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Download Print Version - Install Free Acrobat Reader In June of 2009, the Town of Selma, North Carolina commissioned a supervisory control and data acquisition (SCADA) system to monitor and control their lift stations, tanks, wells and water treatment plant. This project was made possible in part, by stimulus funding provided by Construction Grants & Loans, a state-level wastewater agency. Despite strict regulations and extensive paperwork, the project came in on-time and under-budget while still managing to surpass the customer’s expectations by allowing them to identify hidden issues and optimize the efficiency of their system. In this article, project manager John Grey and system integrator Devin Carroll discuss the factors that made the project a success. The Town of Selma, NC In 2008, the town hired Richard Douglas as their Town Manager. One of his first actions was to enter into a general services agreement with the Wooten Company, a Raleigh-based consulting firm, to oversee a new monitoring and control system for the growing town. One of his next actions was to hire Gerald Lanier as the Town’s Water and Sewer Director. Both Mr. Douglas and Mr. Lanier saw the need for improvements in the water and sewer system, especially related to data acquisition and process control. Goals for the New System Remote Monitoring: "State law requires that any wastewater pump station that is not connected to a SCADA system must be visited every day. Town workers had to visit each site and log the run hours from the meters on each pump. It was very important for the town to have a central system tied in through telemetry so they didn't have to visit those stations every day.” Alarming: “They needed the wastewater pump stations to be monitored so that if an alarm condition occurred, such as a pump failure, the town's staff would be notified.” Reporting: "On the water side, they had four elevated water storage tanks with no remote information. There were level gauges on the sides of each tank but that was it. There was no reporting available at all for these sites.” Control: “There were some internal controls at the plant that would start a chemical feed system when flows were sensed. Operators had no way to know what chemical was running or if it stopped working.” Spill Prevention: "The town had no way of knowing there was a spill unless somebody went out and saw it. It was partially the fear that something serious could happen that drove the town to move forward with this project.” However, a full SCADA system, consisting of remote I/O devices, a city-wide communication network and an HMI software package was an ambitious proposition for a town the size of Selma. Grey quickly discovered a way to defray the added cost. The town qualified for a grant made available through the American Recovery and Reinvestment Act of 2009. “To receive this funding, the project had to be shovel-ready and have all the permits already in place. I suggested to Richard that this would be a good project to submit since SCADA systems do not require permits.”
Grey had help from a local instrumentation representative named Larry Wasserman who had many years of experience creating ‘open’ non-proprietary systems. “I had met John Grey at some trade shows and I did a few lunch & learns at The Wooten Company offices.” says Wasserman. “When this project came up, he invited me to do a presentation for the people at Selma. I showed them what an open non-proprietary system is and the kinds of products we work with.” “Basically, a closed system is one where everything is supplied by one manufacturer; the hardware, the software, the communications network, everything. It’s closed and not available to the public. Any changes, modifications, service work or additional parts or equipment pretty much have to be supplied by the same manufacturer.” Grey and Wasserman created a specification that listed a variety of hardware and software options that integrators could choose from when bidding the project. Initially, the new system only included the town’s nineteen wastewater pump stations. “One interesting thing about this project was that the stimulus funding came from a state-level wastewater agency called Construction Grants & Loans.” says Grey. “They would only fund the wastewater portion of the project. However, the town saw a real need to go ahead and make improvements to the water system as well, so we included the connection of the elevated tanks to the water treatment plant and the operation of the treatment plant from the tank levels. We also included control for one of the wells. Previously, someone had to drive out and turn on the pumps in the morning and then basically let it run until someone drove out and turned it off.” “The final spec didn't go into much detail.” Says Grey “It simply specified that the system had to communicate with all remote sites so that the main computer at the water treatment plant would know what's going across the system and indicate if there was a problem with any of the radios. We didn't do any surveying. We developed this project very quickly to take advantage of the stimulus money while it was available.” Bid Process The Design Process The Monitoring and Control Hardware “Back at the water plant we used a central SCADAPack 334 PLC. That unit handles flow control and some chemical pacing at the plant itself. It also provides central polling of all the PLCs at the remote wells out in the field.” The SCADAPack 334 PLC is able to communicate with the HMI software using Ethernet.
Since the government-funded system had to be ‘open’, the HMI needed to be able to communicate with a variety of PLCs or RTUs. VTScada software from Trihedral comes with a library of device drivers that makes it hardware independent. Carroll was already familiar with VTScada. “In my early days, I did maintenance on a system that communicated with VTScada using a proprietary protocol. I determined that if this software could deal with open protocols and at the same time manage this proprietary one, then it was a better choice than some of the other names that we had worked with, at least in applications where the communication protocols are not your standard big names.” The Installation Process “They did a complete project. They never came back to us complaining about surprises that they found or extra things that they needed. For example, a few of the pump stations didn't have the right kind of contacts that would allow them to connect their pump control panels. They modify their panels to make the system work.” For Carroll, these issues are all part of the process. “When we add SCADA systems to old pump stations, we often find that control hardware such as motor starters and HOAs do not have the necessary auxiliary contacts that allow us to connect and monitor this equipment. In these situations we have a few choices: search antique automation warehouses for spare parts, add interposing relays to convert the control voltage to a signal that can be monitored by the RTU, or just upgrade the hardware. In Selma we used a combination of each choice depending on the layout and configuration of the individual control panels.” The town was so pleased with the progress of the installation that they decided to tie-in the remaining seven wells to the SCADA system. These wells had direct lines to the water plant so staff could turn the pumps on and off from there. However, they could not see if they were actually running. By installing SCADA at all of the wells the complete water supply system could be controlled through the SCADA system. The other work at the Water Treatment Plant allowed the plant to start and stop based on the elevation of water in the elevated water storage tanks. “I wanted to get those improvements into the project.” says Grey. “I knew that it would be beneficial to the town to be able to see those tank levels and to have more automation in the plant so they wouldn't have to have someone sit there and turn it on and off over the weekends.”
Once the system was completed, they saw even more benefits. “They quickly started experimenting with some of the reporting features.” says Grey. “They suddenly were able to track the run times for each of the pumps and see which ones were turning off and on a lot and which ones were not. Then they started asking why. This allowed them to find hidden problems and increase the efficiency of the whole system.” During the installation process Carroll had anticipated these needs as much as possible. “The customer often doesn't know what they are going to need because they have never had a SCADA system before. We found ourselves adding features here and there because we knew that once the customer learned what was possible, there would be a few other things they would want.” “For example, levels from their water tanks provide control to the water treatment plant. Normally, it makes more sense hydraulically for a particular tank to handle that control. What happens when you need to do maintenance on that tank? You don’t want to have to run everything in manual mode. We gave them the flexibility, with a few keystrokes in VTScada to move control to one of the other three tanks. We don't nit-pick over things that may not have been part of the original spec. It's easier for us to add things in the beginning than later when the customer realizes what a SCADA system can do. That's what happened in Selma.” Reasons for Success “Sometimes the permitting process can be complicated. However, this project did not require a permit. Construction Grants & Loans (State) were only involved to make sure that stimulus requirements were followed. It was a fairly straight forward project.” Carroll gives credit to the technical support he received from Trihedral. “Their support is phenomenal. It was great to be able to just call and get a person. There were not a lot of hoops to jump through. They have a front line of support people but they can also pull in their engineers when they need the answer to a specific question. That helped to push us towards using VTScada.” Advice Images used with the kind permission of the Town of Selma
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A consultant, an integrator and a vendor discuss the factors for success such as open specifications
Creating an ‘Open’ Specification
VTScada HMI Software
Finding Hidden Problems and Increasing Efficiency 
