Installation of SCADA System Improves Control of Plant Processes
The Ridgway Water Treatment Plant supplies water to approximately 8,000 people in the borough and township of Ridgway, PA.
The Ridgway Water Treatment Plant supplies water to approximately 8,000 people in the borough and township of Ridgway, PA. In the early 1990s, the borough purchased several separate systems from multiple vendors to control its water treatment and five-bay filtration processes. Over the years, technology obsolescence issues led to difficulties in obtaining support and spare parts for all the systems. At one point, the existing systems completely failed, leaving Ridgway employees to manually operate the plant for several months. A new, more efficient system was needed.
Working under an aggressive project schedule that spanned just five months from placement of the order to bringing the system online, Ridgway replaced an outdated Aquatrol plant control system and PLC-based filtration control system with Ovation® control technology. Ovation, from Emerson Process Management Power & Water Solutions (Pittsburgh), incorporates the latest technologies while also providing a product “evolution” approach that allows customers to take advantage of new technologies over the life cycle of their plant.
“We looked at different vendors and different systems, and we were impressed by Emerson’s technology - we knew it would serve us not only today, but into the future,” said Ray Imhof, operations engineer for the borough of Ridgway.
Moving to an open systems approach was a key factor in Ridgway’s decision to work with Emerson, according to Imhof.
“Our previous control systems were outdated soon after they were installed. This time, we definitely wanted a system that could expand and move with us into the future,” he said. “Reliability and support were two key considerations in our decision.”
For this project, Emerson provided a redundant network, redundant controllers, a SCADA (Supervisory Control and Data Acquisition) server, laptop PCs, operator stations and a remote terminal unit (RTU).
The Ovation system provides continuous monitoring and control of the overall plant, as well as its five-bay filtration system. All told, the system monitors and controls roughly 770 I/O points. The Ovation SCADA server, located in the plant’s main building, maintains constant communications with the RTU unit at Laurel Mill, the primary reservoir for the water system. Ovation controllers, also located in the main building, communicate to I/O modules located in the filtration building for executing control strategies for the plant’s filtration system and all other non-filtration processes. The SCADA server is comprised of three main components: a real-time data interface to move process data between the network and the RTU, a redundant interface for failsafe communications and a polling engine for communication between the SCADA server and the RTU.
The SCADA server supports operations and engineering functions, as well as Emerson’s Web Viewer connectivity software. This allows Ridgway plant personnel to remotely monitor and troubleshoot the plant’s control system from wherever the laptop PCs are located, without traveling throughout the plant’s service area.
The Ovation system provides Ridgway with increased operating efficiencies that directly translate into better and safer water production for their consumers. Examples of other benefits attributed to the new control system include:
• Reduced Costs: Replacing several outdated, non-supported systems with one unified platform significantly reduced plant costs by decreasing spare parts expenditures and time spent pursuing multiple vendors for support. New, reliable components have also reduced plant downtime, which had been frequently required to replace components of the old systems.
• Improved Communication: Important information from the SCADA RTU is readily available to the control system and desktops of Ridgway supervisors and managers enabling faster and more effective decision-making. Operators who previously spent a total of two hours per day manually checking reservoir water levels can now dedicate that time to focusing on improving plant processes and water quality.
• Increased Operational Efficiency: The system has greatly increased the efficiency of many Ridgway operations. One example is improvements to the extremely sensitive and complex backwashing system. With Ovation, Ridgway now uses only 15,000 gallons of water, versus approximately 20,000 gallons previously required. This translates into a 25 percent reduction in water and chemical usage during each backwash process.
• Enhanced Reporting: Prior to Ovation, important plant data was collected and compiled manually from each separate control system. Now, the system provides approximately 90 percent of the information required to complete EPA reports. Additionally, improved efficiency of plant operations provides more accurate plant information for reporting.
Although the project is small in scope from a strictly I/O point of view, it is significant in that it demonstrates how the operational and economic advantages made possible by a state-of-the-art control system are within reach of municipalities of all sizes.
“Some of the largest water treatment plants in the country - including the San Diego Metropolitan Wastewater Department and the Los Angeles Department of Water and Power - utilize Ovation technology,” said Doug Johnson, water industries development director for Emerson’s Power & Water Solutions industry center.
Johnson said that municipalities serving smaller populations are now becoming more aware of the control options available to them and the benefits of moving beyond PLC-based control.
“These municipalities are increasingly interested in exploring open, advanced control systems. Ridgway’s adoption of Ovation technology is indicative of that,” he said.