EP2097729A2

EP2097729A2 - Method and device for detecting and/or quantifying water leaks

Info

Publication number: EP2097729A2
Application number: EP07870340A
Authority: EP
Inventors: Daniel Getto; Patrick Burghoffer
Original assignee: Commissariat a lEnergie Atomique CEA
Current assignee: Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Priority date: 2006-12-12
Filing date: 2007-11-27
Publication date: 2009-09-09
Also published as: CA2672255A1; JP5027244B2; US20100064776A1; WO2008081089A3; FR2909764A1; FR2909764B1; WO2008081089A2; JP2010512476A; US8342006B2

Abstract

The invention relates to a method for detecting and/or quantifying water leaks in a water pipe, and to a device for realising said method. The method of the invention comprises measuring the water flow rate in the pipe in at least two different locations, i.e. one downstream and one upstream relative to the suspected leak, the water flow rate being measured by injecting a tracing agent that modifies the water conductivity instantaneously at an upstream location and a downstream location relative to the suspected leak location, continuously measuring the water conductivity downstream from said locations and, from the conductivity values, calculating the water flow rates upstream and downstream relative to the suspected leak location in the pipe. The method of the invention can be used for quantifying a leak flow rate that can even be a very small one.

Description

METHOD AND DEVICE FOR DETECTION AND / OR QUANTIFICATION

LEAKS OF WATER.

The invention relates to a method for detecting and / or quantifying water leaks on a water pipe and a device for carrying out this method.

Water has become a highly guarded and increasingly valuable commodity for most countries around the world. The distribution of drinking water is therefore the subject of all attention. According to various surveys carried out both in France and abroad, everything tends to prove that a significant part of the water distributed is lost due to leaks on the distribution network.

For example, according to a survey conducted in 1991 in Canada by the International Association of Water Distributions (AIDE), the amount of water lost or "not counted" would be between 20 and 30% of total production.

Similarly, the French Institute of the Environment (IFEN) estimates that for about 6 billion cubic meters of water distributed in France in 2001, only three quarters of these volumes were billed to subscribers, the rest being a small part (3%) by unbilled volumes and especially by network leaks of around 24%. These leaks are mainly caused by corrosion, defects in materials, faulty installations, ground movements, vibrations or excessive loads due in particular to traffic, absence or lack of maintenance ...

In addition to the economic loss caused by the shortfall of the distributors, other problems are added, such as public health risks as a result of the leakage of contaminants into the distribution networks.

Economic pressures, the threat to public health and the need to save water are driving water system operators to implement leak detection and quantification programs to eliminate them. The detection of major leaks on a network is most often well controlled by an automatic monitoring of flows that can detect an unusual increase in water consumption in a specific sector. The location of the leak can then be done according to various methods of which the most widespread are the use of ultrasound or acoustic signals, but also by non-acoustic techniques namely the use of tracer gas, geo radars or even infrared imaging

While these methods appear satisfactory to managers with respect to relatively large leaks, high measurement sensitivity is required to capture and locate smaller leaks that are also "quieter".

According to a recent study conducted at the National Research Council of Canada, the problems that usually hinder the use of acoustic instruments to locate leaks, such as interference caused by traffic noise and weakening of signals along are accentuated in the case of plastic pipes, which leads most operators to doubt the effectiveness of acoustic detection equipment. This is a thorny problem because of the increasing use of plastic pipelines in water systems around the world.

There is therefore a difficulty in apprehending and locating leaks of water on a drinking water network by using the various known methods and without being able to quantify a leakage flow, as low as it is.

The invention aims to overcome the disadvantages of prior art detection methods due to the use, in particular, of plastic pipes and especially to allow the quantification of a very low leakage rate.

For this purpose, the invention proposes a method for detecting and / or quantifying a water leak on a water pipe of the type consisting in measuring the flow of water in the pipe in at least two points of water. this pipe, one downstream, and the other upstream of the supposed leak. In the method of the invention, the measurement of the water flow is performed by measuring the conductivity of the water.

For this, in the method of the invention, is injected upstream and downstream of the supposed point of water leakage, and instantaneously, a tracer changing the conductivity of the water.

The conductivity of the water, time t1 tracer injection until time t2 where the conductivity of the water returns to its initial value, is then measured.

The tracer selected for conductivity measurements must first be a good tracer of water, that is to say faithfully reflect the movements of water. In the particular case of drinking water, the tracer must have zero toxicity or acceptable by the water distributors. Therefore, in the invention, the preferred tracer is sodium hypochlorite, NaOCI (bleach) already used in abundance in drinking water to maintain a correct treatment thereof and which will be detected by a measure conductivity meter. Other tracers are conceivable such as Cb (already used in drinking water purification objectives) and therefore nontoxic in the context of this application.

The conductivity measurement is performed using a device comprising two electrodes, the device being placed in the pipe in which the water flows, and imposing an alternating current between the two electrodes, which has the effect of migrating the ions each to an electrode according to its electric charge, and to cause a current.

The resistivity R and the conductivity C of the solution can be accessed from the measurement of the intensity of the current according to the relation C = 1 / R. Conductivity therefore characterizes the capacity of the solution to conduct the current and is directly proportional to the concentration of ions present in the volume delimited by the measuring cell.

Thus, in the method of the invention, the tracer is injected instantaneously at a point 11 upstream of the water leak and at a point 12 downstream of the water leak, and a conductivity measurement is performed. continuously in each of these two points of observation to follow the function of passage of the tracer.

After numerical processing and computation according to the method of Allen described in "Theory of the method of Allen and its practical consequences for the measurement of flows in pipe", by J. Guizerix and R. Margrita published in the Houille Blanche n ° 3 / 4-1976, p291-296, the difference of the first order moments of the conductivity evolution curves obtained makes it possible to calculate the average speed of the water and, knowing the section of the pipe, the flow is accessed directly. flow in the pipe at the level of the conductivity measuring cells.

This type of measurement can be renewed at several points of the network, and thus, by successive differences, makes it possible to highlight a possible flow difference which indicates a leak on the water pipe between the two points considered.

This technique has the advantage of being able to quantify the leakage rate and to locate the leakage between the two measurement points. To locate the leak very precisely, we can then use an acoustic method.

More specifically, the measurement of the conductivity of the water circulating upstream and downstream of the assumed leak is performed by positioning in the pipe, upstream and downstream of the assumed leak point, a conductivity measuring cell, each cell consisting of two devices for measuring the conductivity and a tracer injection point. It should be noted that the distance between two cells has no particular impact on both the detection and the quantization of the leak.

Each measuring device consists of two electrodes, one of which forms the body of the device, this body allowing the passage of water, and the other electrode being electrically connected but isolated from the first electrode (the body of the device ) and dipping directly into the flow of flowing water.

Preferably, the electrodes are made of stainless steel. Each device is provided with flanges for connection at each end of the water pipe.

The invention will be better understood and other features and advantages thereof will appear more clearly in the light of the explanatory description and the examples which follow, which are given with reference to the figures in which: FIG. 1 schematically represents the principle of detection of a leak on a pipe according to the invention, Figure 2 shows a photograph of a conductivity measuring device according to the invention, connected to a water distribution pipe, Figure 3 schematically shows the conductivity measuring device according to the invention shown in Figure 2, and Figure 4 shows the conductivity curves obtained at a conductivity measuring cell, in a particular embodiment of the invention.

The principle of detecting a water leak on a water pipe according to the invention is schematically illustrated in FIG.

The method of the invention therefore consists in instantaneously injecting at a point denoted II in FIG. 1, located upstream of the supposed vanishing point, denoted F in FIG. 1, as well as at a point noted 12 in FIG. downstream of the supposed leak point F, a tracer changing the conductivity of the water.

The conductivity of the water flowing in the pipe, denoted 1 in FIG. 1, is then measured continuously, from the moment t1 of the injection until the moment t2 of return to the initial value of the conductivity, between the points noted A1 and A2 in FIG. 1 on the one hand, and, on the other hand, between the points marked B1 and B2 in FIG.

The conductivity is measured by placing, at each of the points A1, A2 and B1, B2 conductivity measuring devices denoted respectively 2, 3 and 4, 5 in Figure 1.

As can be seen in FIG. 1, the conductivity measuring device 2 is located downstream of the injection point 11 but upstream of the conductivity measuring device 3, the devices 2 and 3 being situated upstream of the assumed leak point F, and the conductivity measuring device 4 is situated downstream of the injection point 12 and upstream of the point B2 to which is positioned the conductivity measuring device 5.

From the conductivity curves obtained at the points A1, A2 and B1, B2, the flow of water Q1 flowing in the pipe 1 upstream of the supposed leak point F and the flow of water Q2 flowing in the pipe 1 in downstream of the assumed vanishing point F, are calculated by the Allen method. If a difference between the flow rates Q1 and Q2 is found, this reveals a water leak between points 11 and 12. In addition, the flow rate of this leak is quantified.

A photograph of a conductivity meter in place in line 1 is shown in FIG.

As seen in FIG. 2, in which the device for measuring the conductivity of the invention is denoted 2, the device of the invention consists of a hollow body 6 positioned in the pipe 1 and allowing the circulation of the water in the pipe 1 and the body of the device 6.

The conductivity measuring device 2 is connected to each end of the pipe 1 by flanges marked 8 and 9 in FIG.

In the hollow body 6 of the device 2, plunges an electrode denoted 7 in FIG.

The structure of the conductivity measuring device according to the invention is more precisely shown schematically in FIG.

As can be seen in FIG. 3, the conductivity measuring device 2 according to the invention consists of a hollow body 6 forming a first electrode and in which water circulates from the pipe 1 (not shown). hollow body 6 is connected by the flanges 8 and 9.

A second electrode 7 electrically isolated from the hollow body 6, but connected thereto, is positioned to plunge into the flow of water flowing in the hollow body 6.

Preferably, the hollow body, that is to say the electrode 6, and the electrode 7 are made of stainless steel. Several examples of implementation of the method of the invention will now be described by way of illustration and not limitation.

In particular, the distances between measurement points, between the injection point and the measuring cell, are easily adaptable by those skilled in the art. Thus, the distance between the injection point and the first measurement point must be sufficient to have a good homogeneity of the tracer in the section when the latter reaches the measurement point. This distance called "good mixing" generally follows the following rule: it usually takes a distance of 50x the diameter of the pipe.

Example 1

This example will be described with reference to FIGS. 1 and 4.

Tests were carried out on a pipe 1 with a diameter of 53 mm and in which the water flow rate is 1000 l / h.

Four conductivity measuring devices 2, 3, 4, 5 have been placed in this pipe 1.

In this example, the devices 2 and 3 are spaced from each other by a distance of 3.8 m, and the devices 4 and 5 are spaced from each other by a distance of 3, 8 m.

The devices 3 and 4 are spaced from each other by 10 m of the supposed leakage point F. The hollow body 6 had a diameter of 53 mm and a volume of 220 cm ³ .

The hollow body forming the electrode 6 and the electrode 7 are made of stainless steel.

1 mL of sodium hypochlorite (bleach 10% active chlorine), is injected instantaneously at time t1 injection points 11 and 12. The injection point 11 is located 2 meters upstream of the device 2, and the injection point 12 is spaced 2 meters from the device 4.

From the injection time t1 to the time t2 at which the conductivity of the water returns to its initial level, the evolution of the conductivity is recorded as curves at points A1, A2 and B1, B2.

The conductivity curves obtained at the points A1 and A2 of measurement are represented in FIG. 4 in which the curve recorded at point A1 is denoted 10 and the curve recorded at point A2 is denoted 11. From these curves and those obtained at points B1 and B2, the flow rates Q1 and Q2 upstream and downstream of the leak F are calculated.

Each flow Q1 and Q2 is obtained by the formula Q = V / Δt where V represents the volume of the section between the two cells and where Δt represents the difference between the average time of the first curve and the average time of the second curve. The average time of each curve is obtained by the center of gravity of the curve. This data is easily accessible by the mathematical treatment of a curve. One could also consider taking the average time corresponding to the top of the curve, a value that can be confused with the gravity of the curve in case of perfect Gaussian. Other mathematical curve treatments are conceivable, such as deconvolution treatment. All these methods are known to those skilled in the art.

The calculated leakage values are reported in Table 1 below.

Table 1 Example 2

The same tests as in Example 1 were carried out except that the flow rate of the water flowing in the pipe 1 is 2500 l / h.

The calculated leakage values are reported in Table 2 below.

Table 2

Thus, it can be seen from the difference Q1 - Q2 that, by the method of the invention, low leakage rates can be detected and quantified, these low leakage rates corresponding to leakages of 5 to 10% of the nominal flow rate. . In addition, it has been found that the difference between the values measured by the Allen method and the actual leakage values is globally less than 5% and of the order of 15% for very low flow rates. Note also that the higher the flow is important, the better the sensitivity.

The same tests were carried out for a pipe diameter of 100 mm. The results obtained are identical.

The method of the invention can be applied to all drinking water networks but also to other types of pipe flow for which there is no reliable means of leakage measurement as minimal as it is.

Claims

1. A method for detecting and / or quantifying a water leak (F) on a water pipe (1) of the type comprising measuring the flow rate of the water flowing in the pipe (1) in at least two distinct points, one downstream of the assumed leakage point F, and the other upstream of the assumed leakage point F, characterized in that: the measurement of the flow of the water is carried out by injecting at a point 11 upstream of the assumed leakage point F and a point 12 downstream of the assumed leakage point F, a tracer changing the conductivity of the water, and by measuring the continuous water conductivity downstream of the each of the points II and 12 during a period starting at the time t1 of the injection until the time t2 at which the conductivity of the water returns to its value before injection of the tracer, and calculating from these values the flow rates Q1 and Q2 of water flowing upstream, and downstream of the leakage point F assumed in the pipe (1).

2. Method according to claim 1 characterized in that the tracer is bleach (NaOCI).

3. Method according to claim 1 or 2 characterized in that the measurement of the flow rate Q1 and the flow rate Q2 is carried out: a) by placing at least four devices (2, 3, 4, 5) for measuring the conductivity of the water, each device comprising two electrodes (6,7) electrically insulated, one (6) of which constitutes the body of the cell and the other (7) is in a central position directly in the flow of water flowing in the pipe 1, the body of the device constituted by the electrode 6 allowing the passage of water, and b) by imposing an alternating current between the two electrodes (6) and (7), the first device (2) being located in the pipe at a point A1 downstream of the injection point 11 and upstream of the assumed leakage point F, the second measuring device (3) being located at an A2 point downstream of the A1 point and upstream of the vanishing point; F assumed, the third device (4) being located at a point B1 located downstream of the injection point 12, and the fourth device (5) being located at a point B2 downstream of the point B1.

4. Method according to claim 3 characterized in that the electrodes (6, 7) of each device (2, 3, 4, 5) are stainless steel.

5. Device (2) for measuring the conductivity of water for carrying out the process according to any one of the preceding claims, characterized in that it comprises: a hollow body (6) constituting a first electrode, whose diameter is preferably equal to the diameter of the pipe (1), a second electrode (7) connected to the hollow body (6) but electrically isolated therefrom, and centered in the hollow body (6), and two flanges (8, 9) for fixing each end of the hollow body (6) respectively to one end of the pipe (1).

6. Measuring device (2) according to claim 5 characterized in that the electrodes (6, 7) are stainless steel.