The present invention relates to a detector for monitoring the presence of a fluid within a material.

In certain applications, particularly in some industrial applications, it may be desirable to detect the presence of a fluid when a fluid should otherwise not be present. As an example, some industrial applications comprise long lengths, for example many kilometres, of pipelines which are used to transfer a fluid, e.g. a liquid or gas. The pipelines are often surrounded by a layer of insulation material which is typically surrounded by a protective layer. At least when the pipelines are initially installed, the protective layer may seal the insulation layer such that fluid in the environment in which the pipelines are placed cannot reach the pipelines. This may, for example, prevent any moisture in the surrounding environment from reaching and corroding the pipeline. However, the protective layer may become damaged and/or degrade over time thereby allowing fluid, e.g. air, to pass from the surrounding environment into the insulation material surrounding the pipeline. The air may contain moisture which may cause corrosion of the pipelines, and indeed any joints or connections thereon. This type of corrosion which occurs under insulation is often known as corrosion under insulation (CUI). As the pipelines degrade, cracks and openings may form in the pipelines which may allow the fluid passing therethrough to leak from the pipelines.

A small amount of degradation of the pipelines may not significantly impact their ability to transfer the fluid, or impact the safety of the fluid they are containing. However, if the degradation becomes significant, the pipelines may no longer be able to fully contain the fluid they are transporting and a significant leak may occur. As a result, the pipeline may therefore no longer be capable of transferring the fluid to its destination. As will also be appreciated, the fluid being transferred by the pipeline may be harmful. For example, the fluid may be flammable. As such, any leak could potentially be dangerous.

Accordingly, there remains a need for a means to detect the presence or composition of a fluid within a material.

When viewed from a first aspect the present invention provides a fluid detector, for monitoring the presence of a fluid within a material, comprising: a deformable body which deforms in the presence of a fluid; and a sensor arranged to detect: a deformation of the deformable body caused by the presence of the fluid; and/or a force applied by the deformable body caused by the presence of the fluid; wherein the fluid detector is shaped for insertion into a material such that the detector is positioned to monitor the presence of the fluid within the material.

Accordingly, the detector may be inserted into a material so as to be capable of monitoring the presence of the fluid within the material itself. In the exemplary case of a fluid pipeline which is surrounded by material in the form of insulation, the detector may be inserted into the insulation. The detector may pass through a protective layer surrounding the insulation. If the protective layer becomes damaged or degraded, fluid within the environment may pass into the insulation. If the fluid leaks into the insulation, this will permeate to the deformable body of the detector which will tend to deform in the presence of the fluid. This may cause a deformation of the deformable body which will be detected by the sensor, or the deformable body may exert a force, in trying to deform, which is detected by the sensor. The deformable body may absorb the fluid, which may cause the deformation of the deformable body and/or the generation of the force by the deformable body. The ability to insert the detector into the material, e.g. the insulation material surrounding the pipeline, may allow the detector to be, at least partially, embedded within the material which may allow the detector to detect the presence of the fluid which has leaked into the material. Upon the detection of fluid within the material, remedial action may be performed, if required, as soon as possible. This may, for example, involve repair to the material, e.g. the protective layer surrounding insulation which covers a pipeline, so as to prevent any further leaking of fluid into the material. This may help to prevent or minimise the amount of corrosion of the pipeline.

In the exemplary case discussed above whereby the detector may be inserted into the insulation material surrounding the pipeline, the detector may extend through an outer protective layer which surrounds the insulation material. The protective layer may encapsulate the insulation material and protect the insulation material, and hence the pipeline, from the external environment. The protective layer may be made from any suitable material, for example: metal, plastic or composites such fiberglass, carbon fibre laminates etc. The use of a deformable body and a corresponding sensor for monitoring the deformable body, may provide a convenient and cost effective solution for monitoring the presence of the fluid within the material.

The deformable body may deform in any appropriate manner when exposed to a fluid, or when a fluid which passes into the material causes a change in the fluid content within the material. For example, air may already be present in the material with a low humidity, i.e. low moisture content, and air from outside the material with a higher humidity may leak into the material and thereby increase the humidity of the air in the material. The deformable body may tend to expand when exposed to a particular fluid, or indeed when the fluid content which it is exposed to changes, e.g. when the humidity increases. The deformable body may thus be considered to be an expandable body. The deformable body may also contract when the fluid content to which it is exposed changes, e.g. when the humidity reduces.

The deformable body may be arranged within the detector such that it is free to deform, e.g. expand, and the sensor may detect such deformation. However, in some examples, the deformable body may be constrained within the detector such that its deformation, e.g. expansion, is constrained, and not necessarily macroscopically observable. In this case, the deformable body may exert a force which is detected by the sensor. Detection of this force may thus be indicative of the presence of a fluid, or the change in the fluid content, within the material. In this instance, the force may be exerted directly, or indirectly, on the sensor.

Detection of the force may thus indicate the presence of the fluid in the material. Of course, the deformable body may deform, e.g. via expansion or contraction, and apply a force on the sensor.

The detector described above may be used to monitor the presence of a fluid in any suitable application whereby it may be advantageous to monitor for the presence of a fluid within the body. As briefly discussed above, the detector may be inserted into an insulation material which surrounds a pipe which conveys fluid. The pipe may be used to convey any fluid, e.g. water, oil, gas etc. The pipe may be present in an industrial or domestic setting. As discussed previously, the detector may detect the presence of fluid which has penetrated into the material from the external environment. The detector may also be capable of detecting a leak of fluid from the pipeline itself. The ability to detect such a leak may advantageously allow for quick and appropriate action to be taken. For example, the pipeline may be temporarily shut down until the pipeline is repaired. Another application whereby it may be beneficial to monitor for the presence of a fluid may be in the hull of a ship. In such an example, the detector may be inserted into a material within the hull of a ship which. This may allow for the monitoring of the presence of a fluid within the hull which may cause corrosion of the hull. Such a detector may also advantageously be used to in the rapid detection of a leak within the hull. The detector could also be used to detect the presence of a particular fluid within soil, e.g. in the soil of indoor or outdoor plants. The detector could also be used in buildings to alert the presence of leaks. For example, the detector may be used in a bathroom anywhere where fluids are transported, e.g. underneath a sink, toilet, bath or shower. The detector may be integrated as part of the construction of a building, e.g. underneath a bathroom floor, so as to detect the presence of a fluid.

The fluid detector may be configured to monitor the presence of any appropriate fluid. For example, the fluid detector may be configured to monitor the presence of a particular gas. In such examples, the deformable body may be made from a material which deforms in the presence of the particular gas. However, the Applicant has found that the detector may be particularly useful in monitoring the presence of moisture as the presence of moisture in a material often negatively impacts the material itself, or indeed a component which the material is adjacent to. For example, moisture within insulation layers surrounding pipelines is known to contribute towards oxidation and corrosion of the pipelines. Accordingly, in a set of embodiments, the fluid detector is a moisture detector which is configured to detect the presence of moisture within the material, and the deformable body is made from a material which deforms in the presence of moisture. In such embodiments, the fluid discussed in the various embodiments above and below may be moisture. Moisture may comprise water or any other liquid which is diffused as a vapour within a gas in the material or which is condensed into liquid form within the material. The liquid may be polar, e.g. water, or non-polar, e.g. oil. The type of liquid may determine the type of deformable body which is used. For example, the material may be specifically chosen to expand for the type of liquid being monitored. The material may also be chosen to expand depending on the properties of the fluid being monitored. For example, the material (i.e. the deformable body) may be chosen for its properties such that it expands/contracts when it experiences changes in the chemical properties of the fluid, e.g. due to protonation/deprotonation following a change in pH level. In this exemplary case, the detector may effectively function to monitor the pH of the fluid it is detecting. The deformable body and sensor may be arranged in any suitable manner such that fluid is able to reach the deformable body, and such that the sensor is able to detect deformation of, or a force applied by the deformable body. In some embodiments, the deformable body may be inserted directly into the material and be in direct contact with the material. In such embodiments, at least part of the deformable body may define an outer surface of the detector. In another set of embodiments, the detector comprises a housing, and the deformable body and sensor are contained within the housing. The housing may be configured to allow fluid to pass from the material into the housing. This may be achieved in any appropriate manner. For example, the housing may comprise a porous, e.g. fluid permeable, material which allows the passage of fluid therethrough. In addition, or alternatively, the housing may comprise at least one opening arranged to allow fluid to pass into the housing. The housing may, for example, comprise a plurality of openings. The housing may be manufactured from a non-permeable material, and have a plurality of openings therein for allowing the passage of fluid into the housing.

The detector may have any suitable shape which facilitates the insertion of the detector into the material in which presence of the fluid is being monitored. In a set of embodiments, the detector comprises an elongate portion shaped for insertion into the material. The elongate portion may be relatively narrow and allow the detector to be easily inserted into the material. The elongate portion may also advantageously allow the detector to penetrate relatively deep into the material and thereby detect the presence of fluid at a relatively deep position within the material. In the exemplary case of an insulation material surrounding a pipeline, the detector may therefore monitor the presence of fluid closer to the pipeline itself, where the fluid is likely to cause corrosion. As discussed previously, the detector may also detect fluid leaks from the pipeline itself. In the example of insulation surrounding a pipe, if the leak is relatively small, it may take a relatively significant amount of time for the fluid to permeate to an outer region of the insulation. Accordingly, by penetrating deeper into the insulation, the detector may be capable of detecting a fluid leak more quickly, and may indicate the location of the fluid leak.

The elongate portion may have any suitable shape and cross section. For example, the elongate portion may have a circular cross section such that the elongate portion has a cylindrical shape. Of course, the diameter of the circular cross section may change along the length of the elongate portion and the elongate portion may, for example, have a conical shape. It will be appreciated that the cross section of the elongate portion is not limited to such circular cross sections and the elongate portion may have any other suitable cross section. In order to allow the elongate portion to be easily advanced into the material, it may be advantageous for the elongate portion to have a relatively small maximum dimension. In a set of embodiments, a cross-section through an elongate axis of the elongate portion has a maximum dimension of 20 mm, e.g. 10 mm, e.g. 9 mm, e.g. 8 mm, e.g. 7 mm, e.g. 6 mm, e.g. 5 mm, e.g. 4 mm, e.g. 3 mm. The Applicant has found that a detector having an elongate portion with such maximum dimensions may be easily advanced into a material, e.g. an insulation material. In embodiments wherein the elongate portion has a circular cross section, the maximum dimension may be the maximum diameter of the elongate portion. The elongate portion may house the deformable body and at least a part of the sensor. In other embodiments, the sensor may be arranged separate from the elongate portion, e.g. in another portion of the housing. In such embodiments, the deformable body may extend from the elongate portion into the other portion of the housing, or any suitable means capable of transferring the force (e.g. a force transfer medium as set out further below or a piston), may transfer a force from the deformable body to the sensor. Arranging the deformable body within the elongate portion may help to ensure that the deformable body is arranged within the material and thereby capable of detecting the presence of fluid within the material. The length of the elongate portion may depend on the particular application of the detector. In a set of embodiments, the elongate portion is between 0.5 - 10 cm long, e.g. between 1 - 5 cm long.

Some materials may resist the insertion of the detector. For example, an insulation material, which has a fibrous composition, may at least partially resist insertion of the detector. Accordingly, in a set of embodiments, the detector comprises a pointed tip configured to penetrate the material into which the detector is inserted. In embodiments which comprise a housing, the housing may comprise the pointed tip. In embodiments which comprise an elongate portion, the elongate portion may comprise the pointed tip. The pointed tip may facilitate the insertion of the detector into the material by displacing the material as it is inserted therein, thereby forming an accommodation space for receiving the detector. Making the insertion of the detector easier may particularly advantageous in embodiments whereby the detector is installed by a machine, as the detector may be installed more quickly and potentially consuming less energy. As the machine may be a battery operated machine, this may allow the machine to install more detectors before requiring recharging, which may improve the installation process. Whilst the detector is shaped for insertion into a material, not all of the detector need necessarily be inserted into the material. In a set of embodiments, the detector comprises a first portion for insertion into the material and a second portion arranged to sit outside of the material. In embodiments comprising an elongate portion, the elongate portion may be considered to be the first portion. The second portion may house other components of the detector which do not need to be exposed to any fluid within the material. For example, the further portion may house a transmitter, a battery and/or any other suitable components. Arranging the transmitter in the second portion which sits outside of the material may mean that the material does not act to attenuate any signal transmitted by the transmitter. This may help to minimise the power required to transmit the signal, which may help to increase the battery lifetime of the detector.

The sensor may comprise any suitable arrangement that is capable of detecting a deformation of the deformable body and/or a force generated by the expandable body in the presence of the fluid. In a set of embodiments, the sensor comprises a piezoelectric sensor configured to detect a deformation of the deformable body and/or a force generated by the expandable body. The use of a piezoelectric sensor may be advantageous as the piezoelectric sensor itself may not consume any power in order to indicate a deformation of, and/or a force applied by, the deformable body and thus the use of such a sensor may minimise the power consumption of the detector. This may be particularly beneficial as the detector may be used in relatively remote environments where it is difficult to access the detectors in order to replace them and/or replace any power source therein.

In a set of embodiments, the piezoelectric sensor is configured to generate a voltage upon deformation, e.g. expansion or contraction, of the deformable body and/or a force applied by the deformable body. In such embodiments, the piezoelectric sensor may comprise a piezoelectric element which is configured to generate a voltage upon the change of a force applied to the piezoelectric element. The generation of a voltage may be used to indicate the presence of the fluid or changes in fluid content of the material. The deformable body may be arranged to apply a force to the piezoelectric element. The piezoelectric element may comprise a ceramic piezoelectric element or any other suitable piezoelectric element. The piezoelectric element may be formed by any suitable means. For example, in the exemplary case of the use of aluminium nitride (AIN) as a piezo material, layers of AIN may be formed by deposition using magnetron sputtering of aluminium targets in an argon-nitrogen atmosphere. As discussed above, as the detector may be installed in remote environments, it may be advantageous to minimise the power consumption of the detector as far as possible. Thus, in another set of embodiments, the detector comprises an electrical component, and wherein the voltage, generated by the piezoelectric sensor, wakes the electrical component. The voltage, generated by the piezoelectric sensor, may cause a current to flow within the detector. The current may cause the waking of the electrical component. For example, the electrical component may comprise an electrical circuit, a processor, a transmitter or any other appropriate electrical component. The electrical component may effectively remain asleep until the piezoelectric sensor detects deformation of the deformable body and generates a voltage. This may further minimise the power consumed by the detector thereby potentially reducing the amount of servicing required or reducing the frequency at which the detector, or a power source therein, has to be replaced.

The sensor may comprise any other sensor that is capable of detecting a deformation of, and/or force applied by, the deformable body. For example, the sensor may comprise a pressure sensor on which the deformable body applies a force. The pressure sensor may comprise an optical fibre arranged to deform in the presence of the force applied by the deformable body, or indeed any other suitable pressure sensor. In some embodiments, the sensor may comprise a capacitive pressure sensor. The sensor may comprise an optical sensor arranged to detect deformation of the deformable body. The optical sensor may comprise a source of light which is directed towards the deformable body, together with a detector arranged to detect light reflected from the deformable body. A deformation, e.g. an expansion or contraction, of the deformable body may change the separation between the deformable body and the light source or the detector, and thus change the time of flight of the light. Based on the time of flight, it may be possible to determine the deformation of the deformable body, and thereby determine the presence of the fluid.

In a set of embodiments, the sensor comprises a pressure sensor. In a further set of embodiments, the pressure sensor comprises a piezoresistive pressure sensor. In such embodiments, the piezoresistive sensor may be configured to detect a deformation of the deformable body and/or a force applied by the deformable body. The piezoeresistive sensor may be capable of detecting expansion and/or contraction of the deformable body. The Applicant has recognised that whilst a piezoresistive pressure sensor may require the consumption of electrical power to probe the sensor to obtain a reading therefrom, the reading at any point will be representative of the current state of the deformable body and thus the fluid content of the material. This is contrasted to piezoelectric sensors which may output a signal upon a change in force applied by the deformable body, but wherein said signal may then diminish/deplete over time potentially no longer accurately indicate the current state of the deformable body. The use of a piezoresistive pressure sensor may also facilitate more accurate measurement of force and/or deformation of the deformable body.

Irrespective of the type of sensor, the deformable body may act directly on the sensor such that the sensor is able to detect deformation of the deformable body and/or a force applied by the deformable body. However, in some embodiments, the deformable body may act indirectly on the sensor. Accordingly, in a set of embodiments, the detector comprises a force transfer medium arranged between the deformable body and the sensor, and arranged to transfer a deformation and/or force applied by the deformable body to the sensor. The force transfer medium thus acts to transfer the deformation and/or force to the sensor meaning that the sensor is no longer in direct contact with the deformable body. This may advantageously facilitate shielding of the electronic components of the detector, e.g. the sensor. This may improve the lifespan of the detector as the electronic components may no longer be exposed to the moisture. Exposure to moisture is known to impact electrical components over time and potentially reduce their accuracy. Additionally, by shielding the sensor in this manner, it may be easier to form a detector which is explosion-proof, i.e. a detector which does not have an exposed ignition source. This may be particularly important as the detector may be used in applications where explosion hazards may exist. For example, the detector may be arranged in the insulation material of a gas-carrying pipeline. Shielding the sensor in this manner may thus mean that it is possible to achieve compliance with one of the various certifications, e.g. the ATEX certification.

The force transfer medium may comprise any material which is capable of suitably transferring the force applied by the deformable body. In a set of embodiments, the force transfer medium comprises a force transfer fluid. For example, the fluid may comprise a liquid. In other embodiments, the fluid may comprise a gas. The fluid may, for example, comprise glycerol, silicone oil or fluorosilicone oil. It may be desirable for the fluid to have a relatively high boiling point and a relatively low freezing point. For example, the fluid may have a boiling point of at least 100 °C, e.g. at least 110 °C, e.g. at least 150 °C, and a freezing point of at least - 20 °C, e.g at least - 30 °C, e.g. at least - 40 °C. This may help to ensure that the detector can be used in a range of environments with different temperatures. In some embodiments, the fluid has a substantially uniform viscosity between its boiling and freezing temperatures. Having a uniform viscosity across this range of temperatures may ensure that the fluid is able to suitably transfer the force to the sensor across the range of operating temperatures. The force transfer medium may be made from a material which does not cause damage to the sensor in which it may be in direct contact.

In a set of embodiments, the force transfer fluid is incompressible or at least substantially incompressible. Using an incompressible fluid may advantageously mean that the force and/or deformation applied to the force transfer medium is largely transferred to the sensor, rather than instead compressing the fluid.

The Applicant has recognised that it is not essential for the force transfer medium to be a fluid in order to transfer the force. In other embodiments, the force transfer medium comprises a deformable solid or gel. When exposed to a force applied by the deformable body, the deformable solid or gel may deform and transfer the force to the sensor. The deformable solid or gel may comprise any material that can suitably deform in order to transfer the force. The deformable solid or gel may even comprise the same material as the deformable body itself.

The force transfer medium may be contained by the deformable body itself. For example, the deformable body may be shaped to at least partially contain the fore transfer medium.

However, in a set of embodiments, the force transfer medium is contained within a deformable housing and wherein the deformable body is arranged to deform and/or apply a force to the deformable housing. The deformable housing may, for example, comprise a tube, e.g. a cylindrical tube, which contains the force transfer medium. The deformable housing may be made from any suitable material that can contain the force transfer medium and may depend on the particular material from which the force transfer medium is made from. In a set of embodiments, the deformable housing is made from silicone. Silicone may advantageously contain the force transfer medium in the form of a fluid, may prevent the ingress of fluid into the housing externally of the housing, and may deform in the presence of a force/deformation of the deformable body.

During assembly of the detector, the deformable housing may be filled with the force transfer medium, and then the sensor may be at least partially inserted into the deformable housing so as to sense forces applied by the force transfer medium. As the sensor is inserted into the deformable housing, this may act on the force transfer medium and increase the pressure within the deformable housing. This increase in pressure may prevent the effective transfer of force by the force transfer medium. Accordingly, in a set of embodiments, the housing comprises a vent configured to release pressure within the deformable housing. The vent may therefore allow the release of pressure within the deformable housing which may ensure that the force transfer medium can suitably transfer the force from the deformable body. The vent may be selectively closable. The vent may operate automatically upon the increase in pressure, or it may require manual operation to open and close the vent. The vent may be in the form of a removable plug which closes an opening in the deformable housing.

In a set of embodiments, the deformable body acts on a first area of the force transfer medium and wherein a second, smaller, area of the force transfer medium acts on the sensor. The Applicant has recognised that this arrangement may effectively amplify the force applied by the deformable body as the force is applied to a large area, and then transferred to a small area on the sensor. This may, advantageously, allow the detector to be more sensitive and detect smaller changes in fluid content within the material. This increased sensitivity may increase the number of applications of the detector. The ratio of the first area to the second area may be at least 2:1, e.g. at least 5:1, e.g. at least 10:1, e.g. at least 20:1, e.g. at least 50:1 , e.g. at least 100:1 , e.g. at least 200:1. The specific ratio chosen may depend on the sensitivity required by the detector. The deformable body may surround the force transfer medium. As set out above, the deformable body may not act directly on the force transfer medium as it may act on a deformable housing which surrounds the force transfer medium. The force transfer medium may be in the form of an elongate cylinder, which may be constrained by the deformable housing described above. In such embodiments, the deformable body may act on the outer curved surface of the cylinder, and one end of the cylinder may act on the sensor. As will be appreciated by those skilled in the art, as long as the cylinder is sufficiently elongate, the surface area of the outer curved surface will be significantly larger than the area of the end of the cylinder. The length of the cylinder may, for example, be at least twice its diameter, e.g. at least five times as long as its diameter, e.g. at least 7 times as long as its diameter.

In embodiments comprising a force transfer medium, the Applicant has recognised that the temperature of the ambient environment in which the detector is present, i.e. the temperature of the material, may impact the temperature of the force transfer medium and hence the force transferred to the sensor by the force transfer medium. For example, the Applicant has recognised that an increased temperature may cause expansion of the force transfer medium which may increase the force applied to the sensor. Absent any means to account for this temperature change, the detector may not be able to distinguish between temperature changes and fluid changes within the material, or may not be able to determine the true amount of fluid change if there has also been a temperature change. In order to account for this, the detector may comprise a temperature sensor which measures the temperature of the ambient environment or the material in which the detector is inserted. The temperature of the ambient environment or the material may then be taken into account when analysing the force applied to the sensor.

However, the Applicant has recognised that it may be difficult to identify the impact of the temperature specifically on the fluid transfer medium, and thus it may be difficult to account for this using a temperature sensor alone. Accordingly, in a set of embodiments, the force transfer medium comprises a first material, and the fluid detector comprises: a temperature measurement medium comprising the same material as the first material and configured to change volume depending on its temperature; a further sensor configured to detect a change in volume of, and/or a force applied by, the temperature measurement medium; and wherein the temperature measurement medium is arranged such that deformation or forces applied by the deformable body do not act on the temperature measurement medium.

The Applicant has recognised that by monitoring the change in volume of a temperature measurement medium which comprises the same material as the force transfer medium, the true impact of the change in temperature on the force transfer medium may be more accurately be accounted for. The further sensor may comprise any sensor that is capable of detecting a change in volume of the temperature measurement medium. It may, for example, comprise a piezoresistive, piezoelectric or capacitive pressure sensor. The output of the further sensor may be used as a modifier for an output of the sensor, such that a more accurate measure of the fluid content of the material is generated.

The temperature measurement medium may be arranged within the detector in a position whereby the deformable body does not act on the temperature measurement medium. However, the Applicant has recognised that it may be beneficial to arrange the temperature measurement medium as close as possible to the force transfer medium, such that its temperature matches the temperature of the force transfer medium as closely as possible. Accordingly, in a set of embodiments, the temperature measurement medium is contained within a rigid housing which is arranged adjacent the force transfer medium. In being arranged adjacent, the rigid housing may not necessarily be immediately next to the force transfer medium, and there may be a gap between. The Applicant has recognised that by arranging the temperature measurement medium in a rigid housing, it may be possible to prevent the deformable body from applying a force to the temperature measurement medium.

The rigid housing may be formed from a thermally conductive material so as to facilitate heat transfer to the temperature measurement medium. This may help to ensure that the temperature of the temperature measurement medium closely matches the temperature of the environment in which the temperature measurement medium is arranged.

The deformable housing and/or the rigid housing may be impermeable to fluid. This may ensure that the force transfer medium and the temperature measurement medium are contained within their respective housings, and ensure that no fluid is able to pass through the deformable housing and/or rigid housing and interact with the medium contained therein. The impermeable deformable housing and/or rigid housing may also ensure that the force transfer medium or temperature measurement medium, contained therein, is not able to escape the deformable housing and/or rigid housing. This may ensure that the pressure within the deformable housing and/or rigid housing does not reduce due to escape of the medium contained therein.

In a set of embodiments, the temperature measurement medium has the same volume as the force transfer medium at a reference temperature. In having the same volume as the force transfer medium, any temperature effects on the temperature measurement medium will likely be identical to those on the force transfer medium. Accordingly, such embodiments may mean that the detector can account for temperature changes in an accurate manner.

In a set of embodiments, the detector is configured to determine a fluid, e.g. moisture, content of the material by taking into account an output from the sensor and output from the further sensor. As such, the detector may determine the fluid content by taking into account the deformation and/or force applied by the deformable material (applied through the force transfer medium) as well as the output of the further sensor which indicates the temperature of the temperature measurement medium, and thus the temperature of the force transfer medium.

The detector may thus be capable of correcting for temperature changes which impact the force applied to the sensor through the force transfer medium. The detector may comprise a processor or any other suitable electronic circuitry that is configured to take the output from each of the sensor and further sensor and generate an indication of fluid content taking into account both outputs. The output from the sensor and the output from the further sensor may be suitably combined to provide a differential reading. In the case when the sensor and further sensor comprise pressure sensors, the differential reading may comprise a differential pressure reading. The differential pressure reading may indicate the difference between the pressure detected by the sensor and the pressure detected by the further sensor. This may be indicative of the force applied by the force transfer medium resulting from the force applied by the deformable body, and not include any force applied due to temperature changes of the force transfer medium.

In embodiments comprising an elongate portion which is configured to extend into the material, the force transfer medium and/or the temperature measurement medium may be arranged within the elongate portion. The force transfer medium and/or the temperature measurement medium may extend along a length of the elongate portion.

Whilst the embodiments discussed above have been described in the context of a temperature measurement medium such that the detector is capable of taking into account temperature changes of the force transfer medium, it will be appreciated that the temperature measurement medium may be used to detect other forces which may be transferred through the force transfer medium but which are not generated by the deformable body. For example, the temperature measurement medium and the further sensor may detect forces applied, for example, due to vibrations in the detector, e.g. due to vibrations in the material in which the detector is arranged. Such vibrations would likely have a similar impact on both the force transfer medium and the temperature measurement medium. As such, any such forces may be accounted for by the temperature measurement medium and its further sensor and thus the detector may thus be capable of more accurately detecting the fluid.

The detector may comprise a battery, or other suitable energy storage means such as a capacitor or supercapacitor, configured to supply components of the detector with power for operation. For example, the energy storage means may supply a transmitter with electrical power in order to be able to transmit a signal. However, the detector may be installed in hard to reach places whereby it may be difficult to reach the detector in order to perform maintenance thereon, e.g. to change the battery. Accordingly, in a set of embodiments, the detector comprises an electrical generator configured to generate electrical energy for use in operation of the detector. The electrical generator may be considered to be an energy harvesting device which captures energy. The electrical generator may supply a battery or other energy storage means with energy. The provision of an electrical generator on the detector may further minimise the service requirement of the detector and may increase the operational life of the detector.

The electrical generator may comprise any suitable generator which is capable of producing electrical energy for use in operation of the detector. For example, the electrical generator may comprise a thermoelectric generator configured to generate electricity from thermal energy transferred to the detector from the material in which it is inserted. Such an example may be particularly advantageous in situations whereby the detector is used to detect the presence of fluid in a material which is heated. For example, when the material, in which the detector is inserted, is used to surround a pipe which transfers heated fluid, or wherein the material surrounding the pipe is heated by the environment which it is placed, e.g. by sunlight, the thermoelectrical generator may utilise the heat within the material to generate electrical energy for use by the detector.

A thermoelectrical generator is not the only form of electrical generator that may be used, and in another set of examples, the electrical generator may comprise a piezoelectric element configured to generate electrical energy. In some instances, the detector may be inserted into a material which vibrates, e.g. when the material is an insulation material on a pipeline. The piezoelectric element may advantageously convert the vibrations of the pipeline into electrical energy for use by the detector. The piezoelectric element may be a standalone element for use in the generation of electrical energy, or in embodiments which comprise a piezoelectric sensor, the piezoelectric element may be part of the piezoelectric sensor. The piezoelectric sensor itself may act as an electrical generator and the energy generated due to the expansion of the expandable material may provide sufficient power to operate the detector. Other forms of electrical generator which may be used include a photovoltaic generator configured to generate electrical energy from light, or a wireless power transfer device configured to generate electrical energy from a varying electric, magnetic or electromagnetic field. The wireless power transfer device may, for example, be part of a radio frequency identification (RFID) device.

The sensor may be arranged in any suitable manner such that it is capable of detecting a deformation of, and/or a force applied by, the deformable body. In a set of embodiments, the sensor and deformable body are separate components. In such embodiments, the sensor may be arranged adjacent the deformable body so as to detect a deformation of, and/or a force applied by, the deformable body. In a further set of embodiments, the deformable body at least partially surrounds the sensor. In another set of embodiments, the sensor at least partially surrounds the deformable body.

In a set of embodiments, the deformable body is in direct contact with the sensor. Such an arrangement may help to ensure that the space occupied by the deformable body and sensor is kept to a minimum. In an alternative set of embodiments, the deformable body acts on the sensor via an intermediate member. The use of an intermediate member may allow more design freedom in the shape of the detector. The intermediate member may have any suitable shape. For example, the intermediate member may be in the form of a piston.

In embodiments in which the sensor comprises a piezoelectric sensor, the piezoelectric sensor may comprise a piezoelectric element configured to generate a voltage when an external pressure is applied thereto. In such embodiments, the deformable body may act directly on the piezoelectric element. The piezoelectric element and deformable body may have any suitable form. In a set of embodiments, the piezoelectric element may have a plate-like shape and the deformable body may be arranged on at least one side, e.g. both sides, of the piezoelectric element. In another set of embodiments, the piezoelectric element may be in the form of a hollow cylinder. In such embodiments, the deformable body may be arranged adjacent the inside and/or outside of the hollow cylinder. In embodiments wherein the deformable body is adjacent the inside of the hollow cylinder, the deformable body may be in the form of a hollow cylinder or a solid cylinder. Having the expandable material both inside and outside of the hollow cylinder may advantageously increase the force applied to the piezoelectric element and thereby increase any voltage generated. An increased voltage may be easier to detect and thus make detection of a fluid change easier.

In another set of embodiments, the piezoelectric element and deformable body are adjacent one another and have a spiral configuration. Such a spiral configuration may increase the area of the deformable body which is susceptible to the fluid and also increase the area of the deformable body which acts on the piezoelectric element. This may increase the sensitivity of the detector and reduce the response time of the detector. The piezoelectric element and deformable body may be formed together as a flat sheet and formed into a spiral configuration depending on the specific diameter of the detector.

In any of the embodiments described above, the piezoelectric element and deformable body may be formed by three-dimensional printing. In embodiments wherein the deformable body is in direct contact with the sensor, the sensor may be at least partially coated with the deformable body. For example, a piezoelectric element of the sensor may be coated with the deformable body. In embodiments comprising a piezoelectric sensor, the piezoelectric sensor may comprise a plurality of piezoelectric elements. For example, each of the piezoelectric elements may be stacked on top of one another. The deformable body may be a single body, or may comprise a plurality of sub-bodies, for example in the form of a granular arrangement of subbodies.

In the embodiments described above, whilst the sensor and deformable body may be in direct contact with one another, they may nonetheless be considered to be separate to one another. In an alternative set of embodiments, the sensor is integrated within the deformable body. For example, the deformable body may comprise a foam material, e.g. a solid foam, and the sensor may comprise a piezoelectric sensor dispersed within the foam material. The piezoelectric sensor may comprise piezoelectric elements in the form of wires or rods arranged within the foam material. The wires or rods may be relatively small, e.g. of the order of nanometres wide. Such an arrangement may advantageously increase the contact area between the deformable body and the piezoelectric sensor thereby increasing the force applied to the piezoelectric sensor. Additionally, a foam may have an increased surface area and therefore the surface area for interaction with a fluid may be increased, which may increase the sensitivity and decrease the response time of the detector. A foam structure may also absorb fluid more easily, due to the capillary effect of the foam structure.

The deformable body may comprise any material that expands in the presence of a particular fluid. In a set of embodiments, the deformable body comprises a hygroscopic material. Such a hygroscopic material may advantageously absorb fluid, e.g. moisture, from the material in which the detector is inserted. Any suitable hygroscopic material may be used. In a set of embodiments, the hygroscopic material comprises a hygroscopic polymer, for example sodium polyacrylate or polyimide.

In some instances, the presence of a particular fluid within the material may be enough to justify action, e.g. inspection or maintenance, being performed as the presence of fluid may indicate a potential problem. Accordingly, in some embodiments, in monitoring the presence of the fluid, the detector is configured to determine that a fluid is present within the material. This may, for example, be applicable in applications whereby the detector is configured to monitor the presence of a fluid which is otherwise not present unless there is some form of a leak, or is only present in small amounts prior to a leak. The presence of the fluid may therefore indicate that the fluid has leaked into the material. When monitoring for the presence of fluid, upon the detection of fluid by the detector, any appropriate action may be taken. In a set of embodiments, the detector is configured to output a signal, indicating the detection of the fluid, when the sensor detects a deformation of, and/or a force applied by, the deformable body. The outputting of the signal may advantageously allow the remote monitoring of the detector. In outputting the signal upon detection of fluid, the detector may advantageously allow for the rapid detection of fluid, and appropriate action may then be taken. For example, maintenance may be organised to inspect the location at which the detector is installed. This may allow any issues to be resolved as soon as possible, and may eliminate the need for routine inspection when the particular fluid is not detected.

The particular application of the detector may impact the form in which the signal is output. For example, if the detector is used in a location whereby the detector can be visually inspected by a user, the detector may comprise a light emitting means, and the signal may be output by the light emitting means. For example, the light emitting means may be caused to illuminate upon the detection of fluid. However, such an arrangement may not be appropriate when the detector is used to detect the presence of fluid in remote locations. Therefore, in a set of embodiments, the detector comprises a transmitter configured to transmit the signal indicating the detection of fluid. Such a set of embodiments may advantageously allow remote monitoring of the detector.

The indication of the presence of fluid within the material may be sufficient in some instances to justify the need for further inspection and/or maintenance at the installation site of the detector. However, in some instances, the presence of fluid alone may not justify immediate action being taken, and it may be beneficial to ascertain the fluid content within the material in order to determine whether any action is to be taken. Accordingly, in a set of embodiments, the detector is configured to determine the fluid content within the material. Appropriate action may then be taken based on the fluid content detected. The fluid content may comprise, for example, the moisture content, i.e. humidity, within the material. For example, if a low moisture content is detected, basic maintenance may be organised for the location of the detector, whereas if a high moisture content is detected more drastic action may be taken, e.g. by shutting off the supply of fluid to a pipeline. In embodiments comprising a transmitter, the signal output by the transmitter may further comprise the fluid content determined. Determining the fluid content within the material may mean that maintenance may be reduced. For example, if it is determined that moisture is present but at a relatively low concentration, maintenance may be postponed until the moisture content reaches a higher concentration which poses a greater risk.

The fluid content may be determined in any suitable manner. The sensor may be capable of determining the fluid content based on the deformation of, and/or force applied by, the deformable body. For example, in embodiments which comprise a sensor in the form of a piezoelectric sensor, the magnitude of the voltage produced by the piezoelectric sensor may be indicative of the fluid content within the material. In addition, or alternatively, the fluid content may be determined by analysing a change in the voltage produced by the piezoelectric sensor over time. The Applicant has found that for some fluids there is a correlation between the fluid content and the integral of the voltage over time. Accordingly, by determining the integral of the voltage over time it may be possible to determine a fluid content within the material.

Accordingly, in embodiments comprising a piezoelectric sensor, the detector may be configured to determine an integral of the voltage generated by the piezoelectric sensor over time and to determine the fluid content based on the integral. The integral may be determined between a point in time at which the voltage changes from a baseline, to a point in time at which the voltage returns to a baseline. The baseline may be 0 V. In the exemplary case of moisture content, when a change in humidity occurs, a voltage pulse is created. The Applicant has found that the size of the pulse may depend on the change in humidity of the fluid within the material. For example, a small change in humidity may create a small pulse, whereas a large change in humidity may cause a large pulse. Accordingly, by determining the size of the pulse by integrating the voltage over time, it may be possible to determine the change in moisture content, i.e. humidity, within the material.

In embodiments comprising a piezoresistive sensor, the fluid content may be determined by analysing the resistance of the sensor which may change depending on the force applied thereto. A larger force applied to the sensor may cause the sensor to have an increased resistance. Measurement of the resistance of the sensor may thus indicate the force being applied thereto which is indicative of the expansion of the deformable body and thus the fluid content of the material.

The deformable body may expand or contract as the fluid content of the fluid within the material changes. For example, in embodiments whereby the deformable body deforms in the presence of moisture, the deformable body may expand as the moisture content of the fluid increases and contract as the moisture content of the fluid decreases. The fluid content may be determined based on whether the deformable body is expanding or contracting. For example, in embodiments which comprise a piezoelectric sensor comprising a piezoelectric element, the piezoelectric element may generate a positive voltage when the deformable body expands. Such a positive voltage may therefore indicate an increase in the moisture content of the fluid. Conversely, the piezoelectric element may generate a negative voltage when the deformable body contracts. The detection of a negative voltage may therefore be indicative of a reduction in the moisture content of the fluid. Accordingly, by monitoring whether the piezoelectric element is generating a positive or negative voltage, it may be possible to determine how the fluid content is changing, e.g. whether the moisture content is increasing or decreasing.

In the exemplary case whereby liquid fills the material and reaches the deformable body, the liquid may cause continuous expansion of the deformable body and the voltage pulse generated may last for a significant period of time, e.g. a number of hours. The detection of such a pulse which lasts for a number of hours may therefore be used to determine the presence of liquid within the material. Of course any other suitable analysis of the voltage produced by the piezoelectric element may also be performed in order to determine the fluid content of the material.

For a piezoresistive pressure sensor, the resistance may simply increase or decrease depending on whether the deformable body is expanding or contracting.

Oher means may be used to determine the fluid content of the material. For example, the sensor may comprise a potentiometer which has an adjustable resistance, and the resistance of potentiometer may be adjusted by expansion or contraction of the deformable body. The fluid content may then be determined based on the resistance as a fluid having an increase moisture content may cause greater expansion of the deformable body. In an alternative set of examples, the detector may comprise a plurality of sensors arranged together to determine the fluid content within the material. For example, the plurality of sensors may be arranged in a staggered arrangement such that at a first fluid content level, e.g. corresponding to first humidity, the deformable body expands to act on a first sensor, at a second fluid content level, e.g. at second humidity, the deformable body expands to act on a second sensor and at a third fluid level, e.g. at third humidity, the deformable body expands to act on a third sensor. Each sensor may be configured to output a signal when it is acted upon. The number of sensors may define the resolution at which the fluid content can be determined. For example, with three sensors, three fluid content levels may be determined. Of course any suitable number of sensors may be used. Each of the sensor may comprise a piezoelectric sensor. The detector may comprise a suitable electronic component or suitable electrical circuitry to determine from which sensor a signal is received and thereby determine the fluid content level detected.

In a set of embodiments, the detector is configured to output a unique identification of the detector. In embodiments comprising a transmitter, the transmitter may also be configured to transmit the unique identification of the detector. The transmitter may comprise a radio frequency identification (RFID) device that is configured to output the unique identification of the detector. Through transmission of the unique identification of the detector, it may be possible to determine the location of the detector which has output the signal. This may be achieved by suitably storing the location and unique identification for each detector during installation of the detectors. Knowledge of the location of the detected fluid may beneficially allow targeted maintenance to be performed quickly at the location of the detected fluid.

The transmitter may comprise any suitable transmitter, using any appropriate frequency, that is able to transmit the signal, optionally also the unique identification of the detector or indeed any other appropriate signal. In a set of embodiments, the transmitter is a Bluetooth transmitter. A Bluetooth transmitter may use a minimal amount of energy to operate, and may thus help to maximise battery life of the detector. Of course, any other suitable frequency or transmission protocol may be used. The transmitter may communicate directly with a receiver on a central controller, a receiver on an intermediate communication node and/or with a receiver on another detector. As such, the detector may comprise a receiver configured to receive a signal from another detector or any other component, e.g. an intermediate connection node.

Fluid within the material may flow naturally from the material to the detector and thereby cause deformation of the deformable body. However, in a set of embodiments, the detector comprises a fluid transport means configured to facilitate the flow of fluid from the material towards the deformable body. For example, the fluid transport means may comprise a plurality of cellulose fibres which act to facilitate the transportation of the fluid towards the deformable body. The deformable body may, for example, be at least partially surrounded by cellulose fibres. The cellulose fibres may be at least partially embedded within the deformable body. The use of a fluid transport means which facilitates the flow of fluid from the material to the deformable body may advantageously allow the detector to more quickly detect the presence of the fluid within the material, thereby improving the response time of the detector. The fluid transport means may also more evenly distribute the fluid in the deformable body. This may cause more uniform deformation of deformable body which may be easier to detect by the sensor. The fluid transport means may actively draw fluid out of the material.

As will be appreciated by those skilled in the art, at least for some materials into which the detector is inserted, even when the detector is fully inserted, a small opening may form between the detector and the material which partially exposes the inside of the material to the external environment. For example, when the detector is inserted through the protective layer surrounding an insulation layer which surrounds a pipeline, there may be an opening formed in which fluid can flow from the external environment into the insulation material via an opening in the protective layer. Accordingly, in a set of embodiments, the detector comprises a sealing element arranged to seal the detector to the material into which it is inserted. For example, the sealing element may seal a hole which is formed as the detector is inserted into the material. In embodiments comprising an elongate portion, e.g. in the form of a cylinder, the sealing element may comprise a sealing element which surrounds the elongate portion. Sealing of the material by the sealing element in this manner may help to prevent any fluid in the external environment, e.g. moisture in the air, from passing into the material and causing damage, e.g. through corrosion of a pipe which the material surrounds. The sealing element may comprise any appropriate element which is capable of sealing the material. For example, the sealing element may comprise a rubber O-ring. In addition, or alternatively, the sealing element may comprise an adhesive that binds the detector to the material, thereby preventing the flow of fluid into the material via the opening formed for the detector. The adhesive may both seal and secure the detector in place. The adhesive may be activated by radiation, e.g. ultraviolet light, or by pressure, such that the detector can be selectively sealed in place. In examples whereby the adhesive is activated by pressure, the adhesive may comprise a pressure sensitive adhesive.

In a set of embodiments, the detector comprises a retention feature arranged to prevent the detector from being retracted from the material in which it is inserted. The retention feature may advantageously hold the detector within the material. This may be particularly advantageous as the detector may be installed into materials which are exposed to particularly harsh environments, for example where there are high winds which may otherwise pull the detector out of the material. Similarly, the detector may be inserted into materials which move, e.g. vibrate, and the retention feature may prevent the detector from becoming dislodged due to the vibrations. The retention feature may also help to ensure that the opening through which the detector passes is kept sealed. The retention feature may have any suitable form that prevents the detector from being retracted from the material. The retention feature may comprise an adhesive which secures the detector in position in the material. The retention feature may comprise at least one hook which engages with the material. The retention feature may also comprise an external thread which engages with the material. The external thread may, for example, be provided around the elongate portion where provided.

The Applicant has recognised that it may be beneficial in some instances to measure other properties of the environment in which the detector is inserted. Accordingly, in a set of embodiments, the detector comprises a further sensor arranged to detect another property of the material in which the detector is inserted or of the environment in which the detector is present. For example, the further sensor may comprise a temperature sensor, a pH sensor, a resistivity meter or any other suitable sensor. This further sensor may be considered to be an additional sensor. This further sensor may be, or be part of, the further sensor in the embodiments described above. The information collected from the further sensor may help to inform what action needs to be taken when fluid is detected. For example, using a resistivity meter it may be possible to determine whether the fluid within the material is fresh water or salt water. This may indicate whether the fluid leak is from, e.g whether it is from a pipe which the material surrounds, or whether there is a hole within the material which is allowing fluid from an environment in which the pipe is placed to pass into the material surrounding the pipe.

In a set of embodiments, the sensor is surrounded by a waterproof layer. In embodiments comprising a piezoelectric element, the piezoelectric element may be surrounded by, e.g. coated in, a waterproof material. Providing a waterproof layer around the sensor may prevent degradation, e.g. due to corrosion, of the sensor and thus ensure the sensor is able to perform its function.

In any of the embodiments described above, the detector may be configured to remain in-situ within the material for an extended period of time, e.g. at least 1 year, e.g. at least 2 years, e.g. at least 3 years, e.g. at least 5 years, e.g. at least 10 years, e.g. at least 15 years, e.g. at least 20 years.

According to a second aspect of the present invention there is provided a fluid monitoring system comprising: a plurality of detectors, according to any of the embodiments discussed above, installed in a material so as monitor the presence of fluid in the material.

Thus, as will be appreciated by those skilled in the art, the fluid detection system may be capable of detecting the presence of a fluid at multiple locations within the material.

In a set of embodiments, the system comprises a central controller configured to monitor the plurality of detectors, and wherein the plurality of detectors communicate with the central controller. The central controller may be capable alerting the appropriate personnel to the detection of fluid. For example, the central controller may transmit a communication to a member of maintenance personnel to perform maintenance at the installation site of the detector. The central controller may also cause a display device to output an alert upon the detection of fluid. In embodiments wherein the detectors are capable of determining the fluid content, the display device may display the fluid content of at least some of the detectors. Personnel may thus monitor the fluid content and take appropriate action when required.

As discussed previously, the detectors may be installed in remote locations and may be installed over relatively large distances. For example, the detectors may be installed along the length of a pipeline which extends for many kilometres. The detectors may be arranged at a set spacing along the pipeline. For example, the detectors may be arranged every metre along the pipeline. Of course the detectors may be placed at any appropriate spacing along the pipeline. In such instances, it may not be possible for the detectors to communicate directly with the controller without using a transmitter which consumes relatively large amounts of power. Accordingly, in a set of embodiments, at least one of the plurality of detectors communicates with the central controller via an intermediate communication node configured to facilitate communication between the detector and central controller. The intermediate communication node may facilitate communication from a plurality of detectors. In such embodiments, any transmitter on the detectors may only need to be capable of communicating with the intermediate communication node and may thus consume less power. The system may comprise a plurality of intermediate communication nodes. Sub-sets of the plurality of detectors may communicate with the most proximal intermediate communication node. The plurality of intermediate communication nodes may communicate with one another. In such embodiments, one intermediate communication node may communicate with the central controller via another intermediate communication node. Of course, at least one of the plurality of detectors may be capable of communicating directly with the central controller if it is sufficiently close thereto. In another set of embodiments, the plurality of detectors are configured to communicate with each other. For example, the detectors may be configured to communicate with proximal detectors. The detectors may thus act as a relay to pass a signal to the central controller. As will be appreciated, this may allow a signal from one detector to be passed along to the central controller along a large distance via at least one further detector. The transmission range of any given detector may therefore be kept to a minimum which may help to reduce the power consumption of the detectors. In such embodiments, the detectors may comprise both a transmitter and receiver, or a transceiver capable of both transmitting and receiving signals.

According to a third aspect of the present invention there is provided a method of installing the detector of any of the embodiments discussed above, the method comprising: inserting the detector at least partially into a material to be monitored.

In a set of embodiments, the method comprises inserting a plurality of detectors into the material to be monitored.

When a detector detects the presence of a fluid, it may then be necessary to perform maintenance, e.g. on the pipeline which the material surrounds. In order to be able to perform such maintenance, it may be advantageous to know the location of the detector which has detected the fluid. Accordingly, in a set of embodiments, the method comprises storing an installation location of the detector and a unique identification of the detector. The installation location may comprise a physical location, e.g. defined by GPS coordinates or by a local positioning system (LPS). In addition, or alternatively, the installation location may comprise a relative location of the detector relative to the material into which it is inserted. In the exemplary case of a pipeline, the installation location may be the distance along the pipeline from a reference point, e.g. a starting point of the pipeline. Storing the location of the detector and a unique identifier of the detector may allow the location of the detector which has detected fluid to be quickly and easily determined. The storing of the location and the unique identifier of the detector may be achieved in any suitable manner. For example, a tool which is used to insert the detector may be location aware, e.g. through the use of a GPS device thereon, and be configured to store the location at which a particular detector is stored, along with its unique identifier. The tool may obtain the unique identifier of the detector by interrogating the detector in any suitable manner. The unique identifier and the location may be transmitted to and stored on a server. The server may be any suitable server, for example a cloud based server. The detector may be installed in any suitable manner. In a set of embodiments, the method comprises installing the detector using a machine, e.g. a tool. The machine may comprise any machine that is capable of inserting the detector. For example, the machine may be a handheld machine which is held by an operator. The machine may be configured to forcible insert the detector into the material. In another set of embodiments, the machine is an autonomous machine. For example, the autonomous machine may comprise a robotic platform which is capable of installing the detector. The autonomous machine may comprise a drone. The machine may be configured to carry and install plurality of detectors. The machine may therefore be capable of installing a plurality of detectors before having to return to a base to be re-stocked with detectors. This may increase the speed at which the detectors can be installed.

One or more non-limiting examples will now be described, by way of example only, and with reference to the accompanying figures in which:

Fig.1 shows a perspective view of a detector in accordance with an embodiment of the present invention;

Fig. 2 shows an insulated pipe with a plurality of the detectors shown in Fig. 1 installed thereon; Fig. 3 shows a cross-sectional of the detector shown in Fig. 1 illustrating the components therein;

Fig. 4 shows a cut-away view of the detector shown in Fig. 1 revealing the deformable body and the sensor;

Figs. 5A-5B illustrate the flow of fluid into and out of the detector of Fig. 1 ;

Fig. 6A shows a graph of humidity plotted against the voltage generated by the piezoelectric sensor within the detector;

Fig. 6B shows a graph illustrating the integral of the voltage peaks plotted against the change in relative humidity;

Fig. 7 shows an alternative arrangement of a deformable body and piezoelectric sensor;

Fig. 8 shows another alternative arrangement of a deformable body and piezoelectric sensor; Fig. 9 shows a further alternative arrangement of a deformable body and piezoelectric sensor; Fig. 10 shows a view focusing on the deformable body and piezoelectric sensor shown in Fig. 9; Fig. 11 shows a schematic view of a system comprising a plurality of detectors in communication with intermediate communication nodes and a central controller;

Fig. 12 is a flowchart illustrating the process of installing a detector;

Fig. 13 is a close-up view of the expandable body comprising a fluid transport means therein; Fig. 14 is a cross-sectional view of a detector in accordance with another embodiment of the present invention;

Fig. 15 is a cross-sectional view through the elongate portion through the line A-A shown in Figure 14;

Fig. 16 is a cross-sectional view of the detector shown in Fig. 14 when experiencing an increase in moisture;

Fig. 17 is a cross-sectional view of the elongate portion through the line A-A shown in Figure 16.

Figure 1 shows a perspective view of a detector 2, in accordance with an embodiment of the present invention, for monitoring the presence of a fluid when installed in a material. The detector 2 comprises a housing 3 which comprises an elongate portion 4 with a pointed tip 6 at the end thereof. The pointed tip 6 may allow the detector 2 to be more easily inserted into a material. The detector 2 also comprises an upper housing 8 in which various components of the detector 2 are housed. As will be appreciated by those skilled in the art, the detector 2 shown in Figure 1 is merely for illustrative purposes and the detector 2 may have any suitable shape and configuration.

Figure 2 shows a view of a pipe 10 which may be used to transport a fluid, e.g. a liquid such as water. The pipe 10 is surrounded by an insulation layer 12 which is surrounded by a protective layer 13. The protective layer 13 may prevent fluid, within the environment which the pipe 10 is placed, from reaching the material 12, and thus the pipe 10. Over time, the protective layer 13 may become damaged and/or degraded and as a result fluid within the surrounding environment may pass into the insulation layer 12. The fluid may, for example, comprise moisture. Moisture within the insulation layer 12 may act to corrode the pipe 10. Over time, the pipe 10 may corrode to the point where a hole in the pipe 10 forms such that the fluid being transported is able to escape the pipe 10. .As will be appreciated by those skilled in the art, failure of the pipe 10 may cause significant down-time. In situations whereby the pipe 10 is used to transfer a fluid within an engineering facility, for example, such down-time may be very expensive.

As depicted in Figure 2, a plurality of detectors 2 may be installed into the insulation layer 12 surrounding the pipe 10. The detectors 2 may extend through the protective layer 13 surrounding the insulation layer 12. In the embodiment depicted, the detectors 2 are installed along the length of the pipe 10. Arranging the detectors 2 on the pipe in the manner depicted may allow for the detection of fluid in the insulation layer 12, which may indicate a leak in the protective layer 13, or indeed in the pipe 10. The presence of multiple detectors 2 may allow the location of the fluid leak to be determined more easily. When the detectors 2 are installed into the insulation 12, their location together with their unique identifier may be stored. Accordingly, when one of the detectors subsequently outputs a signal indicating the detection of fluid, by determining the location which corresponds to the unique identification which may also be output by the detector 2, it may be possible to determine the location of the leak. Appropriate action may then be taken at the relevant location on the pipe 10.

As shown in Figure 2, the elongate portion 4, which may be considered to be a first portion of each detector 2, is inserted through the protective layer 13 and into the insulation 12. The upper housing 8, which may be considered to be the second portion of each detector 2, is arranged to sit outside of the insulation 12.

Figure 3 shows a cross-sectional view illustrating the main internal components of the detector 2 shown in Figures 1 and 2. As shown in Figure 3, a deformable body 14, and sensor 15 configured to detect deformation of the deformable body 14, are arranged in the elongate portion 4 of housing 3 of the detector 2. The elongate portion 4 of the housing 3 allows fluid to pass through the elongate portion 4 so as to reach the deformable body 14. The elongate portion 4 may comprise at least one opening, e.g. a plurality of openings 36, in order to allow the fluid to reach the deformable body. Such openings 36 are illustrated in Figures 5A and 5B and will be discussed further below. In addition or alternatively, the elongate portion 4 may be made from a porous material which allows fluid to pass there through. The deformable body 14 may comprise a fluid transport means which will be described in further detail below with reference to Figure 13.

The detector 2 comprises a sensor 15 which is configured to detect expansion of the deformable body 14. The deformable body 14 may, for example, be made from a hygroscopic material. In the embodiment depicted, the sensor 15 is in the form of a piezoelectric sensor 15 which comprises a piezoelectric element 16 and a voltage detector 18. The piezoelectric sensor 15 operates according to well established principles. The deformable body 14 is arranged to act on the piezoelectric element 16 such that when it deforms, e.g. via expansion or contraction, this causes the piezoelectric element 16 to generate a voltage. The voltage generated is detected and measured by the voltage detector 18. The detector 2 further comprises a signal transmitter 24 which comprises an antenna 26. The transmitter 24 and antenna 26 may be in the form of a transceiver such that it can both send and receive signals. The transmitter 24 may be a Bluetooth device, for example a Bluetooth Low Energy (BLE) device. The transmitter 24 may lay dormant, i.e. in a sleeping state, when the voltage detector 18 does not detect any change in voltage and may be woken by an output of the voltage detector 18. The detector 2 may also comprise a battery 28 arranged within the upper housing 8. The battery 28 supplies the signal transmitter 24 with energy so as to be capable of transmitting a signal. The battery 28 may also supply any other components within the detector 2 with energy as required. Whilst a battery 28 is depicted, it will be appreciated that any other energy storage means, e.g. a capacitor or supercapacitor, may be used. In some embodiments, the battery 28 or other energy storage means may be omitted, particularly where the detector 2 is capable of generating or harvesting its own energy, e.g. via the electrical generator 29 discussed below.

In addition or alternatively to the battery 28, the detector 2 may comprise an electrical generator 29. As depicted, the electrical generator 29 may supply the transmitter 24 with electrical power. The electrical generator 29 may also supply the battery 28 with energy so as to re-charge the battery 28. The electrical generator 29 may comprise any suitable means that is capable of generating its own electrical power. For example, the electrical generator 29 may comprise a piezoelectric element which generates electricity when it vibrates. Alternatively, the electrical generator 29 may form part of the sensor 15, which comprises the piezoelectric element 16, and may harvest energy from the deformation, e.g. expansion and contraction, of the deformable body 14. The electrical generator 29 may also comprise a thermoelectrical generator as discussed previously.

The detector 2 may also comprise a capacitor 20 and a light emitting means in the form of a light emitting diode (LED) 22. The LED 22 and capacitor 20 may be configured such that LED 22 illuminates upon the detection of fluid. The LED 22 may be configured to flash as this may be more noticeable. This may allow the observer to take appropriate action more quickly, which may minimise the risk of further damage occurring due to the fluid.

The detector 2 comprises a sealing element 30 arranged on the underside of the upper housing 8 and extending around the elongate portion 4. The sealing element 30 is arranged to seal the material into which the detector 2 is inserted. This may help to prevent the ingress of fluid, e.g. liquid, from outside the material into the material. In the example depicted in Figure 2, the sealing element 30 may seal to the protective layer 13 surrounding the insulation 12. The sealing element 30 may have any suitable form and be arranged in any location such that it is capable of sealing the detector 2 to the material into which it is inserted.

A retention feature 32, in the form of a hook, is also provided on the proximal end 33 of the elongate portion 4, where the elongate portion 4 meets the upper housing 8. The retention feature 32 acts to help retain the detector 2 in the material in which it is inserted. This may advantageously prevent the detector 2 from falling out of the material. This may be important in applications where the material into which the detector 2 is inserted may vibrate, e.g. when installed into the insulation 12 surrounding a pipe 10 which may vibrate due to the fluid passing therethrough. The retention feature 32 may also act to ensure that the sealing element 30 is pressed against the material and thereby forms an appropriate seal. Whilst the retention feature 32 is depicted in the form of a hook, it will be appreciated that the retention feature 32 may comprise any suitable feature which is capable of holding the detector securely in place.

The detector 2 may also comprise a further sensor 31. The further sensor 31 may measure or detect any suitable property. For example, the further sensor 31 may be a pH sensor, a temperature sensor, a resistivity meter or any other suitable sensor. The further sensor 31 may be in communication with the transmitter 24 such that the transmitter 24 is able to transmit information obtained from the further sensor 31. The further sensor 31 may be housed within the upper housing 8. Alternatively, the further sensor 31 may be exposed to an external environment, or the material into which the detector 2 is inserted.

Figure 4 shows a view of the detector 2 shown in Figures 1-3 with the upper housing 8 removed to reveal the sensor 15 within the elongate portion 4. In the embodiment depicted, the sensor 15 comprises a piezoelectric element 16 in the form of a rectangular plate with the deformable body 14 arranged on either side of the piezoelectric element 16. Electrodes 34 are attached to either side of the piezoelectric element 16 and are connected to the voltage detector 18 (not shown in this Figure). In the embodiment depicted in Figure 4, as the deformable body 14 deforms, e.g. via expansion or contraction, in the presence of a fluid, this applies a force to the piezoelectric element 16 which causes the generation of a voltage. In the presence of the fluid, the deformable body 14 may not deform in a manner which is macroscopically visible, but may nonetheless deform at a microscopic level and thereby apply a force to the piezoelectric element 16. Figure 5A shows a close-up sectional view of part of the elongate portion 4 of the detector 2 shown in Figures 1-4. As shown in this Figure, the elongate portion 4 comprises a plurality of openings 36 along its length which allow fluid to pass from the material to the deformable body 14.

Typical operation of the detector 2 will now be described with reference to Figures 1 to 5A. The detector 2 may be inserted through the protective layer 13 and into the insulation 12 as shown in Figure 2. If the insulation layer 13 becomes damaged or degraded, fluid may pass into the insulation layer 12. Similarly, if the pipe 10 itself becomes damaged or degraded for any reason, fluid passing through the pipe 10 may pass into the insulation layer 12. As depicted in Figure 5A, fluid within the insulation 12 will pass through the openings 36 and be absorbed by the deformable body 14. This will cause the deformable body 14 to expand, or at least try to expand, thereby applying a force to the piezoelectric element 16. A force applied to the piezoelectric element 16 causes the generation of a voltage which is detected by the voltage detector 18. With further reference to Figure 3, the voltage detector 18 may charge the capacitor 20 and thereby cause the LED 22 to become illuminated. In addition or alternatively, the voltage detector 18 may direct a signal to the transmitter 24 indicating the detection of fluid. This may cause the transmitter 24 to wake, after previously lying dormant. The transmitter 24 may then transmit a signal, using the antenna 26, indicating the detection of fluid. The power required for operation of the transmitter 24 may be supplied by the battery 28. The transmitter 24 may also transmit a unique identification of the detector 2 together with the signal indicating the detection of fluid.

In addition, information from the further sensor 31 may also be transmitted by the transmitter 24. For example, the transmitter 24 may also transmit the temperature which may be measured by the further sensor 31 . Further, the detector 2, e.g. the sensor 15 thereof, may be capable of determining the fluid content within the material. In such embodiments, the transmitter 24 may also transmit a signal indicating the fluid content detected.

The fluid content may be determined by any appropriate component of the detector 2. For example, the voltage detector 18 may be capable of determining and outputting a fluid content. The detector 2 may also comprise a processor (not depicted) configured to analyse the voltage detected by the voltage detector 18 and to determine the fluid content. An exemplary means of determining the fluid content is described further below with respect to Figures 6A and 6B, however it will be appreciated that any other suitable means for determining the fluid content may be employed.

As discussed previously, the detector 2 may also be capable of detecting a reduction in the fluid content detected. Figure 5B shows the same close-up sectional view shown in Figure 5A, except Figure 5B illustrates fluid escaping the deformable body 14 out through the openings 36, i.e. in a situation wherein the fluid content, e.g. moisture content, is reducing. In this instance, the deformable body 14 may contract. The force on the piezoelectric element 16 will change and this will cause a voltage to be generated. In this instance, the transmitter may output a signal indicating that the fluid content within the material has reduced or is reducing.

Fig. 6A is a graph illustrating the voltage generated by piezoelectric element 16 of the detector 2 over time and also the corresponding humidity, i.e. fluid content or moisture content, of a material into which the detector 2 is inserted. The line 38 indicates the known relative humidity of the environment in which the detector 2 was placed, which corresponds to the humidity of the material in which the detector 2 was inserted, and the line 40 indicates the voltage generated by the piezoelectric element 16 of the sensor 14. A period of time is shown in which the humidity was changed and the corresponding voltages generated were measured. As can be seen in this Figure, when the humidity suddenly changes, the voltage generated by the piezoelectric element 16 increases simultaneously. This demonstrates how the voltage generated by the piezoelectric element 16 of the sensor 15 can be used to determine the presence of fluid, or change in fluid content, within a material. The Applicant has also recognised that it may also be possible to determine the fluid content, or at least the relative fluid content, by integrating the voltage between a point in time when the voltage deviates from the baseline, to a point in time when the voltage returns to the baseline. The baseline may depend on the particular set up of the piezoelectric element 16, but may, for example, be 0 V. Fig. 6B is a graph of the integral of peaks and troughs of the voltage generated from the point at which the voltage deviates from the baseline, to the point at which it returns to the baseline, plotted for a series of different changes in relative humidity. As shown in this Figure, there is a direct relationship between the change in humidity and the integral of the peak voltage. Accordingly, determining the integral of the voltage may be used as a means to determine a change in the fluid content within the material and thereby facilitate the determination of the fluid content, e.g. moisture content, of the material. Figure 7 shows the elongate portion 104 of a detector 102 in accordance with another embodiment of the present invention. Except for features explicitly discussed, the detector 102 of the embodiment shown in Figure 7 is otherwise identical to the detector 2 shown in earlier Figures and described above. In the embodiment depicted in Figure 7, the piezoelectric element 116, of the sensor 115, is in the form of an elongate cylindrical tube. The deformable body 114 comprises an external deformable portion 114A which is in the form of a cylindrical tube which surrounds the piezoelectric element 116 and an internal deformable portion 114B which is in the form of a cylindrical tube which is arranged within the core 117 of the piezoelectric element 116. As the internal and external deformable portions 114A, 114B deform, e.g. by expanding or contracting, a force will be applied to the piezoelectric element 116.

Figure 8 shows the elongate portion 204 of a detector 202 in accordance with another embodiment of the present invention. Except for features explicitly discussed, the detector 202 of the embodiment shown in Figure 8 is otherwise identical to the detector 2 shown in earlier Figures and described above. Similarly to Figure 7, in the detector 202 shown in Figure 8, the piezoelectric element 216 is in the form of a hollow cylindrical tube. The deformable body 214 comprises an external deformable portion 214A which is in the form of a cylindrical tube which surrounds the piezoelectric element 216 and an internal deformable portion 214B arranged within the core 217 of the piezoelectric element 216. In the embodiment depicted, the internal deformable portion 214B fills the entire core 217 of the piezoelectric element 216. The internal deformable portion 214B may be in the form of a solid cylindrical element or may comprise a plurality of sub-elements which fill the core 217. As the internal and external deformable portions 214A, 214B deform, e.g. by expanding or contracting, a force will be applied to the piezoelectric element 216.

For each of the embodiments shown in Figures 7 and 8, the contact area between the deformable body and the piezoelectric element may be increased. Additionally, the deformable body may be placed on both the inside and the outside of the piezoelectric element. These factors may increase the force generated by the deformable body and applied to the piezoelectric element. This may increase the voltage generated, thereby making detection of the presence of fluid easier. Additionally, where the deformable body and the piezoelectric element are cylindrical, the sensor may provide a uniform response in the presence of a fluid, irrespective of the orientation. This may not be the case for plate-shaped sensors. Whilst in the embodiments depicted Figures 7 and 8 and described above, a portion of the deformable body is present on both the inside and outside of the piezoelectric element, it will be appreciated that this is not essential, and the deformable body may instead only be present on the outside or the inside of the tube-shaped piezoelectric element.

Figure 9 shows the elongate portion 304 of a detector 302 in accordance with another embodiment of the present invention. Except for features explicitly discussed, the detector 302 of the embodiment shown in Figure 9 is otherwise identical to the detector 2 shown in earlier Figures and described above. In the embodiment depicted, the deformable body 314 and piezoelectric element 315 (visible in Figure 10) are arranged in the form of a spiral 317. The spiral 317 can be seen in isolation on the left-hand side of Figure 10 which shows an enlarged sectional view of the spiral 317. As depicted on the right-hand side of Figure 10, which shows a sectional view through the spiral 317, the spiral 317 which has a layered structure. The layered structure of the spiral 317 comprises a piezoelectric element 316 arranged at its centre. A first insulation layer 342A is arranged on one side of the piezoelectric element 316 and a second insulation layer 342B is arranged on the other side of the piezoelectric element 316. The insulation layers 342A, 342B may protect the piezoelectric element 316 from coming into direct contact with moisture. This may be advantageous as the piezoelectric element 316 may otherwise degrade due to contact with moisture. The insulation layers 342A, 342B may also form the electrodes of the piezo element 316.

Adjacent the first insulation layer 342A is a first portion 314A of a deformable body 314 and adjacent the second insulation layer 342B is a second portion 314B of deformable body 314. As discussed previously, a spiral arrangement as depicted may increase the area of the deformable body 314 exposed to the fluid, and also increase the area of the deformable body 314 acting on the piezoelectric element 316. This may increase the sensitivity of the detector 301 and reduce the response time of the detector 302.

Figure 11 shows a schematic view of a fluid monitoring system 44 in accordance with an embodiment of the present invention. The fluid monitoring system 44 comprises a plurality of detectors 2 which are installed into through the protective layer 13 and into the insulation layer 12 surrounding the pipe 10. The fluid monitoring system 44 further comprises a first intermediate communication node 46A, a second intermediate communication node 46B and a central controller 48. In the embodiment depicted, the sensors 2 communicate with one of the first or second intermediate communication nodes 46A, 46B. The first communication node 46A communicates with the second communication node 46B and the second communication node 46B communicates with the central controller. As will be appreciated, the first and second communication nodes 46A, 46B provide a means of relaying a signal from a detector 2 to the central controller 48.

As depicted by the arrows between each of the detectors 2, the detectors 2 may also be capable of communicating with one another. This may facilitate the transmission of a signal to the central controller 48 without necessarily requiring communication with an intermediate communication node. 46A, 46B.

When the detectors 2 output a signal indicating the detection of fluid, optionally together with the detected fluid content, the detectors may also output a unique identifier. When the signal is received by the central controller 48, the central controller 48 may process the signal and use the unique identifier to determine the location of the detector 2 which output the signal. The system 44 may therefore be capable of determining a specific location at which fluid is detected

Figure 12 is a flowchart illustrating a method, in accordance with an embodiment of the present invention, for installing a detector 2 into a material. In step S1 a detector 2 is installed into a material. The detector 2 may be installed using an appropriate machine, e.g. a tool, a robotic platform, a drone, or any other suitable machine. The location and unique identifier of the detector 2 may then be stored in step S2. This may be achieved any suitable manner. In the exemplary case of a tool, the tool may be location aware, e.g. through the presence of a GPS device thereon, and the tool may be capable of extracting the unique identifier from the detector 2. In this case, the location and unique identifier may of the detector 2 may be stored. This information may be stored locally on the tool and downloaded and stored on other means at a later stage. Alternatively, the location and unique identification may be transmitted to and stored on remote server, e.g. a cloud based-server, at the point of installation. Of course the tool need not be location aware and an installer of the detector may manually store the location and store the unique identifier using any other suitable device during installation. This process may be repeated for each of a plurality of detectors 2.

Figure 13 shows a close-up view of the deformable body 14, present in the detector of Figure 3. The deformable body 14 may comprise a fluid transport means in the form of cellulose fibres 50. The bottom part of Figure 13 shows a close-up view of the deformable body 14 and illustrates how a plurality of cellulose fibres 50 may run throughout the deformable body 14. The cellulose fibres 50 may be integrally formed with the deformable body 14 during manufacture. The top left of Figure 13 shows a further enlarged view of the deformable body 14 focussing on two cellulose fibres 50. As illustrated, the cellulose fibres 50 may facilitate the flow of fluid, in this case water, through the deformable body 14. The cellulose fibres 50 may, therefore, allow the fluid to permeate throughout the deformable body 14 more evenly. The fluid may therefore be absorbed by the deformable body 14 more evenly which may cause more even deformation of the deformable body 14.

Figure 14 shows a cross-sectional view of a fluid detector 402 in accordance with another embodiment of the present invention. The fluid detector 402 is similar to the earlier embodiments described above in that it is designed to be inserted into a material and measure the fluid content thereof. However, the way in which the force from the deformable body is transferred to the sensor differs in this embodiment. Any of the features of the embodiments described above not related to the way in which force is transferred to the sensor may equally be applied to the embodiment shown in Figure 14.

The fluid detector 402 comprises a housing 403 which comprise an elongate portion 404 with a pointed tip 406 at an end thereof. Similarly to earlier embodiments, the housing 403 comprises an upper housing 408 which houses various components of the detector 402. In the embodiment depicted, the upper housing 408 houses a power source 428, which may comprise a battery 428, as well as circuit board 429. The circuit board 429 may comprise any suitable electronics depending on the particular application of the detector 402. For example, it may comprise a processor, a wireless transmitter and/receiver and/or any other suitable electronics. Whilst not depicted, the elongate portion 404 may comprise at least one hole, e.g. a plurality of holes, arranged therein to permit the passage of fluid, e.g. moisture, into the elongate portion 404 or the elongate portion may be made from a porous material to permit the passage of fluid therethrough.

As depicted, a deformable body 414 is arranged within the elongate portion 4 of the housing 3. In an embodiment, a force transfer medium 452, contained within a deformable housing 454 is arranged inside the deformable body 414. In some embodiments, as depicted, the deformable housing 454 may have a tubular shape, of any suitable cross section, and the deformable body 452 may at least partially, e.g. fully, surround the tubular deformable housing 454. It will be appreciated that the deformable housing 454 and deformable body 414 may have any suitable shape and arrangement, as long as the deformable body 414 is able to act on the deformable housing 454 so as to apply a force to the force transfer medium.

The detector 402 comprises a sensor 415. The sensor 415 is arranged to detect forces applied by the force transfer medium 452, and thus detect deformation and/or forces applies by the deformable body 414. The sensor 415 may comprise a piezoelectric, piezoresistive or capacitive pressure sensor. As set out above, the use of a piezeoresistive pressure sensor may advantageously facilitate the ability to obtain a measurement of the force applied by the force transfer medium 452, and hence the fluid content of the material, at any time and the reading thereof will not substantially change over time, as may be the case for a piezoelectric sensor.

In some embodiments, one end of the deformable housing 454, which contains the force transfer medium 452, may be closed by a vent 456. During assembly of the detector 402, the deformable housing 454 may be filled with the force transfer medium 452 and then the sensor 415 may be at least partially inserted into the deformable housing 454. Depending on the volume of force transfer medium 452 within the deformable housing 454, as the sensor 415 is inserted into the deformable housing 454, the pressure of the force transfer medium 452 may increase. The Applicant has recognised that an increased pressure may impact the ability of the force transfer medium 452 to effectively transfer the force applied by the deformable body 414. Accordingly, the vent 456 may be used to release, i.e. reduce, the pressure within the deformable housing 454. The vent 456 may comprise a removable plug which may be removed and replaced in order to release the pressure. In addition or alternatively, the vent 456 may be selectively or automatically openable so as to release the pressure within the deformable housing 454. The vent 456 may be used to release pressure within the deformable housing 454 during manufacture and/or during use of the detector 402.

As will be appreciated by those skilled in the art, the outer area of the deformable housing 454 which is in contact with the deformable body 414 is significantly larger than the area 458 of the force transfer medium which contacts the sensor 415. As such, the force applied per unit area on the sensor 415 will be significantly increased when compared to the force applied per unit area on the outer surface area of the deformable housing 454. As such, the deformable housing 454 and force transfer medium 452 together act to amplify the force applied by the deformable body and apply this amplified force to the sensor 415. This may mean that the detector 402 is more sensitive to fluid changes as smaller changes which only produce a small force on the outer surface of the deformable housing 454, nonetheless result in a measurable force on the sensor 415. The area of the outer surface of the deformable housing 454 which contacts the deformable body 414, to the contact area 458 of the sensor may, for example, be at least 2:1 , e.g. at least 5:1 , e.g. 10:1 , e.g. at least 20:1 , e.g. at least 50:1 , e.g. at least 100:1, e.g. at least 200:1. For example, the deformable housing may have a 3 mm diameter and be around 30 mm long. In this case, the ratio of areas would be approximately 280:1.

In some embodiments, the fluid detector 402 may comprise a further sensor 460. As depicted, the detector 402 may comprise a temperature measurement medium 462 arranged to act on the further sensor 460. The temperature measurement medium 462 may be arranged such that the deformation of the deformable body 414 does not act on the temperature measurement medium 462. For example, the temperature measurement medium 462 may be arranged within a rigid housing 464 such that forces generated by the deformable body 414 are not transferred to the temperature measurement medium 462. The rigid housing 464 may, nonetheless, be thermally conductive such that the temperature of the temperature measurement medium is able to reach equilibrium with a material in which the detector 402 is inserted. The volume of the temperature measurement medium 462 may change in accordance with its temperature and thus the sensor 460 may be capable of determining the temperature or at least the change in temperature, of the material in which the detector 402 is inserted. The further sensor 460 may comprise a piezoelectric, piezoresistive or capacitive pressure sensor capable of detecting a force applied by the temperature measurement medium. Of course the sensor 460 may be configured to sense another characteristic, other than volume, of the temperature measurement medium which changes depending on its temperature. The further sensor 460 may comprise a piezoresistive, piezoelectric, capacitive pressure sensor, or indeed any other suitable pressure sensor.

As depicted, in some embodiments, the temperature measurement medium 464 is arranged adjacent the force transfer medium 452 such that the temperature of the temperature measurement medium 464 closely matches the temperature of the force transfer medium 452.

Figure 15 shows a cross-sectional view through the elongate portion 404 of the housing 403, through the line A-A shown in Figure 14. As depicted, the deformable housing 454, containing the force transfer medium 452 runs axially through the elongate portion 404. The deformable body 414 extends around the deformable housing 454. As such, the area on which the deformable body 414 acts will be the outer surface area of the deformable housing 454. In contrast, the area 458 (see Fig. 14) of the force transfer medium 452 which acts on the sensor 415, will be approximately the cross-sectional area of the deformable housing 454. As the deformable housing 454 is significantly longer than it is wide, the cross-sectional area of the deformable housing 454 will be significantly less than the outer surface area of the deformable housing 454. As such, the force applied by the deformable body 414 to the deformable housing 454 will be amplified upon application to the sensor 415.

As shown in Figure 15, the rigid housing 464, which contains the temperature measurement medium 462 runs axially off-centre along the elongate portion 404. The rigid housing 464 may be arranged in any suitable position within the elongate portion 404. It is also conceivable that the rigid housing 464 may be arranged outside of the elongate portion 404. The temperature measurement medium 462 comprises the same material as the force transfer medium 452 and may have the same volume as the force transfer medium 452. The Applicant has recognised that in having the same volume, any changes in temperature will have the same effect on both the force transfer medium 452 and the temperature measurement medium 462. This may make it easier to account for temperature changes. However, this is not essential and the temperature measurement medium 462 may have a different volume. In this case, the detector 402 may be calibrated to account for such a differing volume.

Whilst in the embodiments depicted the force transfer medium 452 is contained within a deformable housing 454, it will be appreciated that this is not essential and the deformable body 414 may act directly on the force transfer medium 452.

Figure 16 shows a cross-sectional view of the detector 402 in Figure 14, when the fluid, e.g. moisture, content in the material in which the detector 402 is inserted is increasing. Similarly, Figure 17 shows a cross-sectional view through the elongate portion 404 through the line A-A when the fluid content in the material in which the detector 402 is inserted is increasing. With reference to both Figures 16 and 17, as the fluid level in the material increases, the fluid, e.g. moisture, will pass through the elongate portion 404 into the deformable body 414. The deformable body 414 will then tend to expand and deform and/or apply a force on the deformable housing 454. This deformation of the deformable body 414 is illustrated by the horizontal arrows contained within the deformable body 414.

Under the application of force from the deformable body 414, the deformable housing 454 will deform thereby deforming the force transfer medium 452. As the deformable body 414 surrounds the force transfer medium 452, the force transfer medium 452 will be forced upwards, as indicated by arrow 466, and apply a force to the sensor 415. As mentioned previously, due to this arrangement whereby the area of contact between the deformable body 414 and the deformable housing 454 is relatively large, compared to the area of contact between the sensor 415 and the force transfer medium 452, the force applied to the sensor 415 is amplified. As discussed previously, this may allow the sensor 415 to be more sensitive to changes in fluid within the material. This may, therefore, allow a higher resolution in fluid measurements in relation to the material in which the detector 402 is inserted. It may also, for example, allow the detection of smaller amounts of fluid changes within the material. In the context of detecting CUI, this may advantageously facilitate earlier remedial action, which may minimise potential damage to a given pipeline.

Any changes in temperature in the material in which the detector 402 is placed may impact the volume of the force transfer medium 452 and hence the force detected by the sensor 415. Absent any means for detecting the temperature, the forces generated by the force transfer medium may be mistaken for forces due to fluid changes and/or even when there is a fluid change, changes in temperatures may make the fluid changes appear to be more or less than they actually are. Accordingly, the detector 402 may utilise the temperature measurement medium 462 to separately identify the temperature of the material in which the detector 402 is inserted. As previously discussed, the temperature measurement medium should eventually reach the same temperature as the material in which the detector 402 is inserted and thus also correspond to the same temperature as the force transfer medium. The temperature of the temperature measurement medium 462 will impact its volume and thus change the force applied to the sensor 460.

The force detected by the further sensor 460 may thus be used to identify temperature changes experienced by the detector 402 and thus temperature changes experienced by the force transfer medium 452. An output of the further sensor 460, which may be considered to be a temperature sensor, may be used to in a determination of the fluid within the material using the output of the sensor 415. The output of each of the sensor 415 and further sensor 460 may be suitably combined to provide a differential pressure reading. For example, the pressure change on the sensor 415 may be measured relative to the pressure change on the further sensor 460. The pressure detected by the further sensor 460 may be subtracted from the pressure measured by the sensor 415 so as to provide a difference in pressure between the two sensors 415, 460. The difference in pressure between the two sensors 415, 460 may thus correspond to the pressure applied by force transfer medium due to deformation of the deformable body, and exclude any pressure generated from temperature changes of the force transfer medium. This embodiment comprising the further sensor 460 may therefore result in a more accurate determination of the fluid within the material.

In some embodiments, in determining the fluid within the material, e.g. the fluid content, an output from the further sensor 460 may be used to modify an output from the sensor 415. Modifying the output of the sensor 415 in this manner may result in a determination of fluid, e.g. fluid content, within the material which more accurately reflects the true content of the fluid within the material, as the expansion of the force transfer medium 452 due to temperature (i.e. a non-fluid related factor) is accounted for. This modification may be performed by suitable control circuitry, e.g. a processor or other electronic circuitry, which may, for example, be arranged on the circuit board 429.

In some embodiments, the temperature measurement medium 462 and the force transfer medium 452 have the same volume. This may simplify the above modification as the force applied due to temperature changes of the temperature measurement medium 462 may be considered to be the same as the force applied due ot temperature changes in the force transfer medium 452. However, even in embodiments, wherein the two mediums 452, 462 do not have the same volume, the detector 402 may nonetheless be calibrated to account for this and the fluid content may nonetheless be determined.

While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.