Control of process plant

In the last 10-15 years tremendous strides have been made in improving the control of process plant however, fewer improvements and innovations have 

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This type of architecture is not generally suited to the computer control of processing plant. 

Although automatic computers are used widely in economic control of process plants and organizations, the incorporation of computers in the process control loop to obtain fully automatic control (automation) has been explored only in preliminary fashion. 

Fire and Explosion Prevention. Prevention of fire and explosion takes place in the design of chemical plants. Such prevention involves the study of material characteristics, such as those in Table 1, and processing conditions to determine appropriate ha2ard avoidance methods. Engineering techniques are available for preventing fires and explosions. Containment of flammable and combustible materials and control of processes which could develop high pressures are also important aspects of fire and explosion prevention. 

The process monitors and controllers typically also have the capabiUty for data logging, analysis, and display. This capabiUty has made on-line control of pilot plants, as well as commercial-scale processes, desirable. Pilot-plant appHcations for on-line control have been described (106), and the use of such systems for both monitoring and process diagnosis has been discussed (107). A number of commercially available process control programs that mn on microprocessors have been reviewed (108). Virtually all of them incorporate graphic display as an integral part of the interactive capabiUty of the program. 

CIA 1990. A Approach to the Categorization of Process Plant Hazard and Control Building Design. Prepared by Working Group 3 of the Major Hazards Steering Group. Issued by the Safety Committee of the Chemical Industry Safety and Health Council of the Chemical Industries Association, Eondon. 

An Approach to the Categorisation of Process Plant Hazard and Control Building Design (1990)... 

The term process is normally used in connection with the control of a plant in industry the term, however, also describes the HVAC installation in industry and buildings. 

Another barrier to a systematic consideration of human error is the belief that increasing computerization and automation of process plants will make the human unnecessary. The fallacy of this belief can be shown from the numerous accidents that have arisen in computer controlled plants. In addition, considerable human involvement will continue to be necessary in the critical areas of maintenance and plant modification, even in the most automated process (see Chapter 2 for a further discussion of this issue). 

The choice of the mode of control of heating plant can have a considerable effect on the efficiency of the process. The process itself may dictate the controls. For example. 

The amount of process plant that can be defined accurately as automatic is relatively small, and manual intervention is often involved at some stage. The relevant design criteria are therefore often IM/12 or IM/18. In practice, fully automatic burner controllers tested and certified by British Gas are available that comply with the requirements of BS 5885. Although these have features which may not be applicable to non-automatic plant, it may be more appropriate to use such a controller, particularly as its safety is well proven. It may also be less expensive than buying and installing separate timers, relays, etc. For some processes (for example, those that do not need and cannot tolerate a long purge) such controllers may not be appropriate. 

Advancing the field of process engineering. Important generic goals for research include the development of separation processes for complex and fragile bioproducts the design of bioreactors for plant and mammalian tissue culture and the development of detailed, continuous control of process parameters by rapid, accurate, and noninvasive sensors and instruments. 

Linear control theory will be of limited use for operational transitions from one batch regime to the next and for the control of batch plants. Too many of the processes are unstable and exhibit nonlinear behavior, such as multiple steady states or limit cycles. Such problems often arise in the batch production of polymers. The feasibility of precisely controlling many batch processes will depend on the development of an appropriate nonlinear control theory with a high level of robustness. 

GPMP is concerned with the manufacture of medicines, and includes control of ingredients, plant construction, process validation, production, and cleaning (see also Chapter 22). QC is that part of GPMP dealing with specification, documentation and assessing conformance to specification. 

Chemical engineering is no longer confined to purely physical processes and the unit operations, and a number of important new topics, including reactor design, automatic control of plants, biochemical engineering, and the use of computers for both process design and control of chemical plant will be covered in a forthcoming Volume 3 which is in course of preparation. 

United Kingdom Chemical Industries Association. 1993. An Approach to Categorization of Process Plant Hazards and Control Building Design. 

The single factors include piping, automatic controls, insulation, painting, electrical work, engineering costs, etc. (Couper, 2003). Table 9-10 shows the Lang factors for various types of processing plants. The boundaries between the classifications are not clear-cut, and considerable judgment is required in the selection of the appropriate factors. 

The instrumentation of processing plants is fully computerized these days, and the use of distributed control systems (DCS) along with advanced network systems makes plant operations highly reliable. 

A control strategy hope lly can then be evolved. It is also necessary to determine the ancillary instruments required for process monitoring, and for plant commissioning and start-up. It is worthwhile at the design stage including connections for instruments which may be required in the future. The location (local or a distant control room) and types of recorders must be specified, and the alarms and interlocks that are required. Control does not occur independently in different units, and an overall and integrated approach to the control of the plant is required. 

Morari, M., Effect of design on the controllability of continuous plants, in Perkins, J. D. (Ed.), IFAC Workshop Interactions Between Process Design and Control, Pergamon Press, Oxford, 1992, 3-16. 

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