FEATURE Machine Safety
Trends in safety engineering
David Dearden, UK&I Country Manager of leading safety specialist Euchner, examines the trends that are influencing the latest developments in machinery safety
D
oor open – door closed! In complex equipment installations, providing functional safety information
about the door position and guard locking is often no longer suffi cient. Comprehensive safety signals and diagnostics data supplied via local and plant-wide fi eldbus systems reduce wiring, help with troubleshooting and give a real- time insight into the status of the safety systems. Issues such as door misalignment due to wear and tear can be highlighted well in advance of any line-stopping fault. Local networks such as IO-Link allow the simplifi ed collection of information including alarms, equipment operating life and potential safety-system manipulation. Where plant uptime is critical, built-in web servers allow quick and easy safety-system status checks and diagnostic interrogation without specialist hardware, software or programming skills.
Managing access rights Not only do people need to be protected from the harm that machines can cause, it is often a requirement that the safety- related control system also prevents a costly manufacturing process being interrupted by unauthorised or accidental interventions. Equally, quality and product safety measures require total traceability. Passwords are commonplace throughout modern manufacturing facilities. Strong passwords are an eff ective security tool as long as they are not revealed, shared or hacked. However, it’s quite common in manufacturing sectors to see passwords or codes for a production line written on a control panel for all to see. This tends to become worse as the plant gets older, whereby the only password that matters, and the one subsequently shared, is the one that grants access to everything. Clearly, passwords no longer provide adequate control.
One solution is an Electronic Key System (EKS) that manages the access rights centrally and is associated with an individual for total traceability. Diff erent keys can be assigned to diff erent operators, a particular access level or even a particular product. Process parameters can also be assigned to a particular key to
16 December/January 2021 | Automation
Euchner safety solutions
ensure continued product quality. Where multiple languages are spoken, the key can be used to select the specifi c language for the operator, again reducing the likelihood of errors occurring in the process.
Electronic prevention When safety systems are bypassed, there is generally a strong desire for doing so. Often, certain tasks can be carried out only when a safety door is open, but this can be dangerous. If defeating the safety control system has a perceived benefi t, e.g. saving time, then the desire to defeat it is likely to be high. As part of the design process, consideration needs to be given to the way the operator is likely to use the equipment and reduce the likelihood of manipulation through good design.
The common ‘fork-type’ actuators found on safety systems within many factories may need to be reconsidered if there is a likelihood of manipulation or overriding. Often an unoffi cial ‘spare’ key is used by a maintenance person or an operator to bypass the safety interlock to carry out a particular task, potentially exposing personnel to signifi cant hazards. Using modern safety-related control technology, almost all types of tampering can be prevented. Electronically-coded actuators that are “married” to the accompanying safety switch can make tampering more diffi cult; here, the spare key would not work. The Euchner CTM switch goes one step further – it sends a unique ‘paired’ actuator code to the machine’s control system or PLC, so even if someone tries to
reprogram a new actuator to the switch, the control system will prevent the equipment from operating.
Flexible solutions As machinery gets more bespoke, the requirement for fl exible user-centric safety solutions becomes greater. HMIs are replacing large desks of pushbuttons, resulting in the remaining on-machine controls becoming more safety-orientated. Customers now want these control elements integrated with the door hardware – for example, the emergency stop being integrated into the door locking mechanism, and the request to enter and acknowledgment buttons fi tted directly to the safety door.
Integrating these elements into the safety devices saves on wiring, special enclosures, fi xtures, and so on, and ensures the control devices are in the most accessible place for the operator. Fortunately, the high level of electronic integration that is now possible has enabled printed circuit boards to be reduced in size. Innovative technologies allow products to be made smaller. The smallest RFID confi gurator from Euchner is the same size as a 6mm plastic wall-plug and is almost invisible once it has been installed in a door, reducing the likelihood of manipulation.
CONTACT:
Euchner
www.euchner.co.uk
automationmagazine.co.uk
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