Data Loggers Monitor Pump Runtimes
In order to reduce water pollution, current federal clean water regulations mandate that wastewater collection systems control the amount of stormwater infiltrating sewage pipes during wet weather. To help control the amount of incoming stormwater, wastewater utilities typically conduct routine inspections on sewer pipes to make sure there are no cracks or leaks, also known as infiltration testing. While this helps locate and fix problems, infiltration testing can be both time-consuming and costly.
South Haven Sewer Works, Inc. of Valparaiso, Indiana has implemented a cost-effective way to minimize the amount of time and money spent on sewer pipe inspection. According to company president David Saylor, the company has been able to turn area lift stations, which act as large sump pumps for elevating wastewater from deep ground levels, into flow meter-like monitoring stations.
“We knew that by monitoring the runtime of lift station pumps, we could understand a lot about flow rates, and ultimately know whether or not stormwater was getting into the upstream pipes during periods of rain or melting snow,” Saylor explains. To monitor runtimes, Saylor evaluated a number of products, from programmable logic controllers (PLCs) to specialized motor runtime monitoring devices. While these products would perform sufficiently, most would require the use of a computer at the lift station site to collect the data, and, in some cases, an additional current-sensing module that would have to be hard-wired into the lift station’s electrical control system. Besides the high expense, these products have a steep learning curve, according to Saylor. This left him “frustrated by the total installation cost.”
“One of the things I like to do,” explains Saylor, “is to go outside my industry, learn about different products and techniques, and then try to bring them into what I’m doing. I happened to be reading a magazine article about the use of data loggers from Onset in a frozen food transportation application. The data logger was used for continuous temperature monitoring. I did some research on the web about Onset data loggers and discovered that they also offered motor on/off loggers. The cost seemed right, and since the devices are battery-powered, we wouldn’t have to deal with any wiring issues.”
Saylor chose Onset’s HOBO® H6 State on/off data loggers, which record on/off status changes, and electronically store time, date, and state information for each change. The H6 incorporates a microprocessor, an internal current sensor, and a user-replaceable battery into a compact, durable housing slightly larger than a matchbox. Two H6 loggers are mounted close to the primary electrical leads attached to each of the lift station’s pumps. Data is collected for each pump cycle. A week’s worth of data is retrieved by South Haven field personnel, using a HOBO shuttle. This hand-held device can offload and store the data from each logger, and then be taken back to an office computer where the data can be graphed and analyzed using Onset’s BoxCar Pro software.
”Once we have collected and analyzed the runtime data, we can compare the pump on/off timing sequence with precipitation data we collect using a weather station,” says Saylor. “If we see a significant increase in pump runtime during a period of precipitation, then we know stormwater is getting into the pipes. If we don’t see a significant change, we know that during pipe inspections, we do not have to include infiltration testing.”
He adds, “For our application, battery-powered data loggers proved to be the most cost-effective way for us to sense runtime. It assures us that we are in compliance with clean water regulations, and gives us a good approximation of how wet weather influences flow rates at given points of the collection system. Most importantly, it has helped us minimize inspection time, which saves us a lot of money.”
For more information about data loggers, please contact Onset at 1-800-LOGGERS, or visit www.onsetcomp.com.