How do you verify that a Safety Instrumented Function (SIF) meets its SIL target?

Verification steps: 1) Architecture analysis - ensure voting (1oo1, 1oo2, 2oo3) meets systematic capability requirement for target SIL; 2) PFD calculation - use IEC 61508 formulas or fault tree analysis with failure rate data, calculate average probability of failure on demand considering proof test intervals, common cause factors, and diagnostics; 3) Compare calculated PFD to SIL requirement; 4) Verify component certification (SIL capability per IEC 61508); 5) Review systematic factors (software, procedures, management). Document in SRS and safety manual. Recalculate for any changes.