DEVELOPING CONTROL SYSTEM STANDARDS AND IMPLEMENTING THOSE STANDARDS AT AN EXISTING PLANT
The King County Department of Natural Resources and Parks, Wastewater Treatment Division (WTD), provides wastewater conveyance and treatment services to various sewerage agencies within King County and a portion of southern Snohomish County, Washington. In 2003, King County WTD embarked
on a division-wide effort to improve its operations by developing instrumentation and control (I&C) standards and guidelines that will be applied across all of its existing facilities, which include two large wastewater treatment plants (the South Plant and West Point), conveyance and
pumping systems as well as the new Brightwater treatment plant presently being designed for a projected 2010 startup. Initially, this I&C standards project is to develop the core WTD-wide control system standards, to build and utilize a test lab for design and component validation purposes,
and then to apply the new standards in conjunction with the South Plant control system replacement project. Lessons learned from the South Plant control system project will then be fed back into the WTD control systems standards as an improvement and refinement process, and will also carry
forward to successive design and installation projects at other plants.
The I&C standards project was broken down into phases to carefully manage costs and deliverables. During Phase I, the team completed development of an initial framework and methodology for I&C standards, and
built, tested, and demonstrated the control system test lab. Tasks included documenting existing WTD standards and practices by surveying existing facilities, documenting user requirements, and developing a direction for the use and long-term management of control system standards and guidelines.
Phases II and III of this project are to use these newly developed standards and guidelines in replacing South Plant's control system while maintaining continual plant treatment operations. Phase II is focused on logically defining plant process areas into manageable modules for design, installation
planning, and configuration of plant-wide control system infrastructure. Following installation of this new infrastructure, composed of control power, communications, controllers and high-level plant control and HMI systems, Phase II will pilot the design and installation of a single process
area, down to the shop floor and device level of control.
Phase II of the project began in December 2004 with pre-design activities which include process area module definitions such that they can be upgraded “on the fly,” capital cost estimating, risk assessment, technology
evaluations, core control system infrastructure design, and selection of a plant process area for control system replacement. Part of the module definition will include determining how much of the instrumentation and motor controls will be replaced using the smart network-type bus devices.
Functional equipment that is relatively new and in good working order will not be replaced unless it cannot support the data and control framework defined by the standards. This functional, older equipment will be placed on a future replacement schedule prioritized by a business case analysis.
Core systems that were identified as high risk for continued as-is operation will be replaced with new equipment that fits within the open-framework approach and selected technologies. Phase II is estimated to be complete by last quarter of 2006 with the core infrastructure supporting a running
and fully operational first process module and new supervisory level control system.
Phase III design work is slated to begin in the first quarter of 2006, and all remaining process modules will be upgraded into the new control system by the end of 2008. With the core control system infrastructure
up and running in Phase II, it is anticipated that the remaining process modules will be integrated seamlessly into the new control system. During this transition period, the operators may need to operate the older, legacy control system alongside the new control system to maintain visibility
and control of a few of the process areas.
The lessons learned during the course of the WTD South Plant control system upgrade will be fed back into the final design of the new Brightwater treatment plant control system. Future projects within WTD will use the refined standards to achieve
the utility's mission to be a world-class agency that is competitive with any privatized wastewater treatment operation in the nation by 2010.
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