Wednesday, July 16, 2008

Safety in Automation (Part 2 of 3) Networking Safety

Networking Safety
Flexibility is a key benefit of implementing Safety at Work technology

With safety in the spotlight, advocates for networked safety have hardwired safety system technologies clearly in the crosshairs. They argue that safety relays, auxiliary contacts and redundant cable runs are all part of systems that deliver poor diagnostics, high setup complexity and create time-consuming installations.

But according to Helge Hornis, Ph.D., manager of Intelligent Systems for Pepperl+Fuchs, the key to acceptance of the technology is helping engineers understand how networking safety provides flexibility in terms of expanding the safety system, implementing multiple safety zones and improving diagnostics.

“The basics of flexibility mean that when you need to have another device (safe or non-safe) in your system, you simply run a spur from anywhere on the network in that new direction and put the new device on the network,” says Hornis. He says the networks provide diagnostics that are not only better than what was before, but also completely impossible.

“How do you detect a contact that is intermittent? In the past, you simply didn't. The flexibility the system gives the engineer, in terms of uptime and what they can do with the machine, goes way up,” he says.

Pepperl+Fuchs has developed safe systems using the AS-Interface Safety at Work networking technology for about five years. Hornis says the possibility of expanding the safety system in minutes is just one of the many advantages the technology brings to the plant floor.

Other advantages include a wiring reduction compared to hardwired solutions while maintaining Category 4 safety and detailed diagnostics down to the contact level without a single inch of additional wire. Multiple safety zones, dependent and independent, can be implemented with no additional wiring and systems have the ability to capture nuisance shutdowns due to faulty safety contacts or wiring connections at the safety device level.

Hornis says even though networked safety solutions have been around almost 10 years, some engineers still question if they are legally allowed to use networked safety and if it is actually safe. “There is too little understanding of the basics of network safety and how it can be safe if it doesn't use four wires,” says Hornis.

When Europe moved to allow networked safety under certain very stringent conditions, still forbidden in the U.S. at the time, it was clear machine builders that wanted to sell into Europe would need to be able to address these requirements. But once a machine is designed that utilizes a modern technology, why build one for the U.S. market which is really very primitive and doesn't give users the abilities of a machine sold in Japan or Europe?

“There is a strong trend toward safe systems and we have been selling these products for about five years,” says Hornis. “We're going through a major upgrade cycle now, where what we have learned over the years from customer input and requirements is resulting in new products and technologies.”

One example is remote safety relay technology that will be available by the end of the year. This new capability will allow systems that run on AS Interface, when there is a need to shutdown a motion safety somewhere else and no original plan to do that, to utilize a safety-rated output module (Category 4, SIL-3 and performance level “e”) in the field to expand the network.

The overall impact of safety networking is continuing to expand, as well. At the end of 2007, the total number of safety installations worldwide based on AS Interface alone totaled 50,000. The number of safety modules or safety inputs in the field totaled more than 350,000 units, numbers Hornis thinks makes Safety at Work the number one solution in terms of customer adoption rate.

Part 3 Continues...
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