Glossary · Stopping functions and safe states
Defined safe state
In machine safety, a defined safe state is a specifically documented safe condition for a machine, zone or function under defined circumstances. It names the concrete condition, such as torque off, brake applied or valve vented, that a safety function or procedure must reach.
- Machine safety
- Risk assessment
- Technical documentation
In one sentence
A defined safe state turns the general idea of “safe” into a documented, checkable condition for one machine, zone or function.
Example
For a robot cell, the defined safe state after a door opens is: robot stopped with Safe Torque Off active, holding brakes applied, gripper pressure retained and conveyor infeed stopped.
How it applies
- Machine safety: Each safety function needs a defined safe state as its target. “The machine stops” is not enough: state which energies are removed, which are retained (for example, gripper pressure holding a part) and for which zone.
- Integrated systems: On a production line the defined safe state can differ per zone and per operating mode. The interfaces between machines must state what each neighbor does when one zone goes to its safe state.
- Technical documentation: The operating manual should describe the defined safe states that users rely on, for example before entering a cell or clearing a jam, and what remains energized.
- Evidence: Validation shows that the function actually reaches the documented state within the required time. The documented state is also the reference for the fault reaction.
Defined safe state vs. safe state
A safe state is the general condition in which risk is acceptable. A defined safe state is the concrete, documented version for a particular machine, zone and situation. A stopped machine is not automatically in a safe state: a vertical axis without a brake or a charged accumulator can still cause harm.