Safe and Non-Safe Coupling Relays – Reliable Signal Transmission for Maximum Safety

In process industries, safety-critical signals, such as the output signals of a safety controller, must be reliably transmitted to the periphery. Simple coupling relays reach their limits in this scenario as they can interrupt the safety chain. As a result, a safe shutdown in the event of a hazard would no longer be guaranteed.

Safe Coupling Relays – Functionality and Advantages
Safe coupling relays solve this problem with a redundant and self-monitoring design. These relays can independently detect and report failures such as contact welding or malfunctions. This ensures that safety-critical signals are reliably transmitted even in the event of an error. They enable standard-compliant coupling of safety-critical signals up to SIL 3 / PL e and offer maximum safety for people and machinery.

Typical applications of safe coupling relays:

• Galvanic Isolation: Secure coupling of 24V digital signals to 230V loads for interference suppression and signal isolation.
• Coupling of Sensor Signals: Safe transmission of pressure switches or other sensors to controllers.
• Contact Reinforcement: Amplification of control outputs with limited output power for controlling higher-power loads.
• Test Pulse Filtering: Filtering of test pulses sent by safety controllers to ensure the flawless function of the control system.

Differences between safe and non-safe coupling relays
| Feature | Safe Coupling Relays | Non-Safe Coupling Relays |
|-----------------------|-----------------------------------|--------------------------------------|
| Application Area | Safety-critical applications | General control signal transmission |
| Safety Function | Yes, ensures the safety chain | No, no safety function |
| Self-Monitoring | Yes, with fault detection | No |
| Redundancy | Redundant switching contacts | Single switching contacts |
| Standards Compliance| SIL 3 / PL e | No safety certification |
| Fault Detection | Yes, detects contact failures | No |
| Example Applications| Connection of safety controllers | Signal forwarding without safety requirements |

Benefits of Safe Coupling Relays

• Maximum Safety: Ensures the safety chain in safety-critical applications.
• Fault Detection and Diagnostics: Detects and reports failures such as contact welding, line breaks, or short circuits.
• Standard-Compliant Coupling: Safe coupling relays comply with the requirements of EN ISO 13849-1 (PL e) and IEC 61508 (SIL 3).
• Reliable Monitoring: Continuous monitoring of the safety status through contact self-supervision.
• Flexible Use Cases: From control signal amplification to sensor coupling in safety-critical processes.

Conclusion
Safe coupling relays are an essential part of modern safety concepts. They ensure safe and reliable signal transmission even under extreme operating conditions. Certified to SIL 3 / PL e, they are perfectly suited for use in safety-critical applications. Unlike simple coupling relays, they guarantee the integrity of the safety chain, protecting both people and machinery.

With ZANDER's safe coupling relays, you ensure that your safety requirements are fully met. Invest in the safety of your systems and benefit from maximum availability and standard-compliant safety technology.