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Some tools are optional. Some tools are not. Governments require machine safety? Ho hum. Machine safety is a good investment? Whatever. Customer wants machine safety? Right away, sir!
Not only are machine safety standards and rules becoming more harmonized and widely accepted, and not only are many builders realizing that machine safety pays instead of costs, but more end users are demanding it, too. Machine safety is becoming a big-time, must-have service that's essential for builders to deliver.However, despite its newfound fame, machine safety is challenged by a combination of new equipment capabilities, different regional needs, and shifting regulatory requirements — all of which need new safety solutions. For instance, Messer Cutting Systems in Menomonee Falls, Wis., juggles all of these factors as it keeps its plasma, oxyfuel and laser cutting machines operating safely and efficiently for its users.
"We've always taken machine safety seriously, which is driven in the U.S. by OSHA's non-prescriptive rules and the ANSI and UL standards. No one says, 'We're policing you,' but we don't want incidents to happen; we don't want to get sued; and we want our users, staff and everyone else to go home safe," says Justin Ponzi, Messer's senior electrical engineer. "Because in the U.S. it's the end user's responsibility to keep their staff safe, they often ask us for help, and we provide recommendations. Originally, this meant bump cords, lifelines, static-tensioned cables, which were followed by normally opened/held-closed safety circuits that were then tied to safety relays with interlocking logic. Next, light curtains were added to allow more access, but then some customers might ask for light barriers around whole machine perimeters."
New Rules Need New Tools
However, Messer's latest machine safety efforts really began when it sold and installed its large Titan cutting machine at a railway equipment manufacturer in Canada about five years ago. The end user and the Electrical Safety Authority (ESA), which is Ontario's version of the Canadian Standards Assn. (CSA) required a pre-start health and safety review (PSR), including an inspection and follow-up to ensure compliance and to specify any added safety equipment.
"We had to build some extra safety stuff into Titan, and it needed a pretty complex solution," Ponzi explains. "The ESA's consultants can say what areas are exposed in their PSR report and give some general ideas, but they can't say exactly what needs to be done because of liability issues. So we tried four or five different design iterations, and the winner involved putting three light curtains around the cutting table — two on the perimeter and one across the middle. This allows one side of the machine to run autonomously, while parts are being loaded or unloaded from the other. Then the inspector comes back, checks the design, and signs off if it's acceptable."
The hurdles in Canada and countries with similar regulations are costly, and can increase shipping time from a normal 8–10 weeks to as much as six months, Ponzi reports. However, customers in regions with less stringent rules for builders, such as the U.S., also are asking for more sophisticated safety solutions.
Besides complying with safety regulations, Messer also is integrating safety equipment as its machines add new operations and cutting technology. "We added material handling, such as intelligent conveying and storage, to our cutting machines," Ponzi says. "Users needed material handling to increase throughput, but we recognized we needed more safety for those functions, and that we had to be more proactive than our customers to add it in. It's not easy to move 20,000 pounds of steel and stop on a dime."
The builder's two material handling devices include its Messer Loading Storage Shuttle (MLSS) that employs a 50x50 ft pad, and its smaller Messer Shuttle Table (MST). Messer already was using safety PLCs for the distributed I/O on its cutting machines, Ponzi notes. However, its evaluation and design for MLSS spurred it to add three laser scanners that sweep in 270° arcs to identify material moving through the system, a light curtain on MLSS's exposed side, a sound abatement enclosure that limits access via interlocks, a hard guard fence, and four video cameras that allow operators to see all aspects of the machine.
"Without a safety PLC, we wouldn't be able to control individual zones on our machines. This is crucial, so one zone can be active, while another zone is safely locked out," Ponzi says. "However, we built the Titan cutter for the railroad manufacturer with relays, but we had to go through so much red tape and it took so long that we didn't have time to build software for it. So we began looking to use micro safety controllers, and adopted Beckhoff's TwinSafe."
Tony Rigoni, Beckhoff's safety expert and sales manager for northern California, adds, "Users are waking up to the value of machine safety and that spending $1 on safety can return $3–12 in productivity. And building safety controls into machine designs to enable safety zones and speeds is even more valuable than trying to protect against hazards after a device is built."
Fieldbuses Pave Way for Safety
So, what's been enabling machine safety to evolve rapidly and serve so many operating advances lately? Well, the same networking revolution that turbocharged all of automation and control in recent years is now dragging machine safety up the same learning curve.
For example, Stolle Machinery in Centennial, Colo., recently simplified the former point-to-point wiring on its machines that form, inspect and decorate cans by replacing it with fieldbus-type networking such as EtherNet/IP and DeviceNet to reach its I/O points and other devices. This saved on materials and interconnection time, but it also provided the networking concept and pathway for later adding safety-related communications.