the same engineering software for both, that means you need to have your control system software also scrutinized by TÜV, because you must be sure that it can’t feed back into the safety system,” de Breet says. So Yokogawa chose to go with TÜV-certified engineering software that is separate from that used for control system engineering, he notes.

At Honeywell Process Solutions, Hillman agrees that separation of control engineering software from safety engineering software is the way to go. A problem with common engineering software, he says, involves human error. A common engineering software approach puts the onus on the end-user to make sure that safety and control functions are segregated, and that those functions act independently if they fail, according to Hillman, who is based in ’s-Hertogenbosch, The Netherlands.

That’s why Honeywell relies on separate Safety Builder and Control Builder engineering software for use by customers who are linking the company’s current flagship safety controller, the Safety Manager, with the current flagship process controller, the C300, under the company’s Experion umbrella, Hillman says. In line with Honeywell’s reading of the international safety standards, this approach relies on separate and diverse processors that are linked in a way that provides “operational integration with secure data access, but no common failure modes,” as Hillman puts it. He believes that some of Honeywell’s competitors “have gone too far overboard on the integration side.”

How fast?

Going forward, the debate over separate vs. integrated safety/control systems appears certain to continue, even as integrated systems gain a greater foothold in the market. The issue may come down to the degree of integration with which each individual end-user feels comfortable.

“At ARC, we say that this new class of safety systems offers different degrees of same but separate,” says Dave Woll, ARC vice president, consulting, for the process industries. “Our feeling from talking to end-users is that the attractiveness of these systems comes from their significantly lower cost of ownership. There’s no question that the market is moving toward different degrees of same but separate,” Woll adds. “The big question is, ‘How fast is it going to move?’ ”          

For more information, search keywords “ process safety ” at www.automationworld.com.

.