WO2011107101A1

WO2011107101A1 - Method and apparatus for leak detection

Info

Publication number: WO2011107101A1
Application number: PCT/DK2011/050063
Authority: WO
Inventors: Kenneth Klokker; Tonny Lemqvist
Original assignee: Kenneth Klokker; Tonny Lemqvist
Priority date: 2010-03-02
Filing date: 2011-03-02
Publication date: 2011-09-09
Also published as: EP2542872A1; EP2542872A4

Abstract

The present invention relates to a method and an apparatus for leak detection in pressurised tubes for flowing substances, which apparatus comprises at least one detector connected to the outside of a tube, which detector measures the actual temperature, which detector is connected to an analogue measuring circuit, which analogue circuit sends a temperature dependent signal to a processor, which processor stores a temperature dependent data set in a memory, which processor repeats the storing of a new temperature dependent data set in the memory after a first defined time period.

Description

Method and apparatus for leak detection

Field of the Invention

The present invention relates to a method and an apparatus for leak detection in pres- surised tubes for flowing substances, which apparatus comprises at least one detector connected to the outside of a tube, which detector measures the actual temperature, which detector is connected to an analogue measuring circuit, which analogue circuit sends a temperature dependent signal to a processor, which processor stores a temperature dependent data set in a memory, which processor repeats the storing of a new temperature dependent data set in the memory after a first defined time period.

Background of the Invention

WO 06036513 relates to a system and method for detecting water and/or gas leaks by monitoring usage patterns. In one embodiment, the existence of a leak is detected by looking for usage patterns wherein water or gas is always being used, at least at a low rate. A leak is indicated if usage does not drop to zero, at least for a period of time, during a given time interval e.g., during a 24-hour period. The severity of the leak is indicated by the minimum amount of usage during the given time period. In one embodiment, the leak detection system is provided in connection with an Automatic Meter Reading (AMR) system

WO 00125743 relates to a method of automatic monitoring a flow condition and to indicators to be used by the method. A method is intended for indicating a possible leak in a cold water supply pipe and a method is intended for indicating a possible low heat exchange in a domestic heat exchanger. The methods use measurements of tempera- tures on the surface of a pipe and measurements of temperatures of the surroundings or of another pipe. The leak indicator monitors a temperature difference between the surface of the cold water supply pipe and the temperature of the surroundings, and the low heat exchange indicator monitors a temperature difference between the surface of an inlet pipe and the surface of an outlet pipe of the heat exchanger. US 05062442 concerns apparatus functions for monitoring small leakages in order to activate an alarm in the event that there has been more than a predetermined volume of small leakage through the water taps or other part of the system and to automatically turn off a main valve if flow continues there through more than a predetermined time and will allow the main valve to open if the discharge of fluid is temporary stopped. The system includes a main valve having a valve seat and a shunt circuit that bridges the valve seat. The shunt circuit includes a volume flow meter and a shunt valve for blocking fluid flow through the circuit. The main valve opens only when the volume in the shunt path exceeds a predetermined value. The shunt circuit includes a throttle that when fluid flows there through, provides a pressure drop in the shunt circuit which results in the main valve diaphragm opening when the shunt circuit predetermined value is exceeded. Control apparatus ascertains the volume of fluid flow through the measuring portion of the shunt circuit and controls the closing the shunt valve, JP 61017928 concerns a leak detection monitor region by providing a moisture heated layer around a part of heat sensitive points of a multipoint heat sensitive sensor having plural heat sensitive points and detecting the difference between outputs of heat sensitive points near this layer and outputs of the other heat sensitive points. A multipoint heat sensitive sensor having heat sensitive points is provided in a heat insulator cover- ing the surface of a cooling system pipe in which a high-temperature and high-pressure cooling water is flowed. Heat sensitive points, are paired, and a moisture heated layer is provided around heat sensitive points of ones of pairs. If leaked water penetrates, the temperature near the heat sensitive point is raised by the moisture heated layer to generate a significant thermo electromotive force in the output of the multipoint heat sensi- tive sensor. By this output signal, an alarm device is operated through an amplifier and a comparator. Object of the Invention

It is the object of the invention to control for leak in tubes, such as water supply installations or in district heating installations by repeating measuring of temperature at the outside of a tube and store measured temperature data in a memory and perform an analysis of the change in a temperature profile.

Description of the Invention

The object of the invention can be fulfilled if the preamble to claim 1 is further modified so the processor performs an analysis of the temperature profile by analysing the change in temperature backwards in a second time period, which processor performs a search in the temperature profile for at least one rapid change of the surface temperature of the tube.

During developing of this new apparatus for leak detection it has surprisingly shown that in a tube in which a substance is flowing, it is possible to indicate a leak if the speed of the flow is changing and there is a temperature difference between the flowing substance and the surroundings. By analysing the actual temperature at the surface of the tube it has shown that a surprising effect is obtained i.e. that there is significant difference in a temperature profile of a normal operating system of tubes to the same system but where a leak is introduced. Even a very small leak can be detected in the temperature profile that can be measured at the outside of the tube. Even a small leak less than maybe one 1 litre per minute will have sufficient influence on the temperature profile so the leak can be detected simply by analysing if there is a change in the slope of the temperature profile. Of course it is easier to detect change in a temperature profile if there is a high temperature difference between the tube and the surroundings. But surprisingly, only a few degrees in difference are enough for performing a very effec- tive indication. The temperature profile has to comprise a change in the flow in order to give the result of the slope of the heat profile. Typically, e.g. in cold water supply simply the flushing of a toilet is sufficient for a change in the flow in a domestic water line. The temperature profile of the change in temperature of the tube will indicate if there is a leak e.g. if the toilet continues using water because a valve is misplaced. That extra demand of water will easily be indicated in that the temperature profile will change.

Also in district heating system, this invention can be used. Here there is probably a temperature of the tube that is sufficient higher than the surrounding temperature. Also by district heating there will be some changes in the demand of heating. Therefore, a temperature profile will exist. Surprisingly, this invention has made it possible to indicate leaks in district heating simply by analysing the temperature profile measured at the outside of the tube. The apparatus can comprise at least one alarm, which alarm is activated if no rapid change in the temperature profile is indicated in the second time period. The alarm can be activated if the rapid change in temperature has not been indicated at least once per 24 hours. This can lead to alarm activation perhaps in the form of flashing LED at the surface of the apparatus or perhaps activating an acoustic alarm. Further possibilities for transmitting an alarm is of course to send an electronic communication signal e.g. to a mobile phone or to a computer network in the form of an email.

The processor can store a pre-alarm in the memory, which pre-alarm activates the alarm in the apparatus if no rapid change in the temperature profile is indicated in the second time period. By continuously activating the pre-alarm, the apparatus as such is always ready to transmit an alarm if no rapid change is indicated in the second time period e.g. one per 24 hours. Then the pre-alarm is activating the visual or acoustic alarm as previously mentioned.

The apparatus can operates in a permanent alarm mode, which permanent alarm mode activates the alarm unit after a defined time period, in which time period a rapid change in the temperature profile stats a new defined time period. By continuous operation in the permanent alarm, the apparatus is in a permanent alarm situation, and only a rapid change in temperature can deactivates the alarm. The detector is connected to the surface of a cold water supply line at the water inlet in a flat or house. By using the leak detector at a cold water supply, it is possible to indicate any leaks in houses. As long as there is sufficient temperature difference between the water inlet and the surrounding temperature of the apparatus, it is possible to indi- cate leak by analysing the temperature profile. In the water supply, there will probably be situations several times a day where the normal flow will be very close to zero. In other situations when food is prepared or toilet is flushing or washing machine is in operation, there is a demand of cold water. But subsequent to a demand, there will probably be a situation of no flow and the change in the temperature profile will show that there is a rapid change in the temperature when no flow is in the tubes and if the rapid change is sufficiently fast, it indicates that there is no leak. This indication is performed each time a flow is changing from an active flow to no flow. Of course there can be many combinations of water demand in houses, so the temperature profile will show different measurements. But if only once in the second time period there is a change in the flow from e.g. a sufficient low value to a few litres per minutes to zero, the temperature profile will clearly show if a leak exist.

The detector is connected to the surface of a district heating inlet in a flat or a house. By district heating inlets it is supposed that there is a relative higher temperature differ- ence because district heating is probably being supplied with the temperature approximately between 60 or 80 degrees Celsius. Therefore, measuring the temperature profile in a tube that is surrounded by air of 20-25 or maybe 40 degrees Celsius, it is possible to measure a very precise temperature profile independent of the actual flow. If a rapid change in the temperature is indicated in the second time period, it indicates that there is no leak. If the temperature flow is indicated as a slow movement in the temperature it indicates a leak.

The apparatus can further comprise a censor, which sensor measures the temperature at the outside of a return line. Hereby can be achieved, that also a temperature differ- ence between an inlet and an outlet can be measured. The line of inlet liquid has probably a relatively high temperature, maybe approximately 70 degrees, and the outlet has a temperature that is maybe 40 degrees lower, so approximately 30 degrees. If the temperature of the return line increases only a few degrees rather fast, it indicates a kind of leak somewhere in a heating system. That leak could be a defect thermostat or maybe a hot water supply system that has a defect valve, where the heating liquid is flowing unlimited through the system. Any rapid changes of temperature in a return line indicate in that way a failure, for example, in a domestic heating system. Therefore, it is very important if those kinds of failures are communicated immediately to people living in the house or the flat, so they can maybe manually close some valves to avoid further costs by just sending the heating liquid backwards at a too high temperature. Therefore, it is very important that the system can comprise, for example, a mobile phone interface, or maybe a computer interface, where the alarm can be transmitted both as a text message or voice call, or it can be transmitted over a Wi-Fi net as an alarm to a computer system. In many domestic heating systems, there is a requirement for the return line to a certain temperature; each time the return line has a temperature higher than specified in the requirement a fine has to be paid. Therefore, if you indicate the temperature in the return line, you can send an alarm each time the return temperature is too high. In that way a house or a flat can adjust, for example, floor heating to a level where the return temperature is far below the critical level.

The present invention also concerns a method for indicating leak in pressurised tubes for flowing substances, which method comprises at least the following steps, measuring the temperature at the surface of a tube, convert the measured temperature into a temperature data set, store the measured temperature data set in a processor memory, repeat storing of the measured temperature data sets after a first defined time period, analysis the temperature data sets in a second time period, define a temperature profile of at least the second time period, analysis the temperature profile for rapid change of temperature, activate an alarm if no rapid change in temperature is indicated in the second time period.

It can hereby be achieved a surprising effect that a leak in a tube system can be indicated simply by measuring the temperature profile at the outside of the tube. In this way a relative simple apparatus can be developed because there is no access to the media that flows inside the tube. If there is a chance in the flow in the tube from e.g. a typical demand to a lower but also defined demand, then there will be a change in the temperature profile measured at the outside of the tube. If the slope measured at the profile is the same as usual in the same situation, it indicates that there is no leak. But if the slope changes, it indicates that there is a leak in the tube system. Analysing the temperature profile over a longer period of time, it is possible to indicate if rapid changes are measured. If rapid changes of the temperature outside the tube are meas- ured, it indicates that there is no leak. If no rapid changes can be indicated, there is no doubt that there is flow in the tube and as such it indicates a leak. Therefore, if an alarm is indicated an alarm can be activated. This alarm can as already previously mentioned be a flashing LED or acoustic alarm or one or more electronic signals can be transmitted to mobile phones or to a computer system.

Description of the Drawing

Figure 1 shows a schematic view of a leak detecting apparatus.

Figure 2 shows a temperature profile of a district heating.

Figure 3 shows the same curvature of the district heating from figure 2 but now with a leak in the tubing inside a house.

Figure 4 shows an alternative embodiment for a leak detecting apparatus

Detailed Description of the Invention

Figure 1 shows an apparatus 2 for leak detection. A tube 4 in which tube e.g. water is flowing, a temperature detector 6 is placed outside the tube and the temperature detector 6 is by a line 8 connected to the leak detector 10. The leak detector 10 is further connected to an alarm unit 12 and by a line 14 the leak detector 10 is further connected to a power supply 16. In operation, the temperature detector 6 will by relative short time intervals deliver the actual temperature at the surface of the tube 4 and transmit that over the wiring 8 to the leak detector 10. In the leak detector, there will at first be performed an analogue to digital conversion 18 and then the data set will be stored in a memory 22. Inside the leak detector 10, there will be a memory 22 that comprises temperature related data together with time related data. In this way, there will be stored a digital temperature profile over the temperature that is measured by the detectors 6 at the outside of the tube 4 in relation to the time where the measuring is performed. A micro computer 20 that can be integratedly placed in the leak detector 10 can perform an analysis of the curvature by e.g. performing a differentiation of the curvature. If the differential quotient e.g. one per day is indicating a relative fast drop in temperature at the tube, it indicates that there is no leak. Analysing the differential quotient for the whole curvature it is rather easy to indicate that a negative value for that curve must be under a certain level in order to indicate the fast falling curve. This is a rather easy algorithm to program in the microprocessor 20 for the digital analysis of the curvature. In this way, there can be performed at highly effective leak detection of a tube 4. This leak detection could be used in as well cold water supply as in district heating systems. As long as there is a temperature difference between the media that flows in the tube 4 and the surrounding temperature around the tube 4, then it is possible to measure a temperature difference depending on the actual flow in the tube 4 and this invention could be used. Figure 2 shows a coordinate system 102 comprising a temperature axis 104 and a time axis 106. A curve 108 indicates the actual change of a temperature in a district heating system. At 110 the temperature is increasing up to a constant level 112 and the temperature is by the line 114 dropping back to the normal temperature 115. This rapid increase in temperature could indicate that a person is taking a bath. The line 115 con- tinues and there is a fall in temperature 116 perhaps because it is a typical day situation in which most people is at work and the demand for heating is reduced. That leads to a falling inlet temperature because the temperature is falling in the whole system because of falling demand. At 118 the temperature is increasing to the normal level because normal activity is probably starting in a whole area of a city. At 120 there is a kind of demand perhaps for normal household use in a house or heating is turned on then by 122 the demand is falling and at 124 again more heating is probably turned on for a short period of time. During night time the temperature 126 is again normal and also during the night the demand is decreasing and thereby also the decreasing temperature 128 is indicated. During the morning the temperature increases to the normal level 130 and by 132 indicates that a shower is being turned on which continues at 134 and 136 indicates the decreasing temperature of the tube when the flow is reduced because the shower is ending. At 138 the line continues. It can be seen at this curvature that the falling temperature measured at the tube after end of e.g. a shower marked 114 and 136 gives a drop in temperature of several degrees over a relative short period of time. Performing a mathematical differential analysis of the curvature will indicate the slope of the curve.

Turning now to the figure 3 that shows exactly the same installation, however, now there is a leak. All numbers at the figure 3 is 100 higher than at the figure 2. It is easy to compare e.g. the line at figure 2, 114, and figure 3, 214, there is sufficient difference in the slope. Each time the temperature is decreasing the curve 208, it can be seen that the drop in temperature is performed very slowly. If there is performed a differentiation of the curvature 208, this will reach a much smaller negative value than what can be indicated at the figure 2. It is easy for a computer system to analyse the difference in the curvature and to see after a few hours that the curvature has changed which indicates that there is a leak in the tubing.

Figure 4 shows an alternative embodiment for an apparatus 302 for leak detection. A tube 304 in which tube a heating media is flowing where this flowing media returns in a tube 305. At the tube 304 are a temperature detector 306 and at the tube 305 is placed a temperature detector 307. The temperature detector 306 is connected by a line 308 towards the leak detector 310. The temperature detector 307 is connected by a line 309 also to the leak detector 310. The leak detector 310 is further connected to an alarm unit 312 which alarm unit 312 is further connected to a transmission unit 313. This transmission unit can be, for example, a Wi-Fi connection or it could be a mobile phone which mobile phone is able to transmit a text message or maybe perform a voice call to previous coded phone numbers inside this transmission unit. In that way it is possible as well to transmit text message or voice indication of an alarm, but also by Wi-Fi connection to transmit a data signal, for example to a computer system. The alarm unit 310 is further by line 314 connected to a power supply 316. This power supply is probably performed as a battery, because the apparatus 310 can operate for a very long time period on simple batteries. Of course it is possible also to use a traditional power supply, if it is possible where the apparatus 310 is operating to access to a external power. Most of the operation that is performed by the leak detector 310 is equal to the technology which is previously described relating to the figure 1, 2 and 3. The major difference to what is previously described is that both the temperature of the supply liquid is measured by the temperature detector 306, and also the return line 305 comprises a temperature detector 307. In that way it is possible to indicate the temperature difference between inlet and outlet liquid.

If, for example, the temperature difference between inlet and outlet is relatively low, and the supply line is having a high temperature and return line is more or less having a temperature as high or that the return line has increasing temperature that indicates maybe not a leak to the surroundings, but it indicates, for example, a very bad regulation somewhere in a household installation. That could be, for example, a thermostat that is constantly open. Also here it is very important to get an alarm. In the systems 302 it is also important to continuously measure the temperature of the return line, simply because there is a limited temperature that the liquid in the line has to be limited to otherwise this will be indicated in a higher price that the customer has to pay for the energy that is used.

Claims

1. An apparatus (2,302) for leak detection in pressurised tubes (4,304,305) for flowing substances, which apparatus (2,302) comprises at least one detector (6,306,307) con- nected to the outside of a tube (4,304,305), which detector (6,306,307) measures the actual temperature, which detector (6,306,307) is connected to an analogue measuring circuit (18,318,319), which analogue circuit (18,318,319) sends a temperature dependent signal to a processor (20,320), which processor (20,320) stores a temperature dependent data set in a memory (22,322), which processor (20,320) repeats the storing of a new temperature dependent data set in the memory (22,322) after a first defined time period, characterized in that the processor (20,320) performs an analysis of the temperature profile by analysing the change in temperature backwards in a second time period, which processor (20,320) performs a search in the temperature profile for at least one rapid change of the surface temperature of the tube (4,304,305).

2. An apparatus (2,302) according to claim 1, characterized in that the apparatus (2,302) comprises at least one alarm (12,312), which alarm (12,312) is activated if no rapid change in the temperature profile is indicated in the second time period.

3. An apparatus (2,302) according to claim 1 or 2, characterized in that the processor (20,320) stores a pre-alarm in the (22,322) memory, which pre-alarm activates the (12,312) alarm in the apparatus (2,302) if no rapid change in the temperature profile is indicated in the second time period.

4. An apparatus (2,302) according to claim 1 or 2, characterized in that the apparatus (2,302) operates in a permanent alarm mode, which permanent alarm mode activates the alarm unit (12, 312) after a defined time period, in which time period a rapid change in the temperature profile stats a new defined time period.

5. An apparatus (2,302) according to one of the claims 1-4, characterized in that the detector (6) is connected to the surface of a cold water supply line at the water inlet in a flat or house.

6. An apparatus according to one of the claims 1-5, characterized in that the detector (6,306,307) is connected to the surface of a district heating inlet or outlet in a flat or a house.

7. An apparatus according to one of the claims 1-6, characterized in that the appara- tus further comprises a censor (307), which sensor (307) measures the temperature at the outside of a return line (305).

8. A method for indicating a leak in pressurised tubes (6,306,305) for flowing substances, which method comprises at least the following steps: a. measuring the temperature at the surface of at least one tube (6,306,305), b. convert the measured temperature into a temperature data set, c. store the measured temperature data set in a processor memory, c. repeat storing of the measured temperature data sets after a first defined time period, d. perform an analysis of the temperature data sets in a second time period, e. define a temperature profile of at least the second time period, f. perform an analysis of the temperature profile for rapid change of temperature, g. activate an alarm if no rapid change in temperature is indicated in the second time period.