WO2013039397A1

WO2013039397A1 - System for detecting leaks in a fluid conduit wall, fluid conduit including the same, method and use

Info

Publication number: WO2013039397A1
Application number: PCT/NL2012/050648
Authority: WO
Inventors: Martin VAN DER VEEN; Johannes Bernardes KUNST; Cornelis Rensen; Hendrikus Wilhelmus Maria Paulus FRIEDERICHS
Original assignee: Plasticon Europe B.V.
Priority date: 2011-09-16
Filing date: 2012-09-14
Publication date: 2013-03-21
Also published as: NL2007437C2

Abstract

System for detecting leaks in a fluid conduit wall, including: -at least a first electrode (1) for electrically contacting an interior of the conduit (C); - an array of at least two electrically conductive layers (3) extending through the conduit wall (W), the conductive layers (3) being electrically isolated from the interior of the conduit (C); -at least one electrical connection (7) for electrically interconnecting adjoining conductive layers (3), wherein an electrical resistance of the connection (7) is higher than an electrical resistance of each of the conductive layers (3); and -at least one current detector (8), electrically connected to at least one of the electrically conductive layers (3), for providing a current detection signal.

Description

Title: SYSTEM FOR DETECTING LEAKS IN A FLUID CONDUIT WALL,

FLUID CONDUIT INCLUDING THE SAME, METHOD AND USE

The invention relates to a system for detecting leaks in a fluid conduit wall.

Fluid wall leak detectors are known from the prior art, see for example WO2007/141153. Particularly, this publication discloses a method to detect the failure of multilayer plastic pipes comprising at least one inner layer of plastic material, at least one layer of a conductive material (solid conductor) adhered to said inner layer and at least one further plastic layer adhered to the surface of the conductive material opposite to the surface adhered to the inner plastic layer. The fluid present inside the pipe is a conductive fluid (fluid conductor). The known method includes electrically connecting in series or in parallel at least one electrical generator and at least one electric current measuring instrument to the solid conductor and to the fluid conductor present inside the pipe, apply a voltage V(A) and measure the flowing current in a first position (A), applying a voltage V(B), equal or different from the voltage V(A), in a second position (B) and measure the flowing current, and determining the failure position.

The known method includes determining a failure position using the known resistance of the fluid conductor. The assumption is made that the resistance of the solid conductor is negligible compared to the fluid resistance and a resistance of a resistor created by fluid escaping through a failure. The publication reports test results regarding a relatively short 2.04 meter polybutene pipe having an aluminium conductive layer.

The publication proposes that a network of plastic pipes can be provided, using 'passive plastic pipe joints' for interconnection of conductive layers and 'active plastic pipe joints' for connection to an electrical generator and an electric current measuring instrument. Publication EP0511343 discloses a device for monitoring the fluid- tightness of open-air or buried pipes and structures made of thermoplastic material. The wall of the device is surrounded by a homogeneous electrically conductive layer extending around the entire periphery and length. The electrically conductive layer is connected by cables to one terminal of a remove high-resistance ohmmeter; another terminal of the ohmmeter is connected to a counter-electrode. The document further proposes to device the pipes and structures into a number of adjacent portions that are electrically insulated from one another, wherein each individual portion is connected to the ohmmeter by respective cabling.

A problem of know proposals is that they are relatively hard to implement in a true, reliable working construction, on site (for example before being buried underground or under a concrete floor). Know solutions assume that all elements of the system will always function as required, and do not take into account potential failure of part of the system, such as the breaking of one of the wires that leads to a remote measuring device, or failure of an electrode. Failure of part of the system can lead to two highly undesired conditions: ignoring a leak, and vice-versa the generating of an alarm without any leak being present.

The present invention aims to provide an improved leak detection system. Particularly, the invention aims to provide a durable and reliable system that can extend over long distances (for example at least 100 meters), wherein false leak detection can be suppressed as much as possible. Also, the invention aims to provide a system having good manufacturability, and having improved handing and installation characteristics.

According to the invention, to this aim there is provided a system that is defined by the features of claim 1.

According to an aspect, a system for detecting leaks in a fluid conduit wall includes: -at least a first electrode for electrically contacting an interior of the conduit;

- an array of at least two electrically conductive layers extending through the conduit wall, the conductive layers being electrically isolated from the interior of the conduit;

-at least one electrical connection for electrically interconnecting adjoining conductive layers, wherein an electrical resistance of the connection is higher than an electrical resistance of each of the respective conductive layers; and

-at least one current detector, electrically connected to at least one of the electrically conductive layers, for providing a current detection signal.

For example, the conduit wall can include a plurality of sections having two or more discrete electrically conductive layers, wherein each neighboring pair of conductive layers is interconnected by an electrical connection having the relatively high electrical resistance. Thus, the conductive layers are not electrically isolated from each other.

During operation, fluid having a certain electrical conductivity can be fed through the conduit, and electrical power (e.g. AC or DC power) can be applied to the at least a first electrode (contacting the fluid). In case of leakage at one of the electrically conductive layers, the applied electrical power can induce electrical current in that electrically conductive layer, the current flowing to and/from at least one current detector. The current detector may be electrically connected to that specific electrically conductive layer that is located at (i.e. surrounds) the location of leakage.

Since the electrically conductive layers are electrically

interconnected, via said electrical connection having the relatively high electrical resistance, the current detector can also be a detector that is connected to another (remote) electrically conductive layer than the layer that is located at the location of leakage. In a preferred embodiment, several current detectors are provided, the current detectors being connected to different electrically conductive layers of the array of layers, wherein a leakage related electrical current can flow via the conductive layers and respective electrical interconnection(s) to and/from several of the current detectors.

Thus, reliable leak detection can be achieved. A leak at a certain section of the conduit can be locally detected, via a respective first detector that is directly connected to a first conductive layer surrounding a leak location, but also remotely by another detector that can be indirectly in contact with the first conductive layer, via one ore more intermediate first conductive layers and respective one or more interconnections.

Moreover, the electrical connection having the relatively high electrical resistance can provide information concerning the leak location, since it will affect the amount of electrical current.

Preferably, the system includes a plurality of current detectors, electrically connected to different conductive layers of the array of layers. The various current detectors can be used to mutually verify detecting signals. Also, the function of a failing detector of the plurality of detectors can be taken over by the remaining detectors. This, a leak can still be detected in case one of the current detectors is out of operation.

Each said electrical connection, having the relatively high electrical resistance, between adjoining conductive layers can be configured in several ways. Herein, it should be noted that the term "electrical resistance" includes electrical impedance, particularly for the case that use is made of alternating current.

For example, a said electrical connection can be an intermediate section of the conduit that extends between opposite ends of two conductive layers of the array of layers, the intermediate section being electrically conductive and having the relatively high resistance.

In a further embodiment, adjoining conductive layers of the fluid conduit can be mutually isolated by an insulator, e.g. an insulating intermediate conduit section, wherein the insulator is bridged by a said electrical connection of the relatively high resistance. This provides particular advantages from manufacturability point of view, whereas the bridging electrical connection can be configured to provide a predetermined local bridging resistance value at high accuracy.

According to a further embodiment, the electrical resistance of each said (bridging) connection has a predetermined resistance value. For example, the resistance can be higher than 1 ΜΩ and lower than 100 ΜΩ (under normal operating conditions). The resistance of each said electrically conductive layer (measured between opposite ends of the layer) can be significantly lower than said predetermined resistance value. As an example, each said electrically conductive layer can have a resistance that is lower than 0.1 ΜΩ, particularly a resistance that is lower than 10 kQ, for example a resistance in the range of resistance about 0-1 1 kQ. Thus, e.g., the electrical resistance of each said connection can be at least 10 times the resistance of each of the respective conductive layers, preferably at least 100 times and more preferably at least circa 1000 times.

In a further embodiment, the system includes a plurality of electrical interconnections, for connecting three or more conductive layers of a layer array. In that case, advantageously, all electrical interconnections provide the same predetermined resistance value. Alternatively, use can be made of different electrical interconnections having mutually different resistance values.

In a preferred embodiment, said electrical connection between adjoining conductive layers is at least partly integrated with the fluid wall.

In a preferred embodiment, said electrical connection between adjoining conductive layers includes a resistor element, providing the relatively high resistance of the connection.

Also, in a preferred embodiment, said electrical connection between adjoining conductive layers can include a printed circuit board, having conductive parts (e.g. electrical terminals) that are connected to the conductive layers. The printed circuit board can be provided with a said resistor element, and may optionally also include various electric or electronic components, for example a current detector, one or more terminals for communicating with a remote data processing unit and/or current detector.

In a further elaboration, the fluid conduit includes at least two pipes that are connected in a fluid-tight manner at opposite ends, each of the pipes being provided with an array of at least two electrically conductive layers extending through the pipe wall, the conductive layers being electrically isolated from the interior of the pipe, and with the at least one electrical connection, for electrically interconnecting adjoining conductive layers. An electrical conductor is provided for electrically interconnecting the electrically conductive layers of opposite pipe ends. In this way, a relatively long fluid conduit can be assembled, from a plurality of pipes, each of the pipes being provided with electrically conductive layers and electrical interconnections.

It is preferred that opposite conductive layers of a pair of pipes, joined with each other at opposite ends, are interconnected with an electrical conductor of a relatively low electrical resistance, e.g. a resistance that is significantly lower (e.g. at least 100 times lower) than a said relatively high resistance of the at least one electrical connection between consecutive conductive layers. It has been found that a durable and strong connection providing a relatively low electrical resistance can be made during installation, on site, providing a conductive section for leak detection at the joint itself. Preferably, opposite conductive layers of the pair of pipes, joined with each other at opposite ends, are interconnected with an electrical conductor that entirely surrounds the joint.

An aspect of the invention also provides a fluid conduit, provided with a system according to the invention, leading to the above-mentioned advantages. The fluid conduit can include e.g. one or more pipes that are joined at opposite ends, the one or more pipes at least being provided with an array of conductive layers (extending with opposite ends next to one another) and intermediate electrically conductive interconnections of a relatively high resistance.

Besides, certain aspects of the present invention relate to the application of at least one an integrity detector for detecting integrity of said at least part of the system. The integrity detector can e.g. be configured to detect the integrity by feeding an electric current through the part that is to be tested. Also, the integrity detector can include at least a second electrode for electrically contacting the interior of the conduit, for example to be applied for testing the (remote) first electrode. Also, the integrity detector can include at least one leak simulator for simulating a leak.

An aspect of the invention provides a method for manufacturing a conduit, particularly a conduit according to the invention, the conduit having at least one electrically conductive layer that is electrically isolated from an interior of the conduit. Advantageously, the method at least includes:

-providing at least one conduit base;

-application of the array of electrically conductive layers onto the base utilizing a coating process.

In this way, the conduit can be made in an economical, efficient manner. The coating process can provide relatively long conduit base parts with the electrically conductive layers, to be used for leak detection, in an array of layers (one next to the other, viewed in a conduit's longitudinal direction). Preferably, the method includes local application of removable masking material, to define the array of layers. For example, the removable masking material (e.g. masking tape) can be applied first to define intermediate sections between conductive layers that are to be formed. Subsequently, the conduit base part can be coated with the electrically conductive layer material. After that, the masking material can be removed, thereby providing one or more electrically isolating sections separating electrically conductive layers. The electrically isolated layers of the array of layers can be interconnected by respective the relatively high resistance connections, for example by application of an electrical connection bridging the electrically isolating section. The mounting of such an electrical connection is preferably carried out when the coating is still wet (i.e. the coated electrically conductive layer material is still in a sticky condition).

Further advantageous embodiments of the invention provide application of one or more conductive, radially protruding electrically conductive rings, to provide electrical connection to respective conductive parts of the conduit. In a most preferred embodiment, the one or more conductive, radially protruding electrically conductive rings are made of conductive windings, e.g. of conductive (adhesive or self-adhesive) tape.

In further advantageous embodiments, the system and method include application of at least one electrical conducting element having a screw threaded stem, for example a screw or bolt. The element can be screwed into the conduit, particularly into a radially outer section of the conduit (for example penetrating an protective outer layer of the conduit), preferably without entirely puncturing the wall of the conduit, for electrically contacting an electrically conductive part of the conduit. Thus, the mounting of the electrical conducting element can be carried out on site, during final installation of the system, on a desired circumferential location of the conduit, e.g. to provide a local electrical terminal or measuring point of the system.

Further embodiments of the present invention are described in the accompanying claims.

Embodiment of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts. Figure 1 schematically depicts an a system according to an embodiment of the invention;

Figure 2 depicts the system of Fig. 1, during a leak detection;

Figure 3 depicts part of the system of Fig. 1, during an electrode integrity testing mode;

Figure 4 depicts part of the system of Fig. 1, during a current sensor integrity testing mode;

Figure 5 is a graph indicating an example of sensor output for an array of measuring units;

Figure 6 is a graph depicting trend monitoring;

Figure 7 schematically depicts a first step of a method for manufacturing a conduit according to an embodiment of the invention;

Figure 8 schematically depicts a second step of the manufacturing method;

Figure 9 schematically shows a plan view of a circuit board, used in the second step of Fig. 8;

Figure 10 schematically depicts a third step of the manufacturing method;

Figure 11 schematically depicts a fourth step of the manufacturing method;

Figure 12 schematically depicts two pipe ends before joining, according to an embodiment of the invention; and

Figure 13 schematically depicts the two pipe ends after joining.

Figures 1-4 schematically show a non-limiting example of a system for detecting leaks in a fluid conduit wall W of a conduit C. The fluid conduit itself can be configured in various ways, as will be appreciated by the skilled person. Particularly, the wall W of the conduit C surrounds a fluid channel T for conducting fluid. The conduit C can be configured for conducting various types of fluid, e.g. liquids, oil, gas, mixtures and the-like. The conduit C can be provided with an essentially circular cylindrical wall W, but that is not essential. Particularly, in the present embodiments, during operation, the conduit C can be used for conducting fluid having a certain electrical conductivity, for example liquids such as water having an electrical conductivity of about 200 pS/cm, liquid acids, liquid hydrogen chloride (HC1) having a conductivity of about 700 mS/cm, sulfuric acid

(H2S04) having a conductivity of about 150mSs/cm. The conductivity of the fluid can e.g. be in the range of 5 to 10⁵ pS/m (measured at 20 °C).

In the example, the conduit C is made of a plurality of conduit sections (three, in the drawing), particularly pipes PI, P2, P3, that are joined with opposite ends in a fluid-tight manner by connecting means 15.

The conduit C as such is preferably relatively long, e.g. having a length of at least 100 m, measured between opposite conduit ends. In the example, the respective conduit sections PI, P2, P3 can also be relatively long by themselves, each section having e.g. a length of at least 10 meters, particularly at least 30 meters. The conduit sections PI, P2, P3 may have the same length or mutually different lengths. Also, the conduit C can include another number of conduit sections, for example only one or two, or four, five or more than five. A width of the interior space of the conduit C, measured normally with respect to a longitudinal centre line of the conduit C, may be for example in the range of about 1 cm to about 1 m, e.g. a range of about 5 cm to 25 cm. The conduit C can also have different dimensions.

The conduit wall W as such can include a number of layers 11, 12 of electrically insulating material, e.g. one or more electrically insulating plastics. In the example, the conduit wall W is provided with an internal electrically insulating section 11 (e.g. including one or more insulating layers) enclosing the inner space T, and an external electrically insulating section 12 (e.g. including one or more insulating layers). Advantageously, there is provided an array of electrically conductive layers extending through the wall W (coaxially with a conduit's centre line), between the internal and external insulating sections 11, 12, each conductive layer surrounding a respective electrically isolating inner section 12 of the wall W. Thus, all conductive layers 3 are electrically isolated from the interior T of the conduit C. Each of the conductive layers 3 can be made of various materials, for example electrically conductive film, one or more conducting metals or alloys, electrically conducting plastic, and the-like. Each of the conductive layers 3 is preferably entirely uninterrupted in both longitudinal and circumferential directions, unless specified otherwise. In a preferred embodiment, each of the conductive layers 3 is a coating layer, coated onto an electrically insulating conduit base during conduit manufacturing, as will be explained below. In a preferred embodiment, each said electrically conductive layer 3 is made of carbon fiber resin material, particularly being coated onto a base 11. A said inner layer/base 11 is preferably a chemical barrier layer, e.g. made of plastic(s).

In the present example, opposite ends of various adjoining conductive layers 3 of the fluid conduit C are mutually separated, and isolated, by a respective insulator 4. The insulator 4 can e.g. be made in one part with the inner insulating section 11 or the outer insulating section 12. Width Q of the insulators 4 (measured in longitudinal conduit direction) are preferably relatively small compared to the lengths of the conductive layers 3. The width Q of the insulator 4 can e.g. be smaller than 25 cm,

particularly smaller than 10 cm, and more particularly smaller than about 5 cm. A minimum width Q each the insulating section 4 can e.g. be at least circa 1 mm, particularly at least circa 1 cm. The present insulating sections 4 are all spaced-apart from the outer ends of the respective conduit sections PI, P2, P3.

Particularly, in this example, each section PI, P2, P3 of the conduit C is provided with an array of two conductive layers 3, mutually separated by a respective electrically insulating section 4. Each conduit section PI, P2, P3 can also include an array of more than two conductive layers, for example three, four or more, and respective insulating sections 4 there- between. The conductive layers 3 of each of the conduit sections PI, P2, P3 can all have the same length, but that is not essential.

Advantageously, at conduit section connections 15 between subsequent pipes PI, P2, P3, adjoining conductive layers 3 of the fluid conduit C are electrically interconnected by respective electrical conductor 5. The conductor 5 can be an electrically conducting section, e.g. a sleeve 5, surrounding the joint between the pipe ends, and electrically contacting each of conductive layers 3 continuously along its circumference. An electrical resistance of each conductor 5 can be e.g. about the same order as the order of a resistance of the layers 3 that are interconnected thereby. For example, an electrical resistance of each of the conductive layers 3 can be significantly lower than 1 ΜΩ, and may for example be in the range of about 0 to 100 kQ, particularly 0 to 10 kQ, for example about 0 to 1 kQ. Similarly, an electrical resistance of each of the conductors 5 can be significantly lower than 1 ΜΩ, and may for example be in the range of about 0 to 100 kQ, particularly 0 to 10 kQ, for example about 0 to 1 kQ.

An example of method of joining pipe ends utilizing such an interconnection will be explained below in more detail. Electrical

interconnection of the opposite adjoining conductive layers 3 can also be achieved in a different manner, as will be clear to the person skilled in the art.

The conduit C further includes at least a first electrode 1 for electrically contacting the interior T of the conduit C. In the present example, the conduit C includes a first electrode 1 and an additional second electrode . A first electrical power source Gl is provided, for powering each electrode, e.g. by feeding AC or DC power to the electrodes 1, 1' during operation via a respective power line L. The first power source Gl can e.g. be configured to generate a low voltage, e.g. a voltage in the range of about 10 to 50 V (AC or DC). In the example, an electrode integrity detection system including electrode integrity detection units B, a neutral line (or return line) N, current detectors 18 and reference current generators, is provided, for testing the electrodes 1, . Further details concerning this integrity detection system are explained below.

The present electrodes 1, 1' are mounted in different sections P2, P3 of the conduit C. Each of the electrodes 1, 1' is electrically insulated from the electrically conductive layers 3 of the conduit C. An electrically conductive layer 3 may for example be locally interrupted by a short insulating section, allowing passage of part of the electrode 1, 1' (as in the drawing), or allowing passage of a power line for powering the electrode 1, 1' in the case the electrode is located entirely inside the inner space T.

Also, there are provided electrical connections 7, for electrically interconnecting adjoining conductive layers 3 in each conduit section PI, P2, P3, by electrically bridging the respective insulating section 4 in this example. An electrical resistance of each such bridging connection 7 is significantly higher than an electrical resistance of each of the respective conductive layers 3. In the present example, an electrical resistance of each such connection 7 is also significantly higher than an electrical resistance of each of conductive interconnections 5 that interconnect conducting layer ends at pipe joints 15.

The electrical resistance that is provided by said connection 7, bridging an intermediate insulting section 4 between conductive layers 3, may e.g. have a predetermined resistance value, for example a resistance higher than 1 ΜΩ and lower than 100 ΜΩ. In a further embodiment, the electrical resistances of the connections 7 are all the same, that is however not required.

In Figures 1-4, the system is shown with the electrical connections 7, bridging the insulating sections in each pipe PI, P2, P3, located

externally with respect of the conduit C. In a preferred embodiment, at least past of these electrical connections 7, particularly a resistor part 7b, is integrated with the conduit wall W, as will be explained below.

Leak detection system

In the schematic drawings of Figures 1-4, several leak detection units (or 'probe sections') U are depicted. Each of the units U is associated with two of the conducting layers 3 of the layer array. Particularly, in the example, each of the units U provides one of the electrically bridging interconnections 7, between two adjoining conducting layers 3, of a conduit section PI, P2, P3. Thus, in the example, each of the several leak detection units U is associated with one of the insulating sections 4 between the conductive layers 3. In the drawing, the units U are numbered #X, #X+1 and #X+2. It follows that in case of n electrically resistive bridging

interconnections 7b there can e.g. be a total of n respective leak detection units U.

Advantageously, part of each leak detection unit U includes a resistor element 7b, providing the relatively high resistance of the connection. In the example, only a single resistor element 7b is provided for each unit U, the resistor element 7b having two terminals that are electrically connected to the respective opposite ends of the conductive layers 3. In a further embodiment, at least the resistor element 7b can be mounted on a printed circuit board 7a. Such a printed circuit board 7a can also provided with further components (e.g. a at least current detector 8) of the leak detection unit U. Alternatively, for example, the leak detection unit U can be provided by different components that are spaced-apart, for example a resistor element 7b that is integrated with a conduit wall W, and a remote section (including a at least current detector 8) that is electrically connected to one of the terminals of the a resistor element 7b to receive a current there-from. In the example, one terminal of each resistor element 7b is electrically connected to a neutral line or return line N of an electric circuit.

The system further includes at least one current detector 8, electrically connected to at least one of the electrically conductive layers 3, via a terminal of a respective resistor element 7b in this example, for providing a current detection signal. Particularly, there is provided a plurality of current detectors 8, connected to mutually different conductive layers 3 and respective resistor elements 7b. In the present non-limiting example, each of the current detectors 8 is part of a respective leak detection unit U. Each current detector 8 of this embodiment is configured to detect electrical current flowing through at least one of the conductive layers 3 of the conduit 3, and particularly to detect such current flowing to a neutral (or return) line of the respective electrical circuit.

It should be observed that in this patent application the current detector as such can be configured in various ways. It can be configured to detect or measure a current directly, or indirectly, in the latter case for example by detecting or measuring a current related parameter, such as a voltage or a resistance/impedance, as will be appreciated by the skilled person.

In this example, each current detector 8 is associated with a reference current generator for generating a predetermined electrical reference current. In this case, each reference current generator includes an electrical circuit containing a reference resistor 7c and a second power source G2. Particularly, the reference resistors 7c of the various detection units U are connected electrically in parallel with the terminals of the power source G2, via a respective power line L and return line N. Each detector 8 is configured to generate a detector signal based on comparison of electrical current flowing to and/or from the respective conductive layer 3, on the one hand, with the reference current on the other hand. For example, the detector signal can be a binary or TRUE/FALSE signal, indicating "no leakage" in case a detected current is lower than a threshold current (e.g. the reference current), the signal indicating "leakage" in case a detected current is at least the same as of higher than the threshold current (e.g. the reference current).

In a further, more preferred embodiment, the detector signal can include detection information concerning the amount of leakage that is detected, e.g. a value or information relating to, being proportional to and/or including the amount of a detected electrical current (flowing to and/or from the respective conductive layer 3).

In a further, more preferred embodiment, the detector 8 of a detecting unit U can be configured to use the reference resistor 7c to determine the resistance of a flow path of the leak current running through the respective detecting unit U. The detector 8 can e.g. be configured to set the reference resistor 7c to a resistance value such that the reference current, flowing through the resistor 7c, is equal to a detected leak current (flowing between the terminal of the measuring resistor 7b and the power return line N), and to read the set resistance value. Thus, the detector 8 (with reference resistor/reference current generator) acts as a resistance measuring unit, measuring electrical resistance of a current flow path of the current. The detector signal can e.g. be or include the determined resistance value of the leak current's path.

It should be observed that, as follows from the drawing, said reference current generator can e.g. include an electrical circuit including the second power source G2 and reference resistors 7c, which -in this example- are adjustable for setting a certain predetermined reference current. The second power source G2 and the first power source Gl are preferably the same, providing the same AC or DC power (i.e. voltage) during operation. In case a single power source is provided as a first and second power source Gl, G2, a power line L for the electrodes 1, 1' and a power line L for powering the leak detection units U can be the same power line. Similarly, in that case, the respective return lines N can be the same.

The present system includes a data processing unit K (e.g. a signal processor unit, a computer or a controller) configured to process the signals of the current detectors 8, and to generate a leak detection signal depending on the detector signals.

In this example, the data processing unit K and current detectors 8 are communicatively connected via a data communication system, e.g. including one or more data transmission lines R, for example a data bus (e.g. a Controller Area Network -CAN- type communication system). The data processing unit K can be configured to receive and process the current detection signals from the various detectors 8 via the communication system. Also, in a further embodiment, the data processing unit K can be configured to control operation of system integrity detection means via the communication system. In a further elaboration, the data processing unit K and detectors 8 can be configured such, that the data processing unit K can address the various detectors 8 independently, requesting e.g. transmission of a detection result (i.e. the current detector signal).

The data processing unit K can be configured in various ways to process current detector signals, and to generate e.g. a warning or an alarm based on those signals, as will be clear to the skilled person. The data processor K can be provided with or connected to a user interface (e.g.

including one or more of a keyboard, display, switch board, loudspeaker, etc.), for user control and to provide a user with information regarding detection results.

In a preferred embodiment, the data processing unit K is configured to combine current detection results, relating to the various detectors 8, to evaluate whether or not there is a leak, and particularly to estimate the location of the leak. For example, the data processing unit K can be configured to determine the location of a detected leak using predetermined information that is associated with the electrical resistance of said bridging interconnections 7 (the information e.g. being a resistance value of each of the bridging resistors 7b, in this example) and the arrangement of said current detector 8 with respect to the electrically conductive layers 3.

Preferably, the system further includes a fluid conductivity detector D, configured to measure conductivity of a content (i.e. fluid) of the conduit C during operation. Such a fluid conductivity detector D can be communicatively connected to the central data processing unit K to transmit a detected conductivity thereto. Application of the fluid conductivity detector D is particularly advantageous in case the conduit C is to be used with different types of fluids and/or in case of use of a fluid having a varying conductivity.

The data processing unit K can be configured to utilize a detected, or alternatively predetermined, conductivity of the fluid in the processing of the detector signals, particularly to refine leak detection.

Basic operation Figure 4 schematically depicts a basic operation of the system.

During operation, the conduit is filled with a said electrically conducting fluid. Preferably, all electrodes 1, 1' are electrically powered, in this case by being electrically connected to the power line L of the first power source Gl.

Also, during operation of the present system, the leak detection units U can be powered for generating respective reference currents 12, particularly by connecting the reference resistors 7c (in parallel, in this example) to the second power source G2 (which may be the same as the first power source Gl, as has been explained above). The reference currents 12 are schematically depicted in the drawing; they may have the same value in case respective reference resistors 7c are set to the same resistor values, or the reference currents 12 can have mutually different values.

In a preferred embodiment, the same operating voltage (AC or DC) is applied to the power line(s) L feeding the electrodes 1, 1' and the reference current generators (i.e. the detecting units' reference resistor circuits).

Operation can further include providing current detection signals by the current detectors 8. As is mentioned above, the current detection signals can include various types of signals. In a most preferred

embodiment, each detector 8 generates detection information concerning the amount of leakage (if any) that is detected, e.g. a value or information relating to, being proportional to and/or including the amount of a detected electrical current flowing to and/or from the respective conductive layer 3.

According to a further embodiment, the information can be, e.g., a detected electrical resistance of a flow path of the leak current running through the detecting unit U (the detector 8 utilizing/cooperating with the unit's reference resistor 7c to determine that resistance). In the present embodiment, said leak current flow path includes a path extending from the electrodes 1, 1' through the fluid to the leak's location, and paths through the conductive layers 3 and any interconnecting resistors 7b that may be present, depending on the arrangement of the relevant detecting unit U with respect to the leak location (see Fig. 2),

Said detection information, i.e. the current detection signal, can be transmitted via the communication means N to the data processing unit K, to be processed. The data processing unit K processes all received current detection signals to evaluate whether or not a leak is present, and can take further action (e.g. generating a warning or alarm) in the case the unit K determines that a leak is detected.

In a further elaboration, during use, the electrical conductivity of the fluid, present in the conduit C, is measured, and the result is used in the processing of the current detection signals. Alternatively, e.g., the data processing unit can be provided with a predetermined value of the conductivity of the fluid, for example being stored in a memory of the unit .

Fig. 2 shows a situation in which a leak is present in the wall W of the conduit C. A location of the leak is indicated at position Z. The leak in the wall W leads to conductive fluid contacting one of the conductive layers 3 of the conduit wall, at a certain leak location. As a result, electrode currents II flow through the fluid and the leak, via the conductive layers 3 and through a plurality (in this example all) of the leak detection units U. The overall electrical leakage current is divided into sub-currents 16, 16', 16" running through the respective leak detection units U, the leakage sub- currents 16, 16', 16" having significantly different current values due to the presence of the resistors 7b that interconnect the various electrically conducting layers 3.

The current detectors 8 detect the leakage related sub-currents 16,

16', 16", flowing through the respective units U, and generate and transmit respective detector signals to the data processing unit K (the detector signals relating to or being proportional to detected sub-currents 16, 16', 16", or providing information concerning the value of the detected sub-current). Preferably, the detector signals include the information concerning the resistance of the flow path of the respective leak current 16, 16', 16".

Once the presence of a leak is determined, the processing unit K is preferably configured to locate the leak's position. The processing unit K can utilize the detectors signals as such to provide a rough estimate of the position of the leak Z (that is, the leak detection units U detecting the highest leak currents will probably be located close to the leak).

A more accurate estimation can be carried out in a relatively simple manner, in case the specific conductivity of the conductive layers 3 is known. That conductivity can e.g. be measured during installation and/or initialization of the system, or it can be calculated or determined differently. Such a pre-determined specific conductivity of the conductive layers 3 can e.g. be stored in a memory of the processing unit K.

However, in the present embodiment, in case the detecting units U generate information concerning the detected resistance of flow paths of respective leak currents 16, 16', 16", a leak location can be determined or estimated without having to use layer conductivity information.

Referring to Fig. 2, the leak location can be determined or estimated using the equation M1/M2=R1/(R2-R3) in which Ml is the distance between the leak position to the bridging resistor 7b on a first side of the leak, M2 is the distance between the leak position to the bridging resistor 7b on an opposite second side of the leak, Rl is the detected flow path resistance (Ohm) of a first leak current 16 regarding the first side of the leak, and R2 is the detected flow path resistance (Ohm) of a second leak current 16' regarding the second side of the leak, and R3 is the

predetermined resistance value (Ohm) of the bridging resistor 7b that conducts one (the second current 16') of the two leak currents 16, 16'. Herein, a resistance of a relatively short, high conductivity interconnection 5 between opposite conductive layers 3 of adjoining pipes PI, P2 can e.g. be neglected. Also, herein, it is assumed that the conducting layers 3 have a constant conductivity along the layer's longitudinal directions. The skilled person will appreciated that a similar determination of the leak's location can be done in case the conducting layers 3 have a predetermined

conductivity that is not constant.

The processing unit K can provide a user with the information concerning the leak's location, or with information that can be used by the user to estimate the leak's location. Them the user can take appropriate action, such as uncovering only a small section of the conduit C that has been found to contain the leak, without having to uncover the entire conduit C. Figure 5 depicts a measuring result concerning a leak, regarding a similar system as described above and shown in Figures 1-4, now containing a plurality of detection units U (in this case 12 units U). Particularly, Fig. 5 is a graph showing flow path resistances (Rfp) detected by the units U versus the unit number n. In this example, several of the detection units U are faulty and do not provide any detection signal; missing signals are depicted by dashed results. Still, the remaining detection units U all provide detection signals, signaling the presence of a leak, somewhere in the conduit wall W. Moreover, the detection signals of the different detection units U differ due to the application of the bridging resistors 7b in the system (more such resistors 7b have the be passed by a leak current in case the current flows to a detection unit that is associated with a remote conducting layers interconnection, i.e. remote from the leak's location). As a result, the location of the leak can still be estimated, albeit a number of the detection units U being out of operation. Therefore, the system is highly reliable, wherein the system is still able to operate to detect a leak in the entire conduit C when certain detection parts of the system are not responding.

Figure 6 depicts a further embodiment of the invention, showing a flow path resistance Rfp versus time, regarding a detection unit's detection result. In case there is no leak, each detection unit U will measure a relatively small (e.g. zero or substantially zero) base current, or a respective high initial flow path resistance Rfp. Particularly, initially, a very low base current might flow between the electrodes 1, 1' and the conductive layers 3 of the conduit wall W. However, the base current may slowly increase over time, e.g. due to diffusion of conductive matter into an inner insulating section of the conduit C. In that case, preferably, the processing unit K can be configured to take into account such long time trends in detection of leaks, for example by following the trend of the base current (or a parameter associated therewith, such as a respective base resistance of a flow path of the base current). The processing unit K can be configured to detect a leak induced deviation from the trend, e.g. a sudden increase of the detected current or a sudden decrease of the flow path resistance Rfp (indicated at H in Fig. 6), and to signal a detected trend break.

Advantageously, the system is also provided with one or more integrity detectors for detecting integrity of one or more parts of the system. The integrity detectors can e.g. be configured to detect the integrity by feeding an electric current through the system part that is to be tested, and detecting a resulting signal.

The system integrity tests, described in the following section, are preferably carried out at least before a first use of the system. Also, the tests can be carried out periodically, for example at least once an hour, at least once a day, or differently. The data processing unit K can be configured to control the timing of the test, so that integrity can be automatically tested. Electrode integrity testing system

Referring to Fig. 1, in the present example, the second electrode 1' can function for testing integrity of the first electrode 1, and vice versa. To this aim, the embodiment is provided with electrode integrity electrode integrity detection units B, having current detectors 18 that can be communicatively connected with the data processor K, e.g. via a said data communication system (e.g. a data transmission line R). In the drawing, these units are mutually numbered #Y and #Y+1. In case of m electrodes, there can e.g. be a total of m respective electrode integrity detection units B.

Each electrode integrity detection unit B further includes a reference current generator, provided by an electrical reference resistor 21 (in this example being adjustable for setting a certain predetermined reference current), that is connectable in an electrical circuit with the first power source Gl via a first switching means 22. Also, a second switching means 23 is provided, for switching the respective electrode 1, 1' between connection with the power line L of the source Gl and the respective return/neutral line N.

The configuration of the current detector 18 of each electrode integrity detection units B can be the same as or similar to the configuration of the current detectors 8 of the leak detection units. As follows from the drawing, in this embodiment, each electrode current detector 18 has one terminal that is electrically connected to the respective electrode 1, 1', for detecting current flowing through the electrode 1, 1' (to and/or from the respective power line L) . Again, the electrode current detector 18 as such can be configured in various ways. It can be configured to detect or measure a current directly, or indirectly, in the latter case for example by detecting or measuring a current related parameter, such as a voltage or a

resistance/impedance (e.g. a resistance of the flow path of a detected test current), as will be appreciated by the skilled person.

Each electrode current detector 18 can be configured to generate a detector signal based on comparison of electrical current flowing to and/or from the respective electrode 1, 1', on the one hand, with a reference current 15 (set by the electrical reference resistor 21 in the respective reference current circuit) on the other hand. For example, the electrode current detector signal can be a binary or TRUE/FALSE signal, indicating "faulty electrode" in case a detected current 13 is lower than a threshold current (e.g. the reference current 15), the signal indicating "electrode intact" in case a detected current 13 is at least the same as of higher than the threshold current (e.g. the reference current 15). In a further, more preferred embodiment, the electrode current detector signal can include information concerning the amount of electrode integrity that is detected, e.g. a value or information relating to, being proportional to and/or including the amount of a detected electrical current flowing through respective conductive electrode 1, i'. Similar to the leak detection units U described above, in a further example, the electrode current detector 8 of an electrode integrity detection unit B can be configured to measure the flow path resistance, e.g. to adjust the reference resistor 21 to a resistance value such that the reference current 15, flowing through the resistor 21, is substantially equal to a detected electrode current 13. In that case, the detector signal can e.g. be or include the determined flow path resistance, e.g. a set resistance value of the reference resistor 21, after having equalized the currents.

The data processing unit K can be configured to process the signals of the electrode current detectors 18, and to generate an electrode integrity signal depending on the detector signals. The data processor K can e.g. be configured to generate a warning signal or an alarm in case it follows that an electrode is not properly functioning, as will be clear to the skilled person.

Operation of the electrode integrity testing system is indicated in

Fig. 3. During testing, the interior T of the conduit C is filled with a conductive fluid. The electrode 1 that is to be tested is connected to the return line N of the respective power source Gl, by adjusting the respective switch 23 to the respective testing state (see Fig. 3). Also, the reference current generator is activated, by setting the first switch 22 to the appropriate state for bringing the reference resistor 21 in an electrical circuit with the power source Gl. Further, the other electrode 1' is powered, by the power source Gl.

As a result, under normal conditions, a test current 13 will flow between the electrodes 1, 1', through the fluid, as is schematically indicated in the drawing, both electrodes 1, 1' taking part in an electric circuit with the power source 1. The electrode current detector 18 that is associated with the electrode being tested can generate a detection signal to the data processing unit K (via the communication system R). In this case, the detection signal can be based on the reference current 15, as is described above. The data processing unit K can process the signal received from the electrode current detector 18, and may generate the warning signal or an alarm when it determines that the electrode 1 under investigation is not properly functioning (e.g. in case a detected current is lower than a certain threshold current value, or in case a detected test current flow path resistance is higher than a predetermined electrical resistance value)..

The same routine can be carried out regarding any of the other electrodes 1' of the system, e.g. one after the other, by setting the switches 22, 23 of the respective electrode integrity detection unit B of the electrode to respective testing states, and by powering at least another electrode 1 via generator Gl and power line L.

Leak simulator In a further preferred embodiment integrity testing, the system includes a leak simulator for simulating a leak. In the example, there is provided a leak simulation unit V, having a switch 25 that is adjustable between a non-conducting state (shown in Fig. 1) to a conducting state (shown in Fig. 4). In the later state, the a leak simulation unit V electrically connects a power source G2 to one of the electrically conducting layers 3 of the fluid conduit C, to simulate a leak in the system. Resulting simulated leak currents 14, 14', 14" are schematically shown in Fig. 4: the currents flow through interconnected electrically conducting layers 3 and respective leak detection units U to and/or from the return/neutral line N.

During a respective leak simulation mode of the present system, the reference current generators of the detection units U are preferably active to generate respective reference currents 12, wherein the current detectors 8 can generate detection signals based on those currents 12 and detected leak simulation currents 14, 14', 14" . Thus, the detection units U and their detectors 8 can be active in the same manner as has been described above, regarding leak detection under normal operating conditions.

Also, during leak simulation, the data processing unit K can e.g. interrogate the current detectors 8 of the leak detection units U, to receive respective detection signals there-from. Based on those signals, the data processing unit K can evaluate if there is a fault in the system. Such a fault can be e.g. that one or more of the detection units U has/have not found the simulated leak, or that a detection signal deviates from an expected signal. Also, the data processing unit K can be configured to generate leak simulation results, for example a warning signal or an alarm in case the data processing unit K determines that there is a fault in the system.

From the above it follows that the present system and method provide a highly reliable way of monitoring a conduit C for leaks. Integrity tests can provide for reducing/avoiding false leak detection. The system allows for a significant redundancy in detecting leakage in an area. Also, the present system allows for a significant cost reduction in cabling and installation compared to known systems. Also, the bridging resistors can be selected such that the system can still be used to detect leaks in case of relatively high variations/fluctuations of e.g. fluid resistances and possible variations of the conductive layer resistances.

In the following a production and installation method are described for manufacturing a conduit C, which can advantageously be part of the system described above. In the manufacturing process, the separation between the various conducting layers 3 of the conduit C can be created in a highly controlled manner.

Manufacturing

Figures 7-11 schematically depict a method for manufacturing parts PI, P2, P3 of a conduit C, particularly a conduit of the system described above. Basically, the method includes providing a conduit base 11, and application of an array of electrically conductive layers 3 onto the base

11 utilizing a coating process.

The conduit base 11 as such is e.g. a plastic pipe, e.g. for providing an internal chemical barrier layer of the conduit. The base pipe 11 can be made of various plastics, e.g. fiber reinforced plastic. The base 11 can e.g. include or consist of at least one of the following materials: PP

(Polypropylene), PVDF (Polyvinylidene fluoride, PE (Polyethylene), E-CTFE

(Ethylene Chloride Trifluorethylene), FEP (Fluor Ethylene Polypropylene), PFA (Perfluor Alkoxy), MFA (Methoxy Perfluor Alkoxy). The base 11 can consist of a single (plastic) material, or a mixture of plastic materials, and/or a layer of plastic materials and/or mixtures.

The base 11 as such is preferably a circle cylindrical tube, e.g. having a length of at least 10 m, for example a length of at least 30 m. The base 11 can have various widths, such as e.g. an internal diameter in the range of about 1 cm to about 1 m, e.g. a range of about 5 cm to 25 cm. The base 11 can also have different dimensions, as will be appreciated by the skilled person.

It should be noted that the same method can also be applied to manufacture relatively short sections of a conduit C that is to be assembled, for example pipe bends, T-sections, reducer sections, elbow-sections, U- sections and the-like. Such conduit elements can e.g. be shorter than 10 m.

As is shown in Fig. 7, the manufacturing process can include local application of removable masking material 101 first. The masking material can e.g. be removable masking tape, for example Teflon tape. In the present example, both ends of the base 11 are provided with such masking material. Also, masking material 101 is applied on the longitudinal centre of the base pipe 11; in this example, the centrally applied masking material will define an electrically insulating barrier 4 between adjoining conductive layers 3 of the conduit C to be manufactured. In a further embodiment, the base 11 is provided with a plurality of such masked sections, spaced-apart from each other and from the opposite base ends, for providing a plurality of spaced- apart insulating barriers 4.

The outer side of the (masked) base 11 is provided with the electrically conductive coating, to create the electrically conductive layers 3. A result is shown in Fig. 8, particularly after the optional central masking material 101 has been removed. The conductive coating can e.g. be a curable conducive resin, for example a resin containing conductive particles, e.g. conductive carbon particles or conductive carbon fibers. In the resulting pipe element, an electrically isolating section 4 having a certain width Q separates the electrically conductive layers 3. As is mentioned before, the width Q of the insulating section may e.g. be smaller than 25 cm, particularly smaller than 10 cm, for example in the range of about 1 to about 5 cm.

An electrical connection 7a, 7b is applied to bridge the electrically isolating section 4, e.g. after the respective masking material 101 has been removed. Preferably, the electrically bridging connection 7a, 7b is applied when the coated electrically conductive layer material is still in a sticky (i.e. not fully cured) condition.

Figure 9 shows a preferred embodiment of the bridging connection.

In this case, the connection includes an electronic structure, particularly a printed circuit board 7a having two electrical terminals 102 for electrically contacting the ends of the respective conductive layers 3, and a resistor element 7b that electrically interconnects the two terminals 102.

Figure 10 shows the tube in a further manufacturing state. Each electrical bridging connection (in this case: one) has been electrically connected to the respective electrically conductive layers 3 using electrically conductive tape 103, for example carbon tape. Particularly, rings of tape windings 103 are applied to the tube, to electrically contact the terminals 102 of the bridging part (printed circuit board) 7a, providing a very reliable electrical contact. The conducting rings 103 protrude radially outwardly with respect to the external surfaces of the conductive layers 3, and can e.g. have a radial thickness of at least about 1 mm, e.g. in the range of about 1 mm to 1 cm, and preferably at least about 3 or 4 mm (for receiving and holding a screw threaded terminal element).

The conducting rings 103 can fix the bridging element 7a onto the base 11 and conductive layers 3. Also, each of the electrically conducting rings 103 electrically contacts an end section of a respective conductive layer 3. It should be noted that the electric terminals 102 of the bridging element 7a can also be electrically connected to the conductive layers 3 in another manner, e.g. by laying the terminals with conducting surfaces directly onto the layers 3.

Thus, after application of the bridging element (i.e. the printed circuit board 7a, in this example), the opposite ends of the conductive layers 3 are bridged via the resistor element 7b (acting as a bridging resistor). As follows from the above, referring to figures 1-4, preferably, the resistor element 7b is used in a circuit of a leak detection system, as part of a said leak detection unit U of such a system.

Referring to Fig. 10, further conducting rings 104 can be applied at or near a longitudinal end of each conduit base 11. In this example, the further conducting rings 104 are located a short distance away from the end faces of the base, leaving small ends sections 11a of the insulating base 11 (previously being covered by said masking material 101) exposed. Each of the end sections 11a of the base, may e.g. have a width (measured in longitudinal direction of the base 11) in the range of about 1 mm to 10 cm, or another dimension. Again, preferably, the further conducting rings 104 can be made by locally winding electrically conductive tape onto the respective conductive layer 3. The further rings 104 may e.g. protrude radially outwardly with respect to the external surfaces of the conductive layers 3, and can e.g. have a radial thickness of at least about 1 mm, e.g. in the range of about 1 mm to 1 cm, and preferably at least about 3 or 4 mm.

Figure 11 depicts a pipe PI, P2, P3, after a further manufacturing step including application of an external electrically insulating layer 12, for example including a structural laminate, foil or tape, and e.g. being made of one or more plastics. The external structure 12 can e.g. entirely enclose the bridging parts 7a, 7b and electrically conducting terminal rings 103 of each insulating section 4. In this example, the external structure 12 leaves the outer electrically conducting rings 104 at least partly exposed.

The pipe PI, P2, P3 produced in this way can then be tested.

Particularly, test equipment can be electrically connected to said conducting rings 103, 104 for carrying out electric measurements, such as measuring the resistances of the various conducting layers 3 and of the bridging structure(s) 7b. Making contact with the rings 103 that are buried below the external structure 12 can be achieved in a simple manner, by screwing an electrically conducting element 105 having a screw threaded stem (e.g. a screw or bolt 105) through the structure 12 and into the ring 103; the element 105 can penetrate the protective outer layer 12 for electrically contacting the electrically conductive part 103 that is integrated in the pipe wall. Similar screw threaded elements can e.g. be applied to the conducting rings 104 at the ends of the pipe element.

Installation A plurality of the pipes PI, P2, P3 can be joined to form a conduit

C. Interconnection of opposite ends of the pipes is schematically depicted in Figures 12-13. The opposite electrically conductive layers 3 of the abutting pipes PI, P2 are electrically interconnected, via the respective conducting ring sections 104. Figure 12 shows a cross-section of part of the opposite pipe ends before joining, and Fig. 13 after joining. Preferably, for joining, pipe ends are aligned with respect to each other. An electrically insulating sealing material 150 (e.g. a curable resin) is applied in an area between opposite electrically conducting rings 104 of the pipes PI, P2, and onto the respective final sections 11a of the two base parts 11. The sealing material is preferably a chemical barrier material.

In the example, the sealing material 150 can seal a circular slit 140 between respective ends of the pipes. Leakage of sealing material into the interior of the conduit via the slit 140 can e.g. be avoided by installing a backing (e.g. a balloon or a pp-shell) in the conduit's interior opposite the slit 150. The end sections 11a of the base may optionally be provided with removable masking material, for example peel-off tape; such masking material is removed before the sealing material 150 is applied.

After the sealing material 150 has been applied (providing a fluid- tight connection between the inner layers 11 if the pipes), the electrically conductive layers 3 of the abutting pipes PI, P2 can be electrically interconnected. In the example, this electrical connection is provided via an electrical conducting sleeve 5, electrically connecting the respective conducting rings. As is mentioned before, the resistance of the conductor sleeve 5 is relatively low, e.g. a resistance in the range of about 0 to 100 kQ, particularly 0 to 10 kQ, for example about 0 to 1 kQ. It is preferred that the conductor 5 entirely encloses the opposite ends of the pipes, and electrically contacts respective conductive layers continuously along respective layer contours. Good results have been obtained using an electrical conducting sleeve 5 that is made of at least one winding of an electrically conductive material, for example carbon fabric (a veil) or carbon tape.

It is further preferred to enclose the conductor 5 with an external layer 160 (shown in dashed lines), particularly an electrically insulating layer, for example including a structural laminate, foil or tape, and e.g. being made of one or more plastics. In the present example, this further external protective layer also encloses both conductor rings 104 and contacts the external protective layers 12 of the pipes PI, P2.

The above installation steps can be repeated for connecting more pipes (P3) to the assembly of pipes (PI, P2), to manufacture the conduit C. Installation can further include connecting electrical and/or electronics components to the integrated conductive layers 3 of the conduit C, e.g. to build the leak detection system according to one or more of the above aspects of the invention. For example, electrical wiring can be electrically connected to internal conducting rings 103 of the conduit C, for transmission of leak detection currents. Above-described current detectors 8 can be electrically connected to the electrically conductive layers 3, via respective wiring, for providing said current detection signals during use. Further installation steps can include providing the conduit C with one or more electrodes 1, 1' of the leak detection system, installing any other further components such as the data processing unit K, power source(s) Gl, G2 and power lines L, N, communication means R and reference current generators, as will be appreciated by the skilled person.

In the foregoing specification, the invention has been described with reference to specific examples of embodiments of the invention. It will, however, be evident that various modifications and changes may be made therein without departing from the scope of the invention as set forth in the appended claims.

In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word 'comprising' does not exclude the presence of other features or steps then those listed in a claim. Furthermore, the words 'a' and 'an' shall not be construed as limited to 'only one', but instead are used to mean 'at least one', and do not exclude a plurality. The mere fact that certain measures are recited in mutually different claims does not indicate that a combination of these measures cannot be used to advantage. For example, the method for manufacturing a conduit that is described in this patent application can be used to great advantage in building a leak detection system. The conduit, manufactured in the manner described, can also be used for different applications. For example, the conduit can be installed without using the integral conducting layers 3 and respective bridging connections 7 as leak detection system components. In that case, for example an installed conduit can still take part in the leak detection system at a later stage (e.g. after a certain operational period).

Also, for example, above-described integrity testing and relating system components can be applied as an independent aspect of the present invention. For example, there can be provided a system for detecting leaks in a fluid conduit wall, including:

-at least a first electrode 1 for electrically contacting an interior of the conduit C;

- at least one electrically conductive layer 3 extending through the conduit wall W, the conductive layers 3 being electrically isolated from the interior of the conduit C; and

-at least one current detector 8, electrically connected to at least one of the electrically conductive layers 3, for providing a current detection signal.

the system further including an integrity detector for detecting integrity of at least part of the system,

the integrity detector may be configured to detect the integrity by feeding an electric current through the part that is to be tested,

wherein the integrity detector may (also) include at least a second electrode 1' for electrically contacting the interior of the conduit,

wherein the integrity detector may (also) include at least one leak simulator for simulating a leak.

Claims

1 System for detecting leaks in a fluid conduit wall, including:

-at least a first electrode (1) for electrically contacting an interior of the conduit (C);

- an array of at least two electrically conductive layers (3) extending through the conduit wall (W), the conductive layers (3) being electrically isolated from the interior of the conduit (C);

-at least one electrical connection (7) for electrically interconnecting adjoining conductive layers (3), wherein an electrical resistance of the connection (7) is higher than an electrical resistance of each of the conductive layers (3); and

-at least one current detector (8), electrically connected to at least one of the electrically conductive layers (3), for providing a current detection signal.

2. The system according to claim 1, including a plurality of current detectors (8), connected to mutually different conductive layers (3).

3. The system according to claim 1 or 2, including a data processing unit (K) configured to process the signal of the at least current detector (8), and to generate a leak detection signal depending on the detector signal.

4. The system according to claim 3, wherein the data processor (K) is configured to determine the location of a detected leak using predetermined information that is associated with the electrical resistance of said connection (7) and the arrangement of said current detector (8) with respect to the electrically conductive layers.

5. The system according to any of the preceding claims, wherein the at least one current detector (8) is arranged in an electrical circuit with an electrical power source and the first electrode (1).

6. The system according to any of the preceding claims, wherein the current detector (8) includes or is associated with a reference current generator for generating a predetermined electrical reference current, wherein the detector (8) is configured to generate a detector signal based on comparison of electrical current flowing to and/or from the respective conductive layer with the reference current.

7. The system according to any of the preceding claims, wherein adjoining conductive layers (3) of the fluid conduit (C) are mutually isolated by an insulator (4), wherein the insulator is bridged by a said electrical connection (7).

8. The system according to any of the preceding claims, said electrical connection (7) between adjoining conductive layers (3) is at least partly integrated with the conduit wall.

9. The system according to any of the preceding claims, wherein said electrical connection (7) between adjoining conductive layers (3) includes a printed circuit board (7a), having conductive parts that are connected to the conductive layers.

10. The system according to any of the preceding claims, wherein said electrical connection (7) between adjoining conductive layers (3) includes a resistor element (7b), providing the relatively high resistance of the connection.

11. The system according to any of the preceding claims, wherein each said electrically conductive layer (3) is made of carbon fiber resin material .

12. The system according to any of the preceding claims, wherein said electrical connection (7) is attached to respective two conductive layers (3) via a conductive ring, for example made of carbon tape windings.

13. The system according to any of the preceding claims, wherein the fluid conduit (C) includes at least two pipes that are connected in a fluid- tight manner at opposite ends, each of the pipes being provided with an array of at least two electrically conductive layers (3) extending through the pipe wall (W), the conductive layers (3) being electrically isolated from the interior of the pipe(T), and with the at least one electrical connection (7), for electrically interconnecting adjoining conductive layers (3), the electrical resistance of the connection (7) being higher than an electrical resistance of each of the conductive layers (3);

wherein an electrical conductor (5) is provided for electrically

interconnecting opposite electrically conductive layers (3) of the two pipes.

14. The system according to claim 13, wherein an electrical resistance of the conductor (5) is significantly lower than the resistance of said electrical connection (7) between adjoining conductive layers (3) of a pipe as such.

15. The system according to claim 13 or 14, wherein the conductor (5) encloses the opposite ends of the pipes and electrically contacts respective conductive layers continuously along respective layer contours.

16. The system according to any of claims 13-15, wherein the opposite ends of the pipes include conductive, radially protruding rings, being interconnected by the electrical conductor (5).

17. The system according to any of the preceding claims, including an integrity detector for detecting integrity of at least part of the system.

18. System according to claim 17, wherein the integrity detector is configured to detect the integrity by feeding an electric current through the part that is to be tested.

19. System according to claim 17 or 18, wherein the integrity detector includes at least a second electrode ( ) for electrically contacting the interior of the conduit.

20. System according to any of the claims 17-19, wherein the integrity detector includes at least one leak simulator for simulating a leak.

21. The system according to any of the preceding claims, wherein the electrical resistance of each said connection (7) has a predetermined resistance value, (for example higher than 1 ΜΩ and lower than 100 ΜΩ)

22. Fluid conduit, provided with a system according to any of the preceding claims

23 Method for manufacturing a conduit according to claim 22, the conduit having at least one electrically conductive layer that is electrically isolated from an interior of the conduit, the method at least including:

-providing at least one conduit base;

-application of the array of electrically conductive layers (3) onto the base utilizing a coating process.

24. Method according to claim 23, including local application of removable masking material first, then application of an electrically conductive layer material, and subsequently removing the masking material to provide an electrically isolating section separating electrically conductive layers (3).

25. Method according to claim 23 or 24, wherein an electrical connection (7) is applied to bridge an electrically isolating section between adjoining conductive layers (3), preferably when coated electrically conductive layer material is still in a sticky condition.

26. Method according to claim 25, wherein the electrical connection (7) is electrically connected to the respective electrically conductive layers (3) using electrically conductive tape, for example carbon tape, preferably a ring of tape windings.

27. Method according to any of claims 25-26, wherein the electrical connection (7) includes an electronic structure and/or a printed circuit board (7a).

28. Method according to any of claim 23-27, wherein at least one electrically conducting ring is applied onto the electrically conductive layer by locally winding electrically conductive tape thereon.

29. Method according to claim 28, wherein at least one electrically conducting ring is positioned at or near a longitudinal end of each conduit base.

30. Method according to any of claims 23-29, wherein the conduit (C) is assembled using at least two pipes having respective electrically conductive layers (3) and the respective at least one electrical connection (7), wherein opposite electrically conductive layers (3) of abutting pipes are electrically interconnected

31. Method according to claims 28 and 30, wherein the electrically conductive layers (3) of abutting pipes are electrically interconnected via respective electrically conducting rings and an electrical conductor (5) electrically bridging the conducting rings.

32. Method according to claim 31, wherein a sealing material is applied in an area between the electrically conducting rings of two pipes, for sealing a slit between respective ends of the pipes.

33. Method according to claim 31 or 32, wherein the electrical conductor (5) includes at least one winding of an electrically conductive material, for example carbon fabric or carbon tape.

34. Method according to any of claims 23-33, wherein the electrically conductive layers (3) are made of a carbon fiber resin material.

35. Method according to any of the claims 23-34, including application of at least one protective layer over the array of electrically conductive layers (3).

36. Method according to claim 35, wherein at least one electrical conducting element having a screw threaded stem is applied for penetrating the at least one protective outer layer and to electrically contact an electrically conductive part of the conduit.

37. Method according to any of the claims 23-36, including providing at least one current detector (8), electrically connected to at least one of the electrically conductive layers (3), for providing a current detection signal.

38. Use of a system according to any of claims 1-21, including:

-feeding a fluid having a certain electrical conductivity through the conduit (C); -applying electrical power to the at least a first electrode (1);

-providing at least one current detection signal via the at least one current detector (8); and

-generating a leak detection signal depending on the current detection signal.

39. Use according to claim 38, including measuring the electrical conductivity of the fluid, and utilizing the measurement result in a processing of the at least one current detection signal.

40. Use according to claim 38 or 39, including testing integrity of at least part of the system by simulating a leak, particularly by application of a current to the array of electrically conductive layers (3).

41. Use according to any of claims 38-40, including testing integrity of the first electrode using a second electrode, electrically contacting the fluid remotely from the first electrode.