Siemens SIRIUS 3SK2 Safety Relays

Siemens SIRIUS 3SK2 Safety Relays Suppliers, Exporters in India

ARP IMPEX supplies and exports Siemens SIRIUS 3SK2 Safety Relays for machine safety panels, robotic cells, conveyor systems and industrial automation projects. The range includes software-configurable safety relays with multiple fail-safe inputs and independently controlled safety outputs.

Siemens SIRIUS 3SK2 relays are suitable for machines that use several safety devices or require different sections to shut down separately. They are commonly selected where a basic emergency-stop or guard-door relay cannot handle the complete safety logic.

A 3SK2 relay can monitor emergency-stop push buttons, safety doors, light curtains, laser scanners, pressure-sensitive mats, two-hand controls, enabling switches and other safety devices. The required safety logic is created through Siemens SIRIUS Safety ES software instead of setting individual functions through switches on the front of the relay.

This makes the Siemens 3SK2 configurable safety relay suitable for packaging machines, robotic cells, conveyors, presses and production equipment with more than one safety zone. For example, opening one guard door can stop only the affected section while another part of the machine remains available, provided the machine risk assessment and safety design allow it.

The range includes compact 22.5 mm basic units with 10 fail-safe inputs and two fail-safe semiconductor outputs. Larger 45 mm versions provide 20 fail-safe inputs and four fail-safe outputs. Both screw-terminal and push-in-terminal models are available.

The 3SK2 series can support safety functions up to SIL 3 and Performance Level PL e when the complete safety circuit is correctly designed, installed and validated.

ARP IMPEX supplies and exports Siemens SIRIUS 3SK2 Safety Relays for machine builders, automation companies, industrial panel manufacturers and plant maintenance requirements. Send the complete Siemens part number, number of safety inputs and outputs, terminal type and required quantity for price and availability.

Technical Specifications

• Brand: Siemens
• Product range: SIRIUS
• Series: 3SK2
• Product type: Software-configurable safety relay
• Control supply: 24 V DC
• Available basic-unit widths: 22.5 mm and 45 mm
• 22.5 mm basic unit: 10 fail-safe digital inputs, two fail-safe digital outputs and one standard signalling output
• 45 mm basic unit: 20 fail-safe digital inputs, four fail-safe digital outputs and two standard signalling outputs
• Safety outputs: Short-circuit-protected semiconductor outputs
• Configuration software: Siemens SIRIUS Safety ES
• Safety functions: Emergency stop, guard door, safety light curtain, laser scanner, pressure-sensitive mat, two-hand control and enabling-switch monitoring
• Muting functions: Available for applicable optoelectronic safety applications
• Start functions: Automatic and monitored start can be configured
• Stop categories: Stop Category 0 and Stop Category 1, depending on the safety design
• Safety level: Up to SIL 3
• Performance level: Up to PL e
• Safety category: Up to Category 4
• Terminal options: Screw terminals or spring-loaded push-in terminals
• Mounting: DIN rail mounting
• Degree of protection: IP20
• Operating temperature: Generally -25°C to +60°C
• Output expansion: Compatible Siemens 3SK1 output expansion modules can be added
• Motor switching: Compatible fail-safe 3RM1 motor starters can be connected through the Siemens device connector
• Communication: Optional PROFINET interface available for parameter setting and diagnostic data
• Diagnostics: LED indication, software diagnostics and optional cabinet-mounted diagnostic display

The number of inputs, outputs and terminal type must be checked against the complete Siemens article number before ordering. The 22.5 mm and 45 mm basic units cannot be selected only by their physical size because their input and output capacities are different.

Software-Configurable Safety Functions

Unlike a basic safety relay with one fixed operating function, the Siemens 3SK2 allows several safety functions to be created in one unit.

The safety program is prepared through SIRIUS Safety ES using ready-made function blocks. These blocks cover common applications such as emergency stops, guard doors, light curtains, two-hand controls, selector switches, pressure-sensitive mats and muting arrangements.

The software can also be used during commissioning and fault diagnosis. This helps the engineer see which safety input has changed state, which condition is preventing a restart and why a safety output has switched off.

For machines manufactured in quantity, the same approved configuration can be transferred to other 3SK2 units. This can reduce repeated programming work and help maintain the same safety logic across similar machines.

Independent Safety Outputs

One of the main reasons for selecting a Siemens 3SK2 safety relay is the ability to control more than one safety output independently.

In a conventional safety relay, operating one safety device will normally switch off all enabling outputs together. The 3SK2 can assign different safety inputs and logic conditions to different fail-safe outputs.

For example:

• An emergency stop can shut down the entire machine.
• Opening a loading-side safety door can stop only the loading section.
• A light curtain can stop the hazardous movement near the operator.
• A maintenance door can remove power from a separate drive or motor group.
• One output can stop immediately while another output follows a controlled time sequence.

The final arrangement must follow the machine risk assessment. Independent shutdown should not be used only to keep production running when the protected area is still exposed to a hazard.

Optional PROFINET Interface

An optional Siemens PROFINET interface module can connect the 3SK2 to a higher-level control system. It allows parameter assignment through SIRIUS Safety ES and transfers operating and diagnostic information over PROFINET.

This can help maintenance teams identify an operated emergency stop, open safety door, wiring fault or other safety condition from the machine HMI or control system.

The PROFINET connection is used for parameterisation and diagnostics. It should not be confused with a PROFIsafe safety controller connection; Siemens lists the 3SK2 PROFINET interface without PROFIsafe communication.

Expansion and Motor Starter Connection

The 3SK2 basic unit can be expanded when the machine requires additional safety-related switching outputs. Compatible Siemens 3SK1 output expansion relays can be connected through the SIRIUS device connector, reducing the amount of wiring required between modules.

Siemens 3RM1 fail-safe motor starters can also be connected through the device connector. This provides a compact arrangement for safely switching smaller motors without using a separate safety contactor arrangement for every motor.

Coupling relays may be required where the semiconductor safety output cannot directly switch the connected load. The output current, contactor coil and required switching arrangement should be checked before selecting the interface relay.

Features

• Handles several machine safety functions in one relay
• Allows independent shutdown of different machine sections
• Configured through Siemens SIRIUS Safety ES software
• Ready-made function blocks simplify safety logic creation
• Compact versions provide up to 10 fail-safe inputs in a 22.5 mm housing
• Larger versions provide up to 20 fail-safe inputs
• Semiconductor safety outputs suit frequent switching
• Automatic and monitored restart functions can be configured
• Supports emergency-stop and protective-door monitoring
• Suitable for safety light curtains, scanners and electronic safety sensors
• Supports muting arrangements for suitable material-handling applications
• Can monitor two-hand controls and enable switches
• LED and software diagnostics help locate faults
• An optional diagnostic display can be mounted on the control-cabinet door
• Optional PROFINET interface supports remote diagnostic information
• Compatible output expansion modules can add more switching circuits
• Compatible fail-safe motor starters can be connected through the device connector
• Screw and push-in terminal versions are available
• Suitable for safety applications up to SIL 3 and PL e
• Useful for new machine panels and older Siemens safety relay replacement projects

Siemens currently lists the 3SK2 basic units and PROFINET interface as active products.

Applications

Siemens SIRIUS 3SK2 Safety Relays are commonly used for:

• Emergency-stop circuits with several safety zones
• Multiple guard-door monitoring
• Safety light curtain monitoring
• Safety laser scanner circuits
• Robotic cell access protection
• Conveyor safety and zone control
• Packaging machine safety systems
• Palletising and material-handling equipment
• Press and forming machinery
• CNC and machine tool safety circuits
• Two-hand control stations
• Pressure-sensitive safety mats
• Enabling switches used during maintenance
• Muting applications on conveyor lines
• Automated assembly machines
• Food and beverage processing equipment
• Pharmaceutical and filling machinery
• Automotive production lines
• Warehouse automation systems
• Machines requiring independent safety shutdown outputs
• Replacement of selected discontinued Siemens 3TK28 safety relays

Siemens lists the 3SK2 series as the preferred successor family for certain discontinued 3TK28 safety relays. The replacement must still be checked against the original wiring, output contacts, delay function and required safety logic.

Siemens 3SK1 or 3SK2 Safety Relay?

A Siemens 3SK1 relay is normally sufficient for a straightforward emergency-stop, guard-door or light-curtain circuit where all safety outputs can switch together.

The Siemens 3SK2 is more suitable when:

• The machine has several safety devices.
• Different sections must stop independently.
• More safety inputs and outputs are required.
• Muting or more detailed safety logic is needed.
• The machine requires better diagnostic information.
• The configuration will be reused across several machines.
• Operating data must be made available through PROFINET.
• The circuit needs expansion for several contactors or motor starters.

Using a 3SK2 for a single basic emergency-stop circuit may add unnecessary software and commissioning work. For a larger machine with several safety zones, it can reduce the number of individual relays and simplify fault finding.

Selecting the Correct Siemens 3SK2 Safety Relay

The relay should not be selected only by the supply voltage or the number printed at the beginning of the article code.

The following details should be checked:

• Complete Siemens article number
• Number of emergency stops and safety switches
• Number of single-channel and dual-channel safety inputs
• Number of independent shutdown groups
• Number of fail-safe outputs required
• Immediate or delayed stopping requirement
• Type of connected safety sensor
• Light curtain or muting requirement
• Screw or push-in terminal preference
• Need for output expansion modules
• Need for fail-safe motor starters
• PROFINET diagnostic requirement
• Required SIL or Performance Level
• SIRIUS Safety ES software and licence availability

For replacement enquiries, send the existing relay part number, machine wiring diagram and details of the connected safety devices. A replacement should not be chosen only because it has the same number of terminals or the same 24 V DC supply.

Important Safety Note

The 3SK2 relay alone does not determine the safety level of the machine. The emergency-stop device, safety sensors, wiring, contactors, feedback circuit, stopping time, fault detection and software configuration all form part of the complete safety function.

Machine safety selection, programming and validation should be carried out by a qualified safety or automation engineer. The final circuit must meet the risk assessment and applicable machinery safety standards.

Siemens 3SK2 Safety Relay Supplier and Exporter

ARP IMPEX supplies Siemens SIRIUS 3SK2 Safety Relays for automation companies, industrial machine manufacturers, panel builders, system integrators and plant maintenance departments.

Our supply scope includes:

• Siemens 3SK2 10-input configurable safety relays
• Siemens 3SK2 20-input configurable safety relays
• Screw-terminal and push-in-terminal basic units
• Siemens 3SK2 PROFINET interface modules
• Diagnostic displays
• Starter kits with SIRIUS Safety ES
• Compatible 3SK1 output expansion modules
• Compatible coupling relays and fail-safe motor starters
• Siemens 3TK28 replacement requirements