Automatically regulated systems

Many control problems can be better solved with a diaphragm controller. The function of the diaphragm controller (see Fig. 3.27) can be easily derived from that of a diaphragm vacuum gauge the blunt end of a tube or pipe is either closed off by means of an elastic rubber diaphragm (for reference pressure > process pressure) or released (for reference pressure < process pressure) so that in the latter case, a connection is established between the process side and the vacuum pump. This elegant and more or less automatic regulation system has excellent control characteristics (see Fig. 3.28). 

In recent years, the automatic regulation of processes has steadily gained a foothold ia the brewiag iadustry. The aim has beea to produce beer with a better and more even quahty and at lower costs. Today, with new equipment and experience ia automatioa within the process iadustry, it is possible to build an advanced automatic system for the brewiag iadustry. Many factors influence the level of automation needed, and judgment must be used to decide what is best for optimum profit. 

The word process is from Latin and defines many different aspects. The automation process relates to the automatic regulation required to control the physical conditions in a system. The term process relates to both the optimal conditions within which the operation is maintained and when the operation varies with time or by a predetermined plan. 

Systems that permit automatic regulation of the gas pressure in the box within present limits are preferable to those that do not. This feature can prevent accidents that may result from over- or underpressurizing the box. All-metal boxes with glass or plastic windows (Fig. 19.2) are generally better than allplastic boxes. Metal boxes offer the advantages of durability, resistance to chemical attack, and increased ease of modification. 

Figure 4.38. Extrusion die with automatic pumping of a lubricant. Layout of regulating system 1 - high pressure cylinder 2 - air pressure regulator 3 - joining tubes 4 - lubricating chamber 5 - porous element 6 - room for the liquid lubricant 7 - transducer for lubricant pressure 8 - transducer for polymer material pressure 9 - electronic governing unit 10 - recording unit.

L. R. Rey, Automatic regulation of the freeze-drying of complex systems, Biody-namica 8 2A 1 -260 (1961). 

Reactor. The polymerization tests were carried out in a stainless steel reactor with approximately 7.6-liter (2-gallon) capacity. The reactor was built by Bench Scale Equipment, Dayton, Ohio, specifically for Phillips R D to be used in anionic polymerization studies. The monomer and solvent tanks are connected directly to the reactor and form a closed system. The weights of monomers and solvent tanks can be read directly and the errors are less than 1% ( 40g.) for the solvent and 0.1g. for the monomers. For this study, a nitrogen pressure of about 350 k.Pa (50 psig) in the reactor was maintained and the impeller mixing speed was 300 r.p.m.. The temperature was controlled by the automatically regulated steam pressure in the reactor jacket. 

The control of the concentration of certain chemical substances in mixtures is a key problem of fluidic processes. Current systems, which automatically regulate a chemical or physical condition of a liquid, are expensive and consist of sensors. 

Table 4.3 shows typical per unit values for the gains, limits and time constants used in the automatic voltage regulation systems for generators having ratings up to 50 MW. 

All parameter changes were within the operational permissible limits, and they were easily compensated by the automatic control systems without intervention of the operators. Personnel support was only required on the water-steam circuit in order to bring parameters of No.6 turbine generator back to the normal values after all the transients were over (pressure regulator of TG No.6 was opened for pressure reduction in the controlled stage chamber of the turbine). 

To achieve these objectives, an effective design must incorporate innovative solutions. The general question to be resolved is to create a reactor design with passive, inherent physical responses to achieve self-regulation, heat production and heat removal in balance. NPP s safety with an inherently controlled reactor could be less dependent on correct control action and less vulnerable to automatic control system fault and/or to operator or maintenance errors because the power would eventually passively adjust itself, thus minimizes the potential for human error initiation. 

The control rod system provides for automatic control of the required reactor power level and its period reactor startup manual regulation of the power level and distribution to compensate for changes in reactivity due to burn-up and refuelling automatic regulation of the radial-azimuthal power distribution automatic rapid power reduction to predetermined levels when certain plant parameters exceed preset limits automatic and manual emergency shutdown under accident conditions. A special unit selects 24 uniformly distributed rods from the total available in the core as safety rods. These are the first rods to be withdrawn to their upper cut-off limit when the reactor is started up. In the event of a loss of power, the control rods are disconnected from their drives and fall into the core under gravity at a speed of about 0-4 m/s, regulated by water flow resistance. 

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