"A Chemical Plant Contractor's Approach to Computer Control"

Abstract

The paper describes how one chemical plant contractor made himself able to install a computer as part of the instrumentation and control system for new plants. First there is an appreciation of what a contractor can and can not be expected to do. Then follows a discussion of the design criteria used to produce a universal system for chemical plants.The design employs DDC and provides backup with a digital presentation. The operators' panels were designed by the contractor and all the system programs were written by him in a low level language.It was realised that a very heavy client training load would be imposed on the contractor and solutions to the problems have been chosen which result in ease of explanation rather than technical brilliance. By the same token the computer used was chosen for the reliability of its hardware and its ease of programming rather than for economy in first cost.Absolute priority has been given to the aim of leaving the client with a system he understands and can exploit by adding extra plant supervisory programs. He is expected to start by writingrelatively short programs which are best written in machine code. Consequently no use has been made of a back ng store and a high level language is not expected to be necessary, although there is adequate provision for the use of any high level language for which a compiler has been written. It was considered more important that when he has written his program, be it long or short, he should be able to get it into the machine, check it, and put it on line, all without stopping the computer or disturbing the plant.The time shared operating system “Simcos” and the commissioning aids programs “Simcom” and “Simcheck” make this possible.The second part of the paper describes what happened when these ideas were put into practice for the first time.