Trapped Key Interlocking (TKI)
Trapped Key Interlocking (TKI) is a highly reliable safety solution used in industrial automation and electrical systems. It ensures that equipment follows a strict, predefined sequence — especially where hazardous motion or energy is involved.
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What Is Trapped Key Interlocking (TKI)? | Industrial Safety System Explained
Trapped Key Interlocking (TKI) is a highly reliable safety solution used in industrial automation and electrical systems. It ensures that equipment follows a strict, predefined sequence — especially where hazardous motion or energy is involved.
TKI is a mechanical or electromechanical safety mechanism designed to prevent unsafe access or startup during maintenance, inspection, or emergency operations.
How Trapped Key Interlocking Works (Step-by-Step)
This process ensures zero possibility of human error in restarting equipment during unsafe conditions.
Here’s how the trapped key system operates:
1. Key Is Trapped – A safety key remains locked inside the control lock while equipment is powered or running.
2. Power Off → Key Released – After safe shutdown, the key is released from the isolation lock.
3. Unlock Access – The key is then used to open a machine guard, access door, or panel.
4. Key Held During Access – The key stays in the access lock, making it impossible to restart the equipment while someone is inside.
5. Sequence Restored → Power On – Once access is closed and the key is returned, the system can be safely restarted.
Use Cases: Where Trapped Key Interlocking Systems Are Used
TKI is widely adopted in high-risk industrial setups, including:
- Machine guarding for robotic and automated cells
- Electrical switchgear and MCC panels
- Conveyor systems and packaging lines
- High-voltage and substation operations
- Hazardous process lines in chemical, food, or pharma industries
Benefits of Trapped Key Interlocking Systems
- Mechanical Simplicity – No complex software or programming required
- Fail-Safe Operation – Physical safety sequencing prevents bypassing
- Highly Tamper-Proof – Only the correct key can enable system access or restart
- Durable & Reliable – Ideal for harsh industrial environments
Key Components in a TKI System
- Isolation Locks – Secure circuit breakers, switches, or control panels
- Access Locks – Used on guard doors or hatches
- Key Exchange Boxes – Manage multi-step safety procedures
- Solenoid Locks – Enable electrical signal integration with mechanical safety