felsäkert

Felsäkert, or fail-safe, is a concept in safety engineering describing systems, components, or processes that are designed to avoid or minimize harm in the event of a fault. The core idea is that a fault should cause the system to move toward a safe condition rather than continue operating in a potentially dangerous state.

Design principles commonly associated with felsäkert systems include fault detection and diagnostics, redundancy and diversity of critical paths, and the establishment of reliable safe states or safe shutdown procedures. Devices and controls are often designed to default to a safe position or to de-energize automatically when a fault is detected. Documentation and verification aim to prove that the system behaves safely under specified fault conditions.

Applications of felsäkert design span many safety-critical areas, such as industrial automation, process control, railway signalling, aviation, and medical devices. Examples include emergency stop systems that cut power or operation when activated, and mechanical or electrical safeguards that return actuators to a predefined safe position if control signals are lost or corrupted.

Standards and regulation in many sectors emphasize functional safety and fail-safe behavior. Notable frameworks include IEC 61508 for electrical/electronic/programmable safety-related systems and ISO 26262 for automotive functional safety. The term is also used in Swedish engineering practice to describe systems intended to protect people and equipment by ensuring safe outcomes during faults.