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Papermakers get single window control.

Papermakers Get Single Window Control

Historically pulp and paper mills have embraced new control technology on a piece-meal basis, installing separate often black box systems to improve specific parts of the process. Some two decades of fast-paced technological innovation have left them with a multitude of systems with differing operator interfaces, maintenance procedures and limited system-to-system linking capability.

Although the advantages of a unified mill-wide control system have been long recognised, the tough and complex demands on software and hardware to meet this challenge have frustrated many suppliers' attempts to achieve this goal. Now Asea Brown Boveri has developed a system to meet the ever increasing demands of industrial automation.

The ABB Master system was designed from the outset to cover the three traditional levels of control (see Figure 1) namely instrumentation, optimization and mill-wide control. At level 1, both regulatory control, logic and sequential control were for the first time brought into a single system which replaces the traditional PLC and single loop controllers.

Global Data Base

The ABB Master system uses a global data base which is accessible from any part of the system. All applications programs have access to all process signals without becoming interdependent, thanks to the fact that the signal descriptions are separated from the applications programs. The users own signal names are used just as they are out there in the process. Similarly engineering units are used in the control program and documentation.

Programming is done through a high level process-oriented language, the ABB Master Piece Language (AMPL). A very comprehensive library of function blocks called PC elements enables the process engineer to set-up the control program by connecting the appropriate PC elements together in the same way as the functions are in the process. All-in-one functions cover the control and operation of the most common object types such as motors, valves and PID controllers. For large systems, repetitive programming can be reduced to a minimum by the creation of type circuits: standard control configurations used in different parts of a specific installation need only be programmed once and merely cloned into the control program whenever required.

Full graphic presentation of function elements, menudriven programming and help functions guide the programmer through his work. Automatic graphic documentation of process control programs ensures that clean up-to-date hard-copies of the program are available as soon as any changes are made.

The ABB Master communication networks linking the various process and operator stations are self-configuring and automatically detect and talk to a newly inserted station so that the programming work of the expansion is limited to the process control and/or display configuration.

Distributed Intelligence

In a typical Master system, Master Piece process stations are distributed throughout the plant. To save wiring costs, rugged remote I/O modules handle distant instrumentation signals and communicate back to the Master Piece cubicle on a high speed MasterFieldBus link without sacrificing performance.

Many design details have been incorporated to protect the system for the environment and to ensure dependable operation. In particular all electronic circuitry is protected from spikes in signals and power input as well as static charges. At the same time, such procedures such as circuit board replacement can be performed under power without disruption to the system - an important consideration for large complex processes that can't tolerate downtime.

The operator communicates with the process through Master View operator stations with high resolution color VDUs. A keyboard and trackball enable him to select the parts of the process to examine and to implement whatever action is necessary to control it either manually or automatically. Particular attention was paid to the ergonomic design of the station to facilitate the operator's task and minimize eye and hand movements. Experience has shown that softer colours and filled-in graphic shapes are clearer and less tiring on the operator. Similarly customers are encouraged to involve operators in the design of displays to ensure that they reflect their needs. This has shown that operators favour comprehensive displays which would appear particularly complex to someone not familiar with the operation in question; however, they have the advantage of reducing the need to change displays to a minimum.

Single Window Control

The capability of the Master Piece process stations and the AMPL language are such that they can perform both level 2 (optimization) as well as level 1 controls, where dedicated mini-computers and microprocessors were needed previously. This means that the operator can supervise the complete process for one standard type of process station. For example, a Master system on a paper machine will cover instrumentation control, logic and sequential control, sectional drive control, machine direction and cross direction optimization controls including the display of measurement profiles all within the one system. This reduces considerably the number of video stations and standardises operator interfacing and communication with the process.

Mill-Wide Information and Control

Level 3, mill-wide control is a task which is performed in the Master system by the Super View software residing in the widely accepted VAX series of DEC computers together with the ABB Master Tesselator graphic system. It allows for the monitoring of the many different control areas within an integrated mill and supports reporting and long term process data storage as well as any of the user's own software programs.

ABB has also developed a sophisticated production optimization tool which models the complete mill and calculates optimum storage tank levels and production rates to maximize production and reduce off-grade and quality rejects to a minimum. This system can take into account planned shut-downs and recommend appropriate action to keep disruption of production to a minimum. The simulation function generates a proposed operation plan covering the next two or three-day period and allows the production planner to evaluate alternative courses of action using what-if hypotheses. Meanwhile, the system continuously monitors current operations and notifies the planner immediately of any deviations so that corrective action can be taken without delay.

Training and Applications Know-How

Training is a very important part of a D.C.S. installation. Training courses are offered by ABB on the maintenance, operation and configuration of the Master system so that the customer makes the maximum use of the system and adapts it to the evolving needs of the process. In particular, users are encouraged to add new capabilities to the system and can easily expand the system themselves to meet new requirements.

No D.C.S. system is complete without the integration of applications and control software to optimize the process to the full. ABB has in-house experience in-house on the operation and control of pulp and paper mills to draw on and makes this knowledge available to customers to ensure that the control strategies are properly adapted to the process and objectives of the project, and to facilitate their prompt implementation. [Figure 1 Omitted] ROGER EVANS Sales and Marketing Manager, Pulp and Paper Process Automation Asea Brown Boveri Inc., Montreal
COPYRIGHT 1989 Chemical Institute of Canada
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1989 Gale, Cengage Learning. All rights reserved.

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Title Annotation:paper mill process stations and programming
Author:Evans, Roger
Publication:Canadian Chemical News
Date:Sep 1, 1989
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