Venezuela has large reserves of iron ore and iron, and steel production is one of the most important industries. The Sidor steelworks in the capital city of Caracas produces thousands of tons of sheet steel each day for a wide range of industries in the whole of South America. The steelworks extends over a very large area. Large numbers of steel and cast iron rollers are aligned as long rolling mills which produce rolled sheet steel with a wide range of cross-sections and thicknesses from hot steel ingots. The company decided to install a new a new sheet steel production automation system.
Control of the sheet steel production is based on a modern distributed automation system which uses PROFIBUS for data communication between the PLC's and the variable-speed motor drives. The numerous very powerful three-phase motors and associated frequency inverters result in a very high level of electromagnetic interference which places stringent requirements on the communication system used. Accordingly, the plant's PROFIBUS network is constructed with fiber-optic cable. The electrical RS-485 signals from the PROFIBUS device interface are converted to light impulses in an external RS-485 <-> fiber-optic converter before being fed to the fiber-optic cable. The physical topology of the bus is star-shaped and in some cases a redundant fiber-optic link is provided as a back-up connection for particularly critical parts of the plant. The PROFIBUS network which interconnects the various pieces of equipment has a total length of more than 10 kilometers and the PROFIBUS data transfer through the fiber-optic cable operates error-free even over the large distances involved.
The plant has been producing successfully since the new installation and helps to maintain the key position of Venezuela in the South American steel production industry.
PROFIBUS has proven to be a very reliable technology, even in environments with very high electromagnetic interference.