Feilsikkert

Feilsikkert is a Norwegian term for a design principle in safety engineering that aims to ensure a system moves to a safe state in the presence of faults. It translates roughly to “fail-safe” in English. The core idea is that, when something goes wrong, the system behaves in a predictable, non-harmful way to protect people, property and the environment. Feilsikkert design emphasizes safe outcomes and often prioritizes stopping rather than continuing operation after a fault.

By contrast with fault-tolerant systems, which may continue operating after faults but with degraded performance, feilsikkert systems prioritize automatic actions that bring the system to a safe condition at the first sign of trouble. Key principles include defining a safe state, ensuring that faults cannot trigger dangerous acts, incorporating redundancy and continuous safety monitoring, and automatically triggering protective actions such as shutdown, isolation, or interlocking.

Common patterns include fail-closed or fail-safe elements (for example, valves that close on power loss), safety interlocks, emergency-stop devices, and redundant sensors with health checks and watchdogs. Feilsikkert design is frequently part of safety-critical engineering and is guided by risk assessments and safety standards. Standards such as IEC 61508 and ISO 26262 provide frameworks for functional safety, safety functions, and verification of safe-state behavior. Applications span railway signaling, medical devices, industrial automation, aviation, and nuclear power.

Limitations exist: a feilsikkert system depends on correct safety analysis, regular maintenance, and proper implementation. While it reduces risk by ensuring safe outcomes after faults, it cannot eliminate all hazards or account for every possible failure mode.