Well filtered
Remote I/O helps Evonik Degussa cut installation costs by 35 percent

How can new process automation components be integrated into existing systems simply, effectively, within budget, to tight deadlines, and without upsetting the original process control architecture? The Process Technology & Engineering Group of Evonik Degussa North America has had to face this challenge again and again. One answer lies in the use of excom intrinsically safe remote I/O stations supplied by Turck.
Ryan Kromhout
Evonik Degussa is a chemical producer based in Essen/Germany, with numerous production facilities in America, Africa, Europe, and Asia. The Evonik Group operates a plant in Hopewell, Virginia/USA, producing raw materials and additives for the cosmetic and detergent industries. Products include betaines, fatty acids, emollient esters, and silicone surfactants.

In 2008, Evonik Degussa’s Process Technology & Engineering Group, which is based in Mobile, Alabama/USA, won a contract to oversee the engineering and construction of a new filtration system at the Hopewell site. While this was still in the planning stages, the company migrated to the DeltaV distributed control system from Emerson Process Management. With the DeltaV system already receiving signals via conventional point-to-point cabling from about 1,600 field measuring and control devices, adding more of the same was not attractive to the engineers from the Process Technology & Engineering Group. The new filtration system was to be installed in a Class 1 Division 2 hazardous area, meaning that every connection would have to be installed in such a way that it could not ignite an explosion.

Intrinsically safe excom remote I/O stations from Turck quickly turned out to be the most cost-efficient alternative to conventional wiring. Installed in an air-purged enclosure near the new filtration system, the excom station receives signals from approximately 50 field devices and uses the Profibus DP protocol to forward them to the higher-level DCS over a single fieldbus cable.

Intrinsically safe and cost-efficient

Turck’s excom remote I/O stations offer many advantages, both for new installations and for additions to existing control systems. The system is certified for use in hazardous area zones 1 and 2, while the field current circuits are certified for zone 0 too. A further advantage is that excom systems comprising a power supply, gateway, I/O modules, and carrier systems can operate redundantly with either 24 V DC or 115/230 V AC power. Conventional remote I/O stations operating exclusively with 24 V DC require larger cable cross-sections to compensate for voltage drop over long distances. The ability of excom to operate at mains voltage guarantees stable power, even with long cables.

This allows plant operators in Hopewell not only to keep procurement costs low, but also to reduce cabling and maintenance expenses. “This is where we saved money,” said Ken Mead, process control engineer with the process technology and engineering group. “We ran only one cable from the remote I/O to the DCS rack room, eliminating the need to install conduit and pairs of wires from each field device to the marshalling cabinets. This was about 35 percent less than the anticipated engineering and construction costs with traditional wiring, and we also got an intrinsically safe installation.”

According to Mead, Degussa will also be able to “piggy back” on the installation, using the fieldbus cable for additional I/O, if and when such a need occurs in the future. Commissioning the new filtration unit was another positive factor, and was about as easy as any Mead had ever seen: “It didn’t take any time at all. It was just like Turck told us – plug and play.”

The success of this project has led Mead and the other process engineers at Evonik Degussa to look for more opportunities to use Turck’s remote I/O “The installation in Hopewell was a big cost saver for us,” explained Mead. “That included savings on conduit, explosion-proof fittings and construction. We are very happy with the results, and we have some other plants where we are considering doing the same thing or something similar when new equipment is installed or older field devices are replaced. It all went so well; that was a very easy upgrade.” n

 ACHEMA  Hall 10.2, Stand D3-E8