Eugene/Springfield Water Pollution Control Facility 1984-1991

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Page 60 Section I: TBC~tIC~u. SBaaviCES mote terminal units, CRT display/keyboard inter- faces,alarm/eventandlogprinter, lineprinter,and storage drive module. The computer and three CRT display/keyboards were located in the Ad- ministration Building. PERFORMANCE HISTORY OF CENTRALIZED PROCESS COMPUTER The original purpose of the plantprocess computer was to provide automated control and data logging capabilities that would minimize the number of staff required. But the computer proved to be unreliable, inefficient, and expensive to maintain. Its two biggest problems were limited memory and heavy maintenance requirements. • Maintenance Maintenance of the old centralized computer sys- temwas difficult andcostly. Due to the rapid changes in computer technology in the 1980s and the delay be- tween computer installa- tion and plant start-up, the original computer system was outdated from the day it was put into operation. Many parts and compo- nentswere nolonger manu- factured, and because the computer had no diagnos- tic program, troubleshoot- ingwas very time consum- ing. Failure of some key componenr~ of the system could easily result in partial or complete failure for an indefinite period. Due to the system's complex- ity, maintenance had to be done by contract with the manufacturer's representative. The mainte- nance contract was expensive, and service was slow because there was only one contractor in the area qualified to work on the system. PLANT COMPUTER SYSTEM The existing centralized process control system had so many deficiencies and problems that staff decided a new control system should be installed. A team of plant staff developed the specifications for the new system. The team ultimately selected a distributed system design, which divides the processing power into various sections in the plant. Each section is ca- pable of operatingindependently,butisconnected by a "Data Highway° -similar to a LAN. The Data Highway is a dual redundant configuration thatprovides virtually 100 percentreliabiliry. The distributed control system (DCS) has operator consoles (windows into the control system) in nearly all process areas, as well as in the mainte- nance shop and operations building. It also is connected to off-site pumping stations by both telephone and microwave telemetry systems. An operator can check or change any process variable in any part of the plant from any one of the consoles. Information on alarms and operating conditions also is available from anyplant operator console. Plant personnel installed the control system and a MicroVAX mini-computer system in several phases. Phase 1 documented the wiring, functions, and configuration of the hardware and software of the existing control system. The second phase was two-fold: developing configurations for the new system and preparing the signal, power, data, and wiring to ensure a quick transfer to the new system. The third phase was the actual installation of the DCS equipment and the changeover to the DCS. Each plant process was converted and debugged before moving on to the next step. During the fourth and final phase, the auxiliary equipment was brought on-line, and testing of the system started. Are electrician installs components in the distributed control system.