System and method for locating sources of fugitive gas emissions

Abstract

The present application relates to systems and methods for locating sources of fugitive gas emissions. The fugitive gas detection system includes an inertial measurement assembly (IMA) that measures changes in the position of an inlet of a gas analyzer and applies a time slip to the concentration data detected by the analyzer to generate a time series of gas concentrations in three dimensions. Using statistical methods, the relative position of the source of the fugitive gas can be determined from the time series. Furthermore, in some embodiments, the data can be interpolated to create a map of the fugitive gas plume.

Description

Technical Field

[0001] The present invention relates to a method and apparatus for mapping the concentration of fugitive gas emissions to detect and locate the source of fugitive gas emissions. More particularly, the present invention relates to a method and apparatus for mapping the concentration of fugitive gas emissions and locating specific fugitive gas emission sources using a handheld detector capable of providing dead reckoning. Background Art

[0002] Detecting fugitive gas emissions is of great concern to both utility providers and the public because such emissions can cause financial losses and, in some cases, be dangerous if the gases are toxic or flammable. A variety of low-sensitivity tools exist to help utilities identify leaks in their distribution systems. These tools generally fall into two categories: handheld and vehicle-mounted.

[0003] Handheld devices such as flame ionization detectors (FIDs) or infrared (IR) absorption detectors are used by walking surveyors whenever a leak is suspected, and on a periodic basis to check mains and property service lines for unknown leaks. During a walking survey, the surveyor walks along the main line, holding a handheld wand over surface service pipes and features that could indicate an underground leak (e.g., sewer grates, cracks in roadways, sidewalk edges, service risers, etc.). Large leaks can be detected, but the process is time-consuming because the handheld device is only sensitive to concentration changes in parts per million (ppm) and responds slowly to changes in gas concentration, requiring the surveyor to check a specific location by holding the wand in a fixed position. As such, this survey technique is time-consuming and reserved for detecting leaks at suspected locations.

[0004] In other uses, placing the sensor on a mobile platform is one way to increase the speed and sensitivity of detection. For example, the optical methane detector (OMD) provided by Health Advisor is an IR light source and detector tuned to the absorption band of methane and an open path of approximately 1.5 meters. The system is sensitive to absorption of approximately 1 ppm-m. Although it can operate at driving speeds up to approximately 15 miles per hour, the system has limited sensitivity and must pass in close proximity to the leak source (e.g., within 25 feet). The sensitivity of the mobile sensor is improved by using Integrated Cavity Output Spectroscopy (ICOS), which is a methane detector that has a measurement accuracy of approximately 2 parts per billion (ppb) for methane and when paired with GPS and optional wind measurement, it is possible to detect very small or very remote natural gas leaks.

[0005] However, the workflow after using a more sensitive mobile method to identify a leak still requires the surveyor to exit the vehicle and use a less sensitive handheld device to search the indicated area for leaks. Because the handheld device must be in close proximity to the leak source to sense gas, the surveyor typically spends 30 to 60 minutes walking with the handheld sensor before finding the actual leak location. This long search time is not only costly and frustrating, but in many cases, the walking surveyor will not find the leak at all. Without a sensor that can detect gas plumes at the ppb level, the walking surveyor's only recourse is to visually identify possible leak locations. Summary of the Invention

[0006] The present invention comprises the features recited in the appended claims and / or one or more of the following features, which alone or in any combination may comprise patentable subject matter.

[0007] According to a first aspect of the present invention, a gas leak detector includes an inertial measurement assembly, a high-precision gas analyzer, a wand, and a controller. The wand has an inlet tip that receives ambient air and directs the ambient air to the high-precision gas analyzer. The wand is physically coupled to the inertial measurement assembly such that movement of the wand is detected by the inertial measurement assembly.

[0008] The controller receives signals from the inertial measurement assembly and the high-precision gas analyzer. The controller includes a processor and a memory device, the memory device including instructions that, when executed by the processor, cause the controller to: monitor the signals from the inertial measurement to identify real-time changes in the position of the tip of the wand. The instructions further cause the controller to record the position changes as a time series. The instructions still further cause the controller to: monitor a signal from the high-precision gas analyzer indicating the concentration of one or more specific types of fugitive gases dispersed in the ambient air; and record the concentration of specific molecules of each of the one or more specific types of fugitive gases dispersed in the ambient air as a time series. The instructions also cause the controller to apply an adjustment factor, depending on the characteristics of the wand, to the time series of the concentration of the specific type of fugitive gas in the air to offset the time series so that when the measured concentration of the specific type of fugitive gas enters the wand, the measured concentration aligns with the position of the tip of the wand to create an adjusted concentration time series. The instructions still further cause the controller to record changes in the adjusted concentration time series and the position time series to create a combined time series that includes both position and fugitive gas concentration data.

[0009] In some embodiments, the inertial measurement assembly measures three-dimensional changes in position of the inertial measurement assembly and measures changes in pitch, roll, and pitch of the inertial measurement assembly to provide signals to the controller indicative of changes in position of the tip of the wand.

[0010] In some embodiments, the inertial measurement assembly includes a structure capable of measuring acceleration in three orthogonal axes.

[0011] In some embodiments, the inertial measurement assembly includes structure capable of measuring gyroscopic deviations about the three orthogonal axes.

[0012] In some embodiments, the high precision gas analyzer utilizes integrated cavity output spectroscopy to measure the concentration of a particular type of gas in the ambient air.

[0013] In some embodiments, the memory device includes further instructions that, when executed by the processor, cause the processor to utilize a Gaussian plume model to evaluate the combined time series including both position and concentration data to determine a vector indicative of a probable location of a source of the fugitive gas.

[0014] In some embodiments, the memory device includes further instructions that, when executed by the processor, cause the processor to utilize Bayesian estimation to evaluate the combined time series including both position and concentration data to determine a vector indicative of a likely location of a source of the fugitive gas.

[0015] In some embodiments, the memory device includes other instructions that, when executed by the processor, cause the processor to determine a vector indicating a possible location of a source of the fugitive gas utilizing multiple winds surrounding a peak in several spatial or temporal methane peaks in the combined time series that includes both location and concentration data.

[0016] In some embodiments, the gas leak detector further comprises a user interface in communication with the controller, the memory device including instructions that, when executed by the processor, provide an output to the user interface, causing the user interface to provide a real-time indication of a possible direction and / or location of a source of the fugitive gas relative to the gas leak detector.

[0017] In some embodiments, the controller receives a signal indicative of a geospatial reference datum from a geospatial location satellite system while a sequence of position data is being collected, and wherein the memory device includes instructions that, when executed by the processor, cause the processor to process real-time changes in the position of the inertial measurement assembly to create an adjusted time series of position data referenced to the geospatial location of the inlet of the wand, and to create a combined time series including both geospatial location and fugitive gas concentration data.

[0018] In some embodiments, the gas leak detector further comprises a user interface in communication with the controller, the memory device containing instructions that, when executed by the processor, provide an output to the user interface, causing the user interface to provide a real-time indication of a possible location of a source of the fugitive gas relative to the gas leak detector.

[0019] According to a second aspect of the present invention, a method for identifying the source location of a gas leak includes: moving the inlet of a handheld gas analyzer in space to collect ambient air samples; using an inertial measurement assembly to measure real-time changes in the position of the inlet of the gas analyzer; and recording a time series of the changes in the position of the inlet. The method further includes: using a high-precision gas analyzer to measure the real-time concentration of a specific fugitive gas; adjusting the real-time concentration of the specific fugitive gas using a time slip factor to account for the delay in the transfer of the fugitive gas from the inlet to the high-precision gas analyzer, thereby generating a time-slipped data series of the concentration. The method also includes: combining the time-slipped concentration data series with the time series of changes in the position of the inlet to create a time series indicating the relative position of the inlet and the concentration of the fugitive gas at the inlet over time.

[0020] In some embodiments, the method further includes: determining a reference geospatial position of the inertial measurement assembly during real-time changes in collection location; offsetting the time series of the relative positions of the inlet relative to the reference geospatial position to create a time series of the geospatial position of the inlet; and combining the time-slipped concentration data series with the time series of the geospatial position of the inlet to create a time series indicating the geospatial position of the inlet and the concentration of fugitive gas at the inlet over time.

[0021] In some embodiments, the method further includes: utilizing a Gaussian plume model to evaluate the combined time series comprising both position and concentration data to determine a vector indicative of a possible location of a source of the fugitive gas; and outputting a visual representation of the possible location of the source of the fugitive gas on a display device.

[0022] In some embodiments, the method further includes: utilizing Bayesian estimation to evaluate the combined time series comprising both location and concentration data to determine a vector indicating a possible location of a source of the fugitive gas; and outputting a visual representation of the possible location of the source of the fugitive gas on a display device.

[0023] In some embodiments, the method further includes: processing the time series indicating the geospatial location of the inlet and the concentration of the fugitive gas at the inlet over time using statistical interpolation to create a three-dimensional dataset approximating the concentration of the fugitive gas in space; and plotting the three-dimensional dataset approximating the concentration of the fugitive gas in space to create a visual representation of the concentration on a map.

[0024] According to a third aspect of the present invention, a system for measuring the distribution of fugitive gases in three dimensions includes an inertial measurement assembly, a high-precision gas analyzer, a wand, a user interface, and a controller. The inertial measurement assembly provides signals in real time indicating changes in the three-dimensional position and three-axis orientation of the inertial measurement assembly. The high-precision gas analyzer measures gas concentration in real time. The wand has an inlet tip that receives ambient air and directs it to the high-precision gas analyzer. The wand is physically coupled to the inertial measurement assembly such that movement of the wand is detected by the inertial measurement assembly. The user interface includes a user input device and a display. The controller communicates with the inertial measurement assembly, the high-precision gas analyzer, and the user interface and includes a processor and a memory device coupled to the processor. The memory device stores instructions that, when executed by the processor, cause the user interface to display a prompt to a user to enter data regarding the configuration of the wand. The instructions cause the processor to receive a signal from the user input device indicating the configuration of the wand. The instructions cause the processor to establish time-gapped parameters for monitoring ambient air for the concentration of the gas and establishing an offset from an inlet tip to the inertial measurement assembly based on the configuration of the wand. The instructions cause the processor to record a time series including changes in position of the inlet tip and time-gapped concentration data as the inlet tip moves in space.

[0025] In some embodiments, the memory device includes instructions that, when executed by the processor, apply statistical interpolation to the time series record to create a three-dimensional data set that approximates the concentration of the fugitive gas in space.

[0026] In some embodiments, the memory device includes instructions that, when executed by the processor, apply a Gaussian plume model to evaluate the time series including the position changes of the inlet tip and the time-slipped concentration data as the inlet tip moves in space to determine a vector indicative of a probable location of a source of the fugitive gas.

[0027] In some embodiments, the memory device includes instructions that, when executed by the processor, apply Bayesian estimation to evaluate the time series including the position changes of the inlet tip and the time-slipped concentration data as the inlet tip moves in space to determine a vector indicative of a probable location of a source of the fugitive gas.

[0028] In some embodiments, the memory device includes instructions that, when executed by the processor, cause the processor to signal the user interface to prompt a user to enter a geospatial reference location and adjust the time series including the position change of the inlet tip and the time-slipped concentration data as the inlet tip moves in space to convert the position change into geospatial location data.

[0029] In some embodiments, the memory device includes instructions that, when executed by the processor, apply a Gaussian plume model to evaluate the time series including the position changes of the inlet tip and the time-slipped concentration data as the inlet tip moves in space to determine the geospatial location of the source of the fugitive gas.

[0030] In some embodiments, the system further includes an acoustic or mechanical anemometer in communication with the controller, the memory device including instructions that, when executed by the processor, cause the processor to update the time series including the position changes of the inlet tip and the time-slipped concentration data as the inlet tip moves in space to include wind vector information, and wherein the wind vector is used to apply a Gaussian plume model to determine the geospatial location of the source of the fugitive gas.

[0031] In some embodiments, the system further includes an anemometer in communication with the controller, the memory device including instructions that, when executed by the processor, cause the processor to update the time series including the position changes of the inlet tip and the time-slipped concentration data as the inlet tip moves in space to include wind vector information, apply statistical interpolation to the time series records to create a three-dimensional data set that approximates the concentration of the fugitive gas in space, and generate a visual representation of the distribution of the concentration of the fugitive gas in space on the display of the user interface.

[0032] These and other features of the invention will become apparent from the following description of illustrative embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The concepts described in the present invention are illustrated in the accompanying drawings by way of example and not by way of limitation. For simplicity and clarity of illustration, the elements illustrated in the figures are not necessarily drawn to scale. For example, the dimensions of some elements may be exaggerated relative to other elements for clarity. Furthermore, where considered appropriate, reference numerals have been repeated among the figures to indicate corresponding or similar elements. In particular, the detailed description refers to the accompanying drawings, in which:

[0034] Figure 1 is a side view of a handheld gas detector having an onboard gas analyzer and an inertial measurement assembly that detects relative movement of the handheld gas detector in six axes;

[0035] Figure 2 yes Figure 1 Block diagram of the inertial measurement unit;

[0036] Figure 3 is a diagrammatic representation of three different gas plumes emanating from three different leak sources;

[0037] Figure 4 is a diagrammatic representation of a gas plume emanating from a leak source when viewed along a first direction;

[0038] Figure 5 is a diagrammatic representation of a gas plume emanating from a lead source when viewed along a second direction, the second direction being orthogonal to the first direction; and

[0039] Figure 6 yes Figure 1 A plan view of the user interface of a gas detector. DETAILED DESCRIPTION

[0040] While the concepts of the present invention are susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and will be described in detail herein. However, it should be understood that there is no intention to limit the concepts of the present invention to the particular forms disclosed, but on the contrary, the invention is to cover all modifications, equivalents, and alternative forms consistent with this invention and the appended claims.

[0041] References in the specification to "one embodiment," "an embodiment," "an illustrative embodiment," etc. indicate that the described embodiment may include a particular feature, structure, or characteristic, but every embodiment may or may not include the particular feature, structure, or characteristic. Moreover, such phrases do not necessarily refer to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in conjunction with an embodiment, it is understood that it is within the scope of those skilled in the art to implement such feature, structure, or characteristic in conjunction with other embodiments, whether or not explicitly described.

[0042] In the drawings, some structural or method features may be shown in a particular arrangement and / or ordering. However, it should be understood that such a particular arrangement and / or ordering may not be required. Rather, in some embodiments, such features may be arranged in a manner and / or order different from that shown in the illustrative figures. Furthermore, the inclusion of a structural or method feature in a particular figure is not intended to imply that such feature is required in all embodiments, and in some embodiments, such feature may not be included or may be combined with other features.

[0043] exist Figure 1 , a diagrammatic representation of a gas detector 10 according to the present invention is shown as including a wand 12 that serves as an inlet to a gas analyzer 14. The gas detector 10 also includes an inertial measurement unit (IMU) 16, a user interface 44, and a controller 18. The controller 18 includes a processor 20 and a memory device 22 that contains instructions that are executed by the processor 20 to operate the gas detector 10 in the manner described below. In some embodiments, the IMU 16 and the user interface 44 are controlled by a first processor device of the controller 18 and the gas analyzer 16 is controlled by a second processor device of the controller 18. It should be understood that other configurations of processor devices for operating the functional components of the gas detector 10 may be employed, depending on the processing requirements of each of the functional units.

[0044] exist Figure 3 An example use of the gas detector 10 is diagrammatically illustrated in FIG, wherein a portion of a road 50 is shown with a gas main 52 located underground alongside the road 50. An underground service line 54 traverses the road and connects to a meter 56 for a particular customer. The meter 56 is connected to a supply line 58 that delivers a metered flow to the customer site. Figure 3illustratively depicted in FIG, three possible leak sources, wherein a first leak source 60 is a faulty connection at meter 56, a second leak source 62 is a faulty connection between gas main 52 and service line 54, and a third leak source 64 is a fault in service line 54 that escapes to the surface through a crack 66 in the surface of road 50. A user 68 moves along road 50, thereby moving gas detector 10 in space to move tip 38 of wand 12 back and forth, as represented by arrow 68. Arrows 70, 72, and 74 represent vectors that can be mathematically determined to provide information to the user to identify the location of each of sources 60, 62, and 64, respectively, as will be discussed in further detail below. It should be understood that the fugitive gas escaping from each of leak sources 60, 62, and 64 is dispersed into plumes 80, 82, and 84, with the concentration of the respective plumes varying as the gas dissipates from the respective sources 60, 62, and 64.

[0045] Each of plumes 80, 82, and 84 has a varying concentration throughout the respective plume 80, 82, and 84 as a result of the rate of the respective leak source 60, 62, and 64 and the environmental conditions. Environmental conditions that affect the dispersion of fugitive gases may include ambient temperature, humidity, and wind vector. The dynamic nature of the concentration variations throughout the plumes 80, 82, and 84 makes modeling the plumes 80, 82, and 84 a complex problem.

[0046] exist Figure 4 and 5 An example plume 90 is shown in FIG. Figure 4 In FIG, a view of plume 90 emanating from source 78 is shown in two dimensions (x and y). Figure 5 The same plume 90 is shown in the z and y dimensions. Figure 5 A wind vector 78 is shown acting on the plume 90 in the z-direction. Figure 4 and 5 Lines 92, 94, 96, 98, 100, 102, 104, and 106 in FIG are diagrammatic representations of the dispersion direction of the fugitive gas concentration. It will be appreciated that when the concentration data is plotted in three-dimensional space, the variation in dispersion (although challenging to model) provides a good indication of the likely location of the source 76. The gas detector 10 is configured for simple data collection for such mapping. Additional statistical techniques, as described below, can be used to draw inferences from the collected data to characterize the shape and location of the plume 90 and identify the likely location of the leak source 76.

[0047] Now refer to Figure 2, the IMU 16 is shown as including a spatial detector 24 embodied as three accelerometers 26, 28, and 30 and three gyroscopes 32, 34, and 36. These three accelerometers and three gyroscopes cooperate to provide six axes of detection for detecting spatial movement of the detector 10, and specifically the tip 38 of the wand 12, thereby mapping the position of the tip 38 over time. In some embodiments, the IMU 16 may further include a magnetometer 31 for determining magnetic north, wherein the three accelerometers 26, 28, and 30 and the three gyroscopes 32, 34, and 36 are used to determine x, y, and z coordinates along with roll, pitch, and roll. The accelerometers 26, 28, and 30 measure relative movement of the IMU 16 along three orthogonal axes. The gyroscopes 32, 34, and 36 measure rotation about the three orthogonal axes, namely, roll, pitch, and roll. As ambient air enters the tip 38 and is conducted through the wand 12 to the gas analyzer 14 , the controller 18 pairs the gas concentration data determined by the analyzer 14 with the relative position of the tip 38 determined by the IMU 16 to produce a three-dimensional map of the concentration of one or more gases being detected by the gas analyzer 14 .

[0048] Significantly, the IMU 16 is configured to provide dead reckoning of the position of the detector 10, and more specifically, the tip 38. The offset position of the tip 38 relative to the IMU 16 depends on the characteristics of the wand 12, which may be known at the time of manufacture or provided by the user if the wand 12 is modified. Using Kalman filtering, or other known methods of extracting relative position data from the IMU 16, a three-dimensional (3D) map of the position of the tip 38 is generated without the need for real-time absolute Global Positioning Satellite (GPS) position information. This eliminates the system's reliance on GPS data to accurately map position, thereby allowing the user to move faster than would be possible with a GPS-reliant system or to operate in GPS-challenged environments (such as those found between tall buildings or under bridges). As the IMU 16 collects data, the 3D map generated by the IMU 16 can be referenced to a specific location by referencing a baseline GPS location. Thus, a single GPS coordinate can be referenced by the IMU 16 when generating the 3D map. For example, a starting GPS position can be determined and used as a reference position, with the 3D map being referenced from the starting position. Similarly, a reference point can be referenced during the detection process or at the end of the detection process, where the controller 18 is operable to offset the detected movement from the GPS reference to generate a 3D map of the position of the tip 38 on the existing site map. GPS signals can also be used in conjunction with IMU data. For example, the GPS signal can be included in a Kalman filter together with the IMU data to provide a combined estimate of the entry tip position. The degree to which the GPS signal is weighted in the Kalman filter can be increased or decreased depending on the GPS signal quality (e.g., satellite count). The reference GPS position can be provided by a GPS sensor resident in the detector 10 and coupled to the controller 18. In the present application, GPS information is determined from a separate device and input to the user interface 44.

[0049] While the IMU 16 provides dead reckoning for the position of the tip 38, the gas analyzer 14 continuously analyzes the ambient air entering the tip 38 of the wand 12 to determine the concentration of the gas by detecting the concentration of the target gas over time using integrated cavity output spectroscopy (ICOS). In other embodiments, detection of the target gas concentration may be accomplished using cavity ringdown spectroscopy (CRDS), a Harriot cell, a White cell, cavity enhanced absorption spectroscopy, mid-infrared laser-based absorption spectroscopy, tunable diode laser absorption spectroscopy, or any sensor that functions as a high-precision gas analyzer sensitive to methane concentrations below 10 ppb. In other embodiments, the detector 10 combines ICOS technology with the dead reckoning capability of the IMU 16 to combine the position of the tip 38 with the gas concentration data from the gas analyzer 14, thereby generating a 3D visual representation of the dispersion of the target gas. Using the combined data from the IMU 16 and the gas analyzer 14 , the gas plume may be modeled using statistical interpolation to provide a 3D visualization of the gas plume and help determine the location of the source of the gas plume.

[0050] Importantly, analysis of gas dispersion requires reconciling the inherent time delay of the gas flow through the rod 12 relative to the current position of the tip 38 of the rod 12. This time delay is affected by the length 40 of the rod 12, the internal dimensions of the rod 12, and the flow rate of the gas. Through empirical analysis, a time slip factor is determined for a specific configuration and applied to the detected gas data to provide an appropriate time offset / time slip to account for the position of the tip 38 when the measured value enters the rod 12. Instead of using real-time concentration data, the combined data sequence includes paired relative position information and time-slipped concentration data to provide the gas analyzer 14 with an accurate accounting for the offset from the tip 38 of the rod 12. The time offset / time slip varies depending on the characteristics of the rod 12, and in some embodiments, a particular rod 12 may have zero time offset. The concentration at time (t) is found by selecting the concentration at time (t'), where t'=t+d, where (d) is the delay time.

[0051] In the illustrated embodiment, the wand 12 is connected to the housing 42 of the gas detector 10, as shown. Figure 4 The user carries the gas detector 10 using the handle 48 and moves the wand 12 in three dimensions as the user walks across the ground, as shown in FIG. Figure 2. In the disclosed embodiment, the wand 12 has a length 40 of six (6) feet. In other embodiments, the length 40 may be as short as two (2) feet or as long as thirty (30) feet, depending on the particular use case. It is contemplated that the wand 12 may have a variable length that may be adjusted in the field for a particular survey. As described above, the length 40 is one variable used to determine the time slip for the gas concentration data. While different lengths 40 of wand 12 may be used with the detector 10, information regarding the characteristics of the wand 12 is input into the controller 18 via the user interface 44. Figure 6 , the user interface includes a display 86 and a user input device 88, which in the illustrative embodiment is a QWERTY keyboard. In other embodiments, the display 86 may be a touch screen display, wherein user input is performed on the touch screen display. The controller 18 independently communicates with each of the user interface 44, the analyzer 14, and the IMU 16 via a serial peripheral interface (SPI). In other embodiments, the communication between the controller 18, the user interface 44, the analyzer 14, and the IMU 16 uses a standard bus-based communication protocol, such as RS-232, RS-485, or other similar communication protocols. In some embodiments, one or more of the user interface 44, the analyzer 14, and the IMU 16 may be connected via a wireless connection (e.g., Bluetooth TM or websocket protocol) to communicate with the controller 18.

[0052] like Figure 1 As shown in , the gas detector 10 may also be connected to an optional anemometer 46 (such as a sonic anemometer) that provides real-time wind speed and direction information to the controller 18 so that the wind data can be used to modify the data collected by the detector 10. Figure 1 In some embodiments, the anemometer 44 communicates with the controller 18 via a wireless connection 84. In other embodiments, the anemometer 44 may be connected to the gas detector 10 via a wired connection. The anemometer 44 may be carried by the surveyor, attached to a backpack or other on-the-go mount, or mounted nearby, for example, on a tripod.

[0053] In addition to collecting data to provide visualization of the gas plume, controller 18 is also operable to provide for the determination of the location of the source of the fugitive gas. Applying Gaussian plume modeling principles, the observed data is fitted to a model to determine deviations from the modeled values ​​of the gas concentration from the emission source in a single dimension. This method performs a nonlinear fit of the observed data to a Gaussian plume model for a specific fugitive gas. By minimizing the difference between the observed data and the modeled gas concentration, the location of the leak can be determined in the observed dimension x, y, or z. Fitting errors are minimized by adjusting parameters that model the leak rate, location, and wind vector. In some embodiments, separate fits can be performed in each of the three dimensions x, y, or z to establish a vector for the leak in each dimension. Resolving the three single-dimensional vectors into a final 3D vector yields the source of the leak. Estimating the source location can also be accomplished using Bayesian estimation. An estimate of the source direction can also be created using very simple methods, such as a pointer that is upwind whenever a temporal or spatial methane maximum is detected.

[0054] Now refer to Figure 6 , it can be seen that the display 86 of the user interface 44 can display information conveying the location of the source of the fugitive gas leak as determined by the Gaussian plume model. For example, arrow 108 provides an indication of the relative direction of the leak source as determined by the Gaussian plume model. The size of arrow 108 can be dynamically changed to provide additional information relative to the location of the leak source. In addition, text 110 can be displayed to provide specific information relative to the location of the leak source. In some embodiments, the gas analyzer 14 is operable to detect multiple types of gases, such as methane, ethane, propane, or added odorants. In this case, the additional gas type can indicate the source type. Text 110 can provide the user with an indication of the predicted source type. Furthermore, the ratio of two different gases (e.g., ethane / methane) can help identify the source type of the leak.

[0055] In the illustrative embodiment, the detector 10 includes a compass and can dynamically display the absolute north direction 112 to provide a reference for the user 68 as they move the wand 12 to search for the leak source. In other embodiments, other methods of conveying the relative location of the leak source to the user are used. For example, a varying audible signal or illuminating an indicator light located on the housing 42 of the detector 10 can be used. Other indicators can also provide an indication of the vertical location of the leak source to identify leaks emanating from the top or other upper portion of a structure. The display 86 can also be used to display a graphical representation of the detected plume in 3D to help the user understand the collected data. This is particularly useful when nearby leak sources may have overlapping plumes.

[0056] Although the gas detector 10 has been described as a dedicated device, it should be understood that the principles described herein can be applied using existing hardware such as a personal tablet computer, a smartphone, etc. For example, a tablet computer can be used as a standalone controller with a user interface. The tablet computer communicates with a wand containing an integrated gas analyzer 14 and an IMU 16, where data from the gas analyzer 14 and the IMU 16 are fed to the tablet 16 for processing and visualization of the plume or indicating the location of the leak source.

[0057] It should also be understood that the memory 22 may be sufficient to store historical data, which can then be downloaded to another computing device by known methods. Furthermore, the detector 10 may have cellular or wireless capabilities, thereby allowing data to be transferred from the detector 10 and the memory 22 to other storage locations, including cloud storage. The storage of historical data provides the ability to compare plume shapes detected at different points in time or to provide a record of plume characteristics for regulatory or risk management purposes.

[0058] The display may also present a representation of data collected by other systems, which the user can interpret to better guide the search for fugitive emissions. Examples include infrastructure data, such as the location of buried pipelines, past inspection results from another handheld survey or from a vehicle-mounted survey.

[0059] Although specific illustrative embodiments have been described in detail in the figures and the foregoing description, such illustrations and descriptions should be considered exemplary and non-restrictive in nature, and it should be understood that only illustrative embodiments have been shown and described and that protection is desired for all changes and modifications that fall within the spirit of the invention. There are a number of advantages of the present invention that derive from the various features of the methods, systems, and articles described herein. It will be noted that alternative embodiments of the methods, systems, and articles of the present invention may not include all of the features described, but still benefit from at least some of the advantages of such features. Those skilled in the art can readily envision their own method, system, and article implementations that incorporate one or more of the features of the present invention.

Claims

1. A gas leak detector comprising Inertial Measurement Unit, High-precision gas analyzer, a wand having an inlet that receives ambient air and directs all or a portion of the ambient air to the high precision gas analyzer, the wand being physically coupled to the inertial measurement assembly such that movement of the wand is detected by the inertial measurement assembly, a controller that receives signals from the inertial measurement assembly and the high-precision gas analyzer, the controller comprising a processor and a memory device, the memory device comprising instructions that, when executed by the processor, cause the controller to: monitoring the signal from the inertial measurement assembly to identify real-time changes in the position of the inlet of the wand, recording said real-time changes of said position, monitoring a signal from the high precision gas analyzer, the signal being indicative of the concentration of one or more specific types of fugitive gases dispersed in the ambient air, recording the concentration of specific molecules of each of the one or more specific types of fugitive gases dispersed in the ambient air, applying an adjustment factor that depends on characteristics of the wand to the time series of the concentration of the particular type of fugitive gas in the ambient air to shift the time series so that when the measured concentration of the particular type of fugitive gas enters the wand, the measured concentration is aligned with the position of the inlet of the wand to create an adjusted concentration time series, and The real-time changes in the adjusted concentration time series and the position time series are recorded to create a combined time series that includes both position and fugitive gas concentration data.

2. The gas leak detector of claim 1 , wherein the inertial measurement assembly measures three-dimensional changes in the position of the inertial measurement assembly and measures changes in pitch, roll, and pitch of the inertial measurement assembly to provide a signal to the controller indicative of a change in the position of the tip of the wand.

3. The gas leak detector of claim 1, wherein the inertial measurement assembly comprises a structure capable of measuring acceleration in three orthogonal axes.

4. The gas leak detector of claim 3, wherein the inertial measurement assembly includes a structure capable of measuring gyroscopic deviations about the three orthogonal axes.

5. The gas leak detector of any one of claims 1 to 4, wherein the high-precision gas analyzer utilizes integrated cavity output spectroscopy to measure the concentration of a specific type of gas in the ambient air.

6. The gas leak detector of claim 5 , wherein the memory device includes further instructions that, when executed by the processor, cause the processor to utilize a Gaussian plume model to evaluate the combined time series including both position and concentration data to determine a vector indicative of a probable location of a source of the fugitive gas.

7. The gas leak detector of claim 5 , wherein the memory device includes further instructions that, when executed by the processor, cause the processor to utilize Bayesian estimation to evaluate the combined time series including both position and concentration data to determine a vector indicative of a likely location of a source of the fugitive gas.

8. The gas leak detector of claim 5 , wherein the memory device includes further instructions that, when executed by the processor, cause the processor to determine a vector indicative of a probable location of a source of the fugitive gas comprising methane using a pointer that is upwind whenever a temporal or spatial methane maximum is detected in the combined time series comprising both position and concentration data.

9. The gas leak detector of any one of claims 1 to 4, wherein the gas leak detector further comprises a user interface in communication with the controller, the memory device including instructions that, when executed by the processor, provide an output to the user interface that causes the user interface to provide a real-time indication of the likely direction and / or location of the source of the fugitive gas relative to the gas leak detector.

10. The gas leak detector of any one of claims 1 to 4, wherein the controller receives a signal indicative of a geospatial reference datum from a geospatial location satellite system while a sequence of position data is being collected, and wherein the memory device includes instructions that, when executed by the processor, cause the processor to reference the geospatial location of the inlet of the wand by referencing the position of the inertial measurement assembly to the geospatial reference datum, processing real-time changes in the position of the inertial measurement assembly to create an adjusted time series of position data, and creating a combined time series including both geospatial location and fugitive gas concentration data.

11. The gas leak detector of claim 10, wherein the gas leak detector further comprises a user interface in communication with the controller, the memory device containing instructions that, when executed by the processor, provide an output to the user interface that causes the user interface to provide a real-time indication of a possible location of a source of the fugitive gas relative to the gas leak detector.

12. A method for identifying a source location of a gas leak, the method comprising: Move the inlet of the handheld gas analyzer in the space to collect ambient air samples, using an inertial measurement assembly to measure real-time changes in the position of the inlet of the gas analyzer, recording a time series of said real-time changes in the position of said entrance, Use high-precision gas analyzers to measure the real-time concentration of specific fugitive gases. adjusting the real-time concentration of the particular fugitive gas using a time slip factor to account for a delay in the transfer of the fugitive gas from the inlet to the high-precision gas analyzer, thereby generating a time-slipped data series of the real-time concentration, and The time-slipped data series is combined with the time series of the real-time changes in the position of the inlet to create a time series indicating the relative position of the inlet and the real-time concentration of the particular fugitive gas at the inlet over time.

13. The method according to claim 12, further comprising: determining a reference geospatial position of the inertial measurement assembly during real-time changes in collection position, offsetting the time series indicating the relative positions of the portal relative to the reference geospatial position to create a time series of geospatial positions of the portal, The time-slipped data series is combined with the time series of the geospatial locations of the inlet to create a time series indicating the geospatial locations of the inlet and the real-time concentration of the particular fugitive gas at the inlet over time.

14. The method according to claim 12, further comprising: utilizing a Gaussian plume model to evaluate a combined time series comprising both position and concentration data to determine a vector indicative of a likely location of a source of the fugitive gas, wherein the location comprises a relative location of the inlet, and A visual representation of the possible location of the source of fugitive gas is output on a display device.

15. The method of claim 13, further comprising: utilizing a Gaussian plume model to evaluate a combined time series comprising both location and concentration data to determine a vector indicative of a likely location of a source of the fugitive gas, wherein the location comprises the geospatial location of the inlet, and A visual representation of the possible location of the source of fugitive gas is output on a display device.

16. The method of claim 12, further comprising: utilizing Bayesian estimation to evaluate a combined time series comprising both position and concentration data to determine a vector indicative of a likely location of a source of the fugitive gas, wherein the location comprises a relative location of the inlet, and A visual representation of the possible location of the source of fugitive gas is output on a display device.

17. The method of claim 13, further comprising: utilizing Bayesian estimation to evaluate a combined time series comprising both location and concentration data to determine a vector indicative of a likely location of a source of the fugitive gas, wherein the location comprises the geospatial location of the inlet, and A visual representation of the possible location of the source of fugitive gas is output on a display device.

18. The method of claim 13, further comprising: processing the time series indicating the geospatial location of the inlet and the real-time concentration of the particular fugitive gas at the inlet over time using statistical interpolation to create a three-dimensional dataset approximating the concentration of the fugitive gas in space, and The three-dimensional data set approximating the concentration of the fugitive gas in space is plotted to create a visual representation of the concentration on a map.

19. A system for measuring the distribution of fugitive gases in three dimensions, the system comprising: an inertial measurement unit that provides signals in real time indicating changes in the three-dimensional position and three-axis orientation of the inertial measurement unit, High-precision gas analyzer, which is used to measure the concentration of gas in real time, a wand having an inlet tip that receives ambient air and directs the ambient air to the high precision gas analyzer, the wand being physically coupled to the inertial measurement assembly such that movement of the wand is detected by the inertial measurement assembly, a user interface having a user input device and a display, and a controller in communication with the inertial measurement assembly, the high precision gas analyzer, and the user interface, the controller comprising a processor and a memory device coupled to the processor, wherein the memory device stores instructions that, when executed by the processor, cause the user interface to: displaying a prompt to the user to enter data regarding the configuration of the wand, receiving a signal from the user input device indicative of the configuration of the wand, Based on the configuration of the rod, establishing a time slip parameter for monitoring ambient air for the concentration of the gas and establishing an offset from an inlet tip to the inertial measurement assembly, and A time series is recorded that includes position changes of the inlet tip and time-slipped concentration data as the inlet tip moves in space.

20. The system of claim 19, wherein the memory device includes instructions that, when executed by the processor, apply statistical interpolation to the time series to create a three-dimensional data set that approximates the concentration of the fugitive gas in space.

21. The system of claim 19, wherein the memory device includes instructions that, when executed by the processor, apply a Gaussian plume model to evaluate the time series including the position changes of the inlet tip and the time-slipped concentration data as the inlet tip moves in space to determine a vector indicative of a probable location of a source of the fugitive gas.

22. The system of claim 19, wherein the memory device includes instructions that, when executed by the processor, apply Bayesian estimation to evaluate the time series including the position changes of the inlet tip and the time-slipped concentration data as the inlet tip moves in space to determine a vector indicative of a likely location of a source of the fugitive gas.

23. A system according to claim 19, wherein the memory device includes instructions that, when executed by the processor, cause the processor to signal the user interface to prompt the user to enter a geospatial reference location and adjust the time series of the time-slipped concentration data including the position change of the inlet tip and as the inlet tip moves in space to convert the position change into geospatial location data.

24. The system of claim 23, wherein the memory device includes instructions that, when executed by the processor, apply a Gaussian plume model to evaluate an adjusted time series including the geospatial location data of the inlet tip and the time-slipped concentration data as the inlet tip moves in space to determine the geospatial location of the source of the fugitive gas.

25. The system of claim 23, wherein the system further comprises an acoustic or mechanical anemometer in communication with the controller, the memory device comprising instructions that, when executed by the processor, cause the processor to update the time series comprising the positional changes of the inlet tip and the time-slipped concentration data as the inlet tip moves in space to include wind vector information, and wherein the wind vector is used to apply a Gaussian plume model to determine the geospatial location of the source of the fugitive gas.

26. The system of any one of claims 19 to 25, wherein the system further comprises an anemometer in communication with the controller, the memory device comprising instructions that, when executed by the processor, cause the processor to update the time series comprising the position changes of the inlet tip and the time-slipped concentration data as the inlet tip moves in space to include wind vector information, apply statistical interpolation to the time series records to create a three-dimensional data set that approximates the concentration of the fugitive gas in space, and generate a visual representation of the distribution of the concentration of the fugitive gas in space on the display of the user interface.

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