Flow Detection Device

Abstract

A flow detector for detecting flow rates of fluid in pipes by measuring the temperature of the pipe and the ambient temperature and determining from the signals whether there is a flow in the pipe,by the shape of the temperature signals without providing any heat input to the pipe or fluid.

Claims

1-48. (canceled)

49. A fluid flow detector for detecting a water leak in a pipe system comprising at least one of a domestic water supply pipe system and an office water supply pipe system, the detector fluid flow comprising: a first temperature sensor to detect ambient temperature; a second temperature sensor to detect a pipe temperature, the second temperature sensor configured to be coupled adjacent or in thermal contact with a pipe of the pipe system; and a processing means for determining a plurality of temperature differences between the first and second temperature sensors over a predetermined period of time, and whether fluid is flowing in the pipe system by comparing the plurality of temperature differences to a predetermined set of at least one parameter to indicate a convergent approach of the ambient temperature and pipe temperature.

50. A fluid flow detector of claim 49, wherein the processing means performs a calibration to account for an expected rate of convergence of the ambient temperature and the pipe temperature.

51. A fluid flow detector of claim 49, wherein the comparison determines if the temperature differences are approximating an exponential approach.

52. A fluid flow detector of claim 49, wherein the processing means determines that no fluid is flowing if said comparing indicates convergence of the ambient temperature and the pipe temperature.

53. A fluid flow detector of claim 49, wherein the predetermined set comprises a plurality of said parameters and the processing means is configured to, if the temperature differences remain within or equal to the predetermined set of parameters for a predetermined period, determine that no fluid is flowing in the pipe system.

54. A fluid flow detector of claim 49, wherein the predetermined set comprises a plurality of said parameters and the processing means is configured to, if the temperature differences remain outside the predetermined set of parameters for the predeteiiriined period, determine that fluid is flowing in the pipe system.

55. A fluid flow detector of claim 49, wherein the predetermined set comprises a plurality of said parameters and the processing means is configured to, if the temperature differences fall outside the predetermined set of parameters for the predetermined period, determine that fluid is flowing in the pipe system.

56. A fluid flow detector of claim 49, wherein the processing means estimates a temperature of the fluid based on dips or peaks in the pipe temperature, wherein the determination whether fluid is flowing in the pipe system comprises comparing detected said pipe temperatures to the estimated fluid temperature.

57. A fluid flow detector of claim 49, wherein the predetermined set of at least one parameter comprises at least one predetermined threshold.

58. A fluid flow detector according to claim 49, comprising a housing to hold the second temperature sensor, the housing comprising a biasable pipe clip to securely clip the detector to the pipe and to ensure thermal contact of the second temperature sensor with the pipe.

59. A detector according to claim 49, further comprising means to generate an alarm signal if the temperature differences fall outside the predetermined parameters for a predetermined time.

60. A detector according to claim 49, wherein the processing means restarts the determination of the predetermined period of time if the difference between the ambient and pipe temperatures suddenly change at a rate above a predetermined value.

61. A detector according to claim 49, wherein the processing means restarts the determination of the predetermined period of time if temperature values suddenly change at a rate above a predetermined value, wherein the temperature values are at least one of the values of the ambient temperatures, and the values of the pipe temperatures.

62. A detector according to claim 49, wherein the processing means determines, based on the plurality of temperature differences, if the temperature difference between the ambient and pipe sensors is tending to or approximating to an exponential approach to 0 and, if so, indicating there is no flow in the pipe system.

63. A detector according to claim 49, wherein the processing means is configured to calibrate the detector for its specific installation.

64. A fluid flow detector according to claim 49, in which the absence of fluid flow for greater than a predetermined period causes an alarm signal to be generated.

65. A fluid flow detector according to claim 49, in which the predetermined period is up to 36 hours, preferably between 12 and 24 hours and more preferably between 9 and 18 hours.

66. A fluid flow detector according to claim 49, having the detector is configured to determine whether the detector is subject to a constant heating or cooling from an external heat source or sink.

67. A fluid flow detector according to claim 66, wherein the detector is configured to alert a user that it is unable to determine if a leak condition is present.

68. A fluid flow detector according to claim 49, wherein the detector is configured to rank a water leak rate according to how high the temperature difference is, thus providing an indication of the severity of the leak.

69. A fluid flow detector according to claim 49, wherein the detector is configured with a ‘holiday’ mode that can be set by a user determining that no water flow should be expected for a predetermined period, e.g. 72 hours or 14 days, the detector configured to, when the ‘holiday mode’ is set , trigger an alert if any water flow is detected in that period.

70. A fluid flow detector according to claim 49, the detector is configured to connect to an alert service to alert the user of the presence of leaks by at least one of a text message, an email message, and a smartphone application.

71. A fluid flow detector according to claim 49, the detector is configured to connect to and control a powered shut-off valve.

72. A fluid flow detector according to claim 49, the detector is configured to enable the user to shut off the water for example using at least one of a remote switch, another interface, and a smart phone application.

73. A method for detecting a water leak in a pipe system comprising at least one of a domestic water supply pipe system and an office water supply pipe system, the method comprising: detecting over a period of time a plurality of ambient temperatures; detecting over the period of time a pipe temperature using a temperature sensor coupled adjacent or in thermal contact with a pipe of the pipe system; determining a plurality of temperature differences between the detected ambient and pipe temperatures; and determining whether water is flowing in the pipe system by comparing the plurality of temperature differences to a predetermined set of values to indicate a convergent approach of the ambient and pipe temperatures.

74. A method of claim 73, wherein the comparison determines if the temperature differences define a curve which decreasingly decays to a steady value.

75. A method of claim 73, wherein the comparison determines if the temperature differences are approximating an exponential approach.

76. The method of claim 73, wherein the determining whether water is flowing in the pipe system further comprises performing a calibration to take account of an expected rate of convergence of the pipe temperature and the pipe temperature.

77. A leak detector comprising the fluid flow detector according to claim 49, the leak detector configured to indicate a leak detection if the temperature difference is not below, preferably greater than, a predetermined threshold for the predetermined period, wherein the leak detector is conf.sub.igured to indicate a leak of the pipe system, preferably wherein the pipe system is of a domestic building or of an office water supply system.

78. A fluid flow detector of claim 49, wherein the processing means determines a heat transfer indicator based on a ratio of an indicator of time gradient of the sensed pipe temperature relative to the determined temperature difference between the first and second temperature sensors, the processing means further configured to indicate a leak detection based on the heat transfer indicator.

79. A fluid flow detector of claim 78, wherein the processing means further detetinines if the heat transfer indicator is below a predetermined threshold for a predetermined period and to at least one of: if the heat transfer indicator is below a predetermined threshold for a predetermined period, indicate a leak detection; and if the heat transfer indicator is not below a predetermined threshold for a predetermined period, indicate absence of a leak detection.

80. The leak detector according to claim 78, wherein the processing means determines a best fit exponential function to the sensed temperature of the pipe and determine said indicator of time gradient of temperature of the pipe on the basis of said exponential function.

81. A water supply system comprising the detector according to claim 49 and at least one water pipe, wherein the detector is attached to a said water pipe where water at least one of enters a building and at a stop cock.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Embodiments of the invention will now be described with reference to the accompanying drawings in which:

[0071] FIG. 1 shows an example of a flow detector device attached to a pipe.

[0072] FIG. 2 shows a top view of the detector device. FIG. 3 shows a side elevation indicating how contact is made with the pipe. FIG. 4 shows a block diagram of the inter-connection of the components.

[0073] FIG. 5a is a graph showing the temperature of the pipe and the ambient air over a 5 hour test period with no flow in the pipe where the water is warmer than ambient.

[0074] FIG. 5b is a graph showing the temperature of the pipe and the ambient air over a 5 hour test period with a small amount of flow in the pipe where the water is warmer than ambient.

[0075] FIG. 6a is a graph showing the temperature of the pipe and the ambient air over a 5 hour test period with no flow in the pipe where the water is warmer than ambient.

[0076] FIG. 6b is a graph showing the temperature of the pipe and the ambient air over a 5 hour test period with a small amount of flow in the pipe where the water is cooler than ambient.

[0077] FIG. 7 is the block diagram of the system where a shut off valve is used to shut off the water supply in the event of a leak being detected.

[0078] FIG. 8a is a graph showing the temperature of the pipe and the ambient air over a test period with no flow in the pipe where the water is warmer than ambient.

[0079] FIG. 8b is a graph showing the temperature of the pipe and the ambient air over a test period with a small amount of flow in the pipe where the water is warmer than ambient.

[0080] FIG. 9a is a graph showing the temperature of the pipe and the ambient air over a test period with no flow in the pipe where the water is warmer than ambient.

[0081] FIG. 9b is a graph showing the temperature of the pipe and the ambient air over a test period with a small amount of flow in the pipe where the water is cooler than ambient.

[0082] FIGS. 10 and 11 show further examples of temperature-time traces.

[0083] FIG. 12 shows an example implementation of a fluid flow detector system/device.

[0084] FIG. 13 shows an example computing device or system on which at least the processing means, e.g., electronic control unit, of an embodiment of the invention may be implemented.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0085] Embodiments of the invention will now be described in more detail with reference to the drawings in which like references refer to like features in the various figures.

[0086] FIG. 1 shows an example of a fluid flow detection device according to an embodiment of the present invention. The device is contained within a housing 10, is attachable to a pipe 12 by means of a biasable pipe clip 14. This particular device is used as a water flow detector for a domestic or office environment. Larger scale devices and housings could be used for a factory, but frequently factories operate for large portions of a day and may not have long enough periods of zero flow for satisfactory operation and require more sophisticated and complex monitoring systems.

[0087] FIG. 2 shows a top view of the device which may conveniently include indicator or display elements to show the state of operation of the device. These could include a system operation indicator 22 an alarm indicator 24, or a loud speaker 26 from which an audible alarm could be emitted.

[0088] FIG. 3 shows a side elevation of the housing 10 secured to a pipe 12 by connector 14. A temperature sensor 16 extends from the case of the housing and is shown contacting the pipe 12 to determine the outer temperature of the pipe 12.

[0089] FIG. 4 shows a block diagram of the components comprising the device and their inter connections. The housing 10 encloses an electronic control unit (ECU) 40 for monitoring temperatures, time and controlling the device. The device is powered by a power supply 42, normally comprising one or more batteries. The selection of batteries will be chosen to provide long life in the environment in which the device is installed. Temperature sensor 16 is shown as in contact with pipe 12 to measure the temperature of the pipe. Ambient temperature is measured by temperature sensor 20. An alarm unit 46 can include a visible alarm means, typically an LED, or an audible means or driver therefor. For some applications, a wireless connection 48 will also be provided, so enabling the device to periodically transmit data to a remote station and so send an alarm signal when needed. The wireless connection could also receive information or data from a remote station.

[0090] In another example embodiment of the invention, the power could be supplied by a mains network. In a further example, a more sophisticated power supply system is provided in which the power supply comprises a mains power supply connected with one or more batteries.

[0091] Suitable temperature sensors are for example Resol FKP6 PT1000 temperature sensors. Other devices which have been found to work well can be found in the class of PT1000 platinum sensors.

[0092] FIG. 5a shows a graph of the temperature measured by each of the sensors over a period of time. The graph shows temperature along the Y axis, and time along the X-axis. The dashed line is a trace of ambient temperature over a selected measurement period, in this example 2-3 hours. The solid line shows how the temperature of water in the pipe varies. In region A, a significant flow has been occurring and the water temperature is significantly higher than the ambient temperature. (This can occur in some tropical climates and late in summer when the ground temperature has risen and is consistently (during the course of a day or so) higher than the general air temperature. The spikes indicate how the temperature has risen sharply as a significant draw down occurs and show the temperature has begun to fall towards ambient. This draw down could be a flushing of a toilet or water for a basin or sink.

[0093] In Region B, the water temperature can be seen to fall towards ambient.

[0094] In Region C, the temperatures are considered to be within the predetermined conditions and so equal. This condition would indicate there is no flow of water in the system.

[0095] FIG. 5b shows a similar situation to the one in FIG. 5a, but in this example, the two temperatures never quite converge, as can be seen in all regions. From this it can be concluded that there is always a flow and there is a leak in the system.

[0096] FIG. 6a shows a graph of the temperature measured by each of the sensors over a period of time. The graph shows temperature along the Y axis, and time along the X-axis. In this example the ambient temperature shown by the dotted line is higher than the incoming water pipe temperature shown by the solid line. Such situations can arise in cold or temperate climates where ground temperatures can be and frequently are lower than the ambient air temperature. In region A tap on off events can be seen as indicated by the spikes in the pipe temperature. In region B the pipe temperature is rising towards the ambient temperature. In region C the two temperatures are more or less convergent, and so satisfying the criteria set out that the temperatures must be within narrow bands. This convergent set of temperatures would indicate that there is no leak in the system.

[0097] FIG. 6b shows the ambient temperature (shown by the dotted line) is higher than the incoming water pipe temperature shown by the solid line. The various spikes in Region A show how the inlet water temperature falls as water is drawn off through the system, and then rises towards ambient, until the next draw off, when it falls again. In region B, there is a prolonged period without a significant draw off of water. However, as can be seen in Region C, the two temperatures do not converge closely within the predefined limits, always maintaining a difference of temperature T. Providing this temperature difference (or temperature) is greater than a predetermined value, which can vary according to the geographical and physical location of the device, it can be assumed there is a leak in the system. If it is a significantly large temperature difference (or temperature), as in this example, it can be assumed there is a reasonable flow rate of leak—rather than just a dripping tap. In some regions, a temperature difference of approximately 1° C. will be expected, but more commonly the temperature difference will be expected to remain below approximately 0.3° C. and preferably 0.1° C. for a no flow condition to exist.

[0098] An audible alert—such as a loud speaker will normally be used to provide the alert signal. Optionally the device will also be provided with a wireless or other communications link. The wireless link can be deployed to receive commands and transmit information to a remote station, either continuously on a predetermined period basis.

[0099] It is therefore possible to discriminate between the two main conditions determined by the device, flow and no flow. By monitoring the temperatures during a period when no flow is expected, any detected flow indicates that a possible leak is present in the system. The leak may be due to pipe or pipe joint failure, dripping taps, failed cisterns in toilets or any other condition which would result in continuous water flow in a pressurised plumbing system.

[0100] In one possible embodiment of the device, the device operates for 24 hours a day on a domestic water main. Typically at night there will be no water flowing in the pipes as no taps will be used and appliances such as washing machines will have finished their cycles.

[0101] The device is programmed to monitor and recognise a pattern in temperature change in the detectors. After a period when there are no sudden changes in pipe temperature (due to taps switching on) have stopped or appliances being used the ECU can be programmed to determine if the pipe temperature has not changed rapidly or significantly and compare it to the ambient temperature. It also recognises that the ambient air temperature is stable (within limits) so the device is not being adversely affected by other heat sources (for example being near a radiator or hot water pipe).

[0102] The ECU can be programmed to monitor the changes measured by the temperature detection means of the temperature of the water pipe and the ambient air. The water pipe temperature will generally be an exponential approach towards air temperature with a slope within certain limits. In a “no leak” condition, the asymptotic difference between the pipe and air temperatures will be below a calibrated value, between 0 and 0.5° C., typically between 0 and 0.3° C., but preferably between 0 and 0.1° C. If the asymptotic temperature difference is higher than these values for greater than a predetermined period of time, say an hour or more, then there is usually flow in the pipe indicating a leak.

[0103] In another possible embodiment, the ECU in the detector may determine whether the device is subject to a constant heating or cooling from an external heat source or sink. In this case it may alert the user that it is unable to determine if a flow condition is present.

[0104] In another embodiment, the device may detect that its sensors are giving invalid values due to an error or component failure and alert a user to the fault.

[0105] On detecting a leak the device may alert a user by one of many different means typical of such domestic alarms. For example it may use an audible alert. Alternatively, or additionally, it may also include a light or a display. To avoid waking a user at night, it may wait until it next detects flow (because a user has woken up) before issuing an alert.

[0106] The device may also issue alerts and other information via a remote telemetry system. This could be one of any such technologies known in the art. For example using a cellular phone modem, an internet connection, a home automation protocol (e.g. Z Wave), a landline phone modem, an acoustic modem or any other such transmission mechanism.

[0107] In another possible embodiment, the device detects the sudden changes in pipe temperature relative to air temperature which are characteristic of taps turning on or toilet flushes. It can be calibrated to estimate frequency and quantity of water usage. Dips (or peaks) in the pipe temperature show water usage. Counting short dips shows the frequency of water usage for low use items (hand washing, toilet flushing). The height of the dips give an estimate of the incoming mains water temperature. When the pipe temp is approximately the same as the input water temperature for an extended period of time, we can assume we have constant flow over that time period. This indicates either shower, bath filling or other extended use such as irrigating a lawn.

[0108] According to another feature of an embodiment, the ECU restarts the determination of the predetermined period of time if the difference between the ambient and pipe temperatures suddenly changes to be greater than the predetermined value. Thus if a sudden sharp difference of temperature is detected between the two sensors, the ECU can be programmed to determine that a flow of water has occurred and so restart its monitoring process.

[0109] According to another feature of an embodiment, the ECU determines if the temperature difference between the ambient and pipe sensors is tending to or approximating to an exponential approach to 0 and if so indicating there is no flow in the pipe system. If the two temperatures do not converge exponentially after a period of say an hour, the device can be programmed to generate an alarm signal.

[0110] In yet another possible embodiment, the device can be programmed to note the absence of water usage over a period of time. This information may then be used to check on the presence and activity of a person in the home. For example if an elderly or vulnerable person has not used water for a predetermined period, such as a day, it may indicate that they have a problem and a carer can be alerted.

[0111] In yet another possible embodiment, the device can be programmed to rank a water leak rate according to size of the temperature difference (assuming it has reached a constant or substantially constant difference for a period of time,) thus providing an indication of the severity of the leak. If the pipe temperature stays at close to the estimated incoming water temperature (using the dip height method above), then the leak is a reasonably high flow rate. If it is within 0.5° C. or so of the air temperature, it is typically a dripping leak. Temperatures in the middle indicate a medium flow leak.

[0112] In yet another embodiment, the device may have a ‘holiday’ mode that can be set by a user who knows that no water flow should be expected for e.g. 72 hours or 14 days or however long a user is absent. If any water flow is detected during that period, an alert would then be triggered.

[0113] In a further embodiment the device may connect to a service which could alert the user (e.g. by text, email or smartphone app) of the presence of leaks automatically, or it could send the alert directly to a maintenance company. The service may also alert a service provider or a plumber who could then check the leak. The device could also contact for example a neighbour who may check on a property.

[0114] FIG. 7 shows a possible additional feature in which the device is connected to and controls a powered shut-off valve. The device may then, depending upon the estimated severity of the leak, shut off the water supply in response to a leak. It could also shut-off the water when the device is in holiday mode, or only if any flow is detected when it is holiday mode. FIG. 7 shows a device 10 monitored by the ECU 40 and fitted to the pipe 12 . If a leak is detected or there is flow for more than a predetermined period of time, then the controller can shut off the supply in pipe 12 using the valve 50.

[0115] In this embodiment, the user may also be able to shut off the water for example using a remote switch, or another interface such as a smart phone app.

[0116] In an alternative and further embodiment the ECU may be configured to monitor flow and signal an alarm if there is no flow for a given period of time. For example, the alarm may sound if there is no flow for more than 36 hours.

[0117] In another embodiment the alarm signal may be sent if there is no flow detected for periods between 18 and 24 hours. This embodiment could be particularly useful as an aid to monitor people living in sheltered or supported accommodation where lack of water flow for an extended period could be an indication the person or persons are in need of help. Clearly, a balance needs to be struck between having a period that is not too long so that the person is not left for too long if help is needed and a period which is too short that it leads to false alarms.

[0118] An alarm signal can be generated if the predetermined conditions for flow (or lack of flow) are met. The alarm could be an audible alarm generated by the audible signal generating means on the device itself. Alternatively or additionally, a visible alarm signal could be generated.

[0119] It can be expected that normally devices according to embodiments of this invention will be located close to the place where the water inlet enters a building and so are frequently located in cupboards, cellars, possibly even at a remote stop cock, and so not conveniently visible. It is therefore convenient for the device to be fitted with a wireless transmitter means to transmit the alarm to a station where it is more conveniently received and monitored. Alternatively the device may be located outside in a meter pit, in which case a wireless transmitter may also be more convenient as an audible alert may not be heard.

[0120] Advantageously, the wireless transmitter can also be programmed to transmit additional information from time to time. Such information could conveniently include information about flow rates and periods of zero flow, information about the state and condition of the batteries to provide low battery warnings, other error messages to indicate sensor errors or the like.

[0121] Preferably the power supply is a battery or set of batteries selected to provide long maintenance free life in an environment in which the device operates. However, it could advantageously be connected to a mains power supply.

[0122] In yet another alternative arrangement, the power supply comprises a mains power supply connected to a battery pack up system to provide power in the event of mains failure.

[0123] The following describes features, any one or more of which may additionally or alternatively be present in any embodiment such as an embodiment described above or below.

[0124] Indoor Usage

[0125] Generally, the ECU, or at least the pipe temperature sensor, may be connected to an indoor pipe, e.g., a water pipe preferably close to where the pipe enters a building (for example through the floor). In this regard, it is noted that the pipe may be close to additional heat sources, e.g., other plumbing for example carrying hot flowing water such as for a central heating system.

[0126] Thermal Mass Lag Effect

[0127] In some circumstances, a high heat capacity local object, e.g. a concrete block and/or other plumbing as above, may result in a different temperature versus time progression of the pipe temperature relative to the ambient pressure during a no flow period. This may lead to the pipe temperature crossing the ambient, e.g., air, temperature as mentioned above, and may restrict the ability to confirm presence or absence of a leak.

[0128] In the event of a residual temperature difference after a no flow period of three to four hours for example, it is preferable that no alarm (e.g., visual and/or audible notification or alert) indicating a leak is generated if the residual temperature difference is due to thermal mass lag. Thus, if a crossing point is detected then it may be preferable to disable such an alarm. For example, the alarm may be disabled regardless of whether it is detected that the air and pipe temperatures are converging (see leak detection methods below based on time gradient of pipe temperature). An embodiment may be configured to detect a crossing point and thus to conclude that the mass lag effect is occurring, and to enable or disable a leak alarm accordingly, for example for a predetermined period of time until monitoring for a leak may restart.

[0129] Variable Leak Detection Threshold

[0130] Where in an embodiment a leak condition is determined using a threshold, for example at least based on a temperature difference between the pipe and ambient relative to a predetermined threshold for a predetermined period as described above and/or based on a temperature gradient and predetermined threshold as described below (see equations 4a, 4b, 6a, 6b below), it may be advantageous to vary such a threshold(s) for example according to the time of year. Regardless of whether or not the flow detection system, e.g., ECU thereof, is able to track the time of year for example by means of an internal electronic calendar, the threshold may be varied based on a starting difference between the pipe and ambient temperatures.

[0131] The starting temperature difference may be the difference in readings of the two temperature sensors at the start of the predetermined period used to monitor for a leak. The start of the predetermined period may be identified when it is detected that the difference between the temperatures suddenly changes at a rate above a pre-determined value and/or may be the last detected time point where the temperature versus time gradient of the pipe temperature reverses sign such that the pipe temperature tends towards the ambient temperature.

[0132] If the starting temperature difference is smaller, then a lower threshold may be applicable. For example, if the starting temperature is 4° C. then a pre-determined threshold may have a value of 0.3° C., or if the starting temperature difference is 0.5° C. then the threshold may be 0.1° C.

[0133] Calibration

[0134] Where in an embodiment a leak condition is determined using a threshold, for example at least based on a temperature difference between the pipe and ambient relative to a predetermined threshold for a predetermined period as described above and/or based on a temperature gradient and predetermined threshold as described below (see equations 4a, 4b, 6a, 6b below), the embodiment may further be configured to perform a offset procedure similar to a calibration. This may be advantageous in view of the potential scenario that the pipe temperature does not approach the ambient temperature at least within the predetermined period because of the thermal lag effect of a local object having significant thermal mass capacity.

[0135] Where an embodiment knows that the pipe should have no flow in the absence of any leak, for example based on a communication from a remote entity and/or because it has determined that a stop cock coupled to the pipe is off , the embodiment may determine if there is any residual temperature difference between the pipe and ambient and, if there is, adjust, e.g., increase or decrease, the pre-determined threshold accordingly. Thus, a form of calibration procedure or adjustment may be performed. Alternatively, in such a case where an embodiment determines if there is any residual temperature difference between the pipe and ambient, the embodiment may alert the user, e.g., by a visual and/or audible signal or notification, that the embodiment is unable to detect a leak and/or that the attachment to the pipe (e.g., at least the pipe temperature sensor) needs to be moved to a different position on the pipe, e.g., away from the ground.

[0136] Similarly, a calibration procedure may be carried out for example in a factory before delivery to a user, to reduce any effects due to mismatching of the temperature sensors. An offset to be applied to any determined temperature difference on which a leak status may be detected may be determined by placing the unit in a thermally insulated environment, e.g., insulated box, and waiting for a relatively long duration e.g. six hours, before measuring any temperature difference between the sensor readings and adjusting the offset accordingly. This may be performed by a test mode of the unit when the unit is first powered up.

[0137] Initiating Leak Detection Operation

[0138] An embodiment may be configured to detect when the unit is mounted on a pipe such that operation for monitoring for any leak can be started. The unit may be configured to wait until a sudden change in pipe temperature relative to the ambient temperature is detected, preferably repeatedly such as at least three times in 24 hours. The unit may then effectively know that it is in use, i.e. no longer separate from a pipe to be monitored.

[0139] Such a feature may give confidence for example to an insurer that any readings or notifications arising from the unit relating to leak detection have resulted from events occurring while the unit was fitted to a pipe.

[0140] The start of leak detection operation may be indicated by communicating this to a remotely located control entity and/or may be recorded internally within the unit, preferably recording the date at which the unit was mounted onto the pipe, or incrementing an internal timer so the total time that the device has been fitted to a pipe is known.

[0141] Alarm Re-Set

[0142] An embodiment may have a re-set button to allow a user to deactivate an alarm (e.g., visual and/or audible notification or alert) that has been activated in the event of the system/device indicating a leak. Preferably, the system, e.g., ECU, is configured to store internally and/or communicate externally that the alarm has been re-set (e.g., including a time of the re-set), and may further store and/or communicate when the alarm has been re-set (e.g., including a time of the re-set). This may allow determination for example by an insurer of when the alarm has been re-set but no call out for attending to a potential leak has been initiated. The re-setting of the alarm may be communicated, e.g., wirelessly, to a remote entity.

[0143] Alarm Filtering

[0144] A preferred embodiment does not provide an alarm, e.g. notification to the user and/or an audible and/or visual indication by the unit, every time a potential leak is detected. Such an alarm may be provided only when a potential leak detection occurs repeatedly on each of a pre-determined number of periods when no flow would be expected in the absence of a leak, e.g. three night time such periods.

[0145] Similarly, if a temperature pattern is detected having transition(s) corresponding to at least one leak-no leak transition during each of a pre-determined number of such periods then no alarm may be generated. Such a pattern may merely indicate that a user has a tendency to sometimes leave a tap dripping and not fully off and later to turn it off fully, for example. Preferably, no alarm is generated until at least seven night-time periods (or other periods of no flow expectation during a respective 24 hour periods) have occurred.

[0146] Burst Pipe Indication

[0147] An embodiment may be configured to detect when the pipe temperature stays substantially constant at a temperature that differs significantly by a pre-determined amount at least from the ambient temperature. In this case, the pipe temperature may have previously varied according to fluid (e.g. water) usage but then remain at the substantially constant temperature without beginning any rise towards the ambient temperature. The substantially constant temperature may be detected as corresponding to a water temperature estimated based on the preceding variations according to usage.

[0148] If the pipe temperature remains at the constant temperature for a pre-determined period, preferably longer than the longest period of usage expected for full flow such as when a user is washing a car (e.g. longer than 1 hour), this may indicate a burst pipe condition. Preferably, the detection of the substantially constant temperature for the pre-determined period results in the unit immediately issuing an alarm (e.g., visual and/or audible notification or alert). It is preferable in this case that the generation of a leak alarm is not disabled even for verification over more than one 24 hour period. In other words, preferably no verification is to be performed before issuing an alarm in the case of a potential burst pipe detection.

[0149] Holiday Mode

[0150] An embodiment may be configured to detect when a pre-determined number of, e.g., 24 hour, periods have passed with no flow, for example encompassing seven nights. Such no flow may be detected by determining that the pipe temperature tracks the ambient temperature throughout the predetermined number of such periods. If such an extended no flow period has occurred and the embodiment subsequently detects a sudden change in pipe temperature, for example indicated by a rate of change of pipe temperature greater than a pre-determined amount or a change in magnitude of pipe temperature greater than a pre-determined amount preferably over a pre-determined minimum period such as 60 minutes, an alarm (e.g., visual and/or audible notification or alert) may be generated due to the risk of the change indicating a burst pipe. Preferably no delay e.g. due to verification, is allowed before such an alarm is issued.

[0151] Torbeck Valve

[0152] A property may have one or more valves that allow for automatic re-filling of tanks. Such a valve is for example a Torbeck valve for re-filling the tank or cistern of a toilet. The valve may have hysteresis built in such that it allows flow intermittently, e.g. periodically, for example every few hours. An embodiment may be configured to detect a repetitive, e.g., periodic, flow pattern corresponding to such a valve. Such a pattern may be detected from corresponding changes of pipe temperature. The embodiment may be programmed to filter out such changes from the pipe temperature profile to be monitored for leak detection relative to the ambient temperature. In this way, false leak alarms may be reduced or prevented.

[0153] Remote Communication

[0154] An embodiment may output a minimum of data points from temperature profiles of the air and pipe and send these to a remote entity for determination of a leak/no leak status. Such data points may comprise the ambient temperature, pipe temperature, starting temperature and/or temperature-time gradient(s) of the ambient and/or pipe temperature profiles at the time point when the flow was last detected, e.g. water was last used. Such data points may be transmitted, e.g. wirelessly, to a remote control unit that decides if a leak has occurred based on those data points. This may be advantageous where the remote system decides what should be an appropriate predetermined threshold of temperature difference, for example depending on weather patterns/forecasts. The remote entity may adjust such a threshold on the fly for example in case of a heatwave where the ambient temperature is of the order of e.g. 30° C. and the pipe temperature is therefore not able to catch up during the predetermined period.

[0155] By varying such a threshold remotely, the remote system may be able to ensure that all devices are disabled from providing any leak alarm and/or ensure that any such alarm is ignored. Such remote control of the alarm process may be advantageous where sufficient data on preceding weather conditions is not able to be programmed into a leak detection unit mounted on a pipe. By providing the leak detection remotely, the system has some flexibility.

[0156] Taking into account that a leak detection may not necessarily be in radio communications at all times with a remote entity, a leak detection unit may have two modes of operation. In a first mode where radio communications are possible, the remote system may decide based on data points from the leak detection unit when an alarm is to be generated. In another mode, the unit detects that it is out of radio communication and is then configured to make decisions on alarms internally. An embodiment of the leak detection unit may have an indicator for indicating to the user whether or not the unit is able to perform radio communications with the remote entity. Where the unit is not in radio communications, it may be configured to provide notification to the user, e.g. to the user's mobile phone, to inform that the unit is operating in the independent, isolated mode.

[0157] In a preferred embodiment, data may be sent to a remote unit wirelessly, e.g., using sigfox (RTM) (this may be advantageous where there are bandwidth constraints). A unit that is local to, eg., attached to, the pipe may look for smooth regions where we can check for leaks (for example, it may look to (re-)start a predetermined period each time a water usage/flow is detected), then a predetermined threshold for leak detection may be adjusted at the remote unit to allow for temperature variations, desired sensitivity of the detectors, and/or to classify the leak according to severity.

[0158] Data that may be sent using, e.g. sigfox (RTM), may comprise for example: message type; message count; indication that ambient and pipe temperatures have crossed; pipe temperature sample(s), ambient temperature sample(s); indicator of time interval between each pipe temperature sample; and/or battery voltage.

[0159] Where more bandwidth is available, the ambient/air and pipe temperatures may be sent to the remote unit at every sample point. These may be batched and sent as a group to save battery power (e.g. send the last 10 samples every 1000 seconds). The leak detection algorithm may then be run remotely (permitting updates to be applied without needing to reprogram the detectors in the field).

[0160] Start of Predetermined Period

[0161] The predetermined period during which an embodiment monitors for a leak, e.g., by monitoring to detect a below threshold temperature difference and/or convergence of pipe and ambient temperature profiles, may have a predetermined duration, e.g. 2.7 hours, beginning at a starting time. The starting time may be determined by detecting a peak in d.sup.2T/dt.sup.2, taking into account the sign of this second differential (the term ‘differential’ being used interchangeably with ‘derivative’ throughout this specification, for example the second order derivative d.sup.2T/dt.sup.2 being referable to as a second derivative/differential of temperature with respect to time). Such a peak may be interpreted as indicating a water usage/flow and may thus be used to trigger the start of a new predetermined period, e.g., to re-start an existing monitoring period. When the second order differential is negative and the pipe temperature is greater than the ambient/air temperature, this may indicate the start of the predetermined period. When the second order differential is positive and the pipe temperature is less than the air temperature, this may similarly start a predetermined period.

[0162] Additional or Alternative Leak Detection

[0163] One method of leak detection involves using a determination of temperature difference between pipe and ambient air sensors and determining if the temperature difference is below a pre-determined threshold for a pre-determined period, as described elsewhere in this specification. However, depending for example on the time of year and/or a local climate, the temperature of the pipe may not be substantially constant throughout a period of no flow. Consequently, additionally or alternatively to the above method, an embodiment may determine a leak/no leak state based on whether or not the pipe temperature and ambient temperature tend to converge (as opposed to, e.g., ‘tracking’, i.e., generally staying parallel with a constant or zero offset).

[0164] Generally, in a no flow (e.g. no leak) condition, the pipe and ambient air temperatures may tend to gradually converge. In a flow or leak condition, the pipe temperature may tend to a constant temperature without returning to or at least converging towards the ambient temperature; this may even involve the pipe temperature crossing the ambient temperature.

[0165] In one scenario, in the no flow condition, the pipe temperature may gradually drop or rise depending on the environment so that the temperature difference between the ambient and pipe temperature sensors generally reduces. Bearing this in mind, it may be advantageous for detecting a leak to monitor the progression of the pipe and/or ambient temperature relative to each other, for example by monitoring progression of a gradient of temperature vs time of at least the pipe temperature. Such monitoring may allow early detection of a leak without awaiting detection of a sufficiently low and/or constant temperature difference between the sensors, e.g., without waiting to see if the pipe and ambient temperatures track and/or become closer than a threshold difference apart.

[0166] Thus, a preferred embodiment, additionally or alternatively to the monitoring of the temperature difference relative to a threshold, may monitor whether or not the pipe temperature tends to converge towards the ambient temperature, when there has been no other water usage for a length of time (for example 5 minutes). Detecting such a lack of water usage may be done by monitoring the second differential of the pipe temperature relative to time (i.e., d.sup.2T.sub.p/dt.sup.2), and waiting for it to be below a certain threshold, indicating no sudden changes in temperature and hence no changes in flow due to taps switching off and on or other intermittent usage. To monitor for convergence, an embodiment may monitor the pipe and air temperatures based for example on the equations below.

[0167] The rate of change of the measured local pipe temperature can be considered to be:

dTp/dt=h1.(Ta−Tp)+h2(Tw−Tp)   (1)

[0168] wherein Tp is the pipe temperature, Ta is the ambient temperature and Tw is the temperature of the water entering the pipe from the mains supply. h1 may be considered a (generally constant) transfer coefficient between the pipe and the ambient (e.g. air), and h2 may be considered to be a flow-dependent (thus, may be non-constant) transfer coefficient between the pipe and mains water supply.

[0169] h2 may be strongly dependent upon the rate of flow of the water in the pipe, q. If q is zero (no leak), then h2 will be very close to zero. If q is non zero, then h2 may start to affect, and/or have a greater effect on, dTp/dt.

[0170] If there is flow through the pipe, then the coefficient of heat transfer between the water and the pipe, h2 may be larger relative to h1. Over a period of time (typically 5 mins to 3 hours), Tp will generally tend towards Tw. As Tp approaches Tw, the rate of change of Tp, dTp/dt may be small, even if there is a still a relatively large difference between the air temperature and the pipe temperature (Ta−Tp). This may be indicative of flow in the pipe and presence of a leak.

[0171] One embodiment of implementing this in practice is as follows:

[0172] Rearranging (1) for h1 gives

h1=[(dTp/dt)−h2(Tw−Tp)]/(Tp−Ta)   (2)

[0173] When h2 is large, (1) shows that generally Tp will tend towards Tw over time as Tp will asymptotically approach the water temperature. Tp may approach a steady state as the h2 (Tw−Tp) term becomes smaller, and we can then approximate (2) based on the observables Tp and Ta as

h1′=(dTp/dt)/(Tp−Ta)   (3)

[0174] If h1′ is small, then the gradient in the pipe temperature over time is small relative to the difference between the pipe and the ambient/air temperatures. The pipe temperature may then be not tending towards the ambient/air temperature in a way which would be expected under a no leak condition, i.e., there may be an additional heat source or sink being applied to the pipe, potentially indicating the presence of flow in the pipe and thus a leak.

[0175] Thus, if it is detected that

(dTp/dt)/(Tp−Ta)<THRESH   (4a)

[0176] over a period of several minutes to a few hours, this may be interpreted as indicating a leak, where THRESH is a value that is preferably close to zero but sufficient to allow for variations due to noise and/or water temperature changes.

[0177] And if

(dTp/dt)/(Tp−Ta)>=THRESH   (4b)

[0178] then this may be interpreted as indicating that there is not a leak. Example values of THRESH may be, e.g., 0.001, 0.005, 0.01, 0.1 or 1.

[0179] In an embodiment, rather than calculating the first differential dTp/dt by calculating the difference between Tp.sub.n and Tp.sub.n−1 where Tp.sub.n and Tp.sub.n−1 are the values of Tp in successive time periods (which calculation may amplify any noise in the readings), exponential function(s) may be fitted (e.g., finding a best fit for example by means of a least squares fitting method) to the Tp and/or Ta samples over a region in which there has been no previously calculated water usage (this may have been indicated by other means). The exponential function(s) may then be used to calculate a value indicative of dTp/dt by analytical differentiation of the fitted exponential. Each fitted exponential function for the pipe and air temperature may be of the form a+bt+ce.sup.dt where a, b, c and/or d are generally taken to be constants and t is an indicator of time. In this case analytical differentiation of the function may calculate the value indicative of dTp/dt by calculating b+cde.sup.ct.

[0180] Advantageously, the use of an equation above, e.g., (3), (4a) and/or (4b), may allow an early and/or fast response to a leak condition.

[0181] In an embodiment, leak detection based on a ratio such as in equation (4a) and/or (4b) may be combined with an above described detection method based on detecting when a temperature difference is below/not below a predetermined threshold for a predetermined period. For example, they may run in parallel to provide redundancy and/or to improve robustness. If either algorithm predicted a leak a number (1 or more) of times then a leak could be reported for example by outputting an alarm.

[0182] To further understand an embodiment implementing a method of leak detection, consider first a situation where generally there is no influence on pipe temperature T.sub.p other than the ambient temperature T.sub.a: for example, there is no leak. In this case:

dT.sub.p/dt is proportional to T.sub.p−T.sub.a

[0183] If the pipe is cooling, then dT.sub.p/dt is negative; if the pipe is warming, dT.sub.p/dt is positive. Thus,:

[00001]${\mathrm{dT}}_p/\mathrm{dt}=\frac{-A.Math..Math.h}{\mathrm{Mcp}}.Math..Math.\left(T_p-T_a\right)$

[0184] where Ah is a constant relating to a contact area between the pipe and fluid (e.g., water) and Mcp is a constant relating to a mass of the pipe and water mass, i.e., Ah/Mcp may be regarded as a heat transfer coefficient b.

[0185] If we consider the general mathematical relationship:

dy/dt=−by; y=y.sub.o e.sup.−bt

[0186] where y is a function of time t, then y=T.sub.p−T.sub.a would mean that:

T.sub.p (t)−T.sub.a=(T.sub.o−T.sub.a)e.sup.−bt

where

[00002]$k=\frac{A.Math..Math.h}{\mathrm{Mcp}}=b$

so that:

T.sub.p (t)T.sub.a=(T.sub.o−T.sub.a)e.sup.−bt

T.sub.p (t)T.sub.a+(T.sub.o−T.sub.a)e.sup.−bt

[0187] where T.sub.o is the initial temperature of T.sub.p at t=0.

[0188] The above ‘no other influence’ scenario can be used to understand the following using a term F=bF′ to reflect the presence of a leak.

[0189] Assume that:

dT.sub.p/dt=−b(T.sub.p−T.sub.a)+bF′

[0190] where bF′ is negative is the leak causes the pipe to cool, and positive is the leak causes the pipe to warm.

[0191] then:

dT.sub.p/dt=−b(T.sub.p−T.sub.a−F′)   (5)

[0192] Using a temperature term x including temperature effect F′:

x=T.sub.p−(T.sub.a+F′)

[0193] then:

x=T.sub.p−(T.sub.a+F′)=[T.sub.o−(T.sub.a+F′)]e.sup.−bt

[0194] which can be rewritten to give:

T.sub.p(t)=(T.sub.a+F′)+[T.sub.o−(T.sub.a+F′)]e.sup.−bt

[0195] F′ may be considered to represent a leak, expressed here as an effective reduction in ambient temperature. Thus, determining whether F is large or small may indicate the presence or absence of a leak.

[0196] From (5):

dT.sub.p/dt=−b (T.sub.p−T.sub.a)+F

[0197] Thus:

F=dT.sub.p/dt+b (T.sub.p−T.sub.a)

[0198] If:

dT.sub.p/dt+b (T.sub.p−T.sub.a)>THRESH   (6a)

[0199] then this may indicate the presence of a leak, where THRESH is a predetermined threshold.

[0200] Conversely, if:

dT.sub.p/dt+b (T.sub.p−T.sub.a)<=THRESH   (6b)

[0201] then this may indicate the absence of a leak.

[0202] In this way, the observables T.sub.p and T.sub.a can be used to determine presence and/or absence of a leak. Example values of THRESH may be, e.g., 0.001, 0.005, 0.01, 0.1 or 1.

[0203] In view of the above, to implement leak detection, a leak detector for detecting a leak in a water supply system comprising a pipe may have a first temperature sensor detecting ambient temperature, a second temperature sensor configured to be mounted adjacent or in thermal contact with a pipe of the pipe system, and a processing means configured to determine a temperature difference between the first and second temperature sensors, wherein the processing means is configured to indicate the presence of a leak if a monitored variable is above a predetermined threshold for a predetermined period, wherein the monitored variable is the sum of an indicator of time gradient of the sensed pipe temperature and a multiple of the temperature difference, where the multiple represents a constant heat transfer coefficient. The leak detection method based on such a sum may be combined with either or both of the two methods based on the temperature difference relative to a predetermined threshold and on h1′. Furthermore, optional features provided for either of those two methods, for example with regarding to identifying the starting point for the predetermined period, etc., may be applied for this sum-based method similarly.

[0204] In an embodiment, leak detection in line with equation (6a) and/or (6b) may be combined with an above described detection method based on detecting when a temperature difference is below/not below a predetermined threshold for a predetermined period and/or with a detection method based on a ratio as in equation (4a) and/or (4b). For example, any two or more of these methods may run in parallel to provide redundancy and/or to improve robustness. If either algorithm predicted a leak a number (1 or more) of times then a leak could be reported for example by outputting an alarm.

[0205] Generally speaking, the embodiments described herein are implemented indoors, i.e., are attached to a pipe within a property in order to detect leaks. This may be advantageous depending on geographic location, since an outdoor location may require some thermal insulation to prevent the pipe freezing. Such insulation may interfere with monitoring the ambient temperature, depending on the arrangement of sensors.

[0206] Regarding further examples of temperature-time traces, the above descriptions of FIGS. 5a, 5b, 6a and 6b further serve to describe FIGS. 8a, 8b, 9a and 9b, respectively, the latter drawings however covering different periods of time.

[0207] FIG. 10 shows further example temperature-time traces of pipe temperature Tp and ambient temperature Ta, including monitoring periods for ‘no flow’ and ‘flow’ instances.

[0208] FIG. 11 shows further example temperature-time traces of pipe temperature Tp and ambient temperature Ta. As shown, a maximum ambient/air temperature may be used for a starting temperature difference to trigger a monitoring period. Alternatively, the ambient/air temperature used for the starting difference may be the temperature of the ambient/air at the instant that the pipe temperature curvature is at a maximum.

[0209] FIG. 12 shows an example fluid flow detector system 10a, for monitoring a pipe 12a of a water supply system 100. The water supply system may further comprise a stopcock 150, a valve 140 such as a Torbeck valve, and/or a powered shut-off valve 130 which may be controlled for example by the processing means (preferably comprising one or more processors), e.g., ECU 40a. The fluid flow detector system may be a self-contained device for attaching to the pipe 12a, or may comprise a system of couple devices, e.g., the pipe temperature sensor 16a and/or ambient temperature sensor may be provided externally to a device comprising the processing means 40a, e.g., may be coupled by a wire(s) or wirelessly to such a device. The power supply 42a may be coupled to a mains network 120 and/or may comprise a battery(s). The alarm generator 46a is shown in the fluid flow detector system, e.g., in a device housing at least the processing means, however such an alarm generator may additionally or alternatively be provided at a remote entity 110. The alarm generator 46a may send an alarm preferably, wirelessly, to a user 160 and/or to or via a relaying means 48a and/or a remote entity. The fluid flow detector system, e.g., a device comprising at least the processing means, may comprise a relaying means, e.g., a communication interface comprising a transmitter and/or receiver, preferably wireless, for communication with a remote entity 110 (e.g., remote alarm signal receiving station).

[0210] FIG. 13 shows an example computing device or system on which at least the processing means, e.g., electronic control unit, of an embodiment of the invention may be implemented. Similarly, remote entity, e.g., remote alarm signal receiving station, may by implemented by such a computing device/system. Each element of FIG. 13 is optional. The computing device/system of FIG. 13 comprises a bus, at least one processor, at least one communication port (e.g., RS232, Ethernet, USB, etc.), and/or memory, all generally coupled by a bus (e.g., PCI, SCSI). The memory may comprise non-volatile memory such as read only memory (ROM) or a hard disk and/or volatile memory such as random access memory (RAM, e.g., SRAM or DRAM), cache (generally RAM) and/or removable memory (e.g., EEPROM or flash memory). The processor may be any known processor, e.g., an Intel (registered trademark) or ARM (registered trademark) processor. A user interface, e.g., display screen and/or keyboard may be provided. The processor 24a may be an ARM (RTM) device or a similar processor produced by another manufacturer such as Intel (RTM).

[0211] No doubt many other effective alternatives will occur to the skilled person. It will be understood that the invention is not limited to the described embodiments and encompasses modifications apparent to those skilled in the art lying within the spirit and scope of the claims appended hereto.