Machine safety must be more than an afterthought.
In the old days, machines were built, and guards and other safety features were added later, which wasn't very efficient. More recently, many builders make safety an integral part of their design process, and new safe-speed and zone-control technologies and harmonizing international standards are helping them. And, not only does this proactive, preventive approach reduce the frequency and severity of potential accidents and injuries, it pays added dividends of increasing machine efficiency and reducing downtime.
SEE ALSO: Mainstream Machine Safety
"Validation of safety systems is a process that needs to be planned," says Steve Zuberbier, engineering technical leader for family care R&E at Kimberly-Clark, which makes Huggies, Kleenex, Scott, Kotex and other products. "If you don't plan, you will fail. Will validation cost your company more effort? Yep. Will it cost you more time, resources and money? Yep. But, we've seen our safety validation effort pay for itself over and over again."
Zuberbier adds that safety problems occur because of people. "My safety controller will perform consistently," he says. "My humans will not. Using an engineered, controlled system provides a more reliable safety solution and keeps our people safe. The effort it takes to validate a safety PLC is much greater than it was with the old hardware relays because we didn't have to worry about programming the I/O points. However, we haven't bought a single machine since 2007 that doesn't have a safety PLC system. And, we've taken validation from 48 to 72 hours down to six to 12 hours now."
Savings Go With Safety
Similarly, Automatic Handling International (AHI) in Erie, Mich., makes roll-handling and packaging machines for tissue, non-woven materials, converting and other applications, and it recently began designing and integrating more safety capabilities into its equipment to eliminate hazards, but also to drive costs out of its engineering and manufacturing processes by getting them to work together in a more integrated fashion.
"We were still doing hardwired safety in 2007, but these are big systems, and so the question was how to protect everything because you might not know where everything is," says Dan Pienta, AHI's president. "What are the zones going to be? Who's going to enter those zones? What do we want to keep safe? We learned how to do a good process to work with a hardwired safety system, but it was a challenge because every system was different — everything was custom."
Pienta reports AHI moved to DeviceNet when Rockwell Automation launched its GuardLogix controls, which combined PLC and safety communications in one device and used the same network, but maintained two separate microprocessors. Later, AHI adopted EtherNet/IP when that protocol offered integrated safety, and standardized on GuardLogix and Safety Point I/O.
"It can be a tough transition to implement a new technology," Pienta explains. "I might not be sure how to implement in a way that I might need for the future, so you have to kind of feel your way through it. It's not that safety is so complex, but we do 100 projects per year. Safety is a small part of our business, but it impacts every part of it. So, when safety on Ethernet came out, it made a lot of sense because it allows us to use standard hardware and stay flexible, but also give our customers the most reliable systems. Safety has to be part of what you sell because it can help customers be more productive, reduce risk and add value."