Electricity and Control April 2023

SAFETY OF PLANT, EQUIPMENT + PEOPLE

The advantages of networking safety When designing a safety solution for a machine or application, a fundamental consideration is whether to implement it as a standalone or network safety solution. According to Omron Automation, network safety offers a number of advantages compared to standalone safety.

S tandalone safety involves wiring safety devices point-to-point to a safety relay or controller, which in turn is wired to a contactor or a device that dis connects primary power to a machine. Network safety, by contrast, collects the safety devices and connects them to a network safety system via a fieldbus using a communica tions gateway, a safety CPU (central processing unit), and safety I/O. Network safety offers a number of advantages. Firstly, it is a highly effective way to mitigate risk. In addition to this, due to its ability to improve automation efficiency and boost throughput, network safety can become a key factor for a high-performing, future-ready manufacturing facility. Industrial networking protocols As there are different manufacturers, there are also sever al unique, independent solutions to solve communications networking issues. These particular industrial problems brought networking into focus. Specifically, manufacturers needed their operations to be: - Capable of responding in real time - Deterministic - Reliable/redundant - Secure - Safe, and - Ruggedised. The process of converging protocols motivated the drive to bring together best practices and standardise communications. The cornerstone of interoperability is a

standard communications protocol. EtherCAT (ECAT) is an example of a higher-level networking protocol that uses a multiple-layer model to interact with various fieldbus protocols. Choosing the right configuration While there are various configurations that can address net work safety, choosing the appropriate one is essential to optimising automation efficiency and reducing safety risks. A safety risk assessment is the primary way to establish the specific safety needs and the most appropriate con figuration. Automation architecture is required to provide control, configuration capabilities, and data collection. The two leading network safety architectures are Fail Safe over EtherCAT (FSoE) and Common Interface Protocol Safety (CIP Safety). EtherCAT technology allows for interoperabil ity between participating vendor devices. It is faster, has a wider bandwidth, and supports processing on the move. CIP Safety provides failsafe communication between nodes and enables interoperability between various automation and safety vendors. For effective functional safety communications, eight types of potential network errors must be mitigated. These are: - Corruption of the signal

- Unintended repetition of the message - Incorrect sequence of the message - Loss of the message - Unacceptable delay of the message - Insertion of another unintended message - Masquerade of the message - Not addressing the message as intended.

Functional elements of a networked safety system A networked safety system consists of several key func tional elements. The following examples illustrate some possible choices. The appropriate solution depends on the preferred configuration and/or respective application. ƒ EIP Network Slave Terminal (NX-EIC202 & NX- SL3300) In this solution the EIC202 is the communications coupler, and the NX-SL3300 is the safety CPU. This is for status in formation only, fed back over EIP (EtherNet Industrial Pro tocol) to a control system. It does not take any control in formation but only sends it to the safety system to control or influence it. The purpose of this is to be able to inform

Networked safety is an effective way to mitigate risk – as well as providing for improved automation efficiency and greater throughput.

22 Electricity + Control APRIL 2023