1. Purpose of the gate
The independent functional safety assessment judges that the product and its development meet the target integrity level, and the safety case and safety manual are released.
This gate records the independent judgement that functional safety has been achieved. The assessment looks at the product and at the process: whether the safety lifecycle was followed, whether competence and independence were as planned, whether the evidence supports every claim, and whether the safety manual gives integrators what they need.
The safety case and safety manual are released at this gate and placed under configuration control. Every later modification must update them. Where the plan calls for it, the security evaluation is also complete, with the security user guidance released.
Reviewers do not repeat the assessment. They check that its conclusion is unqualified or that its conditions are understood, that every finding has a recorded closure or an accepted rationale, and that the configuration the assessor judged is the one that will be certified and built. They also read the safety manual as an integrator would: can a customer building a safety instrumented system or a machine control find the failure data, diagnostic test intervals, proof test procedure, environmental limits and conditions of use they need, and are the assumptions made about their system stated plainly enough to check?
Independence is confirmed here rather than assumed. The level of independence the assessor needs rises with the integrity level, and IEC 61508 describes when an independent person, department or organisation is expected. If the assessor's independence was weaker than the plan required, the conclusion cannot be relied on, however good the evidence.
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