Functional safety is a lifecycle, not a calculation. The SIL verification is one step among many, and the other steps are where most real failures originate.
Phases and outputs
| Phase | Main output |
|---|---|
| Hazard and risk assessment | HAZOP, LOPA, list of SIFs with targets |
| Allocation of safety functions | Which layer does what; SIF list |
| Safety requirements specification | SRS per function |
| Design and engineering | Architecture, device selection, verification (PFDavg, HFT, SC) |
| Application program | Program developed, reviewed, tested |
| Installation, commissioning, validation | Loop tests, function tests, validation against the SRS |
| Operation and maintenance | Proof tests, bypass control, failure records |
| Modification | Management of change with impact analysis |
| Decommissioning | Controlled removal |
Functional safety assessments
Independent assessments at defined stages (after hazard analysis and SRS, after design, before start-up, periodically in operation, after modifications) check that the lifecycle was followed.
Competence
Each activity is done by people with defined, recorded competence. Certification schemes for functional safety engineers are one way to show it.
Periodic review
Compare actual demands, failures found at proof tests, bypass hours and spurious trips with the assumptions. Update the verification when they differ.
Where First Out AI helps
LOPA and risk calibration (hazard and risk assessment), SIL verification (design), SRS and proof test drafts, HAZOP worksheets and C&E matrices. It supports these steps; it does not replace the assessment or the competent engineer.
Written for First Out AI as engineering guidance. It supports engineering work and does not replace it; check every value against your standards, certificates and company rules with a competent functional safety engineer.