by R. F. Wall Monsanto Chemical Co.
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Instrumentation Trends in 1958 I N NEW equipment, 1958 seemed a quieter year than 1957, although it had some excellent new equipment. I t was perhaps a more productive year in the work done, for where 1957 seemed a year promising m u c h from the new equipment available, 1958 was more a year of business like appraisal and application. Un doubtedly business conditions of 1958 had something to do with the tenor of the years's development, but it did not delay progress. 1958 was a year of sound accomplishment and conservative development. Electronic Process Controls Electronic process controls were probably the major new develop ment of 1958, with four major process controls manufacturers ex hibiting at the ISA show in Sep tember, equipment that had been promised for several years. Elec tronic control systems have been available for several years, but this new equipment plus the im proved equipment of those originally in the electronic process controls field makes 1958 the year that electronics parallels pneumatics in general availability. Electronics does not have a standard system paralleling the 3 to 15 pounds of air of pneumatics. Both direct current a n d alternating voltage systems are used, with d.c. in the majority and apparently more generally accepted. Although several, and perhaps all, of the manufacturers investigated the opinion of users, they apparently did not talk to the same people, for each has his own standard. Direct current systems vary from 1 to 5 ma. to 10 to 50 ma., and each a.c. system differs in voltage a n d phase. T h e ready compatibility of pneumatics does not exist with electronics; mixed systems are more difficult to use arid usually require conversion equipment. Each manu
facturer has emphasized somewhat different objectives in developing his electronic equipment, and ap parently each felt strongly on the matter, for no agreement as to a standard system was reached. All the equipment, however, emphasizes reliability, through use of transistors, magnetic amplifiers, and minimum use of vacuum tubes. Pricing is stated as competitive to slightly higher t h a n pneumatics, with the emphasis on complete systems, where they expect a cost advantage of wiring over pneumatic tubing to help. T h e proponents of pneumatics argue that the new cabled tubing is as economical as wire. It appears that the capability and availability of electronics now equal pneumatics; the user can take his choice. This may present him with a puzzle in determining which system is best for him. How he solves this puzzle and which electronic control standard becomes preferred in the next few years will be very interesting, particularly for the equipment manufacturers T h e growth of electronic controls has emphasized the problem of the valve operator. It is rather contra dictory to go electronic a n d still require air for valve operation. Motor operators have received at tention and are considerably im proved, although speed remains a problem for fast systems. Electrohydraulics are fast b u t expensive, and present some maintenance prob lems. Work on the problem of valve operators for electronic systems is active, and improvements can be expected in the near future. Analysis Instrumentation for Process Control Gas chromatography became a major process analysis instrument during 1958. While 1957 was largely a year of equipment developI/EC
ment, 1958 was more a year of application, although new manu facturers entered the field and new developments in instrumentation were made. A large number of process chromatographs were placed in operation during 1958, and a great deal of progress was m a d e in developing techniques of application. Gas chromatographs were used for automatic control through reset of conventional control equipment, and control units for this purpose are commercially available. Response time of the gas chromatograph does not appear to have limited this use appreciably. Dual column chroma tographs have been used and have proved very effective for difficult separations. Dual column chroma tography is an easy instrumental technique. Extension to three or more columns is obvious, but pro gramming read-out from multiple columns will require attention to matching column elution times and can be troublesome. Equipment users have been very active in these newer developments in chromatography, and manu facturers have followed closely with commercial equipment. Experience with gas chromatography has been unusually excellent for so new a n instrument. T h e outstanding success of process chromatography seems based o n two characteristics, main tainability and versatility. The operation a n d maintenance of the chromatograph are within the capa bilities of plant instrument personnel; almost anyone can be an expert on chromatography in a few weeks' time. T h e versatility of analysis meets modern concepts of system control. These basic advantages have been the key to the develop ment of gas chromatography into a proved process analyzer in a re markably short time. Research labo ratories are working on new analyti cal systems and new columns, much ORKBOOK
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of this directed at high temperature analysis. A method of introduction for liquid samples in process chromatography is still needed. High sensitivity detectors have received considerable attention and one is now available, but there is still room for new developments in process chromatography. T h e infrared analyzer remains an important process analysis tool. T h e infrared analyzer has been developed to a remarkably high sensitivity, will readily handle liquid samples, and is adapted to direct analytical process control where this is necessary. There was a marked interest in automatic titration equipment suitable for process control during 1958, and this m a y be the major analysis instrumentation breakthrough of 1959 or 1960. A great many of our industrial processes require analyses not adapted to chromatograph, infrared, or similar physical means, but requiring the so-called wet procedures of the control lab. During 1958 considerable equipment appeared which would facilitate control lab analysis, and some of this was adaptable to process stream use. T h e development of analysis equipment to provide the programmed sequence of operations required for a wet analysis procedure is a difficult problem, but major progress has been made. Until now not much has been done toward instrumenting these wet analyses for process control, but this field appears to have a very large potential. Other analysis equipment of more limited application shared in what seems to be a general increase of interest in analytical process control, and there were a number of new instruments and improvements.
Data Reduction and Computer Control Both d a t a reduction and computer control m a d e significant progress during 1958. Reliable equipment was available, and there were enough applications for both users and manufacturers to learn considerably a b o u t what can and cannot be done. Most applications and proposed .applications were based on serious a n d very complete studies of complete systems. Almost always the de90 A
A Workbook Feature tailed knowledge of the systems studied has been extremely valuable, whether or not d a t a reduction or computer equipment was ever justified or installed. T h e real value of the added and detailed information provided about an old and familiar plant was often a considerable surprise to operating personnel. T h e problem of more effective systems control has been under attack from several directions. Data reduction plus simple computing equipment has been used to assemble data in a more meaningful and convenient form to facilitate process control. Computers have been used to convert economic and process data into control settings to optimize returns from a process. Another approach has been to use small analog computers effectively to control the operation of closely related units. There is some indication of a trend toward thus cascading the control of systems of closely related units through the use of small analog computers, a n d to use a master computer to integrate the operation of these smaller systems.
Process Control Equipment While the more prosaic process control hardware received far less publicity than the newer developments, improvements were as evident in 1958 as in preceding years. Almost every manufacturer had some improvements or new models of older equipment on exhibit at the ISA show. Often a great deal more work than is realized is behind apparently minor changes, or not evident at all but present in the form of better materials. This steady improvement has given us the stable, precise, and maintenancefree process control equipment that we have today. There is a wide selection of very excellent process control hardware available now, and improvements a r e proceeding as rapidly as better materials a n d / o r manufacturing techniques permit.
course, the excellent conventional control hardware that is now available; without this precise a n d reliable equipment the more intricate control systems now being developed would be impossible. T h e use of d a t a reduction and computers for process control is demanding far more information than was adequate with the conventional control techniques; and this is emphasizing the trend toward process analysis instrumentation. Conversely, process analysis instrumentation is obtaining much more meaningful information about a process than is given by pressure, temperature, etc., and the proper use of this information is demanding far more sophisticated control techniques. All of this has emphasized very strongly the need for a much better knowledge of how processes really operate, and adds importance to the development of a science of process control. T h e development of more complex equipment and control systems has forced a marked increase in the skills required of maintenance crafts, and realignment of organizations to meet these new needs. Effective maintenance remains perhaps the major problem of modern instrumentation. Apparently each user company is solving this problem, though not without difficulty and some major revisions of organization, in a way characteristic of its own particular structure. T h e application of more advanced and complex process control systems was perhaps the most significant advance of 1958. This opened a lot of problems, perhaps more than have been solved. There have been a number of difficulties, but a great deal of work has been done, and some real progress has been made in taking the witchcraft out of process control.
Instrumentation Perspective T h e interdependence of all the aspects of instrumentation a r e evident in a broad view of modern instrumentation. T h e foundation of modern instrumentation is, of
INDUSTRIAL AND ENGINEERING CHEMISTRY
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