When Michael Miller, business development manager for safety business at Rockwell Automation, explains what functional safety is, he drills the idea into his audience. “An excellent example of how functional safety has developed in industry is a regular drill,” he explains.
Thirty years ago a drill was made out of metal.
“Well, metal’s not a real good thing to have in your hands when the other end of it is 115 volts,” he laughs. “You’ve got quite a shock hazard there.”
So what was done?
Manufacturers added a third prong, which was supposed to be grounded, so if there were ever a short, the user wouldn’t get electrocuted. The problem was, 30 years ago, the overwhelming percentage of receptacles was two pronged. So users cut the third prong off. “That’s an example of how safety was added, but because of circumstances, a good idea went bad,” says Miller. “So let’s just go back a decade.”
Ten years ago, virtually all the drills were made out of Lexan®, a polycarbonate resin thermoplastic, so the potential for electrical shock was greatly reduced. “They designed safety into the device, so it would greatly reduce the possibility of electrocution,” says Miller. “It’s still possible, but highly unlikely.”
“Now look at today’s drills,” Miller continues. “They’re still made out of plastic, but now they’re DC: it’s impossible to get a life-threatening shock from the device. That’s the definition of functional safety: safety that is designed inherently into the device (italics added). It’s designed in, not added on.”
Functional Safety and Sustainability
According to Miller, two questions are asked about machines today: How can we make them sustainable? How can we make them safer?
“They’re not really two different things,” says Miller. “If I design safety into the machine—or give the operator freedom to access the machine, but access it only in a safe way, preventing unexpected start-ups, unexpected movement of any kind—I’m functionally designing safety into that machine. This allows all the features of sustainability, including longer product life, regulatory compliance, and improved productivity. It also addresses all the issues related to safety, such as reducing accidents and injuries, driving down health benefit costs, and mitigating general operational risk.”
So safety, when designed in, actually improves machine operation while keeping operators free from unwarranted hazards. Miller emphasizes that this is throughout the whole system, and the whole life lifecycle of the system. “When a machine is conceived, safety is designed into the idea,” he says. “There’s only one way to design it, and that’s the safe way. Safety isn’t an afterthought. Safety isn’t an add-on. It’s integral to the way the machine works, the way it is set up, the way it is maintained. That’s the only way to do it.”
Typically there is some type of requirement—a legal or industrial standard—that drives the requirements around the development and functionality of a machine. As part of the design process, hazards that may be present will be analyzed. “Obviously, the first thing to do is to try to design them out,” says Miller.
If this can’t be done, ways must be found to detect them or mitigate them to an acceptable level of risk. The risk assessment drives the functionality of a safety circuit design, not only from a control perspective, but also for the way machines are operated, manuals are written, and signage designed and posted. Everything is done to mitigate hazards and to maintain that mitigation throughout the lifecycle of the equipment.
From this point, requirements are taken—typically called a safety requirement specification—and used to design the circuit, assess and secure the proper components, and document the process, from design, through installation and acceptance, to future repairs or changes. “If a change is made, we can go back, reevaluate the risks and hazards involved, and mitigate them, always adhering to the core requirements that remain in place,” explains Miller. “So it continues the lifecycle of a machine or system.”
During this process, notes Miller, users and OEMs alike keep a close eye on costs.
“One thing under scrutiny is how to incorporate safety without unduly affecting the overall costs of an installation,” he says. “Is this cost-effective? How will the safety function impact overall productivity? These are the types of questions customers want to have clear and positive answers to.”
A Sweet Solution
Located in the south of Denmark, Gram Equipment A/S is one of the world’s leading manufacturers of equipment for industrial ice cream production. Gram delivers tailor-made, complete production lines to ice cream producers and other food processing firms looking for integrated solutions. These specially designed solutions include everything from individual assembly lines to complete production plants, mixing equipment, and packaging lines. Gram’s customers are looking for increasingly advanced solutions, as their production processes include complex systems and many specialized functions. Every element in these systems must work reliably and with minimum downtime.
Before implementing the Rockwell Automation safety solution two years earlier, Gram often experienced problems with traditional safety systems, typically composed of a PLC, a separate safety PLC, and a servo system. Staff had to learn how to use three software programs, and how to connect the systems so they could communicate with each other. If the plant had to be modified, it would require time-consuming changes to electrical documentation as well as programming changes; where only a few specially trained staff could execute this work. The customer also often had to do more testing, which resulted in lengthy test periods.
“Close cooperation between Gram and Rockwell Automation changed all that,” says Miller. Specifically, changes related to safety zone control are now commonly carried out in agreement with the end user during commissioning.
Gram simplified system complexity and usability by basing its control topology on an Allen-Bradley GuardLogix platform that combines standard and safety control in a single platform. “This saves Gram cabling and components, as well as the time used to make the systems to communicate with each other,” says Bjarke S. Petersen, an engineer at Rockwell Automation. “Combining the three functions allows more staff to modify the plant according to customer requirements faster and more easily. Staff just needs to learn one software program, and electrical documentation has been simplified significantly.”
The results of incorporating this functional safety system were significant:
- A completely scalable and fully flexible system
- Reduced cabling and components
- Individual parts communication via EtherNet/IP, a great advantage when working with international customers
- The ability to troubleshoot and make repairs from Denmark regardless of the customer’s location, saving both Gram and its customers time and travel costs
- Simplified electrical documentation
- Confirmation to relevant safety standards with third-party approvals
“Gram found out what others are finding out: functional safety improvements can make operations safer while improving productivity and reducing or driving out unwarranted costs,” says Miller.
A Philosophical Shift
Miller believes a major philosophical shift in how manufacturers perceive safety is taking place. He says, “In the past, like with the drill, safety was added on after the fact. Machines never operated as well as they could, often because costs weren’t seen as justified. It was like, ‘I have a machine here and now I have to pay out all this money.’ The barrier was psychological as well as philosophical.”
“With the advent of functional safety, we’re seeing a shift in mindsets from the cost of safety to the value of safety,” he continues. “There’s always a cost, but it’s a justifiable cost; for many OEMs, it’s a differentiator, because now they can show productivity and reliability improvements over the lifecycle of the machine. It’s not additional safety costs, but rather a reduction in operational costs, something their end users are very interested in hearing about. That is something that will sustain functional safety as we move forward.”
Rockwell Automation Inc.