Fluid Leak Detector With Thermal Dispersion Flow Meter and Chronometric Monitor

Abstract

A non-invasive thermal dispersion flow meter with chronometric monitor for fluid leak detection includes a heater, an ambient temperature sensor and a flow rate sensor which are configured to sense the temperature of a fluid in a conduit, and then monitor the flow of that fluid through the conduit. The fluid flow sensor is incorporated into a

Wheatstone bridge circuit which is used to provide increased sensitivity to the outputs of the sensors. Based upon the ambient temperature sensor readings, the flow rate sensor and heater may be adjusted to optimize the operation of the system to detect leaks. An alternative embodiment utilizes a single sensor and separate heater which work together to determine heat propagation times which in turn is used to calculate flow rate.

Claims

1. A fluid leak detector comprising: a fluid flow meter configured to monitor a fluid flow rate of a fluid; and monitoring the fluid flow rate and increasing a timeout counter when the fluid flow rate is above a trip level fluid flow rate and resetting the timeout counter to zero when the fluid flow rate is below the trip level fluid flow rate, wherein a leak is detected when the timeout counter exceeds a timeout value.

2. The fluid leak detector of claim 1 further comprising a valve, wherein the valve is configured to close when the timeout counter exceeds the timeout value.

3. The fluid leak detector of claim 1 further comprising a controller, wherein the controller is configured to send an output signal when the timeout counter exceeds the timeout value.

4. The fluid leak detector of claim 3 further comprising a valve, wherein the output signal from the controller closes the valve.

5. The fluid leak detector of claim 4 further comprising a display, wherein the output signal from the controller is sent to the display to notify of a detected leak.

6. A fluid leak detector comprising: a fluid flow meter configured to monitor a fluid flow rate of a fluid within a conduit; and monitoring the fluid flow rate and increasing a timeout counter when the fluid flow rate is above a trip level fluid flow rate and resetting the timeout counter to zero when the fluid flow rate is below the trip level fluid flow rate, wherein a leak is detected when the timeout counter exceeds a timeout value.

7. The fluid leak detector of claim 6 further comprising a valve attached to an inlet of the conduit, wherein the valve is configured to close when the timeout counter exceeds the timeout value.

8. The fluid leak detector of claim 7 further comprising a controller in communication with the fluid flow meter, wherein the controller is configured to send an output signal when the timeout counter exceeds the timeout value.

9. The fluid leak detector of claim 8 further comprising a valve attached to an inlet of the conduit, wherein the output signal from the controller closes the valve.

10. The fluid leak detector of claim 9 further comprising a display in communication with the controller, wherein the output signal from the controller is sent to the display to notify of a detected leak.

11. A fluid leak detector comprising: a fluid flow meter attached to a conduit and configured to monitor a fluid flow rate of a fluid within the conduit; a controller configured to monitor the fluid flow meter and operate a timeout counter; monitoring the fluid flow meter and accumulating the timeout counter by the controller when the fluid flow meter is above a trip level fluid flow rate and resetting the timeout counter to zero when the fluid flow meter is below the trip level fluid flow rate, wherein a leak is detected when the timeout counter exceeds a timeout value; and wherein the controller is configured to send an output signal when a leak is detected.

12. The fluid leak detector of claim 11, wherein said flow meter comprises an upstream temperature sensor and a downstream temperature sensor separated by a known distance, wherein the upstream temperature sensor and the downstream temperature sensor are configured to measure the temperature of the fluid within the conduit.

13. The fluid leak detector of claim 11 further comprising a valve attached to an inlet of the conduit and in communication with the controller, wherein the valve is configured to close when the output signal from the controller is received by the valve.

14. The fluid leak detector of claim 12 further comprising a display in communication with the controller, wherein the output signal from the controller is sent to the display to notify of a detected leak

15. The fluid leak detector of claim 11, wherein the flow meter comprises: a first RTD probe configured to be responsive to a drive signal to elevate the temperature of the first RTD probe and configured to measure its own temperature; a second RTD probe configured to measure the ambient temperature of the fluid within the conduit, wherein the first RTD probe and the second RTD probe are separated by a known distance; and a means for detecting the fluid flow rate of the fluid through the conduit utilizing the first RTD probe and the second RTD probe.

16. The fluid leak detector of claim 15, wherein the flow meter further comprises an adjustable Wheatstone bridge circuit comprising the first RTD probe and the second RTD probe and having a first output and a second output.

17. The fluid leak detector of claim 16, wherein the flow meter further comprises a servo amplifier configured to drive the first RTD probe comprising: a first input in electrical communication with the first output of the bridge circuit; a second input in electrical communication with the second output of the bridge circuit; and a power transistor having an output in electrical communication with the first RTD probe.

18. The fluid leak detector of claim 17, wherein said flow meter further comprises an adjustable comparator comprising: an input connected to the output of the power transistor; and an output; wherein the power transistor drives the first RTD probe in response to the difference in temperature between the first RTD probe and the second RTD probe; and wherein the adjustable comparator is configured to change state when the output of the power transistor exceeds a threshold.

19. The fluid leak detector of claim 15, wherein said flow meter further comprises a means for generating the drive signal in communication with the first RTD probe to drive the first RTD probe to a temperature above the ambient temperature.

20. The fluid leak detector of claim 19 wherein the means for generating the drive signal for the first RTD probe further comprises an adjustable Wheatstone bridge circuit wherein the first RTD probe represents an element in the bridge circuit responsive to the flow of fluid through the conduit.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0018] The novel features of this invention, as well as the invention itself, both as to its structure and its operation, will be best understood from the accompanying drawings, taken in conjunction with the accompanying description, in which reference characters refer to similar parts, and in which:

[0019] FIG. 1 is an exemplary view of the controller of the present invention as integrated with a structure, and showing the status panel of the system including an alarm indicator, an auxiliary indicator, a flow indicator, and a power indicator;

[0020] FIG. 2 contains three perspective views of the noninvasive sensors when clamped onto a metal pipe;

[0021] FIG. 2A is a perspective view of the sensors and heater when clamped onto a plastic pipe through in-molding thermal carriers;

[0022] FIG. 3 is a basic electrical schematic diagram showing the implementation of a Wheatstone bridge used to sense the energy required to balance the bridge, and to energize an LED when the detected flow rate is above an adjustable level;

[0023] FIG. 4 is a flow diagram of an exemplary operation of the system of the present invention, and includes a sequence of operation when employing a microprocessor controller to monitor the trip level and timer settings;

[0024] FIG. 5 is a flow diagram of an exemplary operation of the system of the present invention, and includes a sequence of operation when employing a microprocessor controller to cycle heater power to conserve energy and prevent excessive heating of the pipe section;

[0025] FIG. 6 is an electrical schematic showing the placement of the temperature sensors on the pipe and amplifiers configured to detect the flow signal;

[0026] FIG. 7 is an exemplary operational flowchart showing the overall operation of the system of the present invention;

[0027] FIG. 8 is a block diagram of an alternative embodiment of the present invention showing dual temperature sensors coupled to analog and digital circuitry, a user interface display and a valve for interrupting fluid flow through a conduit;

[0028] FIG. 9 is a block diagram of an alternative embodiment of the present invention showing a single sensor upstream from a heating element and having a central control unit with various inputs and outputs, alarm and mode control, and timer control. Additionally, the diagram illustrates the interface between the central control unit, the temperature sensor, and the heater;

[0029] FIGS. 10A and 10B consist of a graph and its associated data points respectively. The figures show temperature changes over time for no flow, low flow, and medium flow conditions in response to turning on the heater for a predetermined period of time when the ambient temperature is approximately 75 F.;

[0030] FIG. 11A and 11B consist of a graph with its associated data points which shows temperature changes over time for no flow, low flow, and medium flow conditions in response to turning on the heater for a predetermined period of time when the ambient temperature is approximately 37 F.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

[0031] This invention relates to an electronic thermal monitor system intended to measure fluid flow within a conduit or pipe, by clamping directly to the outside of a pipe or onto a thermally conductive heat transfer medium between the fluid and the system. Referring to FIG. 1, the present invention is suitable for application of leak detection technology into a structure 100 having a water inlet 101, a water leak monitor 102, and a shut off valve 120. The water leak monitor 102 includes a power indicator 104, a timer set 105 with an indicator 106, and a trip level set 108 with an indicator 110. Sensitivity adjustment 109 provides a user the ability to adjust the sensitivity of the device. A reset button 107 is provided to allow for the system to be reset after an alarm condition has been generated.

[0032] In an exemplary embodiment, this invention is discussed in conjunction with a typical thin wall copper pipe section commonly found in commercial and residential plumbing systems that form the water supply line. Since copper is an excellent conductor of temperature, this meter infers the water temperature by measuring the outside skin temperature of the pipe section. Another embodiment is to measure fluid flow within a confined conduit whereby the thermally conductive transfer medium is embedded within the conduit and allows for unimpeded and low heat measurements of fluids such as gasoline, diesel oil, liquid slurries, as well as gases such as air or nitrogen.

[0033] The thermal conduction means in the exemplary embodiment are clamps which mount to the pipe and form not only a mechanical connection between the meter and the pipe, but a thermal connection as well. The clamps are designed to transfer heat to and from the meter and the water within the pipe. The pipe may be any shape to contain the fluid and allow a thermal conduction means to the fluid within.

[0034] In the exemplary embodiment there is one upstream temperature reference clamp that contains an integrated temperature sensing element, such as a thermistor, thermocouple, or resistance temperature detector (RTD), which reads the current temperature of the pipe and fluid within. A second sensor clamp, mounted downstream from the reference, also contains an integrated temperature sensing element and a resistive heater which transfers heat energy into the pipe and the water within. This clamp performs the actual flow rate measurement.

[0035] Referring to FIG. 2, the clamps are comprised of a heat sink mount or shoe 202 and 207 which partially wraps around the outside diameter of the copper pipe 200, and are retained by spring clips 203 and 206 to keep them firmly pressed onto the pipe 200. The sensor/heat shoe 207 has mounting holes for both the thermistor 205 and the heater 204. The reference temperature shoe 202 has mounting holes for the reference thermistor 201. Since copper pipe 200 comes in various diameters, the shoes 202 and 207 may be configured in varying sizes and widths depending on the amount of surface area that is required to perform effective temperature coupling and heater loading.

[0036] While FIG. 2 depicts an exemplary embodiment of the electronic components 201, 204, and 205 with unconnected leads, it should be noted that either a single printed circuit board will be connected to these leads or additional wires will be added to these leads to form a remote control operation.

[0037] Additionally, FIG. 2A depicts a means to transfer heat through plastic pipe 225 by in-molding thermal carriers 226 and 227 and mounting the thermistors 201 and 205 and heater 204 directly to these thermal carriers 226 and 227. This method allows this invention to operate using non-thermally conductive materials such as plastic, Teflon, ABS, PVC, etc.

[0038] Referring to FIG. 3, as the heater R17 increases in temperature, the thermally coupled thermistor R11 senses the temperature change and adjusts the servo amp U1A to maintain the equilibrium of the Wheatstone Bridge circuit by modulating the power transistor Q1. The power transistor Q1 will either add or subtract power to the heater R17 to maintain the Wheatstone Bridge in balance. This system forms a closed loop feedback when the servo amp U1A reads the reference temperature thermistor R10, adds in the sensitivity bias voltage U1D, and then compares it to the current flow R11 temperature. This operation allows the reference thermistor R10 to adjust the circuit for any changes in incoming water temperature and allows the heater R17 to provide a constant temperature above the incoming water main as set by the sensitivity adjustment R5. Greater water flows require more heat to maintain this temperature difference and it is the amount of power consumed by the heater, to balance the bridge, which is read by the comparator U1C, to establish a flow trip threshold which is adjustable via resistor R1. If heater power increases above the preset trip threshold, the comparator U1C will activate and glow the TRIP LED D2 which, in other embodiments, may also be connected to a micro-controller to monitor flow and time.

[0039] FIG. 4 is a flowchart that describes an embodiment with a sequence of operations when employing a microprocessor controller to monitor the trip level and timer settings. When the trip level is exceeded, a counter is continuously incremented until it matches the timeout setting at which time the alarm output is activated. In this example, the alarm will automatically cancel once the trip value falls below the trip threshold, however some installations require latching the alarm on when tripped so it will remain active after the flow has been shut-off by employing an electric water shut-off valve 120 (not shown). The alarm output can be hard wired to existing commercial alarm panels. The alarm output signal may also drive a low power RF transmitter and pass its status via wireless signal.

[0040] Referring to FIG. 5, the micro-controller may also be configured to cycle heater power to conserve energy and prevent excessive heating of the copper pipe section.

[0041] Detection of the leak will still occur when the unit powers up and performs its leak tests over time. After the system wakes up and applies power to the heaters, the system will go into normal operation.

[0042] FIG. 6 is an electrical schematic showing the placement of the flow sensor 610 clamped to a water pipe (conduit) 611, and amplifiers 614 and 616 configured to form a circuit to detect the variations in the resistance of the flow sensor 610 produced by the flow of fluid 625 through the conduit 611. The amplifiers 614 and 616 feed their signals into Analog to Digital Converters 619 and 620 to create a digital representation of the flow signals. The digital representations are then fed to a microprocessor 621 where they are analyzed to determine the flow rate by comparing the flow data to the data stored in the control ROM and flash memory 622. The microprocessor 621 will then perform various functions 624, such as energize a relay, illuminate an LED, or create an audible alarm, based on the measured flow rate as compared to the data stored in memory 622. The microprocessor 621 will also sense the amount of current flow through the flow sensor 610 and adjust it as necessary to maintain a constant electrical current through the flow sensor 610.

[0043] FIG. 7 is an exemplary operational flowchart showing the overall operation of the system of the present invention and is generally referred to as item 250. At the start of the operation 252, the sensor is deenergized to allow it to cool to ambient temperature and establish a baseline temperature for use in future calculations 254. The sensor is then heated to a reference temperature plus an offset temperature 256. If the temperature has not been calibrated 258, then the system will reset the accumulator and alarms 260 and to check to see if the flow timer has expired 262. If the flow timer has expired 262, the system will reset the flow timer 264 then restart the process 254. If the flow timer has not expired 262, the system will go to step 256 to heat the sensor 256.

[0044] If the temperature has been calibrated 258, then the system will check for the presence of a time delay 266. If the delay time value has not been reached, the system will return to step 256 to continue heating the RTD. If the delay time value has been reached 266, the system will add time to the accumulator and record flow 268. If the accumulator has not reached its maximum value 270, the system will return to step 256 where it will continue to heat the RTD. If the accumulator has reached its maximum value 270, the system will compare the calculated flow to the flow trip point 272. If the trip point has not been reached 272, the system will return to step 268 where it will add time to the accumulator and record flow. If the trip point has been reached 272, the system will activate functions such as an alarm, an indicator, and automatic valve closure 274. It should be appreciated by someone skilled in the art that many different functions may be controlled by the system and the functions listed above are not the exclusive functions of the system.

[0045] FIG. 8 is a diagram of an alternative embodiment of the present invention and is generally designated 300. This diagram shows a clamp on temperature sensor package 306 which includes dual temperature sensors 324 and 326 separated by a known distance 328. The temperature sensor package 306 is coupled to a controller 302 having both analog 318 and digital 312 circuitry, and equipped with a user interface display 304 and a valve 308 for interrupting the flow of water through a pipe or conduit 310 should a leak be detected. The controller 302 has an internal power supply 321, a microprocessor 314 with memory 316, and interface circuits to control such things as the isolation valve 308, temperature sensor package 306, and the display unit 304. The display 304 utilizes a microcontroller 331 to control the user display panel 330, and external interfaces 332 such as telephone, internet, and alarm.

An Alternative Embodiment

[0046] Now referring to FIG. 9, an alternative embodiment of the present invention is shown and is generally designated 500. This embodiment consists of one temperature sensor 520, such as a RTD, thermistor, or thermocouple, clamped onto a pipe or conduit 524 and a heating element 518 mounted a distance 522 downstream from the temperature sensor 520. The temperature sensor 520 and heating element 518 are both wrapped or covered with an insulation material 516 thereby increasing the accuracy and sensitivity of the system.

[0047] This alternative embodiment uses heat conduction, propagation, and time to determine if there is liquid flow within an enclosed metallic conduit 524. FIGS. 10A, 10B, 11A, and 11B consist of graphs and the associated data points of temperature response to a known amount of heat energy added to a conduit having a no flow, low flow, and medium flow condition. The graphs and data points are for a warm test and cold test respectively. Two elements are required to electrically perform this function. One is a temperature sensor 520, either analog or digital, and the other is a resistive heater band 518 which wraps around the outside diameter of the conduit 524. It should be noted that the heater 518 and sensor 520 are separated by a short distance 522, such as 1 to 3, in order to create more average heating across the conduit 524 cross section, and also allow the internal flowing liquid 534 to carry away the conducted heat via convection cooling of the conduit 524 itself.

[0048] In normal operation, this embodiment works in an intermittent operation. After a calibrated time has elapsed, the heater 518 becomes energized, which forces heat energy into the conduit 524. The controller 502 would read the temperature sensor 520 just prior to heater 518 activation, and stored that value for further calculations. Conducted heat from the metallic conduit 524 will readily propagate from the center of the heat source 518 and outward eventually reaching the temperature sensor 520. The amount of time it takes for the heat to propagate to the temperature sensor 520 is recorded in the controller 502 and is a direct function of the liquid flow 534 within the conduit 524. Long propagation times reflect large effective flow rates.

[0049] The heater power is removed after a predetermined no-flow condition timer expires. The controller 502 will continue to read the temperature sensor 520 to continually analyze the heat propagation and lock onto a value that represents the peak temperature attained. This value is also a direct function of the liquid flow 534 within the conduit 524. Higher peak temperatures represent low effective flow rates, as the heater 518 is simply creating a no flow pocket of liquid, with little to no convective forces to carry away the applied heat energy.

[0050] Finally, after a predetermined amount of time has elapsed, the controller 502 acquires one final reading from the temperature sensor 520 and compares it to the previously saved value before the heater 518 was activated. The ratio of the before and after temperature readings is also a direct function of the liquid flow 534 within the conduit 524. The closer the two values are, the greater the effective flow rate is within the conduit 524 as the flowing liquid 534 is restoring the ambient fluid temperature to nullify the effects of the previously added heat energy.

[0051] All of the calculated temperature and time variables are scored within an algorithm that normalizes the effective flow rate with respect to ambient temperature and conduit/heater 524/518 thermal conductivity. The calculated score determines the liquid flow 534 rate, then the controller 502 records that rate, powers down for a short period of time as determined by the Master Time value 526, and allows the heater 518 and temperature sensor 520 to return to ambient conditions through natural convection.

[0052] As the system continues to move through heating and cooling cycles, the running status is accumulated. If the flow rate over all the cycles has not provided a single no-flow score, the system will enter an alarm state where it will either activate a relay 514, create an audible alert 512, or do both. The alarm may be cancelled by stopping the fluid flow or by switching to another mode of operation 510, either HOME or AWAY, which effectively resets all timers and scoring status results.

[0053] The heater 518 and temperature sensor 520 must be properly affixed to the conduit 524 to ensure consistent results over a long period of time measured in years. The heater 518 is a flexible silicone band which can wrap around the conduit 524 and be held in place with a self adhesive vulcanizing wrapping tape specifically designed to seal out moisture and provide continuous pressure on the heater 518 ensuring optimal thermal conductivity over time. It is to be appreciated by someone skilled in the art that many heater 518 designs exist that will satisfy the requirements of the system. The temperature sensor 520 also requires the same treatment during installation to ensure that the conduit 524 temperature is properly reported. It is also imperative that the entire heater/sensor 518/520 section, and a few inches beyond, be enclosed in thermal insulation 516. This prevents ambient or environmental air currents from affecting the calibrated flow readings by heating or cooling effects that are not the direct result of the fluid flow 534 within the conduit 524.

[0054] Intermittent operation of the heater 518 is required to provide the extended no-flow time period with an opportunity equilibrate with ambient conditions. Otherwise, the heater 518 and temperature sensor 520 would create a localized hot water heater within the test section of the conduit 524. Therefore, this device may not be used to measure flow rate or flow total as do other technologies, such as Thermal Mass Flow Meters. While this system is currently described to operate through a closed section of copper tubing/pipe 524, it may also operate through plastic conduit provided that the test section has in-molded metal plates or shoes within. The heater 518 and temperature sensor 520 requires direct thermal conduction of the fluid within in order to perform the same operation of an all-metal design.

[0055] An AC/DC power supply 504 may be used since the heater 518 requires significant energy output (>12 Watts) to perform its tests accurately and reliably. Alarm panel interfacing may also be expanded to include both wired and/or wireless operation for command/control facilities.

Installation and Calibration

[0056] This alternative embodiment of the present invention requires about 8-10 of clean copper pipe 524 to properly assemble the test section. The section of water pipe 524 selected should pass all incoming supply to the entire structure and should not be located outside where protecting the heater 518 and temperature sensor 520 elements would be impossible.

[0057] Once the heater 518 and temperature sensor 520 have been properly installed and the wiring and power have been completed, the device must be calibrated to the particular installation. Before activating the calibration function, all water flow in the test section must be halted.

[0058] The calibration function can be activated by an on-board switch, or wireless command, or a unique mode selection. During calibration, the unit will activate the heater 518. When the temperature sensor 520 records a temperature increase of 4 F. -10 F., the time which passes during this test is recorded by the controller 502 and stored for all future heater timing variables. Calibration finishes automatically and the system will be able to alert the installer if there is a problem or start performing normal operations if all is well.

[0059] This invention is a fluid flow meter with many applications and embodiments incorporating a unique method of flow measurement utilizing noninvasive thermal anemometry. The use of a Wheatstone Bridge greatly increases the system sensitivity and accuracy allowing it to be used in many applications.

[0060] While there have been shown what are presently considered to be preferred embodiments of the present invention, it will be apparent to those skilled in the art that various changes and modifications can be made herein without departing from the scope and spirit of the invention.