JP3256889B2 - Fire detection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fire detection system,
More specifically, the present invention relates to a fire detection system in which a temperature sensor made of an optical fiber is installed in a transport path for transporting a combustible substance such as coal to detect the occurrence of a fire or its precursor.

[0002]

2. Description of the Related Art For example, in a thermal power plant or a steel mill, coal discharged from a ship is transported several hundred meters by a belt conveyor.
Alternatively, they are transported to a boiler or coke oven several km away. As is well known, coal may ignite spontaneously due to heat storage. However, such a coal transportation path has not been provided with a means for detecting a fire. This is because the coal in the transport path emits water vapor by sprinkling water to suppress self-heating while releasing flammable gas,
This is because the environment in the transport path is extremely poor.

[0003]

As described above, there is a risk that spontaneous combustion will occur during the transportation of coal on the transport path, and attempts have been made to detect spontaneous ignition by installing a fire detector on the transport path. . However, dimming smoke detectors are suitable for long-distance monitoring, but cannot be used in dusty environments, and air-tube heat sensors have a limited measurement range. Since the distance is limited to about 100 m, it is difficult to arrange them all on a transport path that extends for several kilometers. For these reasons, it has been considered difficult to install a fire detector on a transport path for combustible substances such as coal, and this has not been realized.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and detects the temperature of a combustible substance being conveyed in spite of a bad environment, thereby generating a fire or a precursor thereof. It is an object of the present invention to obtain a highly reliable fire detection method capable of reliably detecting fire.

[0005]

In the fire detection system according to the present invention, an optical fiber is provided along the length direction of a flammable substance conveying path, and the optical fiber is scattered by light incident from one end of the optical fiber. Anomaly is detected by measuring the scattering position of the light using the echo, and measuring the temperature of the scattering position as a function of the temperature using the intensity ratio of the two echoes having different wavelengths due to the scattering of the light, An alarm or the like is issued as necessary.

In the fire detection system according to the present invention, an optical fiber is provided along the length direction of a combustible material conveying path, and an echo caused by scattering of light incident from one end of the optical fiber is used. Measure the light scattering position and the temperature at this position, calculate the average temperature of the line, and if the temperature of each part is higher than the temperature width set for the average temperature, determine that there is an abnormality, A warning or the like is issued in response. Further, in the fire detection method according to the present invention, an optical fiber is installed along the length direction of the flammable substance transport path, and light is reflected by using an echo caused by scattering of light incident from one end of the optical fiber. Measure the temperature of the scattering position and this position, compare the two temperatures for the left-right relationship based on the installation position of the optical fiber, and when both temperatures are different, judge that there is an abnormality or an abnormal sign, and if necessary, An alarm is issued.

In the above-described fire detection system, occurrence or sign of abnormality is detected in the following manner (1) to (3). (1) The average temperature of the line is calculated, and when the temperature of each part is higher than the temperature range set with respect to the average temperature, it is determined that there is an abnormality. (2) The two temperatures are compared with respect to the left-right relationship based on the installation position of the optical fiber, and if the two temperatures are different, it is determined that there is an abnormality or a sign of abnormality. (3) The two temperatures are compared in the vertical relationship based on the set position of the optical fiber, and when the temperature difference between the two exceeds a predetermined range or falls within a predetermined range, it is determined that there is an abnormality or a sign of abnormality.

Further, in the above fire detection system, the detection of abnormality is determined by the following (4) and (5) in addition to the above (1) to (3). From
If there is no content already included in the determination, one or more combinations are performed, and in some cases, one or more selected so as not to overlap the content is performed. (4) The threshold of the temperature rise rate is determined in advance,
When the measured temperature rise rate exceeds the above threshold value, it is determined that there is an abnormality. (5) A maximum temperature upper limit is set for the line, and when the temperature of each part is higher than the upper limit, it is determined that there is an abnormality.

[0009]

According to the present invention, an optical fiber is installed as a temperature sensor along the length of a transporting path along which a combustible substance such as coal is transported to detect the occurrence of a fire or its precursor. . Temperature sensors using optical fibers have developed rapidly due to recent technological innovations, but the principles and configurations of their measurements are not well known,
Here, the measurement principle will be described.

In the temperature sensor using an optical fiber, the entire length of one optical fiber is used as a temperature sensor, and the temperature sensor is used as a transmission line for detecting information. Is an epoch-making temperature sensor that can measure all at once.

The measurement principle of this temperature sensor will be described below with reference to the measurement principle diagram of FIG. 6 and the scattering phenomenon explanatory diagram of FIG. First, as shown in FIG. 6, when the incident pulse light 15 is incident from one end of the optical fiber 5, it propagates as transmitted light 16 in the optical fiber 5. Then, for example, a situation that causes a fire at the point A of the optical fiber 5 (for example,
When the temperature of the coal rises rapidly),
As shown in the figure, the thermal vibration of the glass occurs at point A, and the vibration between the atoms constituting the glass becomes larger than that at room temperature. Therefore, the Raman scattering having a different wavelength from the incident light depends on the temperature at that time. Light 19 is generated.

That is, in addition to the Rayleigh scattered light having the same wavelength as the wavelength λ ₀ of the incident light, two Raman scattered lights 19 having different wavelengths from the incident light are generated due to the interaction between the incident light and the thermal vibration of the glass. I do. The Raman scattered light 19 becomes a Stokes light (λ ₀ + λ) having a long wavelength when the incident light is deprived of energy by the vibration of the glass, and conversely, becomes an anti-Stokes light (λ ₀ -λ) having a short wavelength when the energy is obtained. Become.
Since the intensity of the Raman scattered light 19 depends on the vibration of the glass, that is, the temperature of the glass, the intensity of the Raman scattered light 19 increases as the temperature increases.

A part of the Raman scattered light generated in this way returns to the incident end again as back scattered light 17 as shown in FIG. From propagation time t to return to distance x,
That is, the distance from the incident end to point A can be measured. That is, the position where the temperature suddenly rises in the optical fiber 5 is identified, and the position can be detected. Therefore, 1
By setting up a monitoring unit that can monitor each optical fiber by installing one or more optical fibers and constructing a fire detection system that functionally integrates them, the occurrence of fire or abnormal rise in temperature and its The position can be accurately detected. In this case, light is used, but the principle is the same as radar using radio waves.

Therefore, if only the Raman scattered light 19 returning to the input end is separated and detected by the optical filter and its intensity is measured, the temperature at the point A can be measured. In addition,
In the present invention, two Raman scattered lights having different wavelengths are used together, and, for example, the intensity ratio is used as a function of temperature, so that the measurement accuracy can be improved.

[0015]

FIG. 3 is a block diagram showing the basic configuration of the present invention. The present invention comprises an optical fiber (sensor unit) 5, a measuring unit 6, and a calculator 7 including a CRT. In order to measure the temperature of a transport path on which a combustible substance such as coal (hereinafter referred to as coal) is mounted, a semiconductor laser 10 as a light emitting element is applied to an optical fiber 5 installed along the transport path by a pulse driving circuit 9. When the pulse light 15 from
The above-mentioned Raman scattered light is generated at the position where the transmitted light 16 passes,
A part thereof returns to the measuring unit 6 as backscattered light 17. The returned backscattered light 17 is separated into anti-Stokes light Ia and Stokes light Is by a filter in the optical demultiplexer 11,
Each of them is converted into an electric signal by the light receiving element 12, and the amplified
After being amplified in step 3, the signal is input to the high-speed averaging processor 14.
The high-speed averaging device 14 converts the data into a digital value for each sampling time and adds it to a memory corresponding to each sampling point (proportional to the distance). Then, the above operation is automatically repeated a predetermined number of times (integration processing).

At the last time (N times) of the integration processing, the integrated value in each memory is divided by N and averaged (this is referred to as averaging processing), thereby largely removing noise (background). I do. Then, the averaging processing value is input to the arithmetic unit 7, and the temperature is calculated from the intensity ratio of Ia and Is stored in each memory. Since each memory corresponds to the distance, the temperature distribution is finally obtained by this.
Display on RT8. From the temperature distribution data obtained in this way, it is possible to quickly and accurately detect the occurrence or possibility of fire of coal conveyed on the belt conveyor.

FIG. 4 is a diagram showing the relationship between the intensity ratio of Ia / Is (vertical axis) and the temperature (horizontal axis). The solid line indicates the logical value, and the circle indicates the experimental value. As is apparent from the figure, Ia
It can be seen that the intensity ratio of / Is is a function of temperature and is closely dependent. Therefore, the temperature distribution along the optical fiber 5 can be known by measuring the intensity of the Raman scattered light as a function of time after the incident pulse light 15 enters the optical fiber 5.

An optical fiber as a temperature sensor has a distance resolution (sensor unit length) of 1 m as detection sensitivity, a measurement temperature range of -50 ° C. to + 500 ° C., and a temperature accuracy of ± 1.
It has an excellent performance of ℃. In addition, the measuring unit 6 installed in the coal transport electric room has a high strength because of the stainless steel (SUS steel) structure, and can be operated without being affected by high temperature, high humidity and salt damage. It can be controlled collectively in the coal transportation control room, so monitoring and maintenance are easy.

FIG. 1 is a sectional view schematically showing an embodiment of the present invention, and FIG. 2 is a schematic explanatory view of a fire detection system. In the figure, 1 is a conveying path, 2 is provided on the upper part of the conveying path 1, and an upper belt conveyor on which coal is mounted and moves in the vertical direction of the paper surface, 3 is provided below the upper belt conveyor 2, and an upper belt conveyor is provided. The lower belt conveyor 4 that can move in the opposite direction of 2 and collect the coal dropped from the upper belt conveyor 2 is a bottom surface of the transport path 1.

Reference numerals 5a to 5f denote optical fibers serving as temperature sensors installed in the length direction of the transport path 1, and the optical fibers 5a to 5f.
Is installed on a fixed portion near one side (left side) of the upper belt conveyor 2 (LINE1), and the optical fiber 5b is also installed on a fixed portion near the other side (right side) (LINE2). The optical fiber 5c is installed on a fixed part near one side (left side) of the lower belt conveyor 3 (LINE3), and the optical fiber 5d is installed on a fixed part near the same other side (right side). (LINE4).
Further, the optical fiber 5e is installed near one side (left side) of the floor surface (LINE5), and the optical fiber 5f is also installed near the other side (right side) (LINE).
6).

In FIG. 2, reference numerals 5a to 5f denote optical fibers of LINE1 to LINE6 installed in the above-described transport path 1. 5 g (LINE7) is a spot detector 19
The spot optical fibers a to 19n are connected to detect the temperature of, for example, a belt conveyor driving device, a driving device main body surface, a bearing surface, and the like. The spot optical fiber 5g is not essential to the present invention and may be omitted, but the optical fibers 5a of LINE1 to LINE6 may be omitted.
5f may be provided around. . Reference numeral 20a denotes a termination box for connecting these optical fibers 5a to 5g to a plurality of optical fibers provided in the optical cable 21, respectively.
Reference numeral 0b denotes a termination box for connecting the optical fibers of the optical cable 21 to independent optical fibers.

In the present invention configured as described above,
The temperature of the coal conveying path 1 in the longitudinal direction is measured for each point by the optical cable 5 installed on the conveying path 1 based on the principle described with reference to FIG. 6, and a temperature state as shown in FIG. 5 is displayed on the CRT. . Then, the optical fibers 5a, 5b (LIN) installed near the upper belt conveyor 2 at this temperature, in particular,
The temperature detected by E1, 2) has a value substantially close to the temperature of the coal mounted on the upper belt conveyor 2.

In the above-described fire detection method, an abnormality (the occurrence of a fire or a precursor thereof) is determined by one or a combination of two or more of the following, and an alarm is issued. (1) Temperature rise rate The threshold of the temperature rise rate is set in advance, and the value obtained by dividing the temperature difference between the previously acquired data and the current acquired data by the data acquisition cycle (therefore, the temperature rise rate) is as follows. If the threshold value is exceeded, it is determined to be abnormal. (2) Relative temperature abnormality The average temperature is calculated for each line of each system, and if the temperature of each part is higher than the temperature range set with respect to the average temperature, it is determined that the temperature is abnormal.

(3) Absolute Temperature Abnormality The maximum temperature upper limit is set for each line of each system, and if the temperature of each section is higher than the upper limit, it is determined that the temperature is abnormal. (4) Abnormal left and right temperature The two temperatures are compared in a right and left relationship based on the installation position of the optical fiber. (5) Abnormal upper and lower temperature Compare the upper and lower temperatures based on the installation position of the optical fiber, and if the temperature difference between the two exceeds a predetermined range or falls within a predetermined range, it is determined that there is an abnormality or a sign of abnormality. I do.

In the above embodiment, the present invention is applied to the case where coal is transported by a belt conveyor. However, the present invention can be applied to the case where flammable substances other than coal are transported by a belt conveyor. it can. In addition, although the case where a total of six optical fibers are installed facing each other on both sides of the transport path is shown, the number and the installation location of the optical fibers are not limited to this, and for example, the ceiling part may be appropriately selected. Can be.

[0026]

As described above in detail, in the fire detection system according to the present invention, an optical fiber is installed along the length direction of the flammable substance conveying path, and light is incident from one end of the optical fiber. Abnormality is measured by measuring the scattering position of light using the echo due to the scattering of light, and measuring the temperature at the scattering position as a function of temperature using the intensity ratio of the two echoes having different wavelengths due to the light scattering. Since the detection is performed, a fire detection method with high reliability and high measurement accuracy can be obtained. In addition, the optical fiber has excellent corrosion resistance, so it can be installed in places where corrosive substances exist.In addition, since it does not use electricity, there is no need to take explosion-proof measures, and where there is flammable gas. Can also be installed.

Further, the detection of the abnormality or the precursor of the abnormality includes the relative temperature abnormality, the left and right temperature abnormality, the vertical temperature abnormality, the temperature rise rate,
If there is no content already included as the content of judgment from among all five judgment contents of the absolute temperature abnormality, one or more are combined, and in some cases, one or more selected so as not to overlap with the contents are combined The occurrence of a fire or its precursor can be reliably detected.

[0028]

[Brief description of the drawings]

FIG. 1 is a sectional view schematically showing an embodiment of the present invention.

FIG. 2 is a schematic explanatory diagram of a fire detection system according to the present invention.

FIG. 3 is a block diagram showing a basic configuration of the present invention.

FIG. 4 is a diagram showing the relationship between the intensity ratio of Ia / Is and temperature.

FIG. 5 is a diagram illustrating an example of a temperature state of each system of the optical fiber.

FIG. 6 is a diagram illustrating the principle of measuring temperature using an optical fiber.

FIG. 7 is an explanatory diagram of the light scattering phenomenon of FIG. 6;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Conveyance path 2 Upper belt conveyor 3 Lower belt conveyor 4 Floor surface 5-5f Optical fiber 6 Measuring unit 7 Computing unit 8 CRT

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-62-240833 (JP, A) JP-A-5-266373 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G08B 17/06 G01K 11/12 G08B 25/01

Claims (5)

(57) [Claims] An optical fiber is provided along the length direction of a combustible material conveying path, and a scattering position of the light is measured by using an echo caused by scattering of light incident from one end of the optical fiber. Along with the two echoes having different wavelengths due to the light scattering, the intensity ratio is measured as a function of the temperature, and the temperature at the position is measured to detect an abnormality, and if necessary, an alarm or the like is issued. Fire detection method. 2. An optical fiber is installed along a length direction of a transport path of a combustible substance, and the light scattering position and the position are scattered by using an echo caused by scattering of light incident from one end of the optical fiber. Measure the temperature of the line, calculate the average temperature of the line, and if the temperature of each part is higher than the set temperature range with respect to the average temperature, determine that there is an abnormality, and issue an alarm etc. as necessary. Features a fire detection method. 3. An optical fiber is provided along the length direction of the combustible material conveying path, and the light scattering position and the light scattering position are reflected by using an echo caused by scattering of light incident from one end of the optical fiber. Is measured, the two temperatures are compared for the left-right relationship based on the installation position of the optical fiber, and when the two temperatures are different, it is determined that there is an abnormality or a sign of abnormality, and an alarm or the like is issued as necessary. A fire detection system characterized by the following. 4. An optical fiber is provided along a length direction of a transport path of a combustible material, and the light scattering position and the position are scattered using an echo caused by scattering of light incident from one end of the optical fiber. Are measured, and the temperatures of the two are compared in a vertical relationship based on the set position of the optical fiber, and when the temperature difference between the two exceeds a predetermined range or falls within a predetermined range, an abnormality or an abnormal sign is detected. A fire detection method that determines that there is a fire and issues an alarm, etc. as necessary. 5. The method according to claim 1, wherein a threshold value of a temperature rise rate is set in advance, and when the measured temperature rise rate exceeds the threshold value, a first determination is made to determine that there is an abnormality. The average temperature of the line is calculated. If the temperature of each part is higher than the temperature range set with respect to the average temperature, it is determined that the temperature is abnormal. When the temperature is higher, a third judgment is made to judge that there is an abnormality. In the left-right relation based on the installation position of the optical fiber, the two temperatures are compared. , Comparing the upper and lower temperatures based on the set position of the optical fiber,
When the temperature difference between the two exceeds the predetermined range or falls within the predetermined range, it is determined that there is an abnormality or an abnormal sign.
If there is no content already included as the content of the judgment, perform at least one of the five contents of the judgment, and combine one or more selected so as not to overlap with the content. 2. The method according to claim 1, wherein
The fire detection method according to claim 4.