Glossary · Hazards and harm
Unexpected startup
Also known as: unexpected start-up, unintended start-up
In machine safety, unexpected startup is an unintended activation of a machine that exposes people to hazardous motion or energy, for example caused by a control fault, an external influence or a start command given elsewhere.
- Machine safety
- Maintenance
- Risk assessment
In one sentence
Unexpected startup is unintended machine activation while people are exposed, prevented by isolation, lockout and restart prevention.
Example
While a technician clears a jam inside a conveyor, a colleague at the HMI restarts the line; lockout at the energy-isolating device would have prevented the start.
How it applies
- Machine safety: ISO 14118 names causes such as a start command after a failure of or an external influence on the control system, an inappropriate action on a start control, restoration of the power supply after an interruption, and influences such as gravity on machine parts. Measures include isolation and energy dissipation as well as restart prevention.
- Maintenance: For servicing, the reliable measure is energy isolation with lockout/tagout. A stopped machine or an open guard alone does not guarantee that it cannot start.
- Integrated systems: In a line, a start command from one controller can move equipment of another. Define start permissions and interlocks at the interface.
- Technical documentation: State which stop condition is sufficient for which task. Safe Torque Off prevents torque but does not isolate energy for electrical work.