Intrinsic Safety: A Foreign Concept

Intrinsically Safe I/O Is All the Rage in the Rest of the World, but Not Here in North America. What’s the Problem?

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Joseph MacInerney, principal control systems engineer at Fluor, a systems integrator, says, “The trend in North America is still very much against intrinsic safety. The old ideas are too entrenched, plus most plants are existing, so there is a reluctance to change. We are using more and more in the Far East, where I work. Once one is used to the criteria there is no problem. However, it’s difficult to get all IS instruments, so one ends up with a combination of IS and ex-proof.”

Andre Dicaire, product manager at Emerson Process Management, says his company sees a small percentage of its control system I/O channels in North America that require IS protection. “We do a lot of upgrades and expansions in North America, and typically we just connect to the existing field instrumentation,” he says. “Customers do not rip out their functioning field instrumentation to reinstall it using IS barriers.”

On the other hand, P+F’s Kaulfersch says, “It would be inaccurate to say that intrinsic safety it is not popular in the U.S. That was true 15 years ago, but P+F’s intrinsic safety business has been growing organically—without any acquisitions—by 25% per year for the last five years, and a few of our major competitors have also experienced significant growth. In fact, several industry segments have standardized on intrinsic safety for all of their plants in the U.S., as well as around the world.”

Sonja Anderson, application engineer at MTL Instruments, concurs. “Historically, IS has been considered a ‘European’ technology. Yet in the last two years, MTL doubled its sales in the Americas, with a large portion of those sales in IS products. Has intrinsic safety become an American solution? I certainly think so.”

John Riess, regional product manager for distributed I/O at Rockwell Automation, also says IS is growing. “Manufacturers around the world use intrinsic safety measures, including here in the U.S. Also, Latin America is among the fastest-growing markets using intrinsic safety. What we’re seeing is a lot of different industries have hazardous environments that have to be dealt with, and plants are taking measures to ameliorate any potential problems. These measures include using a physical barrier, purged enclosures and products designed to limit the available energy. Some plants use a mix of all three.”

Greenfield Issues

“Our input from customers is that IS wiring methods are indeed increasing in North America,” says Scott Saunders, vice president of sales and marketing at Moore Industries. “However, the adoption rate is certainly slower than the overall growth rate of our industry. The reason for this is the lack of new greenfield plants being built in North America.”

One reason IS makes sense for new plants, Saunders says, is because it’s less expensive. “We see the growth for intrinsic safety is with new chemical, pharmaceutical and petrochemical plants for a couple of reasons,” he explains. “First, many contractors put their projects out for bid throughout the entire international engineering community. If firms that win these contracts reside outside North America, their tendency has been to use intrinsic safety wiring methods due to their experience with it. Second, many of these firms bid on turnkey fixed-bid projects, and have done a financial analysis that determined that intrinsic safety wiring methods for hazardous areas and zones will actually save overall wiring and installation dollars.”

Jim Peterson, product manager at Turck, agrees and says IS is easy to install. “IS installations allow the same wiring techniques used in non-hazardous industrial installations,” he explains. “This eliminates the need to use rigid conduit, armored cable or specially certified cable in these areas. The NEC allows the same cable types used in ordinary industrial installations, including multicore cable that can support multiple IS signals in the same cable.

“The use of IS installation techniques not only simplifies the overall installation, but it also makes installation in hazardous areas a non-issue with maintenance personnel. Electricians with no hazardous-area experience can use the installation methods they are familiar with in any installation that incorporates intrinsic safety. None of the expertise in special wiring techniques that is required with explosion-proof installations is necessary. The use of quick-disconnect technology may be incorporated and used safely in areas that have even the highest potential for the possibility of an explosion without concern.”

The Wireless Factor

As for adding instrumentation in an existing plant, many companies are going to wireless transmitters. An intrinsically safe, battery-powered transmitter completely eliminates the need for barriers, wiring, explosion-proof cabinets, purging and other safety measures.

Kaulfersch disagrees. “Industry is still trying to cut its costs, so wireless technology is being installed. Wireless still needs to be powered in some way, so intrinsic safety is required.”

Dicaire points out that, “Many companies use fiber-optic transmission in hazardous areas, but even fiber optics have to be IS. If a fiber-optic cable is severed, the laser beam can ignite dust particles. Therefore, Emerson developed an IS fiber-optic repeater.”

MTL’s Ian Verhappen points out that the Fieldbus Foundation has adopted IS, too. “Foundation fieldbus makes extensive use of IS, FISCO and FNICO. FISCO and FNICO are not strictly speaking IS technologies, but they allow ‘live working’—that is, the ability to work on the device without requiring a continuous gas test. Live working is critical to fieldbus installations, because to work on a device, you must be able to communicate with it. Unlike conventional analog systems that only require a DC current, fieldbus systems also require system communications, so they can be addressed and modified. But fieldbus devices don’t need to be connected or disconnected often, so much of the work can be done from the maintenance console over the network.”

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