JPH0711464B2 - Gas leak monitor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared irradiating means for irradiating a gas leakage monitoring target area with detection infrared rays having a wavelength absorbed by a gas to be detected, and irradiating from the background of the gas leakage monitoring target area. The present invention relates to a gas leak monitoring device including an infrared detecting means for detecting reflected infrared rays and a gas leak judging means for judging the presence / absence of a gas leak from the intensity of the infrared rays detected by the infrared detecting means.

[0002]

2. Description of the Related Art A gas leak monitoring device of this type has been proposed for a conventional fixed point monitoring device.

[0003]

However, according to the above-mentioned gas leakage monitoring device of the prior art, it is necessary to always operate the infrared irradiating means, but there is a drawback that the life of the laser oscillator as a light source is shortened. Further, there is a drawback that the power consumption for operating the detection light flux irradiating means becomes large, and that a large-power laser that is expensive and large is required when performing wide area monitoring with a laser. It was An object of the present invention is to eliminate the above-mentioned conventional drawbacks.

[0004]

In order to achieve this object, the gas leak monitoring device according to the present invention is characterized by an infrared irradiation for activating an infrared irradiating means when the gas leak judging means discriminates a gas leak. The control means is provided. In the above-mentioned configuration, the infrared ray detecting means is composed of a filter that transmits a light flux in a band including the wavelength of the infrared ray for detection and a light receiving element that receives the infrared ray that has passed through the filter, and the infrared ray irradiation control means is ,
It is preferable to provide filter switching means for narrowing the band of the filter when the infrared irradiation means is operated.

[0005]

[Function] Rather than constantly operating the infrared irradiation means,
Normally, infrared rays (radiant heat) emitted from the background of the gas leakage monitoring target area (for example, gas related facilities such as gas spherical holders and natural objects such as trees) are detected by the infrared detecting means, and based on the detection result. The presence / absence of gas leakage is roughly determined by the gas leakage determination means based on the intensity of infrared rays having a wavelength absorbed by the obtained gas to be detected. That is, if there is a gas leak, the gas leak determination means determines whether or not there is a gas leak by utilizing the fact that the intensity of the infrared ray having a wavelength absorbed by the gas becomes low. When it is determined that the gas leak has occurred with a coarse accuracy by the gas leak determination means, the infrared irradiation control means irradiates the detection infrared ray toward the background,
The infrared irradiating means is operated in order to enable more accurate gas leak determination based on the intensity of infrared rays reflected from the background. In the above-mentioned configuration, when the infrared detecting means is composed of a filter that transmits a light flux of a band including the wavelength of the detection infrared ray and a light receiving element that receives the infrared ray that has passed through the filter, the infrared ray The irradiation control means is usually set to a filter with a wide band and the S / N ratio is lowered so as not to miss a slight gas leak. When the infrared irradiation means is operated, the filter is switched by the filter switching means. By narrowing the band of S, it is necessary to detect in detail how much gas is leaking.
It is preferable to increase the / N ratio.

[0006]

According to the present invention, a gas leak monitor capable of reliably detecting the occurrence of a gas leak while keeping the life of a laser oscillator as a light source long and reducing the power consumption consumed by the light source. Equipment can now be provided. Furthermore, a higher power laser is required to cover a wider area, but a high power laser is not necessarily required because a laser can monitor a limited range.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIGS. 1 and 2, a gas leak monitoring device 1
Is near the spherical holder 2 in the gas manufacturing plant, particularly the flange connection portion 2 of the pipe connected to the spherical holder 2.
The gas leak monitoring is performed at a, and the detection target gas g is methane, ethane, and
Infrared irradiation means E for irradiating a detection infrared ray L having a wavelength λ absorbed by a combustible gas g such as propane or butane;
Background of the gas leakage monitoring target area A, for example, the spherical holder 2
Infrared detecting means R for detecting infrared rays radiated or reflected from the like, and a gas for discriminating the presence or absence of gas leakage from the intensity of infrared rays having a wavelength absorbed by the gas to be detected g based on the detection result of the infrared detecting means R. The leak determining means J is provided. The infrared irradiating means E includes a laser oscillator E1 that oscillates the detecting infrared ray having the wavelength λ, and a light flux diffuser E2 that irradiates the infrared ray L output from the laser oscillator E1 toward the gas leakage monitoring target area A. I am doing it. The infrared detecting means R is radiated from a gas-related facility such as the spherical holder 2 which is the background of the gas leakage monitoring target area A or a natural object such as a tree, or the infrared irradiating means E.
The infrared ray reflected by the infrared rays emitted by the sensor 1 detects the intensity of the infrared ray transmitted through the gas leakage monitoring target area A, and is composed of an interference filter F and an infrared image sensor R1 as a light receiving element. . As shown in FIG. 3, the gas leakage determination means J displays the infrared energy detected by the infrared detection means R in a two-dimensional grayscale image corresponding to the gas concentration, such as a display device J1 such as a CRT.
And a comparison device J2 that determines that the gas to be detected g is distributed in a region of the grayscale image having a concentration higher than a predetermined threshold value (for example, a value that represents a back shadow in a normal state). It consists of and.

The specifications of each element in the gas leak monitoring device described above will be listed. Infrared laser type helium-neon laser output from laser oscillator E1 Nominal output 8 mW Center wavelength λ 3.39 μm, Transmission spectrum width 0.09 μm Viewing angle maximum 14 ° Distance to background Several m to several 100 m Infrared image sensor R1 Detection wavelength Area 3 μm to 5 μm Maximum detection temperature difference 0.15 ° C or less (NET
D)

[0009]

## EQU1 ## Width of bandpass filter F α + β 0.1 to 2 μm

The gas leak monitoring device 1 is provided with an infrared irradiation control means C for activating the infrared irradiation means E when the gas leak judging means J judges that a gas leak has occurred. That is, the infrared irradiating means E is not always operated, but normally the infrared irradiating means E is stopped and infrared rays (radiant heat) emitted from the background of the gas leakage monitoring target area A are detected by the infrared detecting means R. The gas leak determining means J roughly determines whether or not there is a gas leak. That is, the gas leakage determination means J takes advantage of the fact that if there is a gas leakage, the intensity of the infrared ray having a wavelength absorbed by the gas becomes low, and if the intensity is lower than the set intensity, the gas leakage occurs. If there is a gas leak, determine whether there is a gas leak. When the occurrence of gas leakage with rough accuracy is determined by the gas leakage determination unit J, the infrared irradiation control unit C irradiates the detection infrared L toward the background, and the intensity of the reflected infrared light from the background. The infrared irradiating means E is operated to enable more accurate gas leakage determination based on (in this case, infrared rays are condensed and irradiated in an area narrower than the normal monitoring area). More specifically, when the detection infrared ray L is radiated through the gas leak monitoring target area A toward an area having the spherical holder 2 as a background, the infrared ray L for detection is reflected from the background and the infrared detection means. It is incident on R, and this signal is detected and output to the gas leak determination means J. Here, when the gas to be detected g is present in the gas leakage monitoring target area A, the infrared rays L for detection are absorbed in the forward and backward paths by the gas g, and the infrared rays L for detection are spatially (in the case of a two-dimensional mapping). Intensity at different positions). Therefore, when this information is detected and displayed by the image sensor R1, as shown in FIG. 3, the image is a grayscale image or a different color image according to the presence or absence of gas and the concentration (when such a process is performed. Can be displayed as).

The monitoring operation of the gas leakage monitoring device 1 is as described above. The operating state of the infrared irradiating means E is as follows.
When the single interference filter F is used regardless of the non-operating state, the display screen of the display device J1 may become excessively bright or dark due to the influence of sunlight or the like. However, there is a problem that the difference in brightness on the display screen with respect to the concentration of the gas to be monitored is low, and even if it is displayed, the presence of gas cannot be visually confirmed clearly. The truly necessary infrared intensity signal detected by the image sensor R1 corresponds to a wavelength λ near 3.39 μm, but the infrared irradiating means E is not operated in order to prevent a slight gas leak. In the state, the interference filter F
As a result, it is necessary to detect infrared intensity in a wider detection wavelength range. When the infrared ray irradiating means E is operated to detect the infrared rays having large energy reflected from the background with respect to the image sensor R1 which is normalized to express the light and shade by the intensity signal, the wavelength λ is around 3.39 μm. This is because the intensity signal of is saturated above a certain value and the grayscale cannot be identified. Therefore, as shown in FIG. 4 and FIG. 5, the infrared irradiation control means C normally uses a filter R having a wide band.
When the infrared irradiating means E is operated with the S / N ratio set to 3 so that even slight gas leakage is not escaped, the filter F is switched by the filter switching means FC.
By switching to the filter R2 having a narrower band, the S / N ratio is increased in order to detect in detail how much gas is leaking.

Another embodiment will be described below. In the above-mentioned embodiment, the laser light emitted from the irradiation device E is a single light, and the laser light having a wavelength absorbed by the combustible gas g is selected. A means for irradiating a laser beam having a wavelength not absorbed by the gas g together with the laser beam having a wavelength is provided.
The detection result of this system may be used as the ground, and the result of the absorbed wavelength may be used as gas information, and the gas may be detected by this two-wavelength detection system. In this case, it is possible to determine the gas concentration. Further, as the background of the gas leakage monitoring target area A, in addition to the spherical holder 2, a ground, a concrete wall, a painted steel structure or the like may be used.
Further, a screen may be provided for the specific area.
Further, while the background is generally stationary, the leaked detected gas g flows. Therefore, it is also possible to adopt a configuration in which the state of gas leakage can be grasped by comparing and analyzing the image information visualized by the gas leakage monitoring device 1 of the present application at different times. In the above embodiment, a laser oscillator is used as the infrared irradiation means, but the light source is not limited to the laser oscillator.

It should be noted that reference numerals are given in the claims for convenience of comparison with the drawings, but the present invention is not limited to the configurations of the accompanying drawings by the entry.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a gas leak monitoring device.

FIG. 2 is a block diagram of a gas leak monitoring device.

FIG. 3 is a diagram showing a display state on a display device.

FIG. 4 is a characteristic diagram of infrared intensity due to a change in transmission bandwidth by a bandpass filter when there is no gas leakage.

FIG. 5 is a characteristic diagram of infrared intensity due to a change in transmission bandwidth by a bandpass filter when gas leaks.

[Explanation of Codes] A Gas Leakage Monitoring Area C Infrared Radiation Control Means E Infrared Radiation Means g Detected Gas J Gas Leakage Discrimination Means R Infrared Radiation Means

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Takeshi Nishio Inventor Takeshi Nishio 4-1-2, Hirano-cho, Chuo-ku, Osaka-shi, Osaka Within Osaka Gas Co., Ltd. (56) Reference JP-A-57-122336 (JP, A) Kai 56-147034 (JP, A)

Claims (2)

[Claims] 1. An infrared irradiating means (E) for irradiating a gas leakage monitoring target area (A) with a detection infrared ray having a wavelength absorbed by the gas to be detected (g), and a gas leak monitoring target area (A). Infrared detecting means (R) for detecting infrared rays radiated or reflected from the background, and gas leak judging means (J) for judging the presence or absence of gas leakage from the intensity of infrared rays detected by the infrared detecting means (R). An infrared irradiation control means (C) for operating the infrared irradiation means (E) when the gas leakage determination means (J) determines that the gas is leaked. ) Is provided for the gas leak monitoring device. 2. A filter (F) which transmits a bundle of rays in a band including the wavelength of the infrared ray for detection, and a light receiving element which receives the infrared ray which has passed through the filter (F). R1), and the infrared irradiation control means (C) is provided with a filter switching means (FC) for narrowing the band of the filter (F) when the infrared irradiation means (E) is actuated. The gas leakage monitoring device according to claim 1.