Functional Safety Standards and Certification
Functional safety standards and certification
This domain tests the standards landscape and what certification does and does not prove. Expect IEC 61508, IEC 61511, sector standards, SIL certificates, FMEDA reports, and functional safety assessment.
Core rules
- IEC 61508 is the generic functional safety standard; IEC 61511 applies it to the process industry and adds the safety lifecycle for end users and integrators.
- Sector standards include IEC 62061 and ISO 13849 for machinery, ISO 26262 for automotive, EN 5012x for rail, and IEC 61513 for nuclear. They are not interchangeable.
- A SIL certificate for a device typically covers hardware random integrity, systematic capability, and an FMEDA; it does not certify the user's loop, proof-test interval, or site procedures.
- Functional safety assessment is an independent review of the lifecycle evidence; certification is third-party attestation, not a substitute for the assessment.
- Certification schemes accredit devices, systems, processes, and personnel; check the scope, standard, SIL, and validity.
Worked example
A vendor supplies a pressure transmitter with a SIL 3 certificate and an FMEDA showing λDU. The project team still must confirm the device's systematic capability, its architectural constraints in the actual loop, the proof-test interval, and the common-cause beta with the logic solver. If the certificate covers SIL 3 but the SFF/HFT combination in the installed 1oo1 architecture only supports SIL 2, the loop claim cannot be SIL 3.
Traps
- Treating a certificate as proof that the installed SIF meets its SIL.
- Mixing IEC 61508 and IEC 61511 requirements without justification.
- Accepting a certificate beyond its validity or outside its stated scope.
- Assuming CE marking or an SIL certificate covers software and site procedures.