Customer | Versalis
Project | Connection of field devices to control system via remote I/O
Location | Priolo Gargallo, Italy
What do your running shoes and an apple have in common? Although the answer to that question is admittedly not obvious, a common theme does exist: for both products, ethylene (also known as ethene) plays an important role. Ethylene is the most-produced organic basic chemical. Its production process takes place in steam crackers, and the finished product is used as a rubber-like material for joint-protective midsoles in running shoes.
What do running shoes have to do with an apple? As ethylene is very versatile, there are many different application scenarios – for instance in the food industry. In order to deliver fruits and vegetables as fresh as possible, and to make them look mouth-watering and juicy in supermarkets, the produce is artificially matured by gassing with ethylene. This procedure improves the transport of the goods and protects against mold.
The Italian chemical company Versalis, a subsidiary of the oil company ENI, operates production plants for polyethylene and aromatic compounds in the Italian Priolo Gargallo, and is one of the world’s largest producers of this useful basic chemical. For the production of the gaseous, colorless ethylene, chemicals with an extremely high flammability are used. Consequently, the highest possible safety of people and machines has to be provided at all times inside the process plant.
During the implementation of a new safety guideline, Versalis decided to modernize a manually controlled safety system. Versatility and flexibility in daily operation were on top of the operators' agenda. The new safety guideline required that in case of a fire, every installed extinguishing valve inside the plant must be controlled either locally, or from a central control room. In order to achieve this target, a modernization of the process control system was necessary. It would make the valves available up to the highest administrative company level.
In close cooperation with Versalis, Pepperl+Fuchs developed the technical definition of the customer's solution. 117 motor operated valves (MOVs), located around the entire explosion-hazardous area (ca. 2 km²), now form the new fire protection system. Due to the extremely high requirements for safety critical application inside the petrochemical production plant, every digital communication path is installed with triple redundancy (main line, secondary line, service line). A centralized ring topology helps to bridge distances between the broadly placed motor operated valves.
Seven remote I/O stations by Pepperl+Fuchs, with redundant power supplies and bus couplers, are connected to the ring topology via Ethernet/Modbus TCP-IP and fiber optic converters. To further increase safety, the extinguishing system is redundantly layed out. Binary inputs monitor position feedback and overall status of the fire protection system. The entire remote I/O system is built into a hardy stainless steel enclosure.
During factory inspection and acceptance check, the solution impressed with achieved time savings, as the remote I/O functionalities allowed a quick examination of the entire ring. Each software and hardware mechanism and each ring were tested. Testing routines affected remote I/O technologies as well as digital systems, so all simulations were run with the help of the PACTware tool. The large amount of data generated turned out to be very useful to get a quick overview of the status of the whole system structure.
The new system now provides a modern, diagnostic, and predictive monitoring of the valve position of the extinguishing valves directly over the control system. This reduces plant downtime and ensures a higher production efficiency. When a valve gets stuck, operators receive a diagnostic notification from the control system, which allows them to immediately initiate a targeted service deployment. Time consuming on-site inspection walks by service technicians to each valve are no longer needed to test their functional capability.
Compared to the previously installed point-to-point topology, Versalis now saves several kilometers of wiring with the new remote I/O based network solution. After all, 50 % – 60 % less cabling is needed inside the chemical plant. Pepperl+Fuchs' solution turned out to be a true efficiency booster in several ways while at the same time ensuring a maximum of safety and availability.
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