JPH07167735A - Gas leakage detector - Google Patents

Abstract

PURPOSE:To detect flammable gas leakage position leakage gas concentration, and to grasp leakage gas diffusion condition without requiring a complex wiring over a wide range and without malfunction. CONSTITUTION:The title detector consist of a temperature sensor 7 consisting of an optical fiber, a heat-resistance covering layer 8 provided at the temperature sensor 7, a plurality of detection parts 9 which are mounted with a specific spacing along the temperature sensor 7 via the heat resistance covering layer 8, a power supply for feeding power to the detection part 9, and a gas leakage position estimator. The detection part 9 consists of a heat build-up coil 10 which is wound around the heat resistance covering layer 8, a covering material 11 for covering the surrounding of the heat build-up coil 10, and an oxidation catalyst layer 12 formed on the surface of the covering material 11 as needed. The gas leakage position estimator enables light signal to enter the temperature sensor 7 while the detection part 9 is heated by the heat build-up coil 10, receives scattered light which is reflected, and detects the temperature increases of the detection part 9 due to the contact of flammable gas with the oxidation catalyst layer 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas leak detection device,
In particular, the present invention relates to a gas leak detection device capable of detecting a leak position of a flammable gas, a leak gas concentration, and a grasp of a leak gas diffusion state over a wide range without malfunction without providing complicated wiring.

[0002]

2. Description of the Related Art A conventional leak detection device for flammable gas such as methane (prior art) will be described with reference to the drawings. FIG. 3 is a schematic perspective view showing a conventional gas detector, and FIG.
FIG. 3 is a circuit diagram of a conventional technique.

In FIGS. 3 and 4, reference numeral 1 denotes a gas detector, which is formed on a platinum coil 2, a covering material 3 made of sintered alumina around the coil 2, and a surface of the covering material 3. And an oxidation catalyst layer 4 made of platinum, palladium, or the like.

When a flammable gas such as methane comes into contact with the detection unit 1 in a state where the detection unit 1 is heated to a temperature of 300 ° C. to 400 ° C., an oxidation reaction occurs due to the action of the oxidation catalyst layer 4, and the temperature of the coil 2 rises. Rises. As a result, the electric resistance of the coil 2 increases.

As shown in FIG. 4, the detecting section 1 is connected to a bridge circuit 6 incorporating a compensating element 5. Therefore, the gas leakage is detected by the voltage change.

[0006]

However, the above-mentioned prior art has the following problems. To monitor the gas leakage over a wide range, a huge number of detectors 1 are required. If there are many detectors 1, the length of the lead wire becomes too long,
Since the voltage drop increases, malfunction and detection accuracy are degraded. If the number of detection units 1 is large, the wiring becomes complicated and it becomes difficult to secure a wiring place. Since the gas leakage is captured as a voltage change, malfunction due to the influence of electrical noise is likely to occur.

Therefore, an object of the present invention is to detect a leak position of a flammable gas, detect a leak gas concentration, and grasp a leak gas diffusion state over a wide range without erroneous operation without complicated wiring. To provide a device.

[0008]

The present invention is directed to a temperature sensor made of an optical fiber, a heat-resistant coating layer provided around the temperature sensor, and a predetermined interval along the temperature sensor via the heat-resistant coating layer. A heating coil wound around the heat-resistant coating layer, a coating material surrounding the heating coil, and an oxidation catalyst layer formed on the surface of the coating material as necessary. The gas leakage position estimator comprises a plurality of detection units, a power supply for energizing the heating coil of each of the detection units, and a gas leakage position estimator provided at one end of the temperature sensor. In the state where each of the parts is heated by the heating coil, an optical signal is incident on the temperature sensor, reflected scattered light is received, and the detection is performed by the flammable gas touching the oxidation catalyst layer. Detecting the temperature rise of, thus, the leakage position of the combustible gas, and it has the characteristics to be estimated gas concentrations, the diffusion state.

[0009]

When the combustible gas comes into contact with the oxidation catalyst layer formed on the surface of the detection portion, the catalyst action causes an oxidation reaction to raise the temperature of the detection portion. By this temperature rise,
The detection delay time and intensity of scattered light in the optical fiber temperature sensor to which the detector is attached vary. Therefore,
By measuring the detection delay time and intensity of the scattered light, it is possible to estimate the flammable gas leak position, the leak gas concentration, and the leak gas diffusion state.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the gas leakage detection device of the present invention will be described with reference to the drawings.

FIG. 1 is a partial perspective view showing an embodiment of the gas leakage detection device of the present invention. In FIG. 1, 7
Is a temperature sensor made of an optical fiber, and 8 is a heat resistant coating layer made of carbon and polyamide, which is provided around the temperature sensor 7, and has a heat resistant temperature of about 300 ° C. Reference numeral 9 designates a plurality of detection units which are attached along the optical fiber temperature sensor 7 via the heat resistant coating layer 8 at intervals of about 5 m. Each of the detection units 9 is wound around the heat-resistant coating layer 8 and has a heating coil 10 made of nichrome wire and having a coil width of about 5 mm, a coating material 11 made of sintered alumina covering the heating coil 10, and a coating. Oxidation catalyst layer 1 made of platinum, palladium, or the like formed on the surface of the material 11.
It consists of 2.

The heating coils 10 are connected to each other by a conductive wire 13, and each heating coil 1 is connected from a power source (not shown).
Current is supplied to 0. A gas leak position estimator (not shown) is connected to one end of the temperature sensor 7. The gas leakage position estimator causes an optical signal to enter the temperature sensor 9 in a state where each of the detection units 9 is heated by the heating coil 10.
The reflected scattered light is received, and the temperature rise of the detection unit 9 due to the oxidation reaction caused by the contact of the combustible gas with the oxidation catalyst layer 8 is detected, and thus, the leakage position of the combustible gas, the gas concentration, the gas It has the function of estimating the diffusion state. Details of the gas leakage position estimator will be described later.

By mounting the above-described gas leakage detection device of the present invention along, for example, a pipeline, the flammable gas leakage position, the gas concentration, and the gas diffusion state can be estimated with high accuracy, that is, the power source. To each heating coil 10
Is energized to heat the detection unit 9 to about 300 ° C. When a combustible gas such as methane contacts the oxidation catalyst layer 12 in this state, the temperature of the detection unit 9 rises due to the reaction heat of the oxidation reaction due to the action of the catalyst. The gas leak position estimator estimates the leak position, gas concentration, and diffusion state of the flammable gas based on this temperature change.

In the above-mentioned embodiment, the detecting unit 9 is
Although attached at intervals of about 5 m, the detection unit 9 may be attached over the entire length of the optical fiber temperature sensor 7,
This makes it possible to detect the gas leakage position and grasp the gas diffusion state with higher accuracy.

When the oxidation catalyst layer 12 is not formed on the surface of the coating material 11 of the detection part 9, the flammable gas is not present on the oxidation catalyst layer 12 because the thermal conductivity of air and the flammable gas are different. When they come into contact with each other, heat is taken away, and the temperature of the detection unit 9 drops. Therefore, also in this case, it is possible to estimate the leak position, the gas concentration, and the diffusion state of the combustible gas, as in the above-described embodiment.

Next, an example of the gas leakage position estimator will be described with reference to the drawings. FIG. 2 is a circuit diagram of the gas leakage position estimator. In FIG. 2, 14 is a pulse drive circuit, 15 is a light emitting element that converts a pulse signal from the pulse drive circuit 14 into an optical pulse, and 16 is a light emitting element 15
This is a directional coupler in which the optical pulse converted by is incident on the temperature sensor 7 made of an optical fiber.

Reference numerals 17 and 18 denote interference filters, which reflect the Raman scattered light having temperature information, which is reflected in the temperature sensor 7 after the light pulse is incident and returned through the directional coupler 16, with the Stokes light. It has the function of splitting into Stokes light. Reference numerals 19 and 20 denote interference filters 17, 1
It is an optical detection element such as, for example, an avalanche photodiode, which converts Stokes light and anti-Stokes light from 8 into individual electric signals. Reference numeral 21 is an averaging processing means. The averaging processing means 21 causes fluctuations caused by the Raman scattered light itself being a very weak signal, and S / due to shot noise and thermal noise of the photodetector elements 19 and 20.
It has the function of improving N. 22 is a data processing means. The data processing means 22 includes the pulse drive circuit 14
After receiving the pulse generation timing signal from, the position where scattered light is generated is determined from the delay time until Raman scattered light is detected, and the temperature is determined from the intensity of scattered light. And 23 is a display for displaying data such as a temperature distribution state.

According to the gas leak position estimator described above, the leak position, the gas concentration, and the diffusion state of the flammable gas can be estimated as follows. That is, when the pulse drive circuit 14 generates a pulse signal, the light emitting element 15 converts the pulse signal into an optical pulse. This light pulse
It is incident on the optical fiber temperature sensor 7 through the directional coupler 16. On the other hand, the pulse drive circuit 14 sends the pulse signal or the pulse generation timing signal to the averaging processing means 21 and the data processing means 22 at the same time as sending the pulse signal to the light emitting element 15. When a light pulse enters the temperature sensor 7, the Raman scattered light whose intensity changes depending on the temperature is
The light is reflected in the temperature sensor 7 and enters the interference filters 17 and 18 through the directional coupler 16. The interference filters 17 and 18 separately separate the Stokes light and the anti-Stokes light from the Raman scattered light. Photodetector element 19,
20 converts the Stokes light and the anti-Stokes light into electric signals. The averaging processing means 21 averages these electric signals and sends them to the data processing means 22.

The data processing means 22 performs the following processing. That is, assuming that the speed of light in the optical fiber temperature sensor 7 is known, for example, the following equation L = (C / 2n) · Δt, where C: the speed of light in vacuum, n: the refractive index of the optical fiber temperature sensor 7, Δt: The time from the receipt of the pulse generation timing signal from the pulse drive circuit 14 to the detection of Raman scattered light. The distance (L) from the reference position to the scattering position of the Raman scattered light is calculated according to the calculation formula shown by.

On the other hand, the temperature value detected by the optical fiber temperature sensor 7 is obtained from the intensity ratio of Stokes light and anti-Stokes light.

As described above, the temperature distribution can be obtained by sequentially obtaining the distance (L) and the temperature for each predetermined cycle. From the thus obtained temperature distribution, the leak position of the flammable gas can be obtained. Can be detected.

[0022]

As described above, according to the present invention, since it is only necessary to attach the detection section to the optical fiber temperature sensor, it is possible to detect the flammable gas leak position, the leak gas concentration and the leak gas diffusion state. A useful effect is that it can be performed over a wide range without malfunction without providing complicated wiring.

[Brief description of drawings]

FIG. 1 is a partial perspective view showing an embodiment of a gas leakage detection device of the present invention.

FIG. 2 is a circuit diagram of a gas leakage position estimator in the gas leakage detection device of the present invention.

FIG. 3 is a schematic perspective view showing a conventional gas detector.

FIG. 4 is a prior art circuit diagram.

[Explanation of symbols]

 1: Gas detection part, 2: Coil, 3: Coating material, 4: Oxidation catalyst layer, 5: Compensation element, 6: Bridge circuit, 7: Temperature sensor, 8: Heat resistant coating layer, 9: Detection part, 10: Heat generation Coil, 11: Coating material, 12: Oxidation catalyst layer, 13: Conductive wire, 14: Pulse drive circuit, 15: Light emitting element, 16: Directional coupling property, 17, 18: Interference filter, 19, 20: Photodetection element, 21: averaging processing means, 22: data processing means, 23: display.

Claims (3)

[Claims] 1. A temperature sensor formed of an optical fiber, a heat-resistant coating layer provided around the temperature sensor, and a heat-resistant coating layer, which is attached along the temperature sensor at a predetermined interval. A plurality of detection units each including a heating coil wound around a heat-resistant coating layer, a coating material covering the periphery of the heating coil, and an oxidation catalyst layer formed on the surface of the coating material, and each of the detection units. Of a power supply for energizing the heating coil and a gas leakage position estimator provided at one end of the temperature sensor, the gas leakage position estimator in a state where each of the detection units is heated by the heating coil. , An optical signal is made incident on the temperature sensor, and reflected scattered light is received to detect a temperature rise of the detection unit due to the contact of the combustible gas with the oxidation catalyst layer, and thus, the combustible gas. A gas leakage detection device, which estimates a gas leakage position, a gas concentration, and a diffusion state. 2. A temperature sensor made of an optical fiber, a heat resistant coating layer provided around the temperature sensor, and a heat resistant coating layer provided at a predetermined interval along the temperature sensor. A heat-generating coil wound around a heat-resistant coating layer, and a plurality of detection units each including a coating material that covers the periphery of the heat-generating coil, a power supply for energizing each heat-generating coil of each of the detection units, and the temperature sensor. And a gas leak position estimator provided at one end of the gas leak position estimator, wherein the gas leak position estimator causes an optical signal to enter the temperature sensor and is reflected in a state where the detector is heated by the heating coil. Receiving scattered light, detecting the temperature change of the detection unit due to the flammable gas touching the detection unit,
Thus, the gas leak detection device is characterized by estimating the leak position, the gas concentration, and the diffusion state of the flammable gas. 3. The detection unit is attached over the entire length of the temperature sensor.
Alternatively, the gas leakage detection device described in 2.