HOW MUCH CONTROL SHOULD A DISTRIBUTED CONTROL SYSTEM HAVE IN YOUR PLANT? DESIGN EXPERIENCE FOR THE CONTROL SYSTEM UPGRADE AT THE METROPOLITAN WATER RECLAMATION DISTRICT OF GREATER CHICAGO'S STICKNEY WATER RECLAMATION PLANT

摘要

The Metropolitan Water Reclamation District of Greater Chicago (MWRDGC) hasnearly completed the design of improvements to the control system at its Stickney WaterReclamation Plant (WRP). The design includes the installation of a Distributed ControlSystem (DCS) for the plant and outlying facilities.At the outset of the design process, the stated goal was to standardize controls throughoutthe plant. The intent was to establish hard and fast design rules that would standardizehard-wired control for basic, front-line equipment interlocks, such as motor protectionand personal safety. The intent was for the DCS to provide supervisory control ofequipment, allowing operational changes needed as part of the normal course ofoperation.As a result of the design approach used, the design of the new DCS’s involvement in theelectro-mechanical operation of the facility varied dramatically from process area toprocess area. In some areas, the DCS will replace motor control functions, includingoverload protection for small motors. In other areas, the DCS will be simply linked toexisting PLCs, providing no more than additional operational interface capabilities to theexisting system.This paper looks in detail at several of the various applications for the use of the DCS invarious situations throughout the plant. This project gives an excellent opportunity todemonstrate the gamut of the extent of control that can be provided in the design of aDCS retrofit.