Water/Wastewater
29
Effective Reduction of Water Losses Intelligent Monitoring System Detects Leaks Rapidly and Reliably
Exact knowledge of water losses in drinking water supply networks is an elementary requirement for efficient operation and for the planning of maintenance measures. A specially developed, continuous monitoring system detects leaks in pipeline networks rapidly and reliably, thus helping to reduce water losses. The clamp-on flowmeters used allow simple and cost-effective retrofitting of the required instrumentation.
The demand for clean drinking water is rising, and it is becoming increasingly scarce as a valuable resource – a pressing global problem of our time.
A metropolis like Berlin uses approximately 585,000 cubic meters of drinking water per day. The water networks of municipalities and cities are extremely complex systems in which leaking pipes can rapidly lead to high costs and significant financial losses.
It is essential to detect leaks at an early stage. 90 percent of all water losses result from minor leakages where a period of 100 or more days can pass before they are detected. Altogether, these water losses are usually significantly higher than those from large pipe bursts which are noticed far more quickly.
Water loss volume = leak rate (in m3/d or l/h) x duration (in d or h) per leakage (in accordance with German drinking water worksheet DVGW W392)
Continuous monitoring works magic
Especially for such problems, Siemens has developed an ingenious monitoring and localisation system called Siwa LeakControl which allows rapid and reliable detection of leaks. The continuous monitoring system checks the pipeline network and automatically indicates areas in which a leak has occurred. What is more: it is unnecessary to produce hydraulically separated zones – a great advantage.
The system's method is based on the monitoring of changing flows compared to reference values. For this purpose, sensors are permanently installed at appropriate positions in the network in order to record the inlet and outlet flows of the drinking water in these zones. The best time for such measurements is between two and four o'clock in the morning, since the flow quantity is relatively low and uniform during this period. This increases the success rate and also reduces the number of false alarms. The measuring instruments are permanently active. However, the data is only recorded within an individually defined period in the PLC, preprocessed, and sent to the central unit. Usually three values (min., average min., and max.) are recorded and transmitted from one measuring point per measuring interval. If necessary, however – e.g. for display in the control system – values can be recorded cyclically and transmitted without preprocessing.
The components (transmitter, power supply, backup batteries, controller, and communication) are integrated in an instrument cabinet and the measured values transmitted wirelessly via GSM/GPRS to special evaluation software.
Flexibility is the key Author Details:
Christian Pust, Siemens AG Tel: 0721-595-6893
Email:
christian.pust@siemens.com
A great advantage of the system is that it can be flexibly expanded according to requirements and available budget. Complete coverage of the network is not essential. For example, the first measuring points can be installed by the water suppliers at sensitive positions, i.e. in areas with an increased probability of damage. The Siwa LeakControl system is equally suitable for monitoring small networks with few measuring points or for monitoring hundreds of points in a megacity. Practically no limits exist for the system, since it can be used for almost all sizes and
Figure 1: Siwa LeakControl system from Siemens including Sitrans FST020 trans- mitter for clamp-on flow measurement
types of pipeline. Autonomous use of the Siwa LeakControl software is possible, but the data can also be passed on via an interface to a Scada system (e.g. Simatic WinCC).
This innovative system for early detection of leaks and continuous monitoring of water networks helps to keep water losses as low as possible, which significantly reduces maintenance overhead. It can increase the cost effectiveness of the water supply and reduce consequential damages. Siemens offers customers expert advice and planning in the area of network hydraulics to enable optimum selection of mounting positions for the individual monitoring points.
State-of-the-art flow measurements
An essential component of the solution is the instrumentation. Ultrasonic and electromagnetic instruments are the most widely used technologies for flow measurements on drinking water pipelines:
Ultrasonic flowmeters operate according to the transit time procedure. The sonar wave starting at point A and transmitted upstream reaches the detector at point B faster than the wave transmitted downstream. Ultrasonic transducers function as transmitters and detectors for the ultrasonic signals. The accuracy of ultrasonic flowmeters depends on the
www.envirotech-online.com IET September / October 2012
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