Case Study: Rooks County RWD#3 Controls Upgrade
Rooks County Rural Water District #3 is a small water utility in north central Kansas that serves small communities and farmers. Their facilities include one water tower and 3 different well sites, scattered around the county. These sites are so geographically separated that to drive to every site in a loop was over 50 miles.
The RWD commissioned a study of their system. This study indicated that they needed to build another water tower and upgrade and install new water main piping to provide more interconnection between various parts of their system and to provide better pressure in all parts of their system. As part of this physical upgrade, it was recommended that a new control system be installed to replace the existing hardwired controls.
The biggest issue was how to connect all of the well sites, the two towers, and the office together to provide a cohesive control system that controlled tower levels and provided new functionality to the operator by providing a centralized location to control the system and also provide 24/7 monitoring of the system and alarm notification when something goes wrong. In addition, it was desired to have additional information that would help the district fill out the state required reports for volume of water used.
Geography is the biggest single obstacle to overcome for this system. The straight line distance from the office to the new water tower was approximately 26 miles and the distance from the new tower to the existing tower and well site was an additional 13 miles.
Studying the system revealed that a radio based communication system would work, because the height of the towers and the geography of the land created good line of sight between all of the locations that would have control. It was decided to utilize MDS iNET-II radios, which provide the ability to create an over the air Ethernet network. The listed range for these radios is 30 miles, so it was pushing the envelope of the radio’s capability.
Another advantage of the selected radio was it is an unlicensed radio, meaning a FCC license was not required to install and operate this system. In addition these radios, being Ethernet, provide much higher data transfer rates over similar radios that are only able to communicate serially.
Allen Bradley MicroLogix 1100 PLCs were selected as the controller for the project. These controllers have a built in Ethernet port, so they are able to directly connect to the radios and communicate with other PLCs or the operator interface. These controllers are also very reasonably priced, so they fit into the overall project budget.
Each tower had two level transmitters installed to detect the tower level. Since tower level is critical to the proper operation of the system, it was decided that having redundant transmitters was very beneficial to the project.
At the main office, Rockwell Software’s RSView32 was selected as the computer based operator interface. Graphic screens were built in this system to show the level in the two towers and the status of each of the wells in the system. This is also the location where the operator can set for each well at what level that well will turn on and off, and at what levels are high and low alarms generated. In addition, each well could be manually turned on and off from the central location if needed.
The system was also configured to log tower levels, flow rates, when wells started and stopped, well runtime hours, and flow totalization data. This information was provided in trend charts for the operator to review when diagnosing problems with the system.
This computer was also equipped with a voice card, and configured so that whenever any alarm occurred in the system, it would dial out to the operator and notify him of the condition. In addition, a remote access modem was installed, which provides a telephone line to Ethernet conversion, and allows the ability to dial into the system and assist the operator in troubleshooting problems, and making requested logic changes without having MAC travel to the project site.
The system was installed, and commissioned, with the RWD reaping immediate benefits. Gone were the days that a phone call from an angry customer was the first indication that there was a problem with the system. Now they get calls from their computer, notifying them of a problem long before they run out of water. In addition, because of the specific alarm notification, they can bring appropriate manpower and materials with them to the site thus reducing travel time, and also shortening repair times.
In addition, Ann, the RWD#3 manager stated “It is very beneficial to have the ability to remotely access the system to resolve problems very quickly, without having to pay for a site visit by MAC”.