The Austrian Krems Chemie, founded as a small enterprise in 1948, is a company of international stature. The marketing of menthol is just one of the many Krems Chemie activities. We see the end product daily in handkerchiefs, sweets, perfumes, body care products, salves, cigarettes and spirits. The Krems Chemie expanded its production facilities recently with a new menthol column. With a height of 45 m and at 24 tons, the new menthol column seems to dominates the picture of the Krems Chemie plant. The entire line for the raw materials is stored in the 32 m high building which is designated as Ex-Zone 0. For sensors, actuators and for the 2-wire Fieldbus, this means that this must be intrinsically safe. To enable clear diagnosis and simple commissioning, the complete production is equipped with PROFIBUS as the communication system.
With a few exceptions, the production plant for this material is an exclusive PROFIBUS environment. By networking the more than 170 PROFIBUS components which have since been installed, safe operation is ensured at the highest level. Because everything has been designed for PROFIBUS, there is just one PLC Simatic S7-400 in the control room. As the central management system with visualization, a Simatic PCS7 system is installed above. With its complete decentralization, only three control cabinets are installed in the field which are connected to the PLC via two PROFIBUS-DP/RS485 cables. The one "data gatherer" links 11 units of the ET200M remote I/O with approximately 160 binary inputs, 29 Simocode motor protection switches and one Simovert frequency converter to the central unit. The other "data gatherer" links 18 PROFIBUS-DP/PA segment couplers to the central unit.
The FISCO model (Fieldbus Intrinsically Safe Concept) is used with PROFIBUS-PA ensuring clear-cut limits between current input, voltage supply, cable and instrument inductance and capacitance. This allows 8 to 10 instruments to be connected to one segment coupler via a 2-wire cable. Compared with conventional 4...20mA technology, this means that trunking, point-to-point cabling and an intrinsically-safe transmitter power supply do not have to be made available for every instrument. By using PROFIBUS-PA, cost savings of up to 50% can be made in the chemical industry.
Only the actual measured value is transmitted using conventional analogue 4...20mA instruments. With PROFIBUS-PA, a much greater amount of information is available to the plant user and which can be called up very easily. Thus, a motor protection switch provides information on the number of switchings, the total run time, the actual current consumption and much more. Because data can also be written to the instrument via the Commuwin II operating/calibration tool from Endress + Hauser, the calibration of instruments can be done completely from the switching cabinet or control room. Instrument parameters can also be accessed via the PCS7 with the S7-400. As with software calibration of the instrumentation, hardware installation was also very easy. Advantages such as rapid, flexible and simplified expansion, clear diagnosis, simple commissioning and also the savings in costs and time in the planning, cabling and installation all led to the decision to install PROFIBUS.