Total process control

There is a definite trend in extrusion towards total process control. In a total extrusion control system, temperature measurement and control are tied in with pressure control, thickness gauging, motor load and speed, and possibly other process func- 

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Concentrating on the control of the extrusion process, it is clear from the literature [54-68] that true total extrusion process control is quite complicated and has not been fully achieved in practice. Under true total process control, the process is considered a multivariable system and the interaction between the variables is known and fully taken into account in the control scheme. One can therefore assume that many commercial microprocessor-based controllers that control melt temperature, pressure, and extrudate dimensions are most likely built with more or less independent control loops, each controlling only one variable. These controllers more or less consolidate multiple discrete controllers into one convenient package without major changes to the individual control characteristics. This may reduce cost but does not necessarily improve overall control performance. 

G. Betteley, N. Mettrick, E. Sweeney, and D. Wilson, Using Statistics in Industry Quality Improvement Through Total Process Control , Prentice Hall, New York, 1994. 

Glogauer [34] has reported on how an innovative atmospheric-pressure plasma technique allows in-line rubber and plastic surface treatment processes to become fully automated with total process control. The new process is claimed to achieve microfine cleaning, high surface activation and nanocoating in a more cost-effective and environmentally friendly way than traditional plasma activation techniques. 

Electrode processes are a class of heterogeneous chemical reaction that involves the transfer of charge across the interface between a solid and an adjacent solution phase, either in equilibrium or under partial or total kinetic control. A simple type of electrode reaction involves electron transfer between an inert metal electrode and an ion or molecule in solution. Oxidation of an electroactive species corresponds to the transfer of electrons from the solution phase to the electrode (anodic), whereas electron transfer in the opposite direction results in the reduction of the species (cathodic). Electron transfer is only possible when the electroactive material is within molecular distances of the electrode surface thus for a simple electrode reaction involving solution species of the fonn... 

Although digital control technology was first apphed to process control in 1959, the total dependence of the early centralized architectures on a single computer for all control and operator interface functions resulted in complex systems with dubious rehability. Adding a second processor increased both the complexity and the cost. Consequently, many installations provided analog backup systems to protect against a computer malfunction. 

Process validation is the procedure that allows one to establish the critical operating parameters of a manufacturing process. Hence, the constraints imposed by the FDA as part of process control and validation of an SMB process. The total industrial SMB system, as described, is a continuous closed-loop chromatographic process, from the chromatographic to recycling unit and, with the use of numerical simulation software allows the pharmaceutical manufacturer rapidly to design and develop worst-case studies. 

The IHC stain procedure is a multistep staining protocol, the various steps intended to provide amplification of stain results. Therefore, a control system must include elements to control each step of the stain process. Such a control should also include a range of reactivities, and that range ideally would encompass the total expression range expected for the measured component. The control should also monitor each step of the multistep protocol. This author has devoted a number of years to this concept, resulting in a patented control for multistep staining processes.14 Such a control provides sufficient information to monitor every IHC stain run, and when the control is evaluated quantitatively, normalization of data from one stain run to another within the same laboratory, and even between laboratories. A process control is a measure of the stain protocol and does not take the place of a control for the primary antibody. While the primary antibody control should include range of expression level detection, a different primary control must be present for every primary antibody used in a stain run (Fig. 10.4). 

The aims of the automation group at LGC were very clear and are shown in Table 1.3. Simphcity was considered to be the best approach, with the minimum number of processes being involved. A more complex approach has many more chances of failure. The total systems approach is defined in Chapter 3. Essentially, it sets out to cover all aspects of the analytical process as defined in Fig. 1.2. It provides for the quahty checks at operator, supervisor and managerial levels, and rehable results transferred in a readily digestible format. The Tar and Nicotine Survey described by Stockwell and Copeland [IS] is a good example of the approach. The total process, from the statistical sampHng pattern through to quahty-controlled data, leads in its final format to results tabulated for public information. 

The intention of this book is to provide technical and economical information on the development of the most feasible total environmental control program that can beneht both process industry and local municipalities. Frequently, the most economically feasible methodology is combined industrial-municipal waste treatment. 

Total unit heat dnty will typically be in the range of 500-1000 BTU per pound of feed to the unit. This set of process heat requirements establishes the amount of heat that must be supplied by combustion of coke. Because of the process control schemes that are normally employed in FCCUs, the unit operation will automatically adjust itself so that the energy produced via coke combustion equals the heat requirements of the process. If the balance is shifted by changes to the feed quality or operating conditions, shifts in catalyst circulation rate and regenerator temperature will occur until a new equilibrinm set of conditions is established. 

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