Technical plant system principles

Two main principles of temperature measurement use thermocouples and the so-called resistance thermometer. In chemical plants both methods were applied because they are easy to fit and to maintain.The accuracy of the measurement is influenced by, for example, radiation, which must be taken into account. Thermocouples can be inserted into the pressure system using special sealing techniques, or they may be mounted within a protective tube which is introduced into the pressurized volume. Thermocouple-wires are usually protected with an isulating input in closed-end capillaries with outer diameters of at least 0.5 mm. Thermocouples are technically well tested for pressures up to 6 kbar and temperatures to approx. 800°C. Above these ranges the exact measurement is negatively influenced by several parameters, and the deviations must be taken into account. The accuracy of the temperature measurement devices is normally better than 1 °C. 

The modem industrialized world would be inconceivable without catalysts. There is no other technical principle which combines economic and ecological values as closely as catalysis. The development of chemical products iu advanced, industrialized societies will only be technically, economically and ecologically possible by means of specific catalysts. Examples include the specific production of stereochemicaUy pme pharmaceuticals, the constraction of tailored polymer materials, the reduction of pollutants from manufacturing plants and combustions systems (e.g. power stations, motor vehicles). Another major topic for the 21 century, the production, storage, and conversion of energy, will also be promoted by catalysts [4]. 

This verification is referred to as an operability study [4-20), [4-21], technical safety discussion [4-22J, or PI flow chart review [4-23] and is implemented according to different principles. H. Lawley [4-20] has established a strict system for the procedure. For the detection of the safety-relevant components, he follows the PI flow chart, and for the detection of hazardous plant conditions, a list of code words. H. Ullrich [4-24] describes a different way of proceeding. He applies a series of checklists in a determined sequence to the planning documents to confirm complete technical safety provisions. Individually such checklists are used to examine the completeness of procedure planning and construction documents as well as measuring and control plans. 

In cement manufacture the raw mix control and throughput optimization of the raw mills occupy a special position. Acceptable solutions to both these problems became available only with the advent of the process computer, as these control functions involve elaborate mathematical calculations. Besides, both these controlled systems are characterized - for technical reasons - by long running times. The principle of sampled-data control operated by the computer can advantageously be applied in these cases, i.e., the control system intervenes only cyclically in the process and, after output of new weigher settings, allows the grinding plant to adjust to the altered conditions before another correction is applied. 

The licensing procedure in Germany requires that components used in nuclear power plants shall be qualified before they are employed. A whole set of rules for general aspects of technical computers has existed for some time. However the safety aspects that are so eminently Important in nuclear power are not specifically treated in these national rules. WorJc has been begun on a standard "Principles for computers in systems with safety responsibility". These principles shall be applicable to computer systems in all safety relevant applications, not only nuclear power. 

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