JP5880751B2 - Gas detection device - Google Patents

Description

  The present invention relates to a gas detection device that detects a specific gas leaking from a sealed structure using infrared rays.

  As a technique for detecting a specific gas, there is a method using a characteristic that a specific gas strongly absorbs light of a specific wavelength. In a conventional gas detection device, light from an infrared light source is radiated to a space where the presence of gas is to be determined, and the light passing through the space is passed through a filter that transmits only light of a specific wavelength. Light is converted into a screen display signal and displayed on a display device (for example, see Patent Document 1).

JP 2006-317366 A

  In the conventional gas detection device, when detecting a gas leaking from a crack in a sealed structure such as a pipe, it is necessary to dispose the sealed structure between the infrared light source and the infrared detecting means. Therefore, when a crack in the sealed structure exists at a position where infrared rays from the infrared light source are not irradiated, or when a large number of sealed structures overlap between the infrared light source and the infrared detection means, the sealed structure There was a problem that it was difficult to detect gas leaking from a crack in the body.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a gas detection device capable of detecting leaking gas regardless of the position of the crack in the sealed structure. .

A gas detection apparatus according to the present invention includes a structure heating means for heating a sealed structure in which a gas to be detected is sealed, a temperature measuring device for measuring the temperature of the sealed structure, and a wavelength absorbed by the gas to be detected. An optical filter that receives infrared rays radiated from a sealed structure that transmits infrared rays and is heated by a structure heating unit, an infrared detection unit that receives infrared rays that have passed through the optical filter and converts them into detection signals, and an output of the infrared detection unit The structure heating means is controlled so that the temperature measured by the temperature measuring device becomes a predetermined temperature.
Further, the gas detection device according to the present invention includes a structure heating means for heating at least a part of the sealed structure in which the gas to be detected is sealed, and an infrared ray having a wavelength absorbed by the detected gas. An optical filter that receives infrared rays emitted from a sealed structure that is transmitted by the structure heating means, receives infrared rays that pass through the optical filter and converts them into detection signals, and outputs the infrared detection means. Signal display means for displaying.

According to the present invention, the structure heating means for heating the sealed structure in which the gas to be detected is sealed, the temperature measuring device for measuring the temperature of the sealed structure, and the infrared ray having a wavelength absorbed by the gas to be detected An optical filter that receives infrared rays transmitted from the sealed structure heated by the structure heating means, an infrared detection means that receives the infrared rays that have passed through the optical filter and converts them into detection signals, and displays the output of the infrared detection means The structure heating means is controlled so that the temperature measured by the temperature measuring device becomes a predetermined temperature, so that the leaking gas can be obtained regardless of the position of the crack in the sealed structure. Can be detected.
According to the present invention, the structure heating means for heating the sealed structure covering at least a part of the sealed structure in which the gas to be detected is sealed, and the infrared ray having a wavelength absorbed by the gas to be detected are transmitted. An optical filter that receives infrared rays emitted from the sealed structure heated by the structure heating means, an infrared detection means that receives infrared rays that have passed through the optical filter and converts them into detection signals, and displays the output of the infrared detection means Since the signal display means is provided, the leaking gas can be detected regardless of the position of the crack in the sealed structure.

It is a figure which shows the structure of the gas detection apparatus by Embodiment 1 of this invention. It is a figure which shows the mode of the temperature change of the black body radiation spectrum by Embodiment 1 of this invention. It is a figure for demonstrating the positional relationship of the gas detection apparatus by Embodiment 1 of this invention. It is a figure which shows the example of an output of the gas detection apparatus by Embodiment 1 of this invention.

Embodiment 1
FIG. 1 is a diagram showing a configuration of a gas detection device according to Embodiment 1 of the present invention. The gas to be detected 8 is sealed in the sealed structure 7, and when the crack is generated in the sealed structure 7, the gas 8 to be detected leaks to the outside of the sealed structure 7, and gas leakage occurs. The gas detection apparatus according to the first embodiment of the present invention detects a gas 8 to be detected that has leaked to the outside of the sealing structure 7 due to gas leakage in a detection region where the sealing structure 7 is shown.

  The sealed structure 7 in Embodiment 1 of the present invention is a pipe or a gas tank in which the gas 8 to be detected is sealed. The sealed structure does not necessarily need to realize a strict sealed state using an O-ring or a gasket, and may be used for enclosing the gas 8 to be detected.

  The structure heating means 1 heats the sealed structure 7. The structure heating means 1 may be anything as long as it can heat the sealed structure 7, and may be a sheathed heater, a silicon rubber heater, a heating wire, a nichrome wire, a Kanthal wire, or the like. Moreover, what blows hot air, such as a heat gun, may be used. Moreover, the structure heating means 1 does not need to cover all of the sealed structure 7, and may cover the part and heat the entire sealed structure 7 by heat conduction. Furthermore, a temperature measuring device such as a thermocouple or a thermistor may be incorporated in the structure heating means 1 so that the temperature of the structure heating means 1 is maintained at a predetermined temperature. Alternatively, a temperature measuring device may be installed in the sealed structure 7 to measure the temperature of the sealed structure 7 and the structure heating means 1 may be controlled so that the temperature of the sealed structure 7 becomes a predetermined temperature.

  A black body radiation spectrum corresponding to the temperature is emitted from the sealed structure 7 heated by the structure heating means 1. The intensity B (λ) of the black body radiation spectrum is assumed that the temperature of the object is T [K], the wavelength of the emitted spectrum is λ [μm], and the emissivity of the sealed structure 7 at the wavelength λ is ε (λ). Is represented by the following equation.

  Here, h is the Planck constant, k is the Boltzmann constant, c is the speed of light, and e is the Napier number.

This spectrum includes wavelengths of 2 to 5 μm band absorbed by gases such as CO ₂ , CO, and CH 4, and 8 to 12 μm band absorbed by chlorofluorocarbon gases such as SF ₆ , so that these gases are detected. It can be used as an infrared light source.

The concentration of the detected gas 8 is n, the wavelength of the light absorbed by the detected gas 8 is λ, the amount of light incident on the region where the detected gas 8 is present is I _λ (0), and the region where the detected gas 8 is present The thickness (optical path length) is s, the light quantity after the light of I _λ (0) passes through the detected gas 8 with the optical path length s is I _λ (s), and the proportional multiplier specific to the detected gas 8 is K. _{Assuming λ} , each relationship can be expressed as follows.

Therefore, in order to detect a slight gas leak having a low concentration, it is necessary to increase {I _λ (0) −I _λ (s)} when n becomes small in Equation (2). For that purpose, it is necessary to lengthen the optical path length s or increase the amount of light I _λ (0) incident on the region where the gas 8 to be detected exists. Since the detection gas 8 leaking from the sealed structure 7 diffuses, it is difficult to increase the optical path length s. Therefore, the amount of light I _λ (0) incident on the region where the detection gas 8 exists is increased. Here, attention is paid to the black body radiation spectrum radiated from the sealed structure 7 heated by the structure heating means 1.

  FIG. 2 shows the temperature change of the black body radiation spectrum. As shown in FIG. 2, the black body radiation spectrum is radiated even at 25 ° C., which is about room temperature, but it is understood that the amount of light increases as the temperature rises. Therefore, by making the sealed structure 7 higher than the ambient temperature, it is possible to detect minute gas leaks in which the optical path length is shortened at a low concentration.

  The optical filter 2 is disposed at a position to receive infrared rays that are emitted from the sealed structure 7 heated by the structure heating means 1 and pass through the gas leak detection region. The optical filter 2 transmits only infrared light having a wavelength that is absorbed by the detection gas 8.

The optical filter 2 is selected according to the wavelength of infrared rays absorbed by the detection gas 8. For example, if the gas to be detected 8 is CO ₂ , CO, or CH ₄ , it absorbs infrared rays having a wavelength of 2 to 5 μm, so that the optical filter 2 transmits only infrared rays having a wavelength of 2 to 5 μm. Since SF ₆ and fluorocarbon gas absorb infrared rays having a wavelength of 8 to 12 μm, an optical filter 2 that transmits only infrared rays having a wavelength of 8 to 12 μm is used. Further, in order to distinguish the background gas from the detection target gas, the absorption wavelength band of the gas that is not the detection target may be excluded from the transmission band of the optical filter 2. For example, when SF ₆ is detected in the atmosphere, the wavelength of infrared rays absorbed by SF ₆ is 10.6 μm, so that the optical filter 2 transmits only infrared rays having a wavelength of 10.6 μm. In this case, for example, CO ₂ is assumed as the background gas, but since the wavelength of infrared rays absorbed by CO ₂ is ₂ to 5 μm, only SF ₆ can be detected. The optical filter 2 uses one type of filter when there is one type of gas to be detected. When there are a plurality of gases to be detected, a plurality of optical filters 2 may be prepared and replaced manually or automatically. Further, instead of using the optical filter 2, a light component having a specific wavelength may be dispersed using an interferometer, a prism, a diffraction grating, or the like. Or when using a condensing lens or a condensing mirror, you may vapor-deposit the film | membrane which permeate | transmits only the infrared rays of a specific wavelength on these surfaces.

  The infrared detecting means 3 receives the infrared light transmitted through the optical filter 2 and converts it into a detection signal. The infrared detection means 3 includes a thermal detection element such as a thermopile, a porometer, and a pyroelectric element, and a quantum detection element such as a photodiode and a phototransistor. By using a two-dimensionally arranged infrared detection element such as a thermoviewer, the detection signal can be used as image data. Thereby, it is possible to easily understand the existence position and concentration distribution of the gas. By using an infrared element arranged one-dimensionally in a line and scanning it in the short direction of the arranged sensor, an output signal similar to that of an infrared detecting element arranged two-dimensionally may be obtained. . Further, a condensing lens or a condensing mirror may be arranged on the front surface of the infrared detecting means 3 in order to condense the infrared light transmitted through the optical filter 2.

  The signal processing unit 4 performs enhancement processing so that the output signal from the infrared detection unit 3 can be easily confirmed, and outputs the signal to the signal display unit 6. When the signal processing means 4 processes the output signal from the infrared detection means 3, the signal is stored in the memory 5 as necessary.

  The signal display means 6 displays the signal received from the signal processing means 4 in the form of image data or the like. By confirming the image displayed on the signal display means 6, it is possible to detect the detected gas 8 that has leaked to the outside of the sealed structure 7 due to gas leakage.

  Next, the operation of the gas detection device according to Embodiment 1 of the present invention will be described. First, the structure heating means 1 is operated to heat the sealed structure 7. The structure heating means 1 heats a part of the sealed structure 7 by, for example, direct heating using a heater or the like, or blowing hot air using a heat gun or the like. When a part of the sealed structure 7 is heated, the entire temperature of the sealed structure 7 rises due to heat conduction. If the space to be detected is wide or the outside air temperature is low, the entire sealed structure 7 may be heated by installing a plurality of structure heating means 1 as necessary. From the heated sealed structure 7, infrared rays are radiated as a radiation spectrum according to the emissivity of the surface and the temperature when heated.

  FIG. 3 is a diagram for explaining the positional relationship when the gas detection device according to the first embodiment of the present invention shown in FIG. 1 is viewed in the y-axis direction. In FIG. 3, the gas 8 to be detected leaks from the sealed structure 7 in the x direction. When the sealed structure 7 is heated by the structure heating means 1, infrared rays 9 are emitted as a radiation spectrum, and the detection gas 8 absorbs infrared rays 9 having a specific wavelength. Infrared light 9 that has not been absorbed by the gas 8 to be detected passes through the optical filter 2 and reaches the infrared detection means 3.

  FIG. 4 is a diagram for explaining an output example of the signal display means 6 in the gas detection device according to Embodiment 1 of the present invention shown in FIG. FIG. 4 is an output example when the gas detector according to Embodiment 1 of the present invention shown in FIG. 1 is photographed from the x-axis direction. FIG. 4 shows the imaging region 10 of the signal display means 6. In the example shown in FIG. 4, the place where the infrared detecting means 3 strongly detected infrared rays is displayed in white. For example, the portion of the sealed structure 7 is shown as a white portion 11 because the infrared ray 9 is emitted, and the infrared ray having a specific wavelength is absorbed by the detected gas 8 in the portion where the detected gas 8 exists. Therefore, the black portion 12 appears. When the concentration of the detected gas 8 is high, the darkness of the color of the black portion 12 is also high. The blank area appears as a white area because the infrared rays 9 reach the infrared detection means 3 as they are. Thus, by confirming the presence or absence of the black portion 12 in FIG. 4 which is the output of the signal display means 6, it is possible to confirm the location and concentration of the gas 8 to be detected. Further, when the gas 8 to be detected is intermittently ejected, the infrared detection means 3 stores the data acquired continuously or the data acquired at different times in the memory 5 through the signal processing means 4, By comparing the respective data by taking the difference between the data acquired at different times, it is possible to confirm the temporal change in the ejection of the detected gas 8.

  In a conventional gas detection device, for example, a sealed structure 7 in which a gas to be detected 8 is sealed is disposed between an infrared light source and an infrared detection means 3. In FIG. 3, an infrared light source is disposed on the left side of the sealed structure 7. In this case, since the infrared rays emitted from the infrared light source are interrupted by the sealing structure 7, the portion of the sealing structure 7 appears as a black portion. As a result, in the output of the signal display means 6 shown in FIG. 4, the portion of the sealed structure 11 is shown in black, and the black portion 12 indicating the presence of the detected gas 8 can be confirmed. It was gone. Further, in order to detect the gas 8 to be detected that does not reach the infrared rays emitted from the infrared light source, the positions of both the infrared light source and the infrared detection means are changed so as to sandwich the sealed structure 7. Therefore, it was necessary to perform a gas leak detection work, and the work was very large.

  In the gas detection device according to the first embodiment of the present invention, since the sealed structure 7 is heated by the structure heating means 1, infrared rays are emitted from the sealed structure 7, and the infrared detection means 3 side of the sealed structure 7 is irradiated. The gas 8 to be detected that has slightly leaked can also be detected. Further, since the detected gas 8 is detected using infrared rays radiated from the sealed structure 7 itself, it is possible to detect the detected gas 8 leaking from fine scratches or the like of the sealed structure 7. Furthermore, by changing the positions of the optical filter 2 and the infrared detecting means 3 with respect to the sealed structure 7 heated by the structure heating means 1, it is possible to easily confirm cracks at various positions of the sealed structure 7. it can.

DESCRIPTION OF SYMBOLS 1 Structure heating means 2 Optical filter 3 Infrared detection means 4 Signal processing means 6 Signal display means 7 Sealed structure 8 Detected gas

Claims (4)

A structure heating means for heating the sealed structure in which the gas to be detected is sealed;
A temperature measuring device for measuring the temperature of the sealed structure;
An optical filter that transmits infrared rays having a wavelength absorbed by the gas to be detected and receives infrared rays emitted from the sealed structure heated by the structure heating means;
Infrared detecting means for receiving infrared light transmitted through the optical filter and converting it into a detection signal;
Signal display means for displaying the output of the infrared detection means,
The gas detector according to claim 1, wherein the structure heating unit is controlled so that a temperature measured by the temperature measuring device is a predetermined temperature.   The gas detector according to claim 1, wherein the structure heating unit heats the sealed structure covering at least a part of the sealed structure. A structure heating means that heats the sealed structure covering at least a part of the sealed structure in which the gas to be detected is sealed;
An optical filter that transmits infrared rays having a wavelength absorbed by the gas to be detected and receives infrared rays emitted from the sealed structure heated by the structure heating means;
Infrared detecting means for receiving infrared light transmitted through the optical filter and converting it into a detection signal;
A gas detection apparatus comprising signal display means for displaying the output of the infrared detection means. A memory for storing data acquired by the infrared detection means at a plurality of different times;
Signal processing means for comparing data acquired at the different times,
The gas detection device according to any one of claims 1 to 3, wherein the signal display means displays an output of the signal processing means.

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