Guide to Safety Relays: Function and Application

October 16, 2023

A safety relay is one of the most essential components in an electrical panel. A Safety relay is an electromechanical device whose electrical current activates mechanical contacts. It serves as a contact between two circuits and separates them. This guide will cover the most critical aspects of safety monitoring relays.

What Is a Safety Relay?

safety relay, crucial in electrical panels, acts as a bridge between two circuits, activated by electrical current to engage mechanical contacts. It meticulously monitors safety systems, enabling machine operations or halting them when needed. Ideally suited for failsafe environments due to its complex operation compared to standard relays, it adheres to Safety Integrity Levels (SIL) standards. Single-function safety relays are budget-friendly choices for smaller machines needing a dedicated logic device for safety. With a self-monitoring feature, it autonomously checks its opening and closing in every on-off cycle, ensuring continuous safety functionality even with internal component failures.

How Does Safety Relay Work?

When a fault or unsafe condition is detected, the safety relay activates the necessary outputs to bring the machine to a safe state. It’s designed to be fail-safe, which means even if a component within the relay fails, the safety function is still carried out. Let’s dive into how it works.

  • Monitoring: Continuously monitors the connections and inputs from safety devices.
  • Detection: Identifies any unsafe conditions or faults within the system.
  • Activation: Activates the necessary outputs to bring the machine to a safe state.
  • Autonomous Disconnection: Can disconnect input and output circuit contacts autonomously if issues like fusing or obstruction occur.
  • Cycle Check: Automatically checks the precise opening and closing of its contacts during each on-off cycle.
  • Fail-Safe Design: Ensures safety functionality continues even if internal failures arise.

A safety relay is typically used for field devices that require intensive safety monitoring, such as:

• Light curtains

• Safety Mats

• Enabling Switch Devices

• Magnetic Switches

• Emergency Stop Devices & Buttons

• Non-Contact Safety Sensors

• Safety Interlock Switches

Omron G9SA Safety Relays

Omron G9SA Safety Relays

The Omron G9SA Safety Relays Unit is a great choice for machine builders looking for a simple and reliable safety solution. It works well with common safety devices like safety light curtains and two-hand controls. Its expandable options, easy wiring, and sturdy design make it flexible and reliable for different uses.

The main unit is 45mm wide, and expansion units are 17.5mm wide, making them compact and easy to fit. There’s also a safe OFF-delay timer feature, which helps in shutting off the machine safely. The simple expansion connection makes it easy to add more units as needed.

The G9SA unit has a certification up to PLe according to EN ISO 13849-1 for certain applications, which means it meets high safety standards. With the Omron G9SA Safety Relay Unit, enhancing the safety of machine operations becomes a simpler task.

Omron SR1 Safety Monitoring Relays

The Omron SR1 Safety Monitoring Relay is a compact yet expandable safety solution perfect for standalone applications. It’s designed to cater to basic safety needs while offering flexibility, ease of installation, and quick troubleshooting.

Key Features:

  1. Fixed Terminals: Makes installation a breeze.
  2. Dedicated Safety Functions: Tailored for standalone safety applications.
  3. Expandable: Grow your safety system with your needs.
  4. Easy Troubleshooting: Diagnostic indicators are easily accessible, making identifying issues straightforward.
  5. Compatibility: Accepts power from either 24 VAC/DC or 115 VAC, and has a variety of input and output options to suit different requirements.
  6. Certified Safe: Conforms to multiple safety standards including EN, UL, C-UL, and TÜV Rheinland approved certifications.
  7. External Device Monitoring (EDM): Ensures external devices are working as intended.

The SR1 relay comes with several models catering to different safety monitoring needs:

  • Dual-Channel Safety Monitoring: Monitors two magnetically encoded non-contact switches, with varied input and output options for different applications.
  • Stop Motion Sensing Unit: Detects stop conditions of motors, compatible with various motor control devices.
  • Two-Hand Control Safety Monitoring Relay: Ensures two-hand control switches are operated within a safe timeframe.

The Omron SR1 Safety Monitoring Relay not only simplifies the installation and troubleshooting of your machine safety projects but also ensures robust protection, making it a reliable choice for your standalone safety applications.

Omron G7SA Safety Relays

Omron G7SA Safety Relays (forcible guided relays) are a prime choice for both socket or PCB-mounting, providing a versatile solution to meet your safety requirements.

The compact and slim design of the G7SA series ensures it fits seamlessly into your setup, while the reinforced insulation guarantees a robust performance, minimizing the risks of electrical interference. You have the flexibility to choose between a four or six-pole configuration, based on your needs, and the relay can be soldered directly to a PCB or paired with push-in terminal sockets. The latter option is a time-saver during installation, thanks to Omron’s Push-in Plus Technology which simplifies wiring.

With a rating of 6A at 240VAC and 6A at 24VDC for resistive loads, the G7SA Safety Relay is capable of handling a decent load, making it a reliable component in your safety control system. The forcibly guided contacts conform to EN 50205 standard, ensuring a high level of safety and reliability in monitoring contact state.

Wrapping Up

If you’re looking to upgrade your safety relay system or need more insights on the right relay unit for your application, Proax is here to help.


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