Interlocking monitors guard position
Opening the guard initiates the defined safe response and prevents hazardous operation while the guard is open.
- Suitable where the hazard can become safe before access
- Requires reliable mounting and defeat resistance
- Must interface with the intended machine stop
Guard locking controls when access is possible
The guard remains locked until standstill, safe speed, elapsed time or another suitable release condition is confirmed.
- Consider run-down and stored energy
- Define power-loss and emergency-release behaviour
- Provide escape release for whole-body access where required
Process locking is not the same as safety locking
A lock used to prevent production interruption may not provide a safety-related retaining function.
- Identify whether locking protects people or process
- Select monitored devices accordingly
- Validate the release and fault response
Door hardware is part of reliability
Poor hinges, handles, alignment or impact protection can cause nuisance trips and encourage bypass.
- Use robust mechanical stops and alignment features
- Protect the device from collision
- Include routine inspection points
Apply the guidance to the specific machine.
This guide supports early decision-making but does not replace a project-specific risk assessment, safety-system design or validation. Machine condition, tasks, controls and modification scope can change the correct solution.
Questions
Direct answers.
Can a standard interlock be used on a machine with long run-down?+
Only if access before the hazard ends is otherwise prevented. Guard locking or another access-delay method may be required.
What is power-to-lock versus power-to-unlock?+
It describes whether electrical power engages or releases the locking mechanism. Selection depends on risk, access and power-loss behaviour.
Does guard locking replace safe isolation for maintenance?+
No. Maintenance isolation and control of hazardous energy may still be required for the task.
