FSA Stage 2 examination.
