JP3482568B2 - 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 silo that stores a combustible substance such as coal to detect the occurrence or precursor of a fire.

[0002]

2. Description of the Related Art For example, it is desirable to install a temperature sensor or a fire detector for detecting a fire or its precursor in a silo that stores heat and stores coal that is at risk of spontaneous combustion. Until now, there have been no examples of installing such temperature sensors or fire detectors. This is because the loaded coal is stored by dropping it from the top, and since the internal state is unknown from the surface, it is carried out from the bottom and dropped from the top in a few days without considering spontaneous ignition. It seems that this was because the work of storing the product was repeated. Further, even if a temperature sensor or a fire detector is installed in the silo, it is difficult to realize it due to problems in strength and wiring.

[0003]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
It is also possible to detect the occurrence of a fire by installing a photoelectric separated smoke sensor consisting of a light projecting unit and a light receiving unit above the silo. However, when installing the photoelectric separation type smoke detector, it is necessary to solve the problems of explosion-proof structure, measures against pollution of the light emitting part and the light receiving part, securing of maintenance passages, etc. Met.

The present invention has been made to solve the above-mentioned problems, and it is not necessary to consider problems such as an explosion-proof structure, antifouling measures, and maintenance passages, and it is possible to reliably detect a temperature change of a stored combustible substance. Then, it aims at obtaining the highly reliable fire detection system which can detect the occurrence of a fire or its precursor.

[0005]

A fire detection system according to the present invention is a system in which light is incident from one end of an optical fiber as a temperature sensor installed on the lower surface of a dispensing portion of a silo in which flammable substances are stored. The occurrence of a fire or its precursor is detected by measuring the scattering position and the temperature at that position by utilizing the scattering echo of.

Further, in the above fire detection system, an optical fiber is installed on the lower surface of the top of the hopper of the dispensing part of the silo. Further, in the above fire detection method, two echoes having different wavelengths are used, and the intensity ratio thereof is a function of temperature.

[0007]

According to the present invention, an optical fiber is installed as a temperature sensor on the lower surface of the dispensing portion of a silo in which flammable substances such as coal are stored so that a fire or its precursor can be detected. A temperature sensor using an optical fiber has made rapid progress due to recent technological innovations, but the principle and configuration of its measurement are not well known, so the measurement principle will be described here.

In the temperature sensor using an optical fiber, the entire length of one optical fiber is used as a temperature sensor, and it is also used as a transmission line for detection information, so that the temperature distribution over the entire length from one end to the other end of the optical fiber. It is an epoch-making temperature sensor that can measure all at once.

Therefore, the measurement principle of this temperature sensor will be described below with reference to the measurement principle diagram of FIG. 5 and the scattering phenomenon diagram of FIG. First, as shown in FIG. 5, when the incident pulsed light 15 is made incident from one end of the optical fiber 5, it propagates in the optical fiber 5 as transmitted light 16. Then, for example, a situation that causes a fire at point A of the optical fiber 5 (for example,
(When the temperature of coal rises sharply),
As shown in Fig. 5, thermal vibration of the glass occurs at point A, and the vibration between the atoms that make up the glass becomes larger than that at room temperature. 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 by the interaction between the incident light and the thermal vibration of the glass. To do. The Raman scattered light 19 becomes Stokes light with a long wavelength (λ ₀ + λ) when the incident light loses energy due to the vibration of the glass, and conversely becomes short Stokes light (λ ₀ -λ) with the energy. 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 rises.

Raman scattered light 19 generated in this way
As shown in FIG. 5, a part of the light returns to the incident end as backscattered light 17. The distance x from the propagation time t until returning, that is, the distance from the incident end to the point A can be measured. That is, in the optical fiber 5, the position where the temperature suddenly rises is identified, and the position can be detected. Therefore, by installing one or more optical fibers, forming a monitoring unit that can monitor each optical fiber, and configuring a fire detection method that functionally integrates these, a fire occurrence or temperature abnormality can be detected. The rise and its position can be accurately detected. In this case, light is used, but the principle is the same as the radar using radio waves.

Therefore, the temperature at point A can be measured by separating and detecting only the Raman scattered light returning to the input end with an optical filter and measuring the intensity thereof. In the present invention, two Raman scattered lights having different wavelengths are used together,
For example, since the intensity ratio is used as a function of temperature, the measurement accuracy can be improved.

[0013]

FIG. 3 is a block diagram showing the principle of the present invention. The present invention comprises an optical fiber (sensor section) 5, a measuring section 6 and a computing unit 7 including a CRT. In order to measure the temperature in the silo in which a flammable substance such as coal (hereinafter referred to as coal) is stored, the optical fiber 5 installed on the lower surface of the payout unit is provided with a light emitting element 10 such as a semiconductor laser by a pulse drive circuit 9. When the pulsed light 15 from is input, the Raman scattered light described above is generated at the passing position of the transmitted light 16, and a part of the Raman scattered light returns to the measurement 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 which is converted into an electric signal by the light receiving element 12, amplified by the amplification circuit 13, and then amplified by the processing device 14. input. The processing unit 14 converts it into a digital amount at each sampling time and adds it to the 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 final time (N times) of this integration processing, the integrated value in each memory is divided by N and averaged (this is called averaging processing), so that noise (background) is largely removed. To do. Then, the averaged value is input to the calculator 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 from this, so the temperature distribution of coal in the silo along the optical sensor 5 is displayed on the display 8 from this data. With the data of the temperature distribution thus obtained, the occurrence or possibility of fire of coal stored in the silo can be detected quickly and accurately.

FIG. 4 is a diagram showing the relationship between the intensity ratio (vertical axis) of Ia / Is and the temperature (horizontal axis). The solid line shows a logical value and the circles show experimental values. As is clear 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 these Raman scattered lights as a function of time after the incident pulsed light 15 is incident on the optical fiber 5.

The optical fiber as a temperature sensor has a distance resolution (sensor unit length) as a detection sensitivity of 1 m, 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 hopper has a strong strength because it is made of stainless steel (SUS steel), and it can be operated without being affected by high temperature and high humidity and salt damage. Since it can be collectively controlled by, monitoring and maintenance are easy.

FIG. 1 is a schematic view of an embodiment of the present invention, and FIG. 2 is a sectional view taken along line AA. In the figure, reference numeral 1 is a silo, a dispensing unit 2 having a plurality of hoppers 3 is provided in the lower portion, and coal is stored inside. Reference numeral 4 is a dispensing machine for dispensing the coal in the silo 1. Reference numeral 5 denotes an optical fiber as a temperature sensor installed on the lower surface of the top of the hopper 3 of the payout unit 2. For example, as shown in FIG. 2, one optical fiber 5 is bent and installed. In the examples, an optical fiber was used in which the optical fiber core wire was coated with a stainless steel metal tube having a thickness of 0.2 mm and an outer diameter of about 2.4 mm.

In the present invention constructed as described above,
The temperature of the lower part of the silo 1 depends on the optical cable 5 installed on it.
Is measured for each point based on the principle explained in FIG. 5, and the state of this temperature is displayed on the CRT. And
This temperature is almost the same as the temperature of the coal stored in the lower part of the silo 1 which is the oldest and is prone to spontaneous combustion.

In the fire detection system as described above, an abnormality (fire occurrence or its precursor) is determined by one or a combination of two or more of the following, and an alarm is issued. (1) Temperature rise rate The temperature rise rate threshold is set in advance, and the value obtained by dividing the temperature difference between the previously acquired data and this time acquired data by the data acquisition cycle (hence the humidity increase rate) is If it exceeds the threshold value, it is judged as abnormal.

(2) Abnormal relative temperature The average temperature of each part is calculated, and when the temperature of each part is higher than the temperature range set with respect to the average temperature, it is judged to be abnormal. (3) Absolute temperature abnormality The maximum temperature upper limit of each part is set in advance, and when the temperature of each part is higher than the upper limit value, it is determined to be abnormal.

[0021]

As described in detail above, the fire detection system according to the present invention is capable of producing an echo due to the scattering of light incident from one end of the optical fiber installed on the lower surface of the discharge part of the silo storing the combustible substance. By measuring the light scattering position and the temperature at that position to detect the occurrence or precursor of a fire, the stored flammability is considered without considering problems such as explosion-proof structure and pollution control. It is possible to reliably detect the occurrence or precursor of a fire of a substance, and to obtain a highly reliable fire detection system. Further, since the optical fiber has excellent corrosion resistance, it can be installed in a place where a corrosive substance exists, and since it does not use electricity, it can also be installed in a place where a flammable gas exists.

Further, since the optical fiber is installed on the lower surface of the top of the hopper of the dispensing part of the silo, the optical fiber can be present at the position closest to the stored combustible substance. Therefore, the degree of heat storage due to fluctuations in the heat of the combustible substance stored in the silo can be reliably grasped, and the occurrence or precursor of a fire can be detected with high accuracy.

Furthermore, since the intensity ratio of two echoes having different wavelengths is used as a function of temperature, the measurement accuracy can be further improved.

[Brief description of drawings]

FIG. 1 is a schematic view of an example of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a block diagram showing the 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 principle diagram of temperature measurement by an optical fiber.

6 is an explanatory diagram of a light scattering phenomenon of FIG.

[Explanation of symbols]

1 silo 2 Disbursement department 3 hoppers 5 optical fiber 6 measuring section 7 arithmetic unit 8 CRT

Claims (3)

(57) [Claims] 1. An optical fiber is installed on a lower surface of a payout portion of a silo in which a combustible substance is stored, and an echo caused by scattering of light incident from one end of the optical fiber is utilized to determine the scattering position of the light and the A fire detection system characterized by detecting the occurrence of a fire or its precursor by measuring the temperature at a location. 2. The fire detection system according to claim 1, wherein an optical fiber is installed on the lower surface of the top of the hopper of the dispensing part of the silo. 3. The fire detection system according to claim 1, wherein two echoes having different wavelengths are used and the intensity ratio thereof is a function of temperature.