Allied: Siemens’ SIRIUS 3SK Safety Relays for Autonomous Safety Applications


April 25, 2022

Allied Electronics & Automation supplies Siemens’ SIRIUS 3SK safety relays, which deliver flexible, consistent, cost-effective and user-friendly solutions for a comprehensive range of autonomous safety applications, as well as simplify the planning, commissioning and expansion of today’s modern industrial plants.

Siemens’ SIRIUS 3SK safety relays have a compact, modular design with replaceable terminals for enhanced plant availability, yellow terminal covers that clearly identify the devices as safety components and sensor cables up to 2,000m long. They are designed for quick implementation and, without any programming, enable the fail-safe monitoring of mechanical and electronic sensor safety functions, sensor leads and shutdown circuit actuators, as well as their own functionality, and execute safety-related disconnections when dangers arise. SIRIUS 3SK safety relays can be used as both standalone and integrated solutions and are certified to the internationally recognized IEC 62061 and ISO 13849-1 standards, as well as compliant with the industry’s highest safety requirements, SIL 3 and PL e. The series also supports extensive parameterization, enabling universal employment and outstanding system design flexibility with a lean portfolio of compact evaluation units that reduces device variance and eases device selection and inventory management. Ideal applications for the SIRIUS 3SK series safety relays include emergency stop functionality and protective door monitoring up to SIL 3 and PL e, light arrays, laser scanners, presses and punches.

SIRIUS 3SK series safety relays are available in 3SK1 and 3SK2 versions to meet a vast range of application requirements. SIRIUS 3SK1 safety relays are optimized for quick and easy implementation in simple autonomous safety applications that require detect, evaluate and react functionality and are not connected to a safety-related bus system. They are used to evaluate the sensors and the safety-related shutdown of hazards, as well as to monitor the sensors, actuators and safety-oriented functions of the safety relay. SIRIUS 3SK2 safety relays are optimized for more complex autonomous safety applications that require additional functionality, such as independent shutdown functions or the integration of higher-level control systems for diagnostics via fieldbus protocols like PROFIBUS and PROFINET. Both versions feature relay outputs that allow different voltages to be switched through their floating contacts and support currents up to 5A at 230VAC or 24VDC in addition to wear-free semiconductor outputs that are insensitive to dirt and vibration, exhibit good electrical endurance and are suitable for operation in frequently switching applications.

Siemens’ SIRIUS 3SK1 Standard safety relays are characterized by their compact design, simple operation, relay and semiconductor outputs, wired connections, cost effectiveness and output expansions, which provide additional fail-safe, potential-free relay contacts for controlling actuators. They also feature DIP switches for parameterization, a wide voltage range and a special power supply unit designed for devices rated for 24VDC operation.

Siemens’ SIRIUS 3SK1 Advanced safety relays are characterized by their time-delayed outputs, input expansions that negate the need for individual basic devices to be interconnected if more than one sensor is required and output expansions that provide additional fail-safe, potential-free relay contacts for controlling actuators, as well as their compatibility with device connectors and their universal application possibilities. They also feature DIP switches for parameterization, a wide voltage range and an optional power supply unit designed for devices rated for 24VDC operation.

Siemens’ SIRIUS 3SK2 safety relays are characterized by their SIRIUS Safety ES (TIA Portal) software, which — when used in combination with an external diagnostics module — enables the quick, easy and extensive parameterization, commissioning and diagnostics of these safety relays, as well as the communication and visualization of device configuration, functionality and diagnostic data to ease troubleshooting and reduce plant downtimes. SIRIUS 3SK2 safety relays can also be integrated into the overall safety application for higher-level diagnostics and control capabilities via PROFINET or PROFIBUS and optionally available interface modules that can exchange information with the plant controller. SIRIUS 3SK2 safety relays are available with up to six independent, fail-safe shutdown functions and feature flexible configuration software, powerful semiconductor outputs and output expansions that provide additional fail-safe, potential-free relay contacts for controlling actuators. They also employ device connectors and support universal application possibilities and offer compatibility with Siemens’ SIRIUS Sim simulation software, which allows users to quickly and easily create and test digital applications that behave just like real devices, create and test parameter settings for subsequent applications and load tested configurations directly onto real devices to reduce engineering time and costs.

“SIRIUS 3SK1 safety relays offer high-quality replacements for the largely discontinued SIRIUS 3TK28 safety relays,” said Glenn Symonds, Product Manager at Siemens. “They have a narrower design, are equipped with greater functionality and can replace every SIRIUS 3TK28 device except 3TK2810 devices. These modular safety relays are extremely flexible, consistent and user-friendly and offer an excellent price-performance ratio. They’re certified to internationally recognized safety standards and the industry’s highest safety requirements, which enables universal employment in safety applications all around the world, and they’re key to simplifying the planning, commissioning and expansion of autonomous safety applications including e-stops, protective doors, light arrays, laser scanners, presses and punches.”  

The SIRIUS 3SK series is also available with several additions. Siemens’ 3ZY12 device connectors allow users to quickly construct safety functions involving several sensors and actuators. They reduce the amount of time required to configure and wire components, eliminate wiring errors and considerably reduce the amount of testing required for fully assembled applications, and they are designed for standard rail mounting, which enables flexible connectivity and quick and easy expansion. Siemens’ force-guided 3RQ1 coupling relays can be used as output expansions for 3SK series safety relays up to SIL 2 and PL c and are compatible with both wired connections and device connectors. Siemens’ SIRIUS 3SK1213 power output expansions allow different voltages to be switched through the floating contacts, employ power relay contacts that support switching at up to 10A at 230VAC and 6A at 24VDC, as well as a protective separation between safe outputs and electronics, and exhibit high mechanical and electrical endurance. Siemens’ SIRIUS 3RM1 motor starters combine the benefits of semiconductor and relay technologies to simplify and ease collective assembly shutdowns. The device connectors in these fail-safe, hybrid motor starters shut down the control supply voltage for expansion components in emergency stop situations, eliminating the need for complex connection cables between the safety relays and the motor starters. Their semiconductors briefly conduct the inrush current for motorized load, which protects the relay contacts from arc exposure, mitigates wear and increases service life, while their relay contacts conduct uninterrupted current and generate less heat than semiconductors.

For more information about Siemens’ SIRIUS 3SK safety relays, visit Siemens’ 3SK safety relays product pageSiemens safety relays, as well as additional Siemens products, can be purchased on, and through your local sales office.

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