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Pulp, paper and allied industry digital process control systems status and trends
Automatica, Vol. 13, 547 551. Pergamon Press, 1977. Printed in Great Britain
Survey Paper Pulp, Paper and Allied Industry Digital Process Control Systems Status and Trends* M . A. K E Y E S t
Utilizing survey material, along with more general knowledge of related technologies, projections indicate that distributed digital systems in the pulp and paper industry will make total plant automation technologically practical, from a controls standpoint. Key Word Index
Digital systems; microprocessors; process control; pulp industry.
Summary Digital process control applications in the paper industry are now some 17 yr old. During this development, the Process Control Committee of the Technical Association of the Pulp and Paper Industry has been active in educational programs, defining standards, determining economics and measuring the extent, character, and impact of these systems. Several surveys have been conducted to support these activities. The results of these surveys are summarized in this paper. To provide a more current data base for presentation to the IFAC PRP 3 Conference in Brussels, Belgium, May 24-26, 1976, one of these surveys was updated in February 1976.
The results of this survey were reported at the 1974 TAPPI Engineering Conference[l]. In late February of 1976 another survey was posted that added another dimension to the previous investigation, that of distributed digital and microprocessor based control systems. One hundred thirty-two installations were ultimately reported on in this survey at 86 sites. These surveys establish without cavil that the era of digitally controlled pulp and paper making has indeed come to pass. Two hundred forty-four computer installations were reported by the 314 survey respondents. Statistical extension of the surveyed population to the total industry on a proportionate basis indicates that, at the time, at least 500 systems were actually in place. More recently, at the 1976 Engineering Foundation Conference on Chemical Process Control (January 18-23, 1976, Asilomar, California), over 600 installations were reported by two vendors of packaged systems on this type alone[2]. Extension of the February 1976 data indicated a current "population' of minicomputer based process information and control systems of approximately 700, consistent with the Asilomar data. Microprocessors and distributed digital control systems are only now becoming a factor in industrial control applications of any type. It is precisely for this reason that the February 1976 survey was initiated to try to influence the architecture and detailed design of the next generation of control systems so that they, hopefully, will be compatible with the needs of the pulp, paper, and allied industries. Currently, there are very few microprocessor systems in place in the industry. Twenty were reported in the survey with a statistically projected industry total of less than 90. One-hundred sixteen were reported as currently in the plans for installation in the next 5 yr (a projected U.S. industry total of less than 700 systems). This number will undoubtedly increase due to the far lower cost of these systems compared to conventional computer applications and the extension of their use into the application domain now served by analog pneumatic and electronic panel board instruments. This particular point was emphasized by data presented by Crown Zellerbach[3] at the National TAPPI Show (March 15 17, 1976). They indicated that while 45 % of their production was under digital control, only 24,°/o of their machines were so controlled. Their conclusion was that new technology was required to drive the cost of digital control down to a level that is viable on small applications.
CONCLUSIONS reached from the historical application data and projected purchase profile of the survey base are delineated. From this data it is clear that the application of minicomputer based data acquisition and control systems is mature in the paper industry while the next major technological step, the use of microprocessor based systems to cover greater application range, is only now entering its infancy. Utilizing this survey material as a base, along with more general knowledge of the status of related technology, several projections are made relative to the technical course of this forthcoming evolution. I N T R O D U C T I O N THE SURVEYS In March of 1969, the Process Systems and Control Committee of TAPPI began a study of United States computer applications. This study culminated in an initial industry census in 1973 and 1974 with a detailed questionnaire which was submitted to management personnel at 1873 sites. Three-hundred fourteen responses were received from this initial survey--a surprisingly high response for a direct mail questionnaire. The 1973/1974 Survey centered on questions relating to conventional computer control systems implemented with small scale and medium scale integrated circuits. It attempted to answer questions on Extent of Use Nature of Application Method of Implementation System Cost System Benefits and Return on Invested Capital Nature of Maintenance System Reliability Programming Techniques and Languages Future Trends *Received 20 September t976; revised 4 February 1977. The original version of this paper was presented at the 3rd IFAC
C U R R E N T APPLICATIONS AND F U T U R E PLANS The surveys showed a distribution of applications for conventional systems as shown in Fig. 1. As might be expected, the predominance of installations are related to on-machine gauging based systems. Increased applications in the pulping, stock preparation, power, and recovery areas are shown in the 1976 data. Most of the new purchases will, again, be associated with on-machine applications with further growth in recovery, power, pulping, and bleaching applications. This data is summarized in Fig. 2.
Conference on Instrumentation and Automation in the Paper, Rubber and Plastics Industries which was held in Brussels during May 1976. The published Proceedings of this IFAC Meeting may be ordered from: Federation IBRA-BIRA, Rue Ravenstein, 3 B1000 Brussels, Belgium. This paper was recommended for publication in revised form by associate editor H. A. Spang III. tVice-President of Engineering, Bailey Meter Company (Subsidiary of Babcock & Wilcox) 29801 Euclid Avenue, Wickliffe, OH 44092, U.S.A. 547
548
Survey Paper
Description
1973 1974 Survey percentage
1973 1974 Survey number
1976 Survey percentage
1976 Survey number
0.35 2.45 7.36 4.26 1.(15 0.35 1.40 0.35 0.70 4.91 62.80 3.50 1/t.52
1 6 18 1I) 3 I 4 1 2 12 153 8 26
1.5 6.8 8.3 6. I 3.8 1.5 3.0 1.5 1.5 6.1 4.7 6.1 6.1
2 9 11 8 5 2 4 2 2 8 63 8 8
Woodyard Batch digesters Continuous digesters Bleach plants Recovery boilers Power boilers Energy management Water and waste Environmental monitoring Stock prep. On-machine applications Converting and inventory control Others (includes off-machines, coaters, coating prep. etc.)
*Total installations reported:1973 1974:244 1976: 132 FI(;. 1. Applications ol inslallcd con,,entional computer systems
1973-1974 Survey percentage (period) (1974 19781
Description
Woodyard Batch digesters Continuous digesters Recovery boilers Power boilers Bleach plants Energy management Water and waste Environmental monitoring Stock prep. On-machine applications Converting and inventory control Others (includes off-machines, coating prep., etc.) Total planned system purchases
0 9.6 4.0 4.1 2.3 5.9 5.1 1.6 3.8 4.8 39.6 3.5 15.7
No. 0 65 27 28 16 40 35 11 26 33 269 24 107
1976 Survey percentage (period) (1976-19811
No.
1976 Distributed digital control system plans (period) (1976~1981)
1.5 13.2 7.5 9.7 5.2 10.2 6.0 1.5 1.5 5.2 26.1 5.5 7.0
6 53 30 39 21 41 24 6 6 21 105 22 28
3.5 3.5 1.7 4.3 4.3 1.7 4.3 1.7 3.5 15.5 25.9 23.3 6.9
681
402
N o.
4 4 2 5 5 _'2 5 2 4 18 30 27 8
116
FIG. 2. Future installation plans
Description
1973 1974 Survey return on invested capital "., after tax
1976 Survey return on invested capital ",', after tax
38 42 42 15 32 80 49 32
40 155 61 55 NA 81 45 8(1
Woodyard Batch digesters Continuous digesters Recovery boilers Power boilers Energy management On-machine applications Bleach plants
FIG. 3. Financial benefits.
Current microprocessor applications are confined to onmachine and converting applications. Future microprocessor system plans are also reflected in Fig. 2. ECONOMICS The reason for some optimistic projections and the industries" aggressive pursuit of the total plant management and control system concept was apparent from the surveys. Figure 3 summarizes the financial impact of these systems by application area.
CONFIGURATIONS The installed configurations were also tabulated in both 19731974 and 1976, and these are summarized in Fig. 4. Since this data represent statistical averages, no single 'real' configuration is represented by this tabulation. Future trends in this area include the use of larger main memories as prices drop precipitously. The earliest paper industry computer systems faced a cost of over $4.00 per word of core memory. As of this writing, the cost of memory in a typical minicomputer is approximately $0.10 per word and seems to be
Survey Paper
549
1973-1974 Data 1976 Data in parentheses Description Main memory size Bulk memory size Card reader ? Card punch? Paper tape reader ? Paper tape Punch? Typers or Printers per system Mag tape ? Cassette tape per system Analog inputs per system Status inputs per system Pulse counter Inputs per system Priority Interrupt points per system Digital outputs per system Analog outputs per system
Batch digesters
Continuous digesters
Stock preparation
On-machine applications
Converting, roll handling, and shipping
28.6K (28.8K) 469K (512K) 15% (20 %) 8% o/ (10/o) 31% (60 %) 38% (60%) 2.8 (1.0)
25.3K (30.3K) 843K (358K) 21% ( 11 °0) 21% (11%) 58 % (44.4 %) 58 % (44.40/0) 1.9 (1,4)
18.4K (37.3K) 640K (1152K) 50% (33 %) 500/o (16.2 %) 40% (16.2 %) .20% (16.2%) 3.0 (1.3)
41.9K (65.3K) 561K (512K) 16% (8.3 %) 17% / (4.2 oJo) 55% (66.7 %) 51% (54.2%) 2.3 (1.8)
47K (27.4K) 3131K (2706K) 88% (71.4 %) 63% (28.6 %) 38% (42 o/0) 38 % (57.l%) 2.1 (1.4)
0% (0 %) 0.23 (0.20) 48 (32) 67 (28) 3 (1)
42% (0 %) 0.63 (0.56) 64 (34) 37 (11) 5 (9)
0% (0 %) 0.1 (0.16) 44 (16) 48 (13) 9 (0)
10% (8 % 2.2 (0.25) 33 (35) 35 (36) 8 (5)
38°/0 (14.3 %) 0 (0.57) 2 (1) 8 (6) NA (l)
7 (2)
12 (3)
6 (1)
5 (3)
1 (49)
32 (29)
38 (21)
54 (4)
37 (27)
24 (5)
7 (6)
5 (4)
11 (4)
7 (5)
2 (0)
FIG. 4. System configuration by application area.
following a logarithmically linear downward trend with time. Such advances as reliable semiconductor memory systems incorporating error detection and correction features with low cost LSI memory chips (the largest of the latter presently being 16K x 1 bits with 64K × 1 bit memories now in development) will insure, at least for the short term, a continuation of this downward trend. Another important area that is impacted by technology trends is that of the operator interface. The success or failure of any control system is critically dependent upon an almost symbiotic relationship between plant operator and machine. Much of the current development work relative to all industries is centered upon the desire to allow the operator to manage a process using the measurement and control system as a mechanism to multiply his effectiveness. This desire is seen in the paper and allied industries in the form of graphic CRT based displays, close attention to the true informational needs of an operator, and a general consideration of ergonometric factors in the design of all system elements. It is not surprising that the first real penetration of the paper industry market and wide scale user acceptance of digital control technology was accompanied by the simultaneous introduction of CRT displays and other operator interface features designed from a biotechnological viewpoint. We are far from the end of this evolutionary process. Color CRT displays were introduced in 1970 to the industry and have yet to realize their full application potential. This area, again, will benefit from ongoing technological enhancements that will bring the relative (if not
absolute) price of these advanced display systems down while simultaneously providing greater resolution and flexibility. These conclusions, while not derived from this survey data, bear on its interpretation and use in projecting the shape of future developments. The use of advanced displays for the complete spectrum of control applications is supported by recent introductions by all major instrument vendors of systems which this capability in microprocessor based replacement for, or enhancements to, single loop analog based control system lines. RELIABILITY, MAINTAINABILITY AND MAINTENANCE One of the basic tenets of a Systems Engineer is that he must not only analyze and control by design the reliability of his systems but, also, he must predict and provide for the known failure modes of the system. Our survey and a previous one done under TAPPI Committee Activity CA4225 entitled 'Control Computer Dependability'J4] quantified the importance of these considerations. Figure 5, the details of which are contained in reference [4], summarizes this data and shows how drastically the utility or 'true worth' of a system decreases with decreasing uptime. Even with 100% back-up, loss of as little as 1-1/2% (availability 98.5 %) in uptime decreases the utility by nearly half. Today's systems are on the average 98.8 % available compared with 99.47 ~ available in the 1973 74 survey and an earlier (1970) figure of 98.1% from CA4225. A plot of the availability data on log probability grid is shown in Fig. 6. It is possible that this reduction in availability reflects a
550
Survey Paper t" igurc 7 summarizes the reported ax ailabJlily ol >ott~ arc :uds/;~, those USgI'S IV]IO ]IOU(' 0 ( ' ( ' C 5 3 f l ) IIIC ]~l'o~rOllllllil)<£ !'I :l'l,'?:
Relative utility. ", Availability, %
Full back-up
50 ",, back-up
0 '>,, back-up
99.00 99.94 99.82 99.10 98.20 96.40 92.80
100.0 91.7 81.('1 61.0 45.('1 19.0 16.3
100.0 87.8 75.3 47.8 31.9 17.2 12.8
100.0 66.7 61.3 47.8 30. I 5.3 8.3
lqc;. 5. System utility vs availability'.
tg76
10r3-1~74, DATA / /
/
o
//
/
1.0
/
//
¢
/ / /
/
20
/
Z
/:
40 SYSTF~S w l r ~
O0
O0
It should be noted that this amounted to 455 respondents or 42 % of the survey population, wilh the remaining 58",, being made up of dedicated systems wilh ilo user modification capability or unknown systems proprietary to the vendor. While the precision of the estimates is questionable, due to the small responding sur,,ey population, a trend toward the use ot interpreters (such as enhanced BASICI and real-time compilers is noted because of the case of development documentation, and debugging provided to the system developer and installer. This ad'~antage is balanced by a loss in run-time efficiency which becomes irrelevant with larger low-cost memories and even fasler central processors. M O R E RECENT T R E N D S LSI based distributed digital contol systems using microprocessors or microcomputers us a hardware element a r c just beginning to be considered lot industrial applications. These systems, for the first time, make economically possible the concepts of distributed risk and hierarchial-distributed control in an industrial environment. The microprocessor 'computer on a chip' was introduced commercially in 1971 and, until recently, has seen little use in the process industries. As with the semiconductor memories, the microprocessor has followed the conventional semilogarithmic semiconductor technological and cost growth curves. Initial microprocessors featured 4 bit arithmetic logic units of limited capability'. Today's systems are being designed around 16 bit microprocessors with greater capability than many of the SSI based systems which were covered by our first CA4225 survey in 197014]: 32 bit lnicroprocessor units for even more demanding applications arc on the horizon. The returns from our 1976 survey have now been completely tabulated and several general comments can be made based on this data and on other related developments. The author tenders tire R~llowing conclusions and pr~ziections:
DATA/
/
equipment.
1oo
tES~ ~OWNTIME
EtG. 6. Systems availability plot. shift to more rigorous application from the relatively benign paper-machine environment (bleach plants, digesters, recovery boilers) since it has proved to be impossible, to date, to totally isolate these systems from their environment, even with special enclosures and separate rooms. Because of its profound effect on the usefulness of a system, great engineering care is being exercised today in the design of tomorrow's systems to insure availability and maintainability. Industry trends toward total contract maintenance services provide even greater impetus toward these goals, due to the enforced continuing education programs and greater activity level of contract maintenance personnel. Of the systems covered by the 1973-74 survey, 93.53{; were maintained by vendor supplied personnel either wholly or in part. This trend is further emphasized in the 1976 data with 96 ~:o of all installations vendor maintained. SOFTWARE The area of software support is one of the most "fluid', technologically, of any related to the design of the systems covered by the survey or by projected future industry trends.
Language Real lime F O R T R .*~N Assembler Macro-assembler Block oriented control configurator Real time extended basic Sequential and/or batch language
1. Microprocessor based distributed digital systems have yet to make significant inroads into conventional paper industry control systems. 2. Many users are now looking at this technology and the advantages it offers. A 'Delphi" estimate was included in the survey. Tim substance of this question was "when, in your opinion, will 50",, of new plant instrument and control system instalhttions be based on microprocessor or other LSI teclmology." The answers are
Minimum Time Most Likely Time M a x i m u m Time
Average (yr) 7.2 10.53 18.3
Range (yrl 3 20 5 30 7 40
Relative to the early 1976 time frame of the survey, the most likely date appears to be early 1987. 3. As distributed digital systems based on microprocessor technology replaced conventional panel board instruments. both pneumatic and electronic, the configurations for supervisory control systems will change drastically. Both the system data and input-output interface will be distributed in space to provide contiguity with the maior process elements being controlled. Percentage of users with facility 11973- 1974 data)
Percentage of users with facility' 11976 data)
Number of users with facility, 11976 data)
70.4 100.0 45.2 27.0
73 91 64 82
40 50 35 45
10.4
15
8
2.6
2
I
FIG. 7. Software support.
Survey Paper 4. Software trends toward interpretive systems and structured programming concepts with greater emphasis on reduction of software cost and improved software reliability will continue. 5. Discrete, batch, and modulating (continuous) control systems aspects will be integrated in the new systems, due to the design flexibility inherent in a microprocessor based control system structure. 6. The basic first level control functions of control, record, and alarm will be integrated with higher level display functions using hierarchial display concepts, plant, management, and optimization functions. 7. Information and control networks will be facilitated through the widespread use of high-speed serial digital data transmission techniques. 8. Reliability and Maintainability will be major issues as vendors incorporate acceptable system degeneration modes, automatic fault diagnosis, and redundancy into their system designs. CONCLUSIONS The application of conventional digital process control computers to the proper and allied industries is mature. Major future enhancements of this technology will center upon operator interface and human factors programming systems
551
new sensors to extend the scope of applications. A much broader application based will arise as the microprocessor makes itself felt in the form of enhancements to these older concept systems and as a distributed-hierarchial replacement for more prosaic pneumatic and electronic panel board instruments. The integration of batch, sequential, and modulating control techniques into a single system will make total plant automation technologically practical from a controls standpoint. A review and modernization of process operating practices and plant design is long overdue and must accompany control enhancements to allow operational feasibility of this concept.
References [1] M.A. KEYES:Computer control census. Tappi 58, (6) 71-74 (1975). [2] D. F. CHURCh: Advanced control in the pulp and paper industry. Presented to the Engineering Foundation Conjerenee on Chemical Process Control. January 18 (1976), Asilomar, California, U.S.A. [3] J. PALMER:Future technical needs and trends in the pulp and paper industry. Session Introduction National Tappi Meeting March 15-17, (1976). [4] M. A. KEYES: Equipment implications--Tappi control computer dependability study~CA4225. Presented paper 7appi Engineering ConJerence, September ( 1971 J.
Survey Paper Pulp, Paper and Allied Industry Digital Process Control Systems Status and Trends* M . A. K E Y E S t
Utilizing survey material, along with more general knowledge of related technologies, projections indicate that distributed digital systems in the pulp and paper industry will make total plant automation technologically practical, from a controls standpoint. Key Word Index
Digital systems; microprocessors; process control; pulp industry.
Summary Digital process control applications in the paper industry are now some 17 yr old. During this development, the Process Control Committee of the Technical Association of the Pulp and Paper Industry has been active in educational programs, defining standards, determining economics and measuring the extent, character, and impact of these systems. Several surveys have been conducted to support these activities. The results of these surveys are summarized in this paper. To provide a more current data base for presentation to the IFAC PRP 3 Conference in Brussels, Belgium, May 24-26, 1976, one of these surveys was updated in February 1976.
The results of this survey were reported at the 1974 TAPPI Engineering Conference[l]. In late February of 1976 another survey was posted that added another dimension to the previous investigation, that of distributed digital and microprocessor based control systems. One hundred thirty-two installations were ultimately reported on in this survey at 86 sites. These surveys establish without cavil that the era of digitally controlled pulp and paper making has indeed come to pass. Two hundred forty-four computer installations were reported by the 314 survey respondents. Statistical extension of the surveyed population to the total industry on a proportionate basis indicates that, at the time, at least 500 systems were actually in place. More recently, at the 1976 Engineering Foundation Conference on Chemical Process Control (January 18-23, 1976, Asilomar, California), over 600 installations were reported by two vendors of packaged systems on this type alone[2]. Extension of the February 1976 data indicated a current "population' of minicomputer based process information and control systems of approximately 700, consistent with the Asilomar data. Microprocessors and distributed digital control systems are only now becoming a factor in industrial control applications of any type. It is precisely for this reason that the February 1976 survey was initiated to try to influence the architecture and detailed design of the next generation of control systems so that they, hopefully, will be compatible with the needs of the pulp, paper, and allied industries. Currently, there are very few microprocessor systems in place in the industry. Twenty were reported in the survey with a statistically projected industry total of less than 90. One-hundred sixteen were reported as currently in the plans for installation in the next 5 yr (a projected U.S. industry total of less than 700 systems). This number will undoubtedly increase due to the far lower cost of these systems compared to conventional computer applications and the extension of their use into the application domain now served by analog pneumatic and electronic panel board instruments. This particular point was emphasized by data presented by Crown Zellerbach[3] at the National TAPPI Show (March 15 17, 1976). They indicated that while 45 % of their production was under digital control, only 24,°/o of their machines were so controlled. Their conclusion was that new technology was required to drive the cost of digital control down to a level that is viable on small applications.
CONCLUSIONS reached from the historical application data and projected purchase profile of the survey base are delineated. From this data it is clear that the application of minicomputer based data acquisition and control systems is mature in the paper industry while the next major technological step, the use of microprocessor based systems to cover greater application range, is only now entering its infancy. Utilizing this survey material as a base, along with more general knowledge of the status of related technology, several projections are made relative to the technical course of this forthcoming evolution. I N T R O D U C T I O N THE SURVEYS In March of 1969, the Process Systems and Control Committee of TAPPI began a study of United States computer applications. This study culminated in an initial industry census in 1973 and 1974 with a detailed questionnaire which was submitted to management personnel at 1873 sites. Three-hundred fourteen responses were received from this initial survey--a surprisingly high response for a direct mail questionnaire. The 1973/1974 Survey centered on questions relating to conventional computer control systems implemented with small scale and medium scale integrated circuits. It attempted to answer questions on Extent of Use Nature of Application Method of Implementation System Cost System Benefits and Return on Invested Capital Nature of Maintenance System Reliability Programming Techniques and Languages Future Trends *Received 20 September t976; revised 4 February 1977. The original version of this paper was presented at the 3rd IFAC
C U R R E N T APPLICATIONS AND F U T U R E PLANS The surveys showed a distribution of applications for conventional systems as shown in Fig. 1. As might be expected, the predominance of installations are related to on-machine gauging based systems. Increased applications in the pulping, stock preparation, power, and recovery areas are shown in the 1976 data. Most of the new purchases will, again, be associated with on-machine applications with further growth in recovery, power, pulping, and bleaching applications. This data is summarized in Fig. 2.
Conference on Instrumentation and Automation in the Paper, Rubber and Plastics Industries which was held in Brussels during May 1976. The published Proceedings of this IFAC Meeting may be ordered from: Federation IBRA-BIRA, Rue Ravenstein, 3 B1000 Brussels, Belgium. This paper was recommended for publication in revised form by associate editor H. A. Spang III. tVice-President of Engineering, Bailey Meter Company (Subsidiary of Babcock & Wilcox) 29801 Euclid Avenue, Wickliffe, OH 44092, U.S.A. 547
548
Survey Paper
Description
1973 1974 Survey percentage
1973 1974 Survey number
1976 Survey percentage
1976 Survey number
0.35 2.45 7.36 4.26 1.(15 0.35 1.40 0.35 0.70 4.91 62.80 3.50 1/t.52
1 6 18 1I) 3 I 4 1 2 12 153 8 26
1.5 6.8 8.3 6. I 3.8 1.5 3.0 1.5 1.5 6.1 4.7 6.1 6.1
2 9 11 8 5 2 4 2 2 8 63 8 8
Woodyard Batch digesters Continuous digesters Bleach plants Recovery boilers Power boilers Energy management Water and waste Environmental monitoring Stock prep. On-machine applications Converting and inventory control Others (includes off-machines, coaters, coating prep. etc.)
*Total installations reported:1973 1974:244 1976: 132 FI(;. 1. Applications ol inslallcd con,,entional computer systems
1973-1974 Survey percentage (period) (1974 19781
Description
Woodyard Batch digesters Continuous digesters Recovery boilers Power boilers Bleach plants Energy management Water and waste Environmental monitoring Stock prep. On-machine applications Converting and inventory control Others (includes off-machines, coating prep., etc.) Total planned system purchases
0 9.6 4.0 4.1 2.3 5.9 5.1 1.6 3.8 4.8 39.6 3.5 15.7
No. 0 65 27 28 16 40 35 11 26 33 269 24 107
1976 Survey percentage (period) (1976-19811
No.
1976 Distributed digital control system plans (period) (1976~1981)
1.5 13.2 7.5 9.7 5.2 10.2 6.0 1.5 1.5 5.2 26.1 5.5 7.0
6 53 30 39 21 41 24 6 6 21 105 22 28
3.5 3.5 1.7 4.3 4.3 1.7 4.3 1.7 3.5 15.5 25.9 23.3 6.9
681
402
N o.
4 4 2 5 5 _'2 5 2 4 18 30 27 8
116
FIG. 2. Future installation plans
Description
1973 1974 Survey return on invested capital "., after tax
1976 Survey return on invested capital ",', after tax
38 42 42 15 32 80 49 32
40 155 61 55 NA 81 45 8(1
Woodyard Batch digesters Continuous digesters Recovery boilers Power boilers Energy management On-machine applications Bleach plants
FIG. 3. Financial benefits.
Current microprocessor applications are confined to onmachine and converting applications. Future microprocessor system plans are also reflected in Fig. 2. ECONOMICS The reason for some optimistic projections and the industries" aggressive pursuit of the total plant management and control system concept was apparent from the surveys. Figure 3 summarizes the financial impact of these systems by application area.
CONFIGURATIONS The installed configurations were also tabulated in both 19731974 and 1976, and these are summarized in Fig. 4. Since this data represent statistical averages, no single 'real' configuration is represented by this tabulation. Future trends in this area include the use of larger main memories as prices drop precipitously. The earliest paper industry computer systems faced a cost of over $4.00 per word of core memory. As of this writing, the cost of memory in a typical minicomputer is approximately $0.10 per word and seems to be
Survey Paper
549
1973-1974 Data 1976 Data in parentheses Description Main memory size Bulk memory size Card reader ? Card punch? Paper tape reader ? Paper tape Punch? Typers or Printers per system Mag tape ? Cassette tape per system Analog inputs per system Status inputs per system Pulse counter Inputs per system Priority Interrupt points per system Digital outputs per system Analog outputs per system
Batch digesters
Continuous digesters
Stock preparation
On-machine applications
Converting, roll handling, and shipping
28.6K (28.8K) 469K (512K) 15% (20 %) 8% o/ (10/o) 31% (60 %) 38% (60%) 2.8 (1.0)
25.3K (30.3K) 843K (358K) 21% ( 11 °0) 21% (11%) 58 % (44.4 %) 58 % (44.40/0) 1.9 (1,4)
18.4K (37.3K) 640K (1152K) 50% (33 %) 500/o (16.2 %) 40% (16.2 %) .20% (16.2%) 3.0 (1.3)
41.9K (65.3K) 561K (512K) 16% (8.3 %) 17% / (4.2 oJo) 55% (66.7 %) 51% (54.2%) 2.3 (1.8)
47K (27.4K) 3131K (2706K) 88% (71.4 %) 63% (28.6 %) 38% (42 o/0) 38 % (57.l%) 2.1 (1.4)
0% (0 %) 0.23 (0.20) 48 (32) 67 (28) 3 (1)
42% (0 %) 0.63 (0.56) 64 (34) 37 (11) 5 (9)
0% (0 %) 0.1 (0.16) 44 (16) 48 (13) 9 (0)
10% (8 % 2.2 (0.25) 33 (35) 35 (36) 8 (5)
38°/0 (14.3 %) 0 (0.57) 2 (1) 8 (6) NA (l)
7 (2)
12 (3)
6 (1)
5 (3)
1 (49)
32 (29)
38 (21)
54 (4)
37 (27)
24 (5)
7 (6)
5 (4)
11 (4)
7 (5)
2 (0)
FIG. 4. System configuration by application area.
following a logarithmically linear downward trend with time. Such advances as reliable semiconductor memory systems incorporating error detection and correction features with low cost LSI memory chips (the largest of the latter presently being 16K x 1 bits with 64K × 1 bit memories now in development) will insure, at least for the short term, a continuation of this downward trend. Another important area that is impacted by technology trends is that of the operator interface. The success or failure of any control system is critically dependent upon an almost symbiotic relationship between plant operator and machine. Much of the current development work relative to all industries is centered upon the desire to allow the operator to manage a process using the measurement and control system as a mechanism to multiply his effectiveness. This desire is seen in the paper and allied industries in the form of graphic CRT based displays, close attention to the true informational needs of an operator, and a general consideration of ergonometric factors in the design of all system elements. It is not surprising that the first real penetration of the paper industry market and wide scale user acceptance of digital control technology was accompanied by the simultaneous introduction of CRT displays and other operator interface features designed from a biotechnological viewpoint. We are far from the end of this evolutionary process. Color CRT displays were introduced in 1970 to the industry and have yet to realize their full application potential. This area, again, will benefit from ongoing technological enhancements that will bring the relative (if not
absolute) price of these advanced display systems down while simultaneously providing greater resolution and flexibility. These conclusions, while not derived from this survey data, bear on its interpretation and use in projecting the shape of future developments. The use of advanced displays for the complete spectrum of control applications is supported by recent introductions by all major instrument vendors of systems which this capability in microprocessor based replacement for, or enhancements to, single loop analog based control system lines. RELIABILITY, MAINTAINABILITY AND MAINTENANCE One of the basic tenets of a Systems Engineer is that he must not only analyze and control by design the reliability of his systems but, also, he must predict and provide for the known failure modes of the system. Our survey and a previous one done under TAPPI Committee Activity CA4225 entitled 'Control Computer Dependability'J4] quantified the importance of these considerations. Figure 5, the details of which are contained in reference [4], summarizes this data and shows how drastically the utility or 'true worth' of a system decreases with decreasing uptime. Even with 100% back-up, loss of as little as 1-1/2% (availability 98.5 %) in uptime decreases the utility by nearly half. Today's systems are on the average 98.8 % available compared with 99.47 ~ available in the 1973 74 survey and an earlier (1970) figure of 98.1% from CA4225. A plot of the availability data on log probability grid is shown in Fig. 6. It is possible that this reduction in availability reflects a
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Survey Paper t" igurc 7 summarizes the reported ax ailabJlily ol >ott~ arc :uds/;~, those USgI'S IV]IO ]IOU(' 0 ( ' ( ' C 5 3 f l ) IIIC ]~l'o~rOllllllil)<£ !'I :l'l,'?:
Relative utility. ", Availability, %
Full back-up
50 ",, back-up
0 '>,, back-up
99.00 99.94 99.82 99.10 98.20 96.40 92.80
100.0 91.7 81.('1 61.0 45.('1 19.0 16.3
100.0 87.8 75.3 47.8 31.9 17.2 12.8
100.0 66.7 61.3 47.8 30. I 5.3 8.3
lqc;. 5. System utility vs availability'.
tg76
10r3-1~74, DATA / /
/
o
//
/
1.0
/
//
¢
/ / /
/
20
/
Z
/:
40 SYSTF~S w l r ~
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It should be noted that this amounted to 455 respondents or 42 % of the survey population, wilh the remaining 58",, being made up of dedicated systems wilh ilo user modification capability or unknown systems proprietary to the vendor. While the precision of the estimates is questionable, due to the small responding sur,,ey population, a trend toward the use ot interpreters (such as enhanced BASICI and real-time compilers is noted because of the case of development documentation, and debugging provided to the system developer and installer. This ad'~antage is balanced by a loss in run-time efficiency which becomes irrelevant with larger low-cost memories and even fasler central processors. M O R E RECENT T R E N D S LSI based distributed digital contol systems using microprocessors or microcomputers us a hardware element a r c just beginning to be considered lot industrial applications. These systems, for the first time, make economically possible the concepts of distributed risk and hierarchial-distributed control in an industrial environment. The microprocessor 'computer on a chip' was introduced commercially in 1971 and, until recently, has seen little use in the process industries. As with the semiconductor memories, the microprocessor has followed the conventional semilogarithmic semiconductor technological and cost growth curves. Initial microprocessors featured 4 bit arithmetic logic units of limited capability'. Today's systems are being designed around 16 bit microprocessors with greater capability than many of the SSI based systems which were covered by our first CA4225 survey in 197014]: 32 bit lnicroprocessor units for even more demanding applications arc on the horizon. The returns from our 1976 survey have now been completely tabulated and several general comments can be made based on this data and on other related developments. The author tenders tire R~llowing conclusions and pr~ziections:
DATA/
/
equipment.
1oo
tES~ ~OWNTIME
EtG. 6. Systems availability plot. shift to more rigorous application from the relatively benign paper-machine environment (bleach plants, digesters, recovery boilers) since it has proved to be impossible, to date, to totally isolate these systems from their environment, even with special enclosures and separate rooms. Because of its profound effect on the usefulness of a system, great engineering care is being exercised today in the design of tomorrow's systems to insure availability and maintainability. Industry trends toward total contract maintenance services provide even greater impetus toward these goals, due to the enforced continuing education programs and greater activity level of contract maintenance personnel. Of the systems covered by the 1973-74 survey, 93.53{; were maintained by vendor supplied personnel either wholly or in part. This trend is further emphasized in the 1976 data with 96 ~:o of all installations vendor maintained. SOFTWARE The area of software support is one of the most "fluid', technologically, of any related to the design of the systems covered by the survey or by projected future industry trends.
Language Real lime F O R T R .*~N Assembler Macro-assembler Block oriented control configurator Real time extended basic Sequential and/or batch language
1. Microprocessor based distributed digital systems have yet to make significant inroads into conventional paper industry control systems. 2. Many users are now looking at this technology and the advantages it offers. A 'Delphi" estimate was included in the survey. Tim substance of this question was "when, in your opinion, will 50",, of new plant instrument and control system instalhttions be based on microprocessor or other LSI teclmology." The answers are
Minimum Time Most Likely Time M a x i m u m Time
Average (yr) 7.2 10.53 18.3
Range (yrl 3 20 5 30 7 40
Relative to the early 1976 time frame of the survey, the most likely date appears to be early 1987. 3. As distributed digital systems based on microprocessor technology replaced conventional panel board instruments. both pneumatic and electronic, the configurations for supervisory control systems will change drastically. Both the system data and input-output interface will be distributed in space to provide contiguity with the maior process elements being controlled. Percentage of users with facility 11973- 1974 data)
Percentage of users with facility' 11976 data)
Number of users with facility, 11976 data)
70.4 100.0 45.2 27.0
73 91 64 82
40 50 35 45
10.4
15
8
2.6
2
I
FIG. 7. Software support.
Survey Paper 4. Software trends toward interpretive systems and structured programming concepts with greater emphasis on reduction of software cost and improved software reliability will continue. 5. Discrete, batch, and modulating (continuous) control systems aspects will be integrated in the new systems, due to the design flexibility inherent in a microprocessor based control system structure. 6. The basic first level control functions of control, record, and alarm will be integrated with higher level display functions using hierarchial display concepts, plant, management, and optimization functions. 7. Information and control networks will be facilitated through the widespread use of high-speed serial digital data transmission techniques. 8. Reliability and Maintainability will be major issues as vendors incorporate acceptable system degeneration modes, automatic fault diagnosis, and redundancy into their system designs. CONCLUSIONS The application of conventional digital process control computers to the proper and allied industries is mature. Major future enhancements of this technology will center upon operator interface and human factors programming systems
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new sensors to extend the scope of applications. A much broader application based will arise as the microprocessor makes itself felt in the form of enhancements to these older concept systems and as a distributed-hierarchial replacement for more prosaic pneumatic and electronic panel board instruments. The integration of batch, sequential, and modulating control techniques into a single system will make total plant automation technologically practical from a controls standpoint. A review and modernization of process operating practices and plant design is long overdue and must accompany control enhancements to allow operational feasibility of this concept.
References [1] M.A. KEYES:Computer control census. Tappi 58, (6) 71-74 (1975). [2] D. F. CHURCh: Advanced control in the pulp and paper industry. Presented to the Engineering Foundation Conjerenee on Chemical Process Control. January 18 (1976), Asilomar, California, U.S.A. [3] J. PALMER:Future technical needs and trends in the pulp and paper industry. Session Introduction National Tappi Meeting March 15-17, (1976). [4] M. A. KEYES: Equipment implications--Tappi control computer dependability study~CA4225. Presented paper 7appi Engineering ConJerence, September ( 1971 J.