Hydrogen leak detector and hydrogen leak detection method

Abstract

The present invention provides a hydrogen leak detector and method for detecting leaks in hydrogen gas conduction components and hydrogen-natural gas mixture conduction components, particularly outdoors or in environments not clearly defined. [Solution] A hydrogen leak detector (10) for detecting leaks in hydrogen gas conduction components comprises a hydrogen gas detector (20) configured to measure the concentration of hydrogen gas in the gas within a gas conduction path (18). The hydrogen gas detector (20) comprises a first gas sensor (24) configured to be hydrogen-selective and to respond to a first range of relatively low hydrogen concentrations below a first threshold, and a second gas sensor (26) configured to be hydrogen-sensitive, hydrogen-insensitive, sensitive to at least one secondary gas other than hydrogen, and to respond to a second range of relatively high hydrogen concentrations above a first threshold.

Description

Technical Field

[0001] The present invention relates to a hydrogen gas leak detector and method for detecting leaks in hydrogen gas conducting components such as pipes and tanks.

Background Art

[0002] One of the applications targeted by the present invention is leak detection in gas supply and distribution infrastructure. Hydrogen is widely considered as an alternative fuel to fossil fuels, particularly natural gas. In the field of energy supply, a conversion from natural gas to hydrogen is required. In addition to the infrastructure for the production and distribution of pure hydrogen, emphasis is placed on gradually replacing natural gas with hydrogen. Therefore, in a natural gas and hydrogen mixing system, a leak detector that can appropriately detect and measure hydrogen at any concentration from ppm (or less) to 100 vol.% is required even when other gases such as methane are present.

[0003] Therefore, the need to detect hydrogen in a gas sample composed of natural gas is increasing. For example, hydrogen is transported in a natural gas pipeline, and if the hydrogen content is up to 20 vol.%, there is no need to modify the device that burns natural gas, so natural gas is mixed with hydrogen up to 20 vol.%. General natural gas pipelines transport natural gas over long distances from the source to the end consumer. Natural gas is usually composed of methane or mainly methane combined with other gas components. Common alternatives to natural gas mainly composed of methane include liquefied petroleum gas (LPG) consisting of propane, butane, or a mixture thereof. "Natural gas" (NG) in the present disclosure refers to methane, a mixed gas mainly composed of methane, LPG, or a mixed gas composed of a combination of methane, ethane, propane, and / or butane.

[0004] Natural gas and hydrogen are highly flammable. For safety reasons, it is crucial to be able to detect even small leaks in hydrogen gas transport components, such as natural gas pipelines that carry natural gas and hydrogen. Leak detection is performed during periodic leak surveys and commissioning. Furthermore, it is desirable to be able to measure the actual ratio of hydrogen in hydrogen gas, such as natural gas.

[0005] Most commonly, gas infrastructure detectors are sniffing detectors, where the gas sample is collected by a sniffer probe or inlet and sent to a detector unit for analysis. However, some detectors transport the gas to the detector by diffusion. Another category that does not use sniffing is so-called open-circuit optical detection, where instead of moving the gas sample, light is passed through the sample and the loss of light power at wavelengths that interact with the gas being detected after passing through the sample is analyzed. An open circuit can be provided between the light source and the sensor, and the circuit can be a “half-open” circuit such as a cuvette with a slot along the axis, through which the gas can enter and exit the open circuit by diffusion or convection. The slot is preferably covered with a filter material such as a gas permeable membrane to prevent dust and water from entering the path.

[0006] Sniffing probe detection is used to detect leaks in large, non-moving parts. A vacuum pump is used to draw gas from the sniffing probe's suction port. The sniffing probe is moved to the area under test, such as the outer surface of the part under test. In the case of buried gas pipelines, the sniffing probe moves across the ground surface above the pipeline. The general concept is that the gas taken in by the sniffing probe is analyzed by a gas detector to determine whether the measured gas contains gas components from the part under test.

[0007] Sniffing probes used for leak detection in buried gas pipelines typically utilize gas detectors capable of detecting the presence of natural gas components such as methane, ethane, and propane. As they become more affordable, the concept of infrared absorption in natural gas component detection is gaining attention. Polar molecules like methane can absorb energy at specific wavelengths of infrared light associated with various vibrational modes. The intensity of light passing through a gas sample is measured at one or more wavelengths characteristic of the gas being detected. This technique is known as NDIR (Non-Dispersive Infrared Absorption Spectroscopy). Another excellent infrared absorption technique is tunable semiconductor laser absorption spectroscopy (TDLAS), which can detect methane leaks from a distance. This technique is currently expensive but is gaining popularity. However, because hydrogen is a non-polar molecule, it cannot interact with infrared light in this way, and neither NDIR nor TDLAS can detect hydrogen gas. Therefore, this type of sensor that does not react to hydrogen is referred to as "insensitive" to hydrogen.

[0008] Sensors that react to hydrogen, that is, sensors that generate a measurement signal in response to hydrogen present in the sensor or within the sensor, are called "hydrogen-sensitive" sensors. Hydrogen-sensitive sensors are generally divided into two categories: "hydrogen-selective" sensors and "hydrogen-nonselective" sensors.

[0009] A sensor that is not selective for hydrogen reacts to various different types of gases, including hydrogen, making it impossible to determine from the measurement signal whether it is caused by hydrogen or another gas. On the other hand, a hydrogen-selective sensor generates a measurement signal that clearly indicates whether it is caused by hydrogen or another gas. In this specification, a sensor that is more than 100 times more sensitive to hydrogen than other gases normally present around a hydrogen gas conduction component in which a hydrogen leak is detected is considered to be selective for hydrogen.

[0010] The following are common hydrogen detection techniques applicable to portable hydrogen gas detectors:

[0011] [Table 1]

[0012] Sound velocity technology and thermal conductivity technology share several significant advantages. Both are less susceptible to poisoning by other gases, have high exposure resistance, and exhibit very little drift over time because they do not involve chemical reactions. The challenge for both sensors lies in selectivity. Both react considerably to other common gases. Therefore, in this disclosure, these sensors are described as hydrogen-sensitive but non-selective to hydrogen.

[0013] In these two sensors, hydrogen generally elicits the strongest reaction among the gases produced, but to obtain accurate hydrogen readings, the influence of other gases must be compensated for. This is particularly evident in the low-hydrogen-content natural gas and hydrogen blending systems currently under development.

[0014] A sound velocity (SoS) sensor excites a gas within a volume being measured by an acoustic signal and measures the time it takes for the acoustic signal to travel a certain distance before being detected by a microphone, or it determines the acoustic resonance frequency within the volume being measured. Such SoS sensors are described, for example, in WO2013 / 078308A1 and US5,768,937A.

[0015] When designing a gas detector capable of measuring high concentrations of hydrogen, there are drawbacks that must be considered depending on the type of sensor used. Sensors that are sensitive to hydrogen but non-selective, such as sound velocity sensors and thermal conductivity sensors, can detect high concentrations of hydrogen, but are typically non-selective to hydrogen because they also react to other gases that affect the signal quality, especially for low concentrations of hydrogen. For example, carbon dioxide (CO2) produces a negative sound velocity signal, and hydrogen (H2) produces a positive sound velocity signal, thus reducing the resulting measurement signal for hydrogen in air or CO2. Methane (CH4) and water vapor (H2O) produce a positive sound velocity signal, increasing the resulting measurement signal for hydrogen mixed with CH4 or water vapor.

[0016] Therefore, given the advantages and limitations of each currently available hydrogen sensor technology, there is no single technology that can be applied to the entire range of hydrogen concentrations from a few ppm to 100 Vol.% for non-laboratory use.

[0017] EP 3933403 A1 discloses a natural gas and hydrogen detector for detecting hydrogen in a mixture of hydrogen and natural gas. The disclosed detector utilizes NDIR sensor technology for detecting natural gas and a second sensor for detecting generally flammable gases. If the general sensor detects a flammable gas and the NDIR sensor does not detect a significantly low amount of hydrocarbons, this is considered evidence of the presence of hydrogen. Both technologies have selectivity limitations. "Selectivity" here means being more than 100 times more sensitive to hydrogen than to other gases that would be present in a typical application of detecting leaks in hydrogen gas conduction components.

[0018] Flammable gas sensors, such as TC sensors or SoS sensors, react to other gases that may contribute positively and / or negatively to the measured signal. Some of the most interfering gases in gas pipelines include methane, water, and carbon dioxide, all of which are present in considerable concentrations underground and on the surface at their intended applications, and these concentrations vary.

[0019] The table below illustrates the complexity of compensating for hydrogen signals against commonly present interfering gases in leak detection applications for underground hydrogen gas conduction components.

[0020] [Table 2]

[0021] Drifts in the zero hydrogen signals of SoS and TC sensors due to changes in temperature, carbon dioxide, and methane content further limit the application of these techniques at low concentrations. This selectivity problem is further complicated by the fact that the mixture ratio of hydrogen to natural gas in the pipe or system under investigation is largely unknown. As the hydrogen-to-natural gas ratio decreases, compensation becomes increasingly difficult.

[0022] The most challenging aspect is likely to be sampling gases leaking from underground during a leak investigation. As the detector moves across the surface, the humidity and concentration of carbon dioxide, and even methane, can change dramatically. Therefore, continuous or intermittent zero adjustment of the detector is necessary to ensure stable and accurate measurements across the entire measurement range of sound velocity or thermal conductivity sensors used at high frequencies. "Zero adjustment" here means calibrating the sensor in the presence of very low concentrations of hydrogen, or almost no hydrogen at all, when only the natural hydrogen content in the ambient air is present.

[0023] In addition to zero adjustment, when calculating high-frequency non-zero hydrogen compensation values ​​measured by H2-sensitive but non-selective sensors such as TC sensors and SoS sensors, it is also necessary to compensate for the effects of the aforementioned interfering gases. [Overview of the project] [Problems that the invention aims to solve]

[0024] Therefore, an object of the present invention is to provide a hydrogen leak detector and method for detecting leaks in hydrogen gas conducting components and in components conducting a mixture of hydrogen and natural gas, particularly in outdoor or ill - defined environments.

Means for Solving the Problems

[0025] The leak detector of the present invention is defined by independent claim 1. The method of the present invention is defined by independent claim 11.

[0026] Thus, there is provided a hydrogen gas leak detector configured to measure the concentration of hydrogen gas in a gas sampled in the vicinity of a gas conducting component.

[0027] In the present disclosure, the term "hydrogen gas" means a gas containing hydrogen at 100 volume % (vol.%) or close to 100 Vol.%, for example at least 80 vol.%, and may also mean a mixture of hydrogen and other gases.

[0028] The hydrogen gas leak detector of the present invention comprises a hydrogen gas detector configured to measure the concentration of hydrogen gas conveyed through a gas conduction path. The hydrogen gas detector comprises a first gas sensor having hydrogen selectivity and configured to react to a first range which is a relatively low hydrogen concentration below a first threshold value, and a second gas sensor which is sensitive to hydrogen, non - selective to hydrogen, sensitive to at least one secondary gas different from hydrogen, and configured to react to a second range which is a relatively high hydrogen concentration above the first threshold value.

[0029] The hydrogen leak detector of the present invention is configured to calibrate the second gas sensor to low concentrations of hydrogen present in the atmosphere surrounding the hydrogen gas detector and not originating from a leak in the hydrogen gas conduction component under test. This calibration is performed by measuring the hydrogen concentration in the gas to be measured, sampled from the surrounding atmosphere, using the first and second gas sensors, and if the measurement signal from the first gas sensor of the gas to be measured indicates a hydrogen concentration below a predetermined value, assigning the measurement signal from the second gas sensor of the gas to be measured to correspond to a concentration not caused by a hydrogen leak.

[0030] That is, a gas sample is taken from the surrounding atmosphere and measured by both the first gas sensor and the second gas sensor. If the first gas sensor indicates that the hydrogen concentration in the sample under test is below a predetermined value, each measurement signal from the second gas sensor for the gas under test is considered to correspond to a hydrogen concentration not attributable to a leak in the hydrogen gas conduction component under test. Therefore, the measurement signals from the second gas sensor are assigned to correspond to concentrations not attributable to a hydrogen leak. In one embodiment, the measurement signals from the second gas sensor are assigned to correspond to a concentration of zero volume percent of hydrogen.

[0031] The expression "assign the measurement signal of the second gas sensor to correspond to the concentration of ~" may mean, for example, that a computer or microprocessor has memory to store the assigned result. The computer or microprocessor uses the measurement signal of the second gas sensor in the calibration process and stores this signal or the corresponding signal value in memory as a signal or signal value that does not originate from hydrogen leakage of the hydrogen gas conduction component in subsequent tests. Furthermore, or alternatively, such measurement signal or signal value of the second gas sensor may also be stored as zero volume percent of hydrogen, or as corresponding to zero volume percent of hydrogen.

[0032] In a subsequent leak test of a hydrogen gas conduction component tested using the hydrogen leak detector of the present invention, if the second gas sensor measures a signal or signal value corresponding to a previously measured signal or signal value at or below a predetermined value during calibration, the hydrogen leak detector of the present invention compares the measured value of the leak test with a measured value stored before the calibration process. If these two correspond to each other within a predetermined range, the hydrogen leak detector indicates that this measured signal of the hydrogen gas conduction component under test does not originate from a leak and / or corresponds to zero volume percent of hydrogen as a result of the previous calibration process.

[0033] On the other hand, if the first gas sensor indicates that the hydrogen concentration in the sample under test is above a predetermined value, and the second gas sensor indicates that the hydrogen gas concentration is above a second threshold, the hydrogen leak detector can determine that a hydrogen leak exists in the hydrogen gas conduction component under test. Here, the second threshold may be the same as a predetermined value in the calibration process. This step of determining the presence of a hydrogen leak can also be performed by the computer or microprocessor described above. For example, in one embodiment, the measurement signal or signal value measured by the second gas sensor during testing of the hydrogen gas conduction component is compared by the computer or microprocessor with signal values ​​stored in memory, at least one of which is the aforementioned signal value in the calibration process that is assigned as not corresponding to a concentration originating from a hydrogen leak and / or as corresponding to a concentration of zero volume percent of hydrogen.

[0034] Furthermore, if the first gas sensor indicates a hydrogen concentration above a third threshold, a hydrogen leak can be considered to be present in the hydrogen gas conduction component under test, where the third threshold is less than the second threshold. This step of considering the presence of a hydrogen leak can also be performed by the aforementioned computing device or microprocessor. This expands the range of concentrations in which the hydrogen leak detector reacts, as both different ranges of hydrogen concentrations in which the two sensors react are used for leak detection.

[0035] According to the present invention, if a selective hydrogen gas sensor indicates a hydrogen concentration exceeding a predetermined threshold, a hydrogen leak is considered to exist in the hydrogen gas conducting component under test. For example, the measurement is initiated by a measurement using a hydrogen-selective gas sensor. If the hydrogen-selective gas sensor indicates a significant hydrogen gas concentration that may be attributable to a leak in the component under test, or if the measurement result of the hydrogen-selective gas sensor indicates that the hydrogen-selective sensor is saturated, this is considered to indicate that the component under test may contain a hydrogen leak. As a result, the second gas sensor is used for further gas analysis to quantify hydrogen concentrations exceeding the usable range of the hydrogen-selective gas sensor. In this regard, the second gas sensor may be configured to measure the speed of sound of an acoustic signal passing through a gas taken in from a gas inlet. The speed of sound in a gas mixture is affected by several factors, including the types of gas components present in the gas mixture. For example, the speed of sound in air is slower than the speed of sound in a gas mixture consisting of air and a certain amount of hydrogen gas at the same temperature.

[0036] In embodiments suitable for non-mixed hydrogen conduction components, the hydrogen gas detector comprises a hydrogen-selective gas sensor configured to measure a range of relatively low hydrogen concentrations and a sound velocity (SoS) gas sensor configured to measure relatively high hydrogen concentrations. The SoS gas sensor is configured to measure the speed of sound in the measured gas and to determine the hydrogen concentration in the high concentration range from the measured speed of sound. In this specification, “relatively low” means lower than the hydrogen concentration measured by the sound velocity gas sensor, and “relatively high” means that the hydrogen concentration measured by the sound velocity gas sensor is higher than the hydrogen concentration measured by the hydrogen-selective gas sensor.

[0037] Therefore, measurements using a hydrogen-selective gas sensor cover a range of relatively low hydrogen concentrations, while measurements of sound velocity using an SoS gas sensor cover a range of relatively high hydrogen concentrations.

[0038] Changes in humidity and CO2 content are known to be handled by filters that capture water and carbon dioxide. However, such filter solutions are not suitable for continuous or daily portable devices due to the limited capacity of portable, small, and lightweight filters. Small, selective filters, while not large enough to remove all interfering gases, can be used in gas modulation schemes where the signal is analyzed by the modulation frequency or its overtone. Small filters can slow down changes in the concentration of interfering gases, allowing algorithms to filter the signal to remove variations due to interfering gas concentration fluctuations. Such small molecules pass through most surface-active filters with only a slight delay, making them particularly effective for detecting hydrogen and methane. This principle is described in EP3163299A. Therefore, the influence of methane on SoS or TC signals cannot be handled by such selective filtering.

[0039] According to the present invention, a first hydrogen-selective gas sensor is used to zero-adjust or calibrate a second non-selective gas sensor by measuring the hydrogen concentration in the atmosphere surrounding a hydrogen gas conduction component under test, preferably when there is no leak or only a relatively low hydrogen concentration that is not thought to be due to a leak. Zero-adjustment is used to align the baseline of the measurement signal of the second non-selective gas sensor with the current level of interfering gases in the surrounding atmosphere. The measurement signal captured by the hydrogen-selective gas sensor during zero-compensation is used as a baseline signal of gas that does not contain a significant hydrogen concentration, but rather only a small concentration that is not thought to be due to a leak in the component under test.

[0040] To achieve this, the hydrogen leak detector of the present invention may include a computing device such as a microprocessor having a memory capable of storing the measured signal values. During zero correction, also referred to in this disclosure as "calibration," the measurement signals are taken by both the first and second gas sensors from gas sampled from the ambient atmosphere when no leaks are present in the hydrogen gas conduction component under test. The computing device evaluates the measurement signal from the first gas sensor and compares the signal value with a predetermined value. If the signal value from the first gas sensor is less than or equal to the predetermined value, each signal value simultaneously measured by the second gas sensor is stored in memory as a signal value corresponding to a hydrogen concentration not attributable to a possible leak in the component under test. This also means that the measurement signal from the second gas sensor of the measured gas is now associated with a concentration not attributable to a leak in the hydrogen gas conduction component under test.

[0041] In a subsequent hydrogen gas leak test, if the second gas sensor acquires a measured signal value corresponding to the stored signal value within a predetermined deviation range, the measured value is considered not to originate from a leak in the component under test. The calculation device of the hydrogen leak detector of the present invention compares the measured value acquired by the second sensor during the leak test with the measured value stored in memory during the preceding calibration process. If the measured value during the leak test corresponds to or is lower than the value stored as not corresponding to a concentration originating from a leak in the component under test, the calculation device generates a signal to notify the operator that this value does not originate from a leak or that there is no leak. On the other hand, if the signal value acquired during the leak test exceeds a second threshold that exceeds the predetermined value of the calibration process, the calculation device generates a signal to notify the operator that a leak exists in the component under test or that the measured signal corresponds to a concentration originating from a leak in the component under test.

[0042] Therefore, the first gas sensor is used to calibrate or zero-compensate the second gas sensor, while the second gas sensor is used for actual leak testing of the hydrogen gas conduction component, allowing the second gas sensor to be used over a wider hydrogen concentration range. This wider hydrogen concentration range is particularly greater than the concentration range over which a hydrogen-indifferent hydrogen-sensitive gas sensor would normally be sensitive to hydrogen leak gas leaking from the component under test.

[0043] Therefore, the present invention provides a hydrogen leak detector that uses a hydrogen-sensitive gas sensor, which is non-selective to hydrogen, over a wider concentration range for hydrogen leak detection.

[0044] The second gas sensor may be a sound velocity sensor or a thermal conductivity sensor, as described in US2013 / 0125622A1. These types of sensors are less susceptible to damage or poisoning from excessive exposure. Thus, the second gas sensor can be used to measure the hydrogen gas concentration that causes saturation of the first gas sensor.

[0045] As mentioned above, carbon dioxide (CO2) and methane (CH4), which are interfering gases that are generally present in high concentrations, significantly interfere with the measurement signal from the second gas sensor, especially when using SoS or TC gas sensors.

[0046] Therefore, in the present invention, it is desirable to measure the concentrations of these gases in order to compensate for the measurement signal of the second gas sensor and to achieve accurate quantification of the hydrogen concentration.

[0047] The influence of water, in the form of water vapor (humidity), is expected to be negligible, as it does not change significantly and rarely exists at concentrations exceeding 10 vol.%. An optimal method to further improve the accuracy of hydrogen estimation could also be to measure the water content.

[0048] In embodiments where the second gas sensor is an NDIR sensor, methane, carbon dioxide, and water can all be measured by the NDIR sensor, and data can be provided to compensate for the signal of the first gas sensor, such as an SoS or TC sensor. In such embodiments, methane, carbon dioxide, and water are secondary gases to which the second gas sensor is sensitive.

[0049] The measured speed of sound can be used to determine the amount of hydrogen gas present in the test gas mixture. In embodiments where the second gas sensor is a speed of sound sensor, a first approximation of the hydrogen concentration can be calculated by assuming that the speed of sound measured at the most recent zero adjustment represents the speed of sound in the surrounding gas, and that any change in speed of sound is solely due to the addition of hydrogen.

[0050] A second, more accurate approximation can be calculated by assuming that the surrounding gases consist of air, methane, and carbon dioxide, and that the concentrations of the latter two are measured simultaneously with the hydrogen content being calculated. Since the air concentration is the remainder after subtracting the measured CH4 and CO2 concentrations from the unknown H2, the only unknown value is the hydrogen concentration.

[0051] For now, a more accurate approximation can be obtained by also measuring the water or water vapor concentration, which is considered to be a secondary gas that the second gas sensor is sensitive to. In any case, the speed of sound in air is estimated from the last zero-point measurement, corrected for the concentration of interfering gases at that instant.

[0052] It is desirable to include the gas temperature in all calculations.

[0053] In addition, or by other means, the measured speed of sound may be compared to a baseline value obtained from baseline measurements of a gas mixture at a specific hydrogen concentration, possibly at different temperatures.

[0054] The first hydrogen-selective gas sensor may be a metal hydride (MH-) semi-sensor implemented as a field-effect transistor (FET) or Schottky diode, or another type of hydrogen sensor having at least 100 times greater sensitivity to hydrogen than to CO2, CH4, or water vapor.

[0055] The second gas sensor may be an SoS sensor comprising a measuring cuvette that can be filled with the gas to be measured, a sound source configured to emit an audio signal into the gas in the cuvette, and at least one microphone configured to receive the audio signal transmitted from the sound source through the cuvette.

[0056] The hydrogen concentration can be calculated from the measured speed of sound, especially if the concentrations of all but one gas component and the bulk concentration are known. For example, in a gas mixture of hydrogen, air, and methane (CH4), the concentrations of air and CH4 must be known in order to calculate the concentration of hydrogen gas (H2).

[0057] Further types of sensors may be used to determine the presence and / or concentration of other gaseous components in the gas mixture under test.

[0058] The measurement of the speed of sound may be improved by using at least two microphones at a known distance from each other, in which case the speed of sound is calculated based on the time difference between the reception of sound signals by the two microphones and the distance between the two microphones.

[0059] As an alternative or additional method, the speed of sound may be calculated using the resonant frequency f, which is obtained by dividing the speed of sound c by the wavelength λ at which resonance occurs. In this way, if the resonant wavelength λ and the resonant frequency f are known, the speed of sound can be calculated.

[0060] When using two microphones to measure the speed of sound, the two microphones are positioned at different locations in a tubular arrangement also called a measuring cuvette. The sound signal generated from the speaker (sound source or emitter) travels through the tube to the first microphone and then to the second microphone, which is further away from the speaker. The microphone signals are used to calculate the time it takes for the sound signal to travel the distance between the two microphones. The speed of sound is then calculated by dividing the distance between the two microphones by the time it took for the sound signal to travel this distance.

[0061] In a preferred embodiment of the present invention, the hydrogen gas detector is combined with a third gas sensor configured to measure the concentration of natural gas or a natural gas component in a gas mixture guided through the gas conduction pathway. For example, the third gas sensor may comprise a radiation-absorbing cuvette, which can be filled with the gas to be measured. A radiation source is provided to emit radiation of a known frequency band into the gas in the cuvette. A radiation detector is provided to detect the radiation that has passed through the cuvette in order to determine the absorption band of the detected radiation. For example, the radiation absorption detector may be an infrared absorption detector, such as a non-dispersive infrared (NDIR) analyzer. This concept is particularly advantageous for detecting hydrocarbons in a gas mixture.

[0062] The third gas sensor may be an NDIR sensor, in particular a wide-range CH4NDIR sensor such as the one described in WO2017 / 121688A1.

[0063] When the third gas sensor described above is combined with the hydrogen gas detector of the above type, the hydrogen concentration in natural gas can be detected, and / or the third gas sensor may be used to determine whether a measured sound velocity that deviates from the speed of sound in air is due to hydrogen or to a component of the natural gas.

[0064] The third gas sensor is configured to measure the gas introduced through the gas conduction path and is insensitive to hydrogen but sensitive to at least one secondary gas to which the second gas sensor is sensitive. If the third gas sensor is an NDIR sensor, it may be provided to analyze the measurement signal, such as absorption in an additional wavelength range, and if it is an SoS sensor, it may be provided to measure the concentration of other gases (secondary gases) that affect the measurement signal of the second gas sensor, such as the speed of sound in the sample. Examples of such gases include carbon dioxide and water. This information can be used to further improve the accuracy and selectivity of the detector in the range covered by the second gas sensor.

[0065] Furthermore, the third gas sensor may be used to interpret the measurement signal of the first gas sensor by evaluating whether the measurement signal of the first gas sensor was generated by hydrogen, or by one or more secondary gases that are also sensitive to the first gas sensor.

[0066] The hydrogen leak detector may be a portable leak detector and / or a sniffing Greek detector used to detect leaks in natural gas pipelines that transport a certain amount of hydrogen gas. [Brief explanation of the drawing]

[0067] The embodiments of the present invention will be described below with reference to the figures. [Figure 1] This figure shows a general layout of the first embodiment. [Figure 2] This figure shows a general layout of the second embodiment. [Figure 3] This figure shows details of the embodiment shown in Figure 2. [Figure 4] This figure shows further details of an embodiment. [Figure 5] This figure shows a general layout of another embodiment. [Modes for carrying out the invention]

[0068] Figure 1 shows a hydrogen leak detector 10, which is a sniffing-type leak detector equipped with a sniffing probe 12 having a sniffing inlet 14. The sniffing probe 12 is connected to a vacuum pump 16 via a gas conduction path 18 that includes a hydrogen gas detector 20. The hydrogen gas detector 20 comprises a first gas sensor 24, a second gas sensor 26, and a third gas sensor 22.

[0069] The hydrogen gas detector 20 includes a first hydrogen-selective gas sensor 24 in the form of an MH (metal hydride)-semi field-effect (FET) gas sensor and a second gas sensor 26 in the form of a sound velocity (SoS) gas sensor. The gas guided through the gas conduction path 18 passes through both the first hydrogen-selective gas sensor 24 and the second SoS gas sensor 26. The gas conduction path 18 further includes a third natural gas sensor 22 in the form of a non-dispersive infrared (NDIR) analyzer.

[0070] Although not shown in Figure 1, the second gas sensor 26 includes a measuring cuvette with a gas inlet connected to the gas conduction path 18, so that it is filled with gas guided through the gas conduction path 18. Furthermore, a speaker-shaped emitter and two microphones are positioned along the measuring cuvette, and the sound signal emitted from the emitter passes through the gas-filled measuring cuvette before reaching the first microphone, and then travels to reach the second microphone. Thus, both microphones capture the sound signal at two different timings. The speed of sound in the cuvette is calculated from the distance between the two microphones and the time difference between the capture of the sound signal by the first microphone and the capture of the sound signal by the second microphone.

[0071] The third gas sensor 22 includes an absorption cuvette, which is not shown in Figure 1. The absorption cuvette of the third gas sensor 22 (natural gas sensor) and the measurement cuvette of the second gas sensor 26 (sonic gas sensor) can have similar effects. This is shown, for example, in the embodiments shown in Figures 2-4. For simplification, Figure 1 shows the third gas sensor 22 and the second gas sensor 26 as two separate components.

[0072] Therefore, the absorption cuvette of the third gas sensor 22 also includes a gas inlet connected to an infrared (IR) sensor, infrared emitters 26a and infrared detectors 26b provided on two opposing sides of the cuvette, such that infrared light emitted by the infrared emitters passes through the cuvette and the gas contained therein before being analyzed by the infrared detectors 26b. The analysis is performed in a manner generally known according to the absorption principle. The loss of light intensity due to absorption is analyzed in one or more wavelength ranges in which natural gas is known to absorb light.

[0073] In particular, measuring natural gas and methane concentrations is necessary to accurately measure the hydrogen concentration in samples with significant methane concentrations, where "significant" means 5 vol.% or more of the actual hydrogen concentration in the sample.

[0074] The hydrogen gas detector 20 may be equipped with a third IR sensor 26 to analyze absorption in additional wavelength ranges in order to measure the concentration of other gases in the sample that affect the speed of sound. Such gases include, for example, carbon dioxide and water. This information can be used to further improve the accuracy and selectivity of the detector in the range covered by the second SoS sensor 26.

[0075] Figures 2, 3, and 4 show embodiments in which the second gas sensor 26 and the third gas sensor 22 share the same measuring cuvette 40, respectively.

[0076] In the embodiment shown in Figure 2, the hydrogen leak detector 10 is a sniffing grey detector that, like the one in Figure 1, includes a sniffing probe 12 having a gas inlet 14 and a gas conduction path 18 that connects the gas inlet 14 to a vacuum pump 16 and discharges the gas into the air, for example. The difference between the embodiment in Figure 2 and the embodiment in Figure 1 is the arrangement of the first gas sensor 24, the second gas sensor 26, and the third gas sensor 22. In Figure 2, the second gas sensor 26 is a sound velocity sensor that uses the same measuring cuvette 40 as the third gas sensor 22, which is non-dispersive infrared (NDIR). The third sensor 26 includes a sound source, such as a directional speaker 26a, provided at one end of the cuvette 40, and a microphone 26b provided at the opposite end of the cuvette 40. As a result, the sound signal emitted by the sound source 26a passes through the cuvette 40 and the gas contained therein before being received by the microphone 26b. Similarly, the third gas sensor 22 comprises an infrared source 22a located at one end of the cuvette 40 and an infrared sensor 22b located at the opposite end of the cuvette 40. Thus, the infrared signal emitted by the infrared source 22a passes through the cuvette 40 and the gas contained within it before being received by the infrared sensor 22b. Signal analysis of the measurement signals generated by the three gas sensors 22, 24, and 26, particularly the infrared sensor 22b and the microphone 26b, is performed by a computing device such as a microprocessor or computer, although this is not shown for simplicity. The computer or computing device is electronically connected to at least all of the gas sensors 22, 24, and 26 of the hydrogen gas detector 20.

[0077] In the embodiment shown in Figure 2, the first gas sensor 24 is located in the gas conduction path 18 between the measuring cuvette 40 and the vacuum pump 16.

[0078] Alternatively, the first gas sensor 24 can be placed in the gas conduction path 18 between the sniffing probe 12 and the cuvette 40.

[0079] As a further alternative, in additional embodiments, the gas sensors 24, 26, and 22 may be arranged in parallel within the gas conduction path 18, rather than in series.

[0080] This is shown in Figure 3, which provides details of the hydrogen gas detector in Figure 2. In Figure 3, the remaining arrangement of the hydrogen leak detector 10 with respect to the gas conduction path 18, sniffing probe 12, gas inlet 14, and / or vacuum pump 16 may correspond to those of the embodiments in Figures 1 and 2. Alternatively, the hydrogen gas detector 20 according to Figures 3 and 4 may be a non-sniffing hydrogen gas detector, such as an open-circuit detector with a measuring volume 50 in which the gas to be analyzed accumulates. Opposite the measuring volume 50 are an infrared source 22a and an infrared sensor 22b, as well as a sound source 26a and a microphone 26b. The sound signal emitted by the sound source 26a and the infrared signal emitted by the infrared source 22a pass through the measuring volume 50 and the gas contained therein, and are then received by the microphone 26b and infrared sensor 22b, respectively, similar to the measuring cuvette 40 in Figure 2.

[0081] In Figure 3, the first gas sensor 24, which may take the form of a metal hydride sensor, is positioned adjacent to the measurement volume 50 such that the gas in the measurement volume 50 comes into contact with the first gas sensor 24. Therefore, when the gas in the measurement volume 50 comes into contact with the first gas sensor 24, the measurement signal of the first gas sensor 24 will indicate hydrogen because the first gas sensor 24 is hydrogen-selective.

[0082] The embodiment shown in Figure 4 differs from the embodiment shown in Figure 3 in that the infrared source 22a and infrared sensor 22b of the third gas sensor 22, and the sound source 26a and microphone 26b of the second gas sensor 26 are arranged on opposite sides of the measuring cuvette 40, similar to the embodiment shown in Figure 1. The measuring cuvette 40 has a longitudinal opening 60 covered by a gas-permeable membrane or filter, and the measuring gas enters the measuring cuvette 40 directly from the periphery adjacent to the hydrogen gas conducting member, or from a gas conducting path 18 (not shown in Figure 4). The first gas sensor 24 is mounted on the measuring cuvette 40 such that the gas in the cuvette is in contact with the first gas sensor 24, and as a result, a measurement signal from the first gas sensor 24 is obtained. This measurement signal from the first gas sensor 24 indicates hydrogen when the gas in the cuvette 40 contains hydrogen below a first threshold.

[0083] Figure 5 shows an embodiment in which a first gas sensor 24, a second gas sensor 26, and a third gas sensor 22 are arranged in parallel. The gas inlet 14 leads to a gas conduction path 18 equipped with a vacuum pump 16. The gas conduction path 18 is divided into three separate conduction paths, each consisting of one of the three gas sensors 22, 24, and 26. The upper gas conduction path in Figure 5 includes a second gas sensor along with a sample vacuum pump 32 upstream of sensor 26. The second gas sensor 26 is a sound velocity sensor having a sound source 26a and two independent microphones 26b. The middle gas conduction path consists of the first gas sensor 24 and another sample vacuum pump 34 upstream of the first gas sensor 24. The first gas sensor 24 in the embodiment according to Figure 5 may be a gas FET sensor.

[0084] The lower gas conduction path includes a third gas sensor 22 and another sample vacuum pump 36 downstream of sensor 22. The third gas sensor 22 in the embodiment of Figure 5 is an NDIR sensor that is insensitive to hydrogen but sensitive to methane and carbon dioxide. Methane and carbon dioxide are secondary gases to the second gas sensor 26, i.e., gases to which the second gas sensor 26 is sensitive.

Claims

1. A hydrogen leak detector (10) for detecting leaks in hydrogen gas conduction components, The system includes a hydrogen gas detector (20) configured to measure the concentration of hydrogen gas in the gas within the gas conduction pathway (18), The hydrogen gas detector (20) is A first gas sensor (24) having hydrogen selectivity and configured to respond to a first range of relatively low hydrogen concentrations below a first threshold, The system includes a second gas sensor (26) which is sensitive to hydrogen, non-selective to hydrogen, sensitive to at least one secondary gas other than hydrogen, and configured to respond to a second range of relatively high hydrogen concentrations exceeding the first threshold, The hydrogen leak detector (10) is configured to calibrate the second gas sensor (26) to low concentrations of hydrogen present in the atmosphere surrounding the hydrogen gas detector (20), which may or may not originate from a leak in the hydrogen gas conduction component under test. This calibration is performed by measuring the hydrogen concentration in the gas to be measured, taken from the surrounding atmosphere, using the first gas sensor (24) and the second gas sensor (26). If the measurement signal of the first gas sensor (24) of the gas to be measured indicates a hydrogen concentration below a predetermined value, the measurement signal of the second gas sensor (26) of the gas to be measured is assigned to correspond to a concentration that does not originate from a leak in the hydrogen gas conduction component under test. If the second gas sensor indicates a hydrogen concentration above the second threshold, a hydrogen leak is considered to be present in the hydrogen gas conduction component under test. Hydrogen leak detector (10).

2. A hydrogen leak detector (10) according to claim 1, wherein the second gas sensor (26) is used to measure the hydrogen gas concentration that causes saturation of the first gas sensor (24).

3. The hydrogen leak detector (10) according to claim 1 or 2, wherein the first gas sensor (24) is a metal hydride gate field-effect transistor (FET) gas sensor, a metal hydride Schottky diode gas sensor, or a selective metal oxide (MOS) gas sensor.

4. A hydrogen leak detector (10) according to any one of claims 1 to 3, wherein if the first gas sensor (24) shows a hydrogen concentration equal to or greater than a third threshold that is less than the second threshold, a hydrogen leak is deemed to be present in the hydrogen gas conducting component under test.

5. A hydrogen leak detector (10) according to any one of claims 1 to 4, wherein the second gas sensor (26) is a sound velocity (SoS) gas sensor or a thermal conductivity (TC) gas sensor.

6. A hydrogen leak detector (10) according to any one of claims 1 to 5, wherein the second gas sensor (26) includes a measuring cuvette that can be filled with a gas to be measured, a sound source configured to transmit an audio signal through the gas in the cuvette, and at least one microphone configured to receive an audio signal emitted from the sound source and transmitted through the cuvette.

7. A hydrogen leak detector (10) according to any one of claims 1 to 6, wherein the second gas sensor (26) includes at least two microphones configured to receive an audio signal emitted from a sound source and transmitted through a cuvette, the speed of the audio signal is calculated based on the time difference between the reception of the audio signal by the two microphones and the distance between the two microphones.

8. A hydrogen leak detector (10) according to any one of claims 1 to 7, comprising a third gas sensor (22) configured to measure a gas introduced through the gas conduction path (18), wherein the third gas sensor (22) is insensitive to hydrogen and sensitive to at least one secondary gas on which the second gas sensor (26) is sensitive.

9. A hydrogen leak detector (10) according to any one of claims 1 to 8, wherein the third gas sensor (22) comprises a radiation-absorbing cuvette that can be filled with the gas to be measured, a radiation source provided for emitting radiation of a known frequency band into the gas in the cuvette, and a radiation detector provided for detecting radiation that has passed through the cuvette and for determining the absorption band of the detected radiation.

10. A hydrogen leak detector (10) according to any one of claims 1 to 9, wherein the absorption cuvette of the third gas sensor (22) is used as a measuring cuvette for measuring the speed of sound by the second gas sensor (26).

11. A hydrogen leak detector (10) according to any one of claims 1 to 10, wherein the hydrogen leak detector is a handheld detector.

12. A method for detecting leaks in hydrogen gas conductive components, The concentration of hydrogen gas in the test area is, A first gas sensor (24) is used which has hydrogen selectivity and is configured to react to a first range of relatively low hydrogen concentrations below a first threshold for measuring the first range in the measured gas, and The measurement is performed by using a second gas sensor (26) that is sensitive to hydrogen, non-selective to hydrogen, sensitive to at least one secondary gas other than hydrogen, and configured to react to a second range of relatively high hydrogen concentrations exceeding the first threshold for measuring the second range in the measured gas, For low concentrations of hydrogen present in the atmosphere surrounding the hydrogen gas detector (20) and not originating from a leak in the hydrogen gas conductive component under test, the second gas sensor (26) is used. The hydrogen concentration in the gas to be measured, which is collected from the surrounding atmosphere, is measured by the first gas sensor (24) and the second gas sensor (26). If the measurement signal of the first gas sensor (24) of the gas under test indicates a hydrogen concentration below a predetermined value, the measurement signal of the second gas sensor (26) of the gas under test is calibrated by assigning it to a concentration not caused by hydrogen leakage in the hydrogen gas conduction component under test. The process includes a step in which, if the hydrogen concentration determined by the second gas sensor (26) exceeds a second threshold, a hydrogen leak is considered to be present in the hydrogen gas conduction component. method.

13. A method according to claim 12, wherein a hydrogen leak detector (10) according to any one of claims 1 to 12 is used.

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