1 August 2002

Who condones the use of zones?

By Ellen Fussell

When you're thinking of settings that are perfect for explosion protection, the North Slope of Alaska may not come immediately to mind. But that's the location of the first project in the U.S. to use the European zone method of classification—at a new oil field where developers used the increased safety (type "e") methods of protection for Zone 1. The project wasn't free of difficulties, but Bob Seitz, chief electrical and instrument engineer at TriOcean Engineering in Anchorage, Alaska, for one, is convinced it was the best way to go.

Easy maintenance is one of the main reasons the project developers used the zone method. "The facilities on the North Slope are remote, with a small maintenance workforce," Seitz said. "The large, heavy cast explosionproof enclosures with many bolts are difficult to disassemble and are often not properly reassembled. Bolts are not installed or fully tightened when reinstalling covers."

A systems engineer's needs The zones vs. division debate affects businesses throughout the industry, not just those doing installation in plants. Aces Inc. is an electrical and control systems engineering company in Richland, Wash., that designs and upgrades plants in hazardous or classified locations. "We have to know what the requirements are for each installation," said Erwin Icayan, senior engineer at Aces. "If we're going to go one way or the other, I'll have to know the equivalents from the old to the new style—what's rated for this or that zone." Icayan said when his company specifies equipment, it would have to be rated for the current standards for whatever the company is using. He would need a transition median, or "crosswalk from one to the other to let time determine whether it's useful or not. "If the U.S. wants to use zone-rated equipment, [standards developers] should provide the crosswalk in the standard," Icayan said. "I want to know what products I can use for a specific environment—to design systems for use in hazardous locations. So, in the standard, when they say Zone 0, Group 2A, I need to know what the equivalent of that is because most of our plants are classified in the division method. We need a translation in the standard if we're going to change over. It should be gradual, with a translation or crosswalk. I'd like to see a table in the standard that says, 'Here are the gases, and here's where each of these things belongs.' "

Seitz said determining whether or not it is safer or cheaper will happen only after analysis. To strengthen his case, Seitz wrote a paper for IEEE entitled, "Installation of Zone Equipment in the U.S.—Initial Experiences," but he also gives credence to the skeptics who oppose an overall changeover to the zone method.

"Concerns over loss of market share and other commercial considerations" are included in some of the objections, Seitz said in his paper. "One of the great objections to the adoption of the IEC products is the greater use of plastic," which some perceive results in "products that are not as robust as the familiar NEMA products."

Some concerns

Although Andy Mobley, senior engineer at 3M Co. in St. Paul, Minn., has some reservations about the change, he admitted a big motivator would be "reduced life-cycle cost for manufacturing process areas being changed. Maintenance costs would be reduced. Upgrades and modifications are made easier as a result of not requiring explosionproofing" and the like, he said.

But Mobley's unresolved issues with the new wiring methods revolve around whether zone-rated equipment would be listed and labeled for the U.S.

"Can we purchase increased-safety-rated motors?" Mobley asked, saying increased-safety-rated motors that are listed and labeled "appear to be unavailable in the U.S." He wondered, "If they are available, will the cost justify their use?"

A number of concerns regarding whether the National Electric Code has covered issues related to the installation of zone-rated equipment still loom among skeptics. "There are culture issues between how the Europeans and Americans handle wiring for hazardous-rated equipment," Mobley said. "The Europeans appear to use gland-type fittings, and here in the U.S., the conduit and the explosionproof seal are customary."

Europeans' use of gland-type fittings instead of conduit poses another problem: unemployment in the U.S.

Conduits with a steel surrounding are common in the U.S., said Don Taylor, a field sales representative for Pantech Engineering in Houston. Europeans insulate conductors out of the conduit and cable tray down to another piece of steel or an open-ended conduit, he said.

"It's not a closed raceway [conduit system] like it is here in the U.S.," Taylor said. "If they use conduit at all, it's for mechanical protection." Taylor said companies that now sell fittings for conduit systems might be in trouble if the U.S. stops using them altogether. "I didn't see one fitting in all of Europe," he said. IT

 

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