Engineered safety

Getting risk assessments, mitigation strategies, functional safety specifications, and plant and machinery safety systems themselves right (and legal) is not trivial. But it is critical. Not only does it have a profound bearing on mandatory protection of employees and the public, but, done well, it can also impact on production line uptime and OEE (overall equipment effectiveness) – and hence profit. However, for the vast majority of organisations that have 'right-sized' their engineering departments, this presents a dilemma. Put simply, legislation is constantly adapting to advancing technology. So, without adequate resources, keeping on top of it and related guidance is a challenge. Much the same applies to the safety technology: understanding what's now possible, versus what's sensible and correct, is a specialist business. What are manufacturers supposed to do? For that matter, what about their machinery and packaged process equipment suppliers? And indeed the system integrators contracted to design and install the automation and associated safety systems for production lines and plants? As David Reade, business development consultant with Rockwell Automation and himself a certified functional safety expert through TÜV Rheinland (an accreditation only granted after 10 years in safety engineering), says, the difficulty is a lack of competence. That matters. "The HSE publication 'Out of Control' suggests that 44% of serious incidents in manufacturing are down to incorrect engineering specification," warns Reade. In fact, that HSE book goes on to assert that 20% of accidents have their root cause in changes after commissioning, while 15% are due to the design and implementation, 15% to operation and maintenance, and 6% installation and commissioning. In short, it concludes that 60% of all control system failures are built-in before operation commences. HSE makes no comment as to whether the situation is improving or worsening. However, Reade is concerned that it might be the latter. "So much can be done that we couldn't contemplate even 10 years ago – with, for example, the arrival of advanced PLCs having embedded safety functionality," he observes. "The problem is that the keys of the kingdom have been given to project engineers. But, if they're not fully competent in safety engineering, then potential errors can be overlooked. And remember, what's acceptable in one industry, isn't in another. Think of the differences between a steel plant and a pharmaceutical operation." It's no surprise, then, that manufacturers are increasingly turning to suppliers like Rockwell – which now boasts 137 TÜV certified functional safety engineers, covering machinery, safety instrumented systems, and hardware and software – or accredited system integrators (SIs). In Rockwell's case, safety engineering competence is also cascaded down to its SIs and end users, through the firm's RcSI training and audit programme. Indirect savings Safety system services aren't free, but, if you're looking for the return on investment, remember that it's worth taking into account not only the direct, but also indirect (legal, brand damage) savings arising out of preventing, or at least mitigating, accidents. If that's not enough – and in these straitened times, it might not be – how about exploring the potential for increased productivity and reduced costs from automated safety systems? The obvious question: is that realistic? According to Ian Murgatroyd, Rockwell Automation's product manager for safety components, the answer is a qualified 'yes'. He points first to the key functional safety standards: EN ISO 13849-1 (which superseded EN 954 for automated machinery); IEC 62061, for hybrid environments involving both discrete and process manufacturing; and IEC 61511, for continuous processes. EN ISO 13849-1 expresses safety robustness in terms of PLs (performance levels), while IEC 62061 and IEC 61511 focus on SILs (safety integrity levels) – although work is ongoing to bridge the divide. "Among other things, the functional safety standards require designers to assess the reliability of safety components by adding a quantitative calculation to the design," explains Murgatroyd. "While this means more steps and procedures, it also offers benefits. The standards result in a more methodical design approach – all the way from the initial risk assessment to implementing the safety systems – that can lead to more predictable performance, greater reliability and availability." For Rockwell, securing that potential extra ROI comes through "intelligent safety system design". That, says Murgatroyd, means going beyond the standards and building a safety system that not only increases machine safety, in line with legal requirements, but also "improves efficiency and productivity, while reducing waste". How? Murgatroyd talks about using modern systems that integrate the safety solution with the rest of the automation equipment, so cutting costs – except in process industry systems. There, the potentially much greater scale of human, environmental and production risk means that different approaches – such as harnessing dual-redundant or even triple-modular redundant systems, with voting at every level – necessarily pertain. But there's more. He cites Rockwell's safe-speed monitoring technology – as built into the company's Guardmaster safety relays, PowerFlex AC drives and Kinetix servo drives. This not only cuts system costs (two birds, one stone), but also improves machine flexibility and productivity by allowing operatives to perform tasks, such as maintenance, while a machine is in motion, yet operating safely. He also points to the value of enabling information flow throughout the automation and safety systems. "By using the intelligence associated with the automation system, a safety system is better able to diagnose machine operation and react accordingly," he explains. "The diagnostics, in turn, also reduce the time required for operators and technicians to bring a machine back to a safe operational state, so reducing downtime and improving productivity." And we could add that management also has visibility of key productivity data, alongside the reasons for safety events and the responses taken and their timeframes. Indeed, Murgatroyd suggests that manufacturers might want to think about implementing a proactive safety programme "as an integral part of their lean manufacturing strategies". That's a bit of a leap, but there is clear lean thinking in working to minimise downtime through good, integrated safety/automation and diagnostics... And also in harnessing the safety-related control system to improve OEE and reduce mean time to repair.