The Siemens 3SK11212CB42 is a SIRIUS safety relay basic unit from the Advanced series, designed for implementing safety-related control functions in industrial machinery and automation systems. The unit combines instantaneous and time-delayed relay enabling circuits, providing flexibility for applications where certain outputs need to switch immediately while others require a controlled delay.
The device features 2 NO instantaneous relay enabling circuits and 2 NO delayed relay enabling circuits, with an adjustable time-delay range of 0.5–30 seconds. It operates with a 24 V DC supply and uses spring-type terminals with push-in technology, making it suitable for modern industrial control-panel wiring.
The 3SK11212CB42 SIRIUS safety relay is used in machine safety applications where safety-related signals need to control multiple output circuits with different switching characteristics.
Its combination of instantaneous and delayed outputs can be particularly useful when a machine requires one group of circuits to respond immediately to a safety command while another group needs to remain active for a defined period before being switched.
The adjustable 0.5–30 second time delay allows the delayed outputs to be configured according to the requirements of the machine's safety-control architecture.
Typical applications can include machinery with controlled shutdown sequences, multi-stage stopping processes and systems where connected equipment requires different response times.
The 3SK11212CB42 provides 2 normally open instantaneous relay enabling circuits.
These outputs are designed to respond without the configured time delay when the relevant safety conditions are satisfied.
Instantaneous outputs can be useful for circuits that need immediate switching in response to a safety-related control command.
Depending on the complete machine design, these outputs can interface with appropriate control components such as contactors, machine-control circuits or other safety-related devices.
The exact safety function must be determined from the machine's risk assessment and complete safety architecture.
In addition to the instantaneous outputs, the unit provides 2 normally open delayed relay enabling circuits.
These outputs operate according to the configured time delay, providing additional flexibility for machinery that requires a controlled shutdown sequence.
The delayed outputs can be useful when certain connected circuits need to remain enabled for a defined period before being switched off.
For example, a machine may require different equipment to respond at different stages of a shutdown process. The exact implementation depends on the machine design and safety requirements.
One of the key characteristics of the 3SK11212CB42 is its adjustable 0.5–30 second time-delay range.
This allows the delayed relay outputs to be configured for the required response time within the specified range.
A configurable delay can be useful for machinery where an immediate shutdown of every circuit is not appropriate and a controlled sequence is required.
The selected delay must be determined from the machine's safety design and validated as part of the complete safety function.
The 3SK11212CB42 operates with a 24 V DC supply, a common control voltage in industrial automation and machine-control systems.
This makes it suitable for control panels where 24 V DC is used for PLCs, sensors, safety devices and other control components.
The supply should be installed according to the applicable Siemens documentation and the requirements of the complete control system.
The safety relay uses spring-type terminals with push-in technology.
This connection method can simplify control-panel wiring by allowing compatible conductors to be inserted efficiently into the terminal system.
Push-in terminals can also support easier maintenance and wiring work compared with conventional screw-terminal arrangements.
Panel builders should follow the specified conductor requirements and installation procedures when wiring the unit.
The 3SK11212CB42 belongs to the Siemens SIRIUS 3SK safety relay family and is part of the Advanced series.
The Advanced series provides expanded functionality for machine safety applications where more flexible safety-control arrangements are required.
The combination of instantaneous and delayed relay outputs allows the device to support machine designs with multiple output response requirements.
Before installation, compatibility with the intended safety architecture and connected components should be verified.
The Siemens 3SK11212CB42 safety relay can be considered for appropriately designed applications including:
For OEM machine manufacturers, the 3SK11212CB42 provides a flexible safety-control solution when different output circuits require different response times.
The combination of 2 instantaneous NO outputs and 2 delayed NO outputs can help simplify machine architectures where controlled shutdown sequences are required.
The adjustable 0.5–30 second delay provides configuration flexibility, while the 24 V DC supply integrates well with common industrial control architectures.
The push-in spring terminals make the 3SK11212CB42 convenient for modern control-panel construction.
Panel builders can integrate the safety relay with compatible emergency-stop devices, safety switches, contactors and other safety-related components to create a complete machine safety circuit.
The final wiring and safety performance must always be verified against the machine's design and applicable requirements.
The 3SK11212CB42 is a safety-control component and should not be considered a complete safety system by itself.
Its safety performance depends on the complete safety-related control architecture, including:
The configured time delay should also be selected and validated according to the required machine safety function.
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The 3SK11212CB42 is a Siemens SIRIUS Advanced safety relay basic unit with instantaneous and time-delayed relay enabling circuits.
It has 2 NO instantaneous relay enabling circuits.
It has 2 NO delayed relay enabling circuits.
The specified time-delay range is 0.5–30 seconds.
The unit operates with a 24 V DC supply.
It uses spring-type terminals with push-in technology.
It can be integrated into appropriately designed industrial machinery, machine safety systems, production lines, automation equipment and safety-control panels.
Its combination of instantaneous and delayed relay outputs can support appropriately designed controlled shutdown functions. The complete safety function must be assessed and validated for the specific machine application.
| Parameter | Specification |
|---|---|
| Product Series | Siemens SIRIUS 3SK1 Advanced |
| Model Number | 3SK1121-2CB42 |
| Variant | CB42 |
| Supply Voltage | 24 V DC |
| Output Contacts | 2 NO instantaneous + 2 NO delayed |
| Time Delay Range | ~0.5 to 30 seconds (series dependent) |
| Mounting Type | DIN rail |
| Width | 22.5 mm |
| Terminal Type | Push-in / spring terminals |
| Safety Inputs | 1-channel / 2-channel configurable |
| Feedback Monitoring | Yes (EDM) |
| Cross-circuit Detection | Yes |
| Protection Class | IP20 |
| Operating Temperature | -25°C to +60°C |
| Standards | IEC 61508, ISO 13849-1 |
| Safety Level | SIL 3 / PL e capable system design |
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