JPH0610030B2 - Fire detection device for floating roof tank - Google Patents

Description

The present invention relates to a fire detection device for a floating roof tank.

[Prior art] The number of oil storage tanks installed outdoors that have floating roof type oil storage tanks in Japan is more than one hundred, and these storage tanks can minimize damage in the event of a fire. It is obligatory to install fire extinguishing equipment for this purpose, but the present situation is that there is no equipment for detecting fire.

For this reason, in the past, when fire smoke or the like appeared on the upper part of the storage tank, it was necessary to climb up to the top wind girder to see the fire from the outside and to confirm the position and range of the fire. It is the current situation that a dangerous method such as visual confirmation from a high place in the immediate vicinity of the tank by other methods must be taken.

However, this method is uncertain because everything is checked visually, and it takes a certain amount of time to confirm the fire. There is a problem that the damage is expanded by delaying the period.

For this reason, various fire detection devices have been studied in recent years, but an electrical detection device cannot be applied to the storage tank for safety reasons, and therefore an alarm using an inert gas such as a halide is used. Fire extinguishing equipment with a signal generator is considered. In this system, for example, a gas discharge nozzle connected to a storage container containing an inert liquefied gas is housed in a pressure-resistant glass container, and the pressure-resistant glass container is destroyed by temperature rise due to flame or the like. Thus, the level switch detects that the inert gas is discharged from the nozzle and the liquid level of the liquefied gas in the storage container is lowered, and a fire alarm signal is issued.

[Problems to be Solved by the Invention] However, even in the detection method using the above-mentioned inert gas,
It is technically difficult to cause the pressure-resistant glass container to break due to factors other than flame, such as vibration, or to malfunction, and it is technically difficult to break it at a uniform set temperature, and more than one of the above facilities are arranged in the circumferential direction of a large storage tank. Doing so has a problem of making the entire equipment very expensive.

Further, even if the above equipment is installed, it is not possible to know the position, range, etc. of the fire, and therefore it is not possible to intensively extinguish the fire-occurring portion and effectively extinguish it.

The present invention focuses on the above-mentioned conventional problems, and a fire detection device having an optical fiber sensor wound around the seal portion on the outer periphery of a floating roof constantly raises the temperature and temperature of the seal portion at a position away from the tank. In case of fire, display the range and position without human error, or give an operation signal to automatic fire extinguishing equipment as well as a fire alarm so that appropriate and prompt initial fire extinguishing activities can be performed. It is an object.

[Means for Solving the Problem] The present invention relates to an optical fiber sensor arranged along a seal portion of a floating roof tank, a laser oscillator for injecting pulsed light from an end portion of the optical fiber sensor, and a laser oscillator from the laser oscillator. It is characterized by comprising a computing device for computing the distance and temperature of the optical fiber based on Raman backscattered light returning from the optical fiber sensor upon incidence of pulsed light, and a display device for displaying the computation result of the computing device. The optical fiber sensor is arranged in a zigzag shape, and a disaster prevention monitoring board for outputting an alarm signal is connected to the arithmetic unit. is there.

[Operation] When the pulsed light from the laser oscillator is incident on the optical fiber sensor circulated in the seal part of the floating roof tank, the distance between each part of the optical fiber sensor is determined based on the Raman backscattered light returned from each part of the optical fiber sensor. The temperature is calculated by the calculation device, and the temperature of each part of the optical fiber sensor is displayed on the display device. Therefore, it is possible to know the occurrence of fire from the temperature rise and the rising position of the optical fiber sensor. At this time, if the optical fiber sensors are arranged in a zigzag shape, it is difficult to break the wire, and the distance can be increased to detect the position with higher accuracy. Further, an alarm signal can be output by the disaster prevention monitoring board based on the calculation result.

[Examples] Examples of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention, in which an optical fiber sensor 2 is arranged along a portion of a floating roof tank (4 in the figure) 1 where a fire is likely to occur (in the case of the illustration, 4 floating roof tanks are provided). 1
Are sequentially arranged in series), and the optical fiber sensor 2
Is connected to the temperature detecting device 3.

The temperature detecting device 3 guides the pulsed light G oscillated by the laser oscillator 4 to one end of the optical fiber sensor 2 via the optical fiber 5 and the optical branching device 6, and the optical branching device 6 receives light. Another optical branching device 8 via the fiber 7
2 are connected to the optical branching device 8 through the optical fibers 9 and 10 and the interference filters 11 and 12 for extracting the anti-Stokes light and the Stokes light, respectively, to convert the respective optical signals into electrical signals.
Two photodetectors 13 and 14 are connected.

In addition, the photodetectors 13 and 14 include 2-channel analog
A digital converter 15 is connected, and an arithmetic unit is connected to the 2-channel analog / digital converter 15.
16 is connected, and a display device 17 is connected to the arithmetic unit 16. Reference numeral 18 in the figure denotes a disaster prevention monitoring board which is connected to the arithmetic unit 16 and outputs an alarm signal 19.

When the laser light is pulsed from the laser oscillator 4 and introduced into the optical fiber sensor 2 through the optical fiber 5 and the optical branching device 6, as the pulsed light G propagates through the optical fiber sensor 2, each part of the optical fiber sensor 2 Therefore, the backscattered light E returns in the opposite direction to the pulsed light G.

The backscattered light E is the anti-Stokes light 20 as shown in FIG.
And a Stokes light 21 consisting of Raman backscattered light and Rayleigh scattered light 22, and the light quantity ratio of the anti-Stokes light 20 and the Stokes light 21 is known to depend on temperature as shown in the following formula (I). ing.

h: Planck's constant k: Boltzmann's constant c: Speed of light in optical fiber Ia: Anti-Stokes light intensity Is: Stokes light intensity T: Absolute temperature Therefore, the backscattered light E is extracted by the optical branching device 6 and the optical fiber 7 is used. To the interference filters 11 and 12 to extract the anti-Stokes light 20 and the Stokes light 21, and the respective light 20 and 21 to the photodetectors 13 and 14, respectively. To an electric signal, and further, via a 2-channel analog / digital converter 15, an arithmetic unit 16
Then, the calculation of the above formula (I) is performed.

FIG. 3 shows the amount of the anti-Stokes light 20 of the backscattered light E as an example, and the anti-Stokes light 20 ₁ returns to the pulsed light G ₁ at the Z ₁ point in FIG. _The anti-Stokes light 20 ₂ returns to the pulsed light G ₂ at the _two points, and 20 ₁ returns earlier than 20 ₂ so that the position Z ₁ ′,
Z ₂ ′ corresponds to the points Z ₁ and Z ₂ .

Also, for example, if there is a fire at Z ₃ and the temperature becomes high,
Occur at positions Z _{3 'to} the anti-Stokes light stronger than other points correspond to Z ₃ point.

Therefore, since the time in FIG. 3 corresponds to the distance of the optical fiber sensor 2 in FIG. ₁ , the intensities of the anti-Stokes light 20 ₁ and the anti-Stokes light 20 ₂ incident on the photodetector 13 are time-series. Measurement is performed, and the Stokes light incident on the photodetector 14 is also measured in the same manner, and the arithmetic unit 16 calculates the equation (I) to determine the distance according to the distance of the optical fiber sensor 2. You can know the temperature distribution.

Display the relationship between the distance and temperature calculated by the arithmetic unit 16
By displaying a graph or numerical value on 17, it is possible to inform the observer of the occurrence of the fire and the location of the fire depending on the temperature change and the changing position, and further output the alarm signal 19 via the disaster prevention monitoring board 18. It is possible to operate various disaster prevention and fire fighting equipment manually and automatically, and to notify the fire department of the occurrence of a fire so that fire fighting activities can be carried out very early.

Further, when the above-mentioned optical fiber sensor 2 is cut, the intensity of the backscattered light E at the cutting position becomes extremely large as shown in FIG. 4, and the backscattered light does not return after that point. By looking at the intensity of the backscattered light E, the disconnection of the optical fiber sensor 2 and its disconnection position can be known.

FIG. 5 shows another embodiment of the present invention, in which pulsed light is emitted from either side 2 ', 2 "of the optical fiber sensor 2 in the floating roof tank 1 via the optical fiber switch 23. Temperature detector 3 so that Raman backscattered light can be measured by entering
Are connected, and if this is done, for example, Z ₄
Even if the optical fiber sensor 2 is disconnected at the point and the light cannot pass through due to a fire, etc.
By alternately switching the connection to the 2 ', 2 "side and performing the measurement, it is possible to prevent the situation where the optical fiber sensor 2 can measure the temperature of only one of the Z ₄ points.

In addition, a plurality of optical fiber sensors 2a, 2b ...
By arranging the (book) around the floating roof tank 1 and providing temperature detecting devices 3a, 3a ', 3b, 3b' at the respective ends thereof,
Even if one or several of the optical fiber sensors 2a, 2b ... Are disconnected due to a fire or the like, one or several of the safe optical fiber sensors remain and the temperature can be continuously measured. Even if the optical fiber sensor 2a is disconnected by Z ₅ points, connected to both ends temperature detector 3a of the optical fiber sensor 2a, by 3b ', the temperature distribution along the optical fiber sensor 2a is reduced. Further, since the optical fiber sensor 2b is not broken, it can be measured as usual by the temperature detecting devices 3a 'and 3b. Since the laser beam is reflected in an abnormally large amount due to the fracture surface at the disconnection point, it is possible to give an alarm by measuring the disconnection and the disconnection location by the temperature detecting devices 3a and 3a '.

FIG. 6 shows an example of a floating roof tank. The floating roof tank is composed of a tank side plate 24 provided on the outer circumference of the tank bottom plate and a floating roof 25 floating above the internal oil level. In order to secure a vaporized gas seal with the tank side plate 24 in the peripheral portion of the roof 25, as shown in an example of the seal portion structure of FIG. 7, a seal portion 28 in which an urethane foam 27 or the like is filled in an envelope 26 is provided. And the seal part
A weather shield plate 29 is provided above 28 to prevent rain from entering. Also, on the floating roof 25,
A rolling rudder 30 is provided so as to be laid between the tank side plate 24 and the upper end thereof to inspect the floating roof 25 and the like.
In the figure, 31 is a foam dam plate and 32 is a top wind girder.

When a fire occurs in the floating roof tank,
It is limited to the vicinity of the seal portion 28.

Therefore, as shown in FIGS. 7 and 8, the wire mesh plate 33 having the optical fiber sensor 2 fixed in a zigzag shape is used as the envelope.
26, or as shown in FIGS. 9 and 10, the wire mesh plate 33 in which the optical fiber sensor 2 is fixed in zigzag.
Is supported via a support member 34 fixed to the upper part of the envelope 26 of the floating roof 25.

Besides the method of fixing the optical fiber sensor 2 to the wire mesh plate 33, it may be fixed to the wire mesh pipe 35 as shown in FIG. 11 or by other means as shown in FIGS. 12 and 13. To be supported in a zigzag shape such as a coil shape or a wavy shape.

As described above, when the optical fiber sensors 2 are arranged in a zigzag manner, the optical fiber sensors 2 can be freely deformed following the deformation of the floating roof tank, so that tension is applied to the optical fiber sensor 2 to cause disconnection. It is possible to prevent the occurrence of problems.

Further, since a longer optical fiber sensor can be arranged in a short section on the envelope 26, there is an effect of improving the distance detection accuracy of the temperature distribution.

The end portion of the optical fiber sensor 2 arranged in the seal portion 28 of the floating roof tank as described above is guided to the upper end of the tank side plate 24 along the rolling ladder 30 as shown in FIG. After being guided outside the outside of 24, it is guided to the temperature detecting device 3.

Therefore, in the above-mentioned fire detecting device for a floating roof tank, the optical fiber sensor 2 is arranged along the seal portion 28 where a fire may occur in the floating roof tank, and the end portion thereof is provided with the temperature detecting device 3.
The temperature of the place where the optical fiber sensor 2 is arranged is continuously obtained by the arithmetic unit 16 by connecting the device to the display device 17 and emitting the pulsed light G for detection. If a fire occurs, the temperature rise and its position can be immediately known by the display of, and the disaster prevention monitoring panel can be displayed by the signal from the arithmetic unit 16.
The alarm signal 19 can be output early by the 18,
Therefore, it is possible to quickly extinguish the fire at the beginning of the fire, and to efficiently extinguish the fire at a concentrated location.

Further, as described above, since the optical fiber sensor 2 arranged in the seal portion of the floating roof tank 1 is lightweight and thin, the space for installation is very small, and only the light is transmitted, so that the electric type sensor is used. It does not cause a fire like the above, and even if there is a failure such as a disconnection, the detection can be continued. Furthermore, since the optical fiber sensor 2 is not affected by electromagnetic waves, magnetic fields, etc., accurate temperature measurement is possible.

The present invention is not limited to the above-described embodiment, and the number of optical fiber sensors to be arranged, the arrangement shape, etc. can be arbitrarily selected, and various changes are made without departing from the scope of the present invention. Needless to say, to obtain.

[Effects of the Invention] As described above, according to the fire detection device for a floating roof tank of the present invention, the following excellent effects can be obtained.

(i) It is safe and reliable because the pulsed light is incident on the optical fiber sensor that runs along the seal part of the floating roof tank and the distance and temperature are detected based on the Raman backscattered light returned at that time. It is possible to detect the occurrence of fire.

(ii) Since only the optical fiber sensor is arranged in the floating roof tank, failure is unlikely to occur with an extremely simple configuration,
It can be implemented at low cost.

(iii) By displaying the distance and temperature on the display device,
The fire occurrence and its location can be read accurately, and prompt and efficient initial fire-fighting activities can be performed without causing misidentification.

(iv) By arranging the optical fiber sensors in a zigzag shape, disconnection of the optical fiber sensor is less likely to occur, and the distance can be increased to improve the distance detection accuracy.

(v) A disaster prevention monitoring panel connected to a computing device can automatically issue an alarm signal to promptly carry out fire fighting activities.

[Brief description of drawings]

FIG. 1 is a plan view showing the outline of an embodiment of the present invention, FIG. 2 is an explanatory view of backscattered light, and FIGS. 3 and 4 are explanatory views showing a state in which the backscattered light changes, and FIG. FIG. 7 is a plan view showing an application example of the apparatus of FIG. 1, FIG. 6 is a perspective view of a floating roof tank to which the present invention is applied, and FIG. 7 is an example of arranging an optical fiber sensor in a seal portion of the floating roof tank. Shown cut side view, 8th
7 is a plan view of FIG. 7, FIG. 9 is a sectional side view showing an arrangement example of an optical fiber sensor different from that of FIG. 7, FIG. 10 is a plan view of FIG. 9, and FIGS. FIG. 4 is an explanatory view showing an example of the arrangement shape of the optical fiber sensor. 1 is a floating roof tank, 2 is an optical fiber sensor, 3 is a temperature detecting device, 4 is a laser oscillator, 6 and 8 are optical splitters, 11 and 12 are interference filters, 13 and 14 are optical detectors, and 15 is 2 channels. Analog-digital converter, 16 arithmetic unit, 17 display, 18 disaster prevention monitoring board, 19 alarm signal, 20 anti-Stokes light, 21 Stokes light, 33 wire mesh plate, 34 support material, 35 wire mesh Pipe, G indicates pulsed light, and E indicates backscattered light.

Claims (3)

[Claims] 1. An optical fiber sensor arranged along a seal portion of a floating roof tank, a laser oscillator for injecting pulsed light from an end portion of the optical fiber sensor, and an optical fiber by injection of pulsed light from the laser oscillator. A fire detection device for a floating roof tank, comprising: a calculation device that calculates the distance and temperature of an optical fiber based on Raman backscattered light returned from the sensor; and a display device that displays the calculation result of the calculation device. . 2. The fire detection device for a floating roof tank according to claim 1, wherein the optical fiber sensor is arranged in a zigzag shape. 3. The fire detection device for a floating roof tank according to claim 1, further comprising a disaster prevention monitoring panel for outputting an alarm signal to the arithmetic unit.