Unlocking Safer Automation: Safety PLCs and Safety over Ethernet
September, 2025
Author: Jon Ferrier
A Safety Programmable Logic Controller (SPLC), or safety PLC, is a specialized control system designed to provide enhanced safety functions in industrial applications. It provides enhanced safety by monitoring and controlling critical processes such as emergency shutdowns and interlocks.
Unlike standard PLCs, safety PLCs feature built-in hardware and software redundancies, along with self-checking mechanisms. These measures ensure that if a failure ever occurs, the system transitions into a safe and predictable state. This is done in compliance with stringent safety standards such as IEC 62061 and ISO 13849-1.
They are crucial for applications with a high risk of injury or equipment damage. Safety PLCs integrate standard and safety control, offering advantages like reduced wiring, scalability, better diagnostics, and simpler troubleshooting, especially for multi-zone applications.
Advantages of Safety PLCs
Cost Savings: Reduces wiring, installation, and labor costs, especially for complex, multi-e-stop zone machines.
Scalability & Flexibility: Easily scalable for different system sizes and flexible enough for various safety and control functions within a single unit.
Integrated Systems: Consolidates standard and safety control in one controller, eliminating the need for separate PLCs and associated networks.
Improved Diagnostics: Provides better troubleshooting capabilities, allowing for quick pinpointing of issues with connected safety devices, often displayed on an HMI.
Simplified Design: Features fewer physical components and simpler panel designs.
Enhanced Reliability: Incorporates self-checking mechanisms and diagnostic systems to ensure safe operation and predictable failure.
Safety over Ethernet
Safety over Ethernet further enhances these benefits by reducing installation costs and time. It also allows for extensive data communication over a single cable, and enables remote I/O and integrated diagnostics through unified software and networks.
Advantages of Safety over Ethernet
Reduced Wiring & Costs: Dramatically cuts down on physical wiring, requiring only a network cable and power supply, leading to significant hardware and installation cost reductions.
Increased Data & Functionality: Enables a large amount of safety-related data to be exchanged over a single cable, supporting functions like safe limited speed and direction.
Remote I/O: Simplifies the integration of remote safety I/O, allowing for complex machines with minimal wiring.
Unified Control: Allows for the programming, configuration, and management of both safety and standard control functions within a single software tool.
Improved Visibility: Provides comprehensive visibility into safety events and machine states across the entire system through integrated diagnostics and HMI integration.
Flexibility in Design: Supports flexible and scalable safety configurations, making it easier to implement complex machine safety.
