AWWA CSC91088

When the Elm Fork Water Treatment Plant (Dallas, Texas) was expanded, the instrumentation control system was upgraded. The new system consists of a distributive control system (DCS) using current hardware and computer technology for monitoring and controls, with local control panels for manual backup. The system is arranged in three levels of operation: field instruments and local pushbuttons; local control panels; and distributed control units and operator work stations. The system is modular and flexible and can be expanded or modified. Field instruments are the backbone of the system; eight criteria for selecting field instruments are listed. Local control panels provide backup for process controls. The distributed control system consists of ten distributed control units (DCUs) that will operate pumps, mix, flocculation, powdered activated carbon and carbon dioxide, chemical feed system, filters, ozone, electrical building, and the high service pump station. Fourteen functions of the DCU are listed. Operator work stations consisting of minicomputers will be installed on the data highway. Eleven functions of operator work stations are listed. Brief descriptions of the data highway, historical reporting station, and construction are given.