Water Journal : Water Journal April 2012
automation and telemetry water APRIL 2012 123 In addition to providing an alarm warning us the MNF was rising, we could also quantify the size of the leak. Leak detection was performed by sending a team out in a van to deploy noise loggers with radio communication and then download the data in a drive- by survey the following day to localise the leak position and use a ground microphone and correlator to pinpoint the leak. We have been using this equipment for many years and we have found that only loggers with radio communication could be used efficiently. The loggers are mounted directly on the pipeline with a magnetic connection to provide a good sound recording. It would often take this two-man crew five to ten days to find the leak in this large zone, driving an hour each way every day. The next strategy made to improve efficiency was to install additional flow meters within the zone to localise the leak position to a smaller area within the zone, and reduce the amount of time spent searching for the leak. We were not measuring or analysing total flow into sub-zones, we were just looking at significant changes in daily water flows to localise the leak positions. Our Next Improvement -- the Optimal Solution? With the previously identified systems, we were able to achieve good results. However, there was always still a certain amount of effort to carry the measured data to the office for any detailed analysis and then send a crew to pinpoint the leak before the leak is repaired. Because of our geographical situation, a lot of time was wasted driving back to the office to analyse the data and then back to the field to pin-point the leak. Therefore, we decided to introduce a system that transmits the data every day to the decision makers in the office to reduce the response time and travelling time. Noise loggers have been deployed through the network; as previously, they record the noise levels and sound. If pre-determined limits are exceeded, the logger sends a leak alarm to headquarters. Each logger is connected by radio with a repeater. All repeaters are in contact with a data collector (ALPHA), using radio to collect the data from the repeaters and GPRS to send the data to the server. We then have immediate access to the measurement data and can make a leak assessment. By modeling the system with geographic network data, the loggers are able to recognise their position in the network and create the relationship to its "neighbouring" loggers. This fact allows a direct correlation between the loggers and, thus, a quite precise determination of the leak. The installation was fast and economical, without any structural changes to the distribution system. Eighty loggers, 42 repeaters and two Zonescan ALPHA were deployed in the Braunhartsberg pressure zone, enabling fully automated leak monitoring of the entire zone, consisting of 52km of pipe. Assessment Communication reliability: We found the communication to be very good, without the need to install an antenna close to the surface. Batteries lifetime: We operate in a temperature range from --30°C in winter to +30°C in the summer. In 12 months of operating the Zonescan, there have been no problems. Zonescan correlating noise logger deployed magnetically on a hydrant. Zonescan Repeater installed on Streetlamp Zonescan Alpha installed on a mast above the water tower Figure 4. Installation pictures of the noise logger, radio repeater and GPRS data collection unit. Figure 5. Braunhartsberg pressure zone in Zonescan net software.
Water Journal May 2012
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