Sequential access control
Trapped-Key Interlocking Systems
A trapped-key system can enforce a physical sequence between machine isolation, key release and access to one or more guarded areas.
- Delivery
- Survey to handover
- Coverage
- Great Britain
- Application
- Project-specific
System intent
Designed around the task—not simply the available component.
A trapped-key system can enforce a physical sequence between machine isolation, key release and access to one or more guarded areas.
We develop the guarding arrangement in the context of machine movement, product flow, operator behaviour, cleaning and foreseeable intervention. The scope is then defined clearly for detailed engineering and installation.
Key engineering decisions
What the design needs to resolve.
These points are reviewed together because a change to access, stopping or production flow can alter the required safeguarding approach.
- 01
Sequence
Define the exact isolation, key exchange and access order for normal and emergency conditions.
- 02
Energy sources
Identify which electrical, pneumatic, hydraulic or process energies must be controlled.
- 03
Multiple access points
Determine whether keys are exchanged, multiplied or retained for people entering a space.
- 04
Human factors
Make the sequence clear, practical and resistant to shortcutting during production or maintenance.
Application review
Design considerations.
- Number of energy-isolation points
- Number of access doors and people entering
- Personal-key or key-exchange requirements
- Emergency and rescue arrangements
- Environmental and mechanical durability
- Integration with existing electrical controls
Typical project output
What can be included in the scope.
The precise deliverables are agreed before work proceeds and depend on whether the project covers mechanical guarding only or an integrated safety-system modification.
- Access-sequence study
- Key plan and component schedule
- Mechanical and electrical interfaces
- Installation and labelling
- Sequence testing
- Key-management and maintenance information
