When using modular safety systems it is essential to ensure that key features are considered in order to maximise the benefits, says Kevan Cowley of Wieland Electric
There has been growing recognition in the last few years of the benefits of modular, configurable safety controls. Not least of these is the ability of a modular safety system to reduce the complexity of the wiring, compared to using stand-alone safety relays which need to interact with each other and can require very complex wiring, which often extends design time, installation and commissioning.
Modular, configurable safety control systems use centralised input/output (I/O) systems that reduce the hard wiring requirement and therefore the overall complexity. However, the complexity of the wiring can vary considerably between different types of modular safety systems.
Which modular system?
There are two types of modular solution currently available – mechanically configurable systems and software-based safety circuits. Mechanically configurable options tend to have more complex wiring, so a software system that uses a centralised I/O will be the preferred option in the majority of situations.
However, there is also variation in the level of complexity between different types of software-based systems, particularly in terms of the complexity of the wiring requirements for monitoring and diagnosing of faults.
With some systems there is also a limitation imposed by having a fixed number of I/O or function blocks within the software, so it may then be necessary to pay more for a system where expandable I/O can be beneficial. This can be a particular problem for smaller systems as it may be necessary to bear the cost of many more I/Os than are required upfront, often making the use of a modular system financially beneficial.
In contrast, some solutions offer the controller separately from the I/O module, which makes it very easy to match the I/O requirement precisely to the requirements of the system.
Another issue can be the need for communication with a wider network and, if stand-alone relays are being used, feedback will require additional contacts. When using the software version, you can consider whether it can offer a common protocol.
There are also significant benefits helping to comply with EN-13849-2 where full reports and documentation are required and automatically date and time stamped, making it easier to identify the root cause of the fault and ensuring simple comprehensive compliance documentation.
When using a software-based system it is essential to include a self-validating verification process, according to EN-13849-2, as this will prevent mistakes being made and ensure compliance with appropriate regulations and negating the need to produce written reports, diagrams and photographs necessary for system verification.
Taking time to research the various solutions available at the beginning of the project will pay dividends in the longer term and ensure all potential financial and performance benefits are achieved.