The municipal water system in a North Carolina town is comprised of several remote well
sites, two 500,000-gallon water storage tanks, and one filtration plant. Water is pumped
from each well site through the filtration plant and into the tanks. Before the summer of
2000, the water system was manually controlled with no formal data collection, storage, or
reporting mechanism. Residents calling with problems served as the alarming system for
system faults. And the process of troubleshooting the problem often started with a guess
at which remote site was experiencing the problem, often resulting in several sites
visited unnecessarily.Synchrony,
headquartered in Roanoke, VA, was selected to design, build, and install the control
system necessary to automate the municipal water system. Synchrony’s solution for the
town was based on Allen-Bradley's SLC 5/03 and 5/04 processors and RSView32 software. The
town’s management and engineers were particularly impressed with the hardware and
software because of its high reliability, maintainability, open architecture, and clear
upgrade paths. West Jefferson selected Synchrony because of the scalability and robustness
of the design, and because of Synchrony's expertise in automating water and waste water
systems.
 Synchrony’s design has
an RSView32 SCADA system centrally located in the town hall. The SCADA monitors, displays,
and collects data from seven SLC processors via RF modems. Nearly identical ladder logic
programs were developed for each of the remote well sites and each storage tank. This
"generic" ladder logic design allowed Synchrony to develop two different ladder
logic programs (one for well control and another for storage tank control) that required
only minor modifications to handle the five different types of wells and two storage
tanks. A third ladder logic program was developed for the filtration plant.
With nearly identical ladder logic
programs on the SLC processors, it was very straightforward to program the SCADA system
using node swapping. As with the SLCs, two monitoring screens were developed (one for well
monitoring and another for storage tank monitoring) in RSView32. Each site has its own
folder of RSView32 tags and node swapping is used to change the set of tags used according
to the site selected for investigation. A third screen was developed for monitoring the
filtration plant. In addition to the monitoring screens, the SCADA application includes
overview screens, trending, alarming, data recording, and reporting functionality.
The design developed by Synchrony
is relatively easy to expand as more well sites and storage tanks are added. The existing
SLC ladder logic can be simply copied to new sites with only minor changes required to
identify the site. An existing folder of RSView32 tags can be duplicated with a new folder
name and quickly pointed to the new processor. The node swapping routines will make sure
the proper data is displayed for the selected site.
The implementation of this system
has provided the town with many benefits. Water system troubleshooting now begins before
traveling to a remote site. Centralized data collection allows trends to be analyzed for
future use predictions. Alarming now notifies the town engineers of problems instead of
residents having to report problems.
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