Think about safety at the outset to boost productivity and OEE
Too often when it comes to machine design, safety is addressed towards the end of the product. But by integrating safety into the design and development from the outset, machine builders can create machines that will offer improved performance and reduced downtime. In this article we talk to Rockwell Automation Solution Architect -Safety Paul Davies about how machine builders can turn machinery safety into a real competitive advantage.
With seemingly constantly updated and increasingly stringent legislation, advances in technology ,combined with the very real threat of prosecution by HSE, machinery safety is becoming a more and more complex issue with each passing year. And for many machine builders, it can start to feel as though the safety aspect - vitally important though it may be - is actually compromising machine performance. But it doesn't have to be that way. Regardless of the level of complexity of the machine, if you think about safety from the outset and make it an integral part of the design and development phases of the machine rather than something you build on at the end when the control strategy is already set in stone, then you can actually increase performance. Further, you can access design and validation tools and diagnostics that can help to reduce development and time to market, increase uptime, and so enable customers to raise their OEE figures.
Every machine design starts with a risk assessment, and from this the functional design specification is written. At this point you know the dangers and the safety requirements, this is the crucial stage to implement the safety functions. There are many good reasons to embrace safety right from the outset, and incorporate it as part of the wider control strategy.
Rockwell Automation Solution Architect -Safety Paul Davies explains: "Consider a simple example where some manual intervention is required on a machine, perhaps to load or unload products. If you only consider the safety aspect at the end of the machine design, then you might well end up with a solution that stops the machine completely before the operator can gain access. You have a safe machine, but cycle time is undoubtedly compromised, so you reduce productivity. Suppose instead, though, you had addressed the safety requirements at the outset. Is it necessary to stop the machine completely? Could we maintain the same high levels of safety by isolating particular aspects of the machine (zoning) or by running the machine more slowly at a safe controlled speed?"
Bringing those thought processes to the front end of the machine design, and taking advantage both of dedicated safety technologies and of safety functions such as 'safety torque-off' and 'safe speed control' built into standard automation components such as variable speed drives, can result is vastly superior machine designs, and can also help to reduce time to market. Safety can be integrated more effectively, with products built to meet global standards for reliability, safety and quality. Further, by addressing safety from the outset, the machine builder is in the best position to decide whether the best solution would come from discrete safety products at one end of the of the scale, a fully integrated system at the other, or something in between.
Increasing levels of integration
"All routes are valid as long as they precisely address the safety functionality required," comments Davies. "Smaller machines may well find a 'two box' solution more appropriate, with a safety controller working alongside a standard automation controller. But we are certainly seeing higher levels of integrated safety even on less complex machines, particularly where machine builders can reap benefits from integration at the software and network levels."
One other consideration for a machine builder is the integration of the machine into other machines or existing lines - these existing machines and lines may be connected plant wide or into the higher level enterprise where KPIs are required - how are these requirements met?
An issue for many machine builders is that, as safety standards become more stringent and legislation tighter, they may not be able to keep fully up to speed with the implications and requirements. In that case, third party certified consultants can help - for example the TUV approved safety team at Rockwell Automation. Further, Rockwell Automation offers software tools such as Safety Automation Builder (SAB) to streamline the safety system design, implementation and validation.
Davies explains: "SAB helps you improve compliance and reduce costs by guiding you through the development of your safety system, including safety system layout, production selection and safety analysis to help you meet machinery safety Performance Level (PL) requirements as outlined by global standard EN ISO 13849-1. It also allows the development of a list of parts for each of the safety functions and safety related control systems." For machine builders, using SAB could provide significant time savings through being able to do so much within a single software package. From SAB the machine builder can get the overall conceptual design of the machine, highlighting safety zones, and showing the guards that separate the operator from the hazards on the machine. The hazards themselves can be placed into the zones via icons, and then SAB can show the access points where operators access the machine.
The development of the functional safety system can then be verified through Sistema (an independent software utility that provides developers and testers of safety-related machine controls with comprehensive support in the evaluation of safety in the context of EN ISO 13849-1), and a bill of materials can even be generated through a separate package called Proposal Works. The final function through SAB is then a list of the separate safety functions that have been developed for the safety-related part of the control system.
With these tools, and by looking at safety from the outset, machine builders can boost safety and productivity, but actually reduce the complexity of the machinery safety circuits. They can also save time, cost and efforts in implementing integrated safety systems, allowing you in effect to design out risk as you go along while addressing the design aspects that impact on productivity, uptime and flexibility.
Davies concludes: "By addressing safety early in the design process, and by taking a holistic approach to safety, machine builders can develop and implement innovative safety solutions that improve the functional safety of the machine while simultaneously helping to increase safety, efficiency and productivity, and reduce waste."
Find our more about Rockwell Automation's safety solutions by visiting www.scalabletechnology.eu or www.machinesafetysolutions.com
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