AiVibeInterlock
An interlock is a control function that prevents a machine or process action unless specified conditions are met, or stops it when they cease to be met, such as preventing a motor from starting while a guard is open.
Interlocks combine conditions in logic: a pump may run only if suction pressure is adequate and the discharge valve is open, or two contactors may be prevented from energising together. Operational or process interlocks protect equipment and product quality and are usually implemented in the standard PLC or DCS. Safety interlocks protect people, for example by monitoring guard doors with interlocking devices, and must be implemented in safety-rated systems designed to standards such as ISO 13849 or IEC 62061.
Guard interlocking devices, from tongue-operated and hinge switches to non-contact coded sensors and guard locking devices, are covered by ISO 14119, which also addresses minimising the possibility of defeating them. In process plants, permissives and trips follow a similar logic, with critical trips assigned to safety instrumented systems. Interlocks also prevent incorrect sequences, such as opening a vessel before it is depressurised.
Interlock design must consider failure modes, so that a broken wire or failed sensor leads to a safe condition, and must make bypassing difficult. Operators sometimes defeat interlocks that hinder production, so good design addresses the underlying reasons, and any bypass requires authorisation and logging. Modifying or bypassing a safety interlock must only be done under the applicable standards, OEM documentation and site procedures, by qualified personnel.
Key points
- Permits or stops an action based on defined conditions
- Process interlocks protect equipment; safety interlocks protect people
- Safety interlocks need safety-rated design, for example to ISO 13849
- ISO 14119 covers guard interlocking devices and defeat prevention
- Bypasses require authorisation, logging and qualified personnel
Where AiVibe comes in
AiVibe designs and manufactures the AiAmbA AI Factory, whose edge devices and AI agents let people talk to PLC, CNC and robot controllers in plain language. Agents only propose changes, a trained operator confirms each one, and the AI Factory never replaces a machine's control or safety systems.
Related terms
- Safety PLCPLC & Industrial Control
- ISO 13849 and Performance Level (PL)PLC & Industrial Control
- Functional SafetyPLC & Industrial Control
- Ladder Logic (Ladder Diagram, LD)PLC & Industrial Control
- Safety Instrumented System (SIS)PLC & Industrial Control
- Programmable Logic Controller (PLC)PLC & Industrial Control