By Kristian Miang
In view of increasing water scarcity, all approaches have to be taken into consideration when it comes to ensure drinking water supply. Water leak detection by electromagnetic flowmeters is one easy way of reducing water losses, and at the same time it helps to reduce costs.
With an average of over 50% vanished water in many water distribution systems, the loss of water between treatment plants and consumers is substantial. As an example, Mexico City is supplied with 3.2 billion litres of water every day. It is assumed that more than half is lost during transition. The loss of water is typically attributed to several causes including measurement errors and theft, but leakage remains the major cause.
A conventional leakage control programme primarily consists of a water audit and a leak detection survey. The water audit involves the detailed analysis of water flow into and out of the distribution system, and is mainly carried out from behind the desk. It provides a rough indication of the water loss, but cannot identify the cause of the loss and even less the location of an eventual leakage. The leak detection survey traditionally involves a time consuming extensive check of the distribution system by use of acoustic equipment or other technologies such as thermography, ground penetrating radars, or even tracer gas.
Leak detection using flowmeters, on the other hand, is a very proactive approach. Basically, the entire distribution network is divided into discrete districts – the District Meter Areas (DMA) – and flowmeters are installed at strategic points throughout the distribution system. Earlier, leakage detection by flowmeters was always carried out at night and involved the systematic closing of valves, i.e. close down of whole parts of the network. Now, with the Siemens flowmeter Sitrans F M MAG 8000, no night work and shutting down of various parts of the distribution system is required.
The Sitrans F M MAG 8000 is a battery-powered electromagnetic flow meter comprising a transmitter and a sensor. The meter is obstruction-free and has no moving parts that are subject to wear and tear. It gives high measurement accuracy even under harshest conditions. Compared to traditional mechanical flow meters, the Sitrans F M MAG 8000 furthermore has the advantage of giving error messages in case it is defective. This means that a quick repair can be carried out and loss of valuable information will be reduced to a minimum.
Consumption profile monitoring
The first step in the MAG 8000 leakage detection procedure is to establish the consumption profile of the DMA. MAG 8000 features functions to visualise consumption, and with its builtin data logger it can record data up to 26 months and register alarms on too low and too high consumptions. Furthermore, it has a built-in IrDA interface and a pulse output for easy data collection on site and system integration. It is also equipped with a communication platform for a Modbus RTU (RS232 / 485) “add-on” communication solution.
The consumption profile shows the average consumption in different time intervals and provides the water system manager with an indispensable tool to gain knowledge about sitespecific consumption patterns. With a clear understanding of consumption patterns, the ability to predict water consumption is increased, which in turn strengthens the ability to not only supply water efficiently, but also to detect leakages.
The second step is to find the baseline flow. Here, the MAG 8000 flow meter is set to detect leakage in the DMA in the period where the flow is at its lowest – normally during the night. During leakage detection the MAG 8000 runs very short measurement periods, i.e. it totalises every tenth minute and uses this information to deduce the baseline leakage, which represents an average lowest flow. The accurate determination of a baseline flow is a precondition for realistically determining customers’ night use. Furthermore, any abnormal oscillations in the flow immediately become visible. In a situation where it is time consuming to perform an acoustic leakage survey, it can be beneficial to set the Sitrans F M MAG 8000 to automatic leak detection, say, once a week.
A comparison of the baseline flow of one DMA with similar DMAs also reveals areas of high leakage. This is imperative to any cost-efficient leakage control programme as it provides the possibility of dividing the distribution network into high and low priority zones thus using the resources spent on leakage detection efficiently.
Reducing water loss
The importance of an active leakage control programme cannot be questioned. The current best practice for water loss monitoring, assessment and reduction is definitely the continuous water consumption assessment. With advanced display of information, on-site data collection and remote monitoring via communication networks, MAG 8000 makes sure that all the information needed to optimise water supply and reduce water losses are gathered. Water is a precious resource – Sitrans F M MAG 8000 facilitates water loss reduction.