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attributes.Features

attributes.Supply_Voltage

attributes.Number_of_Channels

attributes.Safety_Contacts

attributes.Function

attributes.Auxiliary_Contacts

attributes.Reset_Method

attributes.Range

attributes.Safety_Category_ISO_13849002d1

attributes.PL_ISO_13849002d1

attributes.SIL_IEC_61508

attributes.TerminalType

attributes.Standards_Met

attributes.BetterWorldProduct

attributes.Better_World_Verification

attributes.Depth

attributes.Hazardous_Area_Certification

attributes.Safety_Category

attributes.Series

attributes.Width

Siemens 2 Auxiliary Contacts Module 110 → 240V ac, 3-Channel

Siemens ECOFAST Safety Relay 690V

Siemens SIRIUS 3SK1 Safety Relay 24V dc, Single Channel


A safety relay is an automation device that monitors for potential errors or faults in machinery or plants and works to prevent injury and reduce risk. If an error occurs, the safety relay initiates the appropriate response to reduce the risk and bring the environment back to a safe, acceptable level. Monitoring processes using safety relays protects both the machinery and the employees, prevents potentially expensive maintenance and equipment replacement, and reduces risk of human injury. Example functions include initiating a controlled pause in machinery or equipment to safely stop movement until an obstacle is removed. They can also be used as an emergency stop mechanism, switching off the power to particular machinery or plants until it is safe to resume power and continue.

## **Where are safety relays used?**

Safety relays are found across many industries where automation is used within a process or for a whole process. Anyone can integrate a safety relay within a circuit to create a safety circuit without any specific training.

Here are some key uses of safety relays:

- They detect faults in [wire contacts](https://sg.rs-online.com/web/c/connectors/pcb-connectors-wire-housings/crimp-contacts/) within a security circuit during earth faults, enhancing system reliability.
- Commonly found in automatic control circuits, safety relays help manage and maintain system safety.
- Safety relays are used primarily to prevent failures in hazardous switching operations.
- They are installed on machinery and equipment to improve the safety rating and ensure secure operation.
- These relays continuously monitor safety input devices like safety gates and e-stop circuits, halting operations if dangerous conditions are detected.
- Safety relays are used in various safety applications including light curtains, safety mats, [two-hand controls](https://sg.rs-online.com/web/c/relays-signal-conditioning/relays/safety-relays/?applied-dimensions=4293780390), interlocked gates, and foot-operated switches.
- They are employed in everyday scenarios to prevent electric shocks and equipment overheating.

## **What types of safety relays are there?**

Here are some common types of safety relays:

- **Single Function Relays:** Single function or channel safety relays monitor for a specific type of activity and are programmed individually to monitor their respective tasks.
- **Multi-Function Relays:** Multi-function safety relays can monitor different functions and can be used in place of several single function individual units to monitor the same number of activities. The benefits of using multi-function relays include simpler installation and less wiring as fewer individual units are needed. This also makes more economical use of panel space, additionally giving greater flexibility to make changes within the design or panel as fewer units need to be removed or repositioned.
- **Configurable Safety Relays:** Configurable safety relays offer flexibility with configurable options that allow users to tailor the safety functions according to specific needs, making them suitable for complex machinery.
- **Dual Channel Safety Relays:** Dual channel safety relays use two circuits for monitoring and control, providing an added layer of safety by requiring both channels to agree before action is taken.
- **Time Delay Safety Relays:** These safety relays include a time delay feature that can be set to delay the activation or deactivation of safety functions, useful in processes where timing is crucial.

## **What are the unique features of safety relays?**

Safety relays incorporate several unique features that enhance their reliability and effectiveness in critical safety applications. Here are some key features:

- The core feature of safety relays is the monitoring chain, which checks for electrical continuity and ensures the integrity of the safety circuit throughout its operation.
- Safety relays typically include two output voltage terminals and two input terminals for the coils. This redundancy ensures that even if one channel fails, the other can maintain the safety function.
- Outputs of safety relays are often used in a daisy-chain configuration, connecting through all safety devices like emergency stop buttons and palm buttons. This setup ensures comprehensive monitoring and control over the safety devices connected in the circuit.
- Safety relay continuously checks for continuity between the output and input terminals. A break in continuity, such as from an activated emergency stop, causes the safety contacts to open, stopping machine motion to prevent accidents.
- The design of the safety relay includes fail-safe mechanisms where the safety contacts will open if continuity is lost, ensuring the machine stops to maintain operator and system safety.
- The inclusion of two outputs and two inputs allows for a level of redundancy. This setup minimises the risk of failure, as the likelihood of both channels failing simultaneously is extremely low.

## **What are the advantages of safety relays?**

Safety relays offer several benefits that make them a preferred choice in various industrial safety applications. Here are some major advantages that safety relays offer:

- Safety relays are more consistent in performance compared to standard relay types, ensuring reliable operation in safety-critical systems.
- They are less expensive than other types of relays, making them an economical option for [enhancing safety in machinery](https://sg.rs-online.com/web/content/discovery/ideas-and-advice/machine-safety-guide) and systems.
- Safety relays are straightforward to use and install, requiring no complex programming, which simplifies integration into existing systems.
- The lack of requirement for software programming for operation simplifies their use and reduces the potential for software-related errors.
- The safety relays provide a higher level of security by safely [switching power supply](https://sg.rs-online.com/web/c/power-supplies-transformers/power-supplies/switching-power-supplies/) or de-powering components, thereby protecting both machinery and operators.
- They help avoid costly maintenance or replacement of equipment by protecting against accidents and malfunctions.
- Safety relays offer flexibility in control, allowing for both automatic and manual activation of safety measures.

## **What are the delivery options for safety relays?**

For safety relays ordered online, we offer complimentary next working day delivery, from 8 am to 6 pm, within Singapore for purchases made Monday to Friday before 3:30 pm. Note that additional lead time may be required for deliveries to specific regional areas. For further details or support, check out our [delivery information](https://sg.rs-online.com/web/content/support/all-articles/delivery) page or call our customer service at +65 6865 3400.



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