PLC Safety Design in 2026: IEC 61508, ISO 13849 and What Changed

Detail

, plus what has changed since the original 2024 draft of this article, and how a multi-brand maintenance team can keep both legacy and modern safety PLCs compliant without a full rip-and-replace.

, safety PLCs and SRP/CS must be re-evaluated against the new harmonised standards before that date.

The five design pillars that survived the 2024→2026 standards refresh: hazard & risk assessment, emergency stop, fault detection & diagnostics, proper grounding & wiring, and a real safety PLC (not a standard PLC with safety code).

Lockout / tagout, periodic proof tests, and firmware change control are now treated as

When replacing an EOL safety module, KOEED stocks both legacy and modern equivalents side-by-side so your migration does not create a compliance gap.

article was published on 2024-03-07 and stayed at a generic “identify hazards, add E-stops, use safety PLCs” level. It did not yet reflect the wave of standard revisions that landed between 2023 and 2026, and it did not address the new EU regulatory deadline. If you are still following only that 2024 guidance, three things will catch you out in 2026:

scoring and added explicit guidance on software parameterisation , a 2024 design that was compliant in 2023 may no longer meet PL d / PL e.