Process interlocks

Process Interlocks for Safe and Continuous Process Monitoring

What is a process interlock?

A process interlock is an advanced safety device that integrates a contactless safety sensor with an electromagnetic locking mechanism in a single unit. It ensures that doors, covers or access panels remain locked as long as a hazardous process is active. Only after the safety controller confirms that the process has reached a safe state will the interlock release.

Where are process interlocks used?

Process interlocks are used in applications where interrupting the process is undesirable or hazardous. Typical use cases include:

• Packaging and filling systems
• Continuous production and conveying lines
• Equipment operating under elevated temperature or pressure
• Automated chemical, pharmaceutical or dosing processes

They prevent operators from opening access points until all hazardous conditions have been removed.

How does a process interlock work?

The integrated electromagnet generates a holding force of either 600 N or 1200 N, depending on the model. This force keeps the actuator locked and prevents access during an active process. Once the controller releases power to the magnet—confirming the process is safely stopped—the locking force is removed and the actuator detaches.

An optional permanent magnet can be added to hold lightweight doors closed even after the electromagnetic lock is released, preventing unintentional opening.

Process interlocks with integrated RFID safety technology

All models incorporate a coded RFID safety sensor for high-reliability detection of actuator position. They are available in:

• Standard coded versions
• Uniquely coded (re-teachable) versions for enhanced anti-tampering protection

Available process interlock models (600 N / 1200 N)

• HoldX RS (600 N): standard- or uniquely-coded RFID safety sensor
• HoldX RL (1200 N): standard- or uniquely-coded RFID safety sensor

Both models are certified for use in applications up to PLe (EN ISO 13849-1) and SIL 3 (EN 62061).

Key advantages of process interlocks

• Fully contactless, wear-free mechanism
• Continuous magnetic-field diagnostics for contamination detection
• Large misalignment tolerance between actuator and interlock
• Optional Bluetooth diagnostics for rapid troubleshooting
• OSSD outputs for safe series connection of up to 30 devices
• Clear LED status indication

Installation and system integration

Each device is equipped with an 8-pin M12 connector and a 200 mm pigtail lead for quick installation. The compact housing allows seamless integration into both new and existing systems, including heavy-duty safety switch networks and industrial interlock architectures.

Limitations of process interlocks

Process interlocks are not suitable for applications involving run-down time of hazardous motion. In the event of a power loss, the electromagnet is immediately de-energised and the lock releases. For such applications, mechanically locked safety interlock switches—such as amGard Pro or other heavy-duty mechanical interlocks—must be used.

Safety standards and certification (EN ISO 13849, SIL3)

All process interlocks meet the requirements for use in high-demand safety circuits:

• PLe according to EN ISO 13849-1
• SIL 3 according to EN/IEC 62061
• EN ISO 14119 high-coded safety interlocking

Why choose process interlocks from MachineSafety-Shop?

• Technical guidance: Support in selecting the correct holding force and coding level
• Certified components: Only high-quality, compliant safety devices
• Fast delivery: Many variants available from stock
• On-site support: Assistance with installation, validation and configuration

Need help selecting a process interlock?

Our safety specialists can help you define the correct interlocking solution based on your risk assessment, process conditions and required PL/SIL levels. Contact us for technical advice or a quotation.