JPH0654261B2 - Fire detection method for long objects - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a method for detecting a fire in a long object, and more particularly, a fire detection method for accurately detecting the occurrence of a fire in an electric wire cable by using an optical fiber. It is about.

<Prior art> In recent years, in a fire in a building or factory, electric cables often serve as a fire spread path and spread.

For this reason, the flame retardance of the electric wire cable itself is being advanced, and measures are taken such as applying an anti-spreading paint to the surface of the existing electric wire cable.

On the other hand, in the unlikely event that the electric cable burns, it is necessary to detect this early and issue an alarm to link it to digestive activity.

Conventionally, as a fire detection method for electric cables laid,
By arranging two conductors coated with plastic and arranging a wire-shaped heat-sensitive sensor with a sheath on it, along the cable, when the surroundings reach a certain temperature, the two conductors are short-circuited. A method of electrically detecting a fire has been proposed.

<Problems to be solved by the invention> However, when a wire-shaped heat sensor is used to electrically detect a fire in a wire cable, it is susceptible to electrical and magnetic induction from the power cable, resulting in a malfunction in the detection of fire. However, there is a problem in that it is likely to occur and the reliability is low.

<Purpose of the Invention> The present invention has been made to solve the above problems, fire detection can be performed without being affected by electrical and magnetic induction of the electric wire cable, reliability of the It is an object of the present invention to provide a fire detection method for a long object which can be improved.

<Means for Solving Problems> In order to solve the above problems, according to the present invention, quartz glass is used for a core, and an optical fiber having a plastic clad is formed into a loop shape and arranged along a long object. Then, the light is projected from one end of the optical fiber and received at the other end, and the fire is detected by the increase of the light intensity attenuation due to the temperature characteristic of the optical fiber.

<Operation> An optical fiber is arranged along the longitudinal direction of a long object, and light is projected from one end and received at the other end, and the amount of light intensity attenuation is constantly monitored.

When the temperature rises due to the fire of a long object, the optical fiber with a quartz glass core and a plastic clad causes an increase in optical transmission attenuation due to its temperature characteristics, and a fire is generated by detecting this and issuing an alarm. Let me know.

<Embodiment> An embodiment of the present invention will be described below with reference to the accompanying drawings.

As shown in FIG. 1, the detection method of the present invention arranges optical fibers 2 in a loop shape along the longitudinal direction of a laid electric wire cable 1 which is a long object, and raises the temperature due to combustion of the optical fibers 2. The occurrence of fire is detected by utilizing the temperature characteristic that the optical transmission attenuation increases.

A light projecting section 3 and a light receiving section 4 are provided at one end of the optical fiber 2 and a change detection circuit 5 and an alarm circuit 6 for the amount of received light are sequentially connected to the output side of the light receiving section 4 in order to prevent a fire. When the optical transmission attenuation amount of the optical fiber 2 increases due to the temperature rise and the light receiving amount decreases with respect to the light emitting amount, the change amount detecting circuit 5 detects this and inputs a signal to the alarm circuit 6 to issue an alarm. It will inform you of a fire.

The types of optical fibers are roughly classified into the following three types, but in the present invention, as will be described later, a plastic clad fiber whose light intensity attenuation due to temperature characteristics increases is used.

(I) Quartz glass fiber (AGF: all glass fiber) Both core and clad are silica glass fibers,
There are cases of pure quartz glass and cases of multi-component quartz glass.

(II) Plastic fiber (APF: all plastic fiber) A fiber whose core and clad are plastic.

(III) Plastic clad fiber (PCP) The core is silica glass and the clad is plastic fiber.

Since the core and clad of the quartz glass fiber of (I) above are quartz glass, there is almost no increase in the optical transmission attenuation until the melting point of the quartz glass (around 1000 ° C) is reached. I can't wait.

Since the plastic fiber of the above (II) has both a core and a clad made of plastic, the optical transmission attenuation increases at a temperature equal to or lower than the melting point temperature of the plastic of the core through which light passes.

PMMA (polymethylmeta
80 to 1 for acrylate) plastic fibers
The optical transmission attenuation increases at 00 ° C.

In the laid part of the electric cable, even if there is no fire, it is possible to reach such a temperature, so it is difficult to use for detecting a fire of the electric cable.

However, it is promising for fire detection in general buildings.

Next, in the above-mentioned plastic clad fiber of (III), the core is made of quartz, but the clad is made of plastic, so that the plastic of the clad melts when the temperature rises.

Moreover, the light does not pass through the clad, but the optical transmission attenuation increases depending on whether the reflectance at the interface between the core and the cladding changes, and the melting point temperature of the plastic increases the optical transmission attenuation as it is. It is not the temperature.

FIGS. 3 to 6 show the optical fibers shown in (I) and (II) above and the optical fibers of the PCF optical fiber of (III) in which silicon resin is used as the plastic material for the cladding,
FIG. 2 shows the result of a combustion test according to the heating curve specified in JIS A1304 shown in FIG.

The quartz glass fiber (AGF) of (I) is as shown in Fig. 3.
There is almost no increase in optical transmission attenuation even at a maximum temperature of 840 ° C x 30 minutes.

In the plastic fiber of (II), as shown in FIG. 4, the optical transmission attenuation increased at a temperature of 80 to 90 ° C. within a time of 1 minute or less.

As shown in FIG. 5, the PCF fiber of (III) showed an increase in optical transmission attenuation at a temperature of 650 to 700 ° C. after 8 to 9 minutes.

By the way, the heating curve of JISA1304 shown in FIG. 2 simulates an actual temperature rise in a flame, but this is the case of the most violent burning. Therefore, P of (III)
Using CF fiber, as shown in Fig. 6, the light transmission attenuation increasing temperature for various fire patterns such as 1/2 fire resistance curve, 1/3 fire resistance curve, 1/5 fire resistance curve, etc. was examined and examined. .

In this way, the PCF fiber of (III) does not show an increase in optical transmission attenuation when a certain temperature is reached, but rather has an interesting characteristic that the optical transmission attenuation increases with time and how the temperature rises. was gotten.

This is the very characteristic feature of the PCF fiber, that is, the structure that the core is quartz glass and the clad is plastic, and this feature is exactly what kind of form such as sudden burning or wrinkling burning case in a real fire. This means that even if there is a fire, it will have a detection function, and by using this PCF fiber, it is possible to realize fire detection for a long object.

Further, since the PCF fiber has a small optical transmission loss even if it is lengthened, it can be sufficiently put to practical use even in the case where it extends to several hundred meters like an electric wire cable electric line.

Next, FIG. 1 shows a concrete example of a configuration for detecting a fire in an electric line by using a PCF fiber. The PCF fiber 2 is formed into a loop along the electric line 1a attached side by side with the electric wire cable 1. The PCF optical fiber 1 is provided with a light projecting section 3 at one end and a light receiving section 4 at the other end.
A light reception light amount change amount detection circuit 5 and an alarm circuit 6 are sequentially connected to the output side of the.

The light supplied to the one end of the PCF optical fiber 2 by the light projecting unit 3 is received by the light receiving unit 4, and the detection circuit 5 detects the light projecting amount and the light receiving amount to constantly monitor the occurrence of fire in the electric line 1a, When a fire occurs on the electric line 1a and the temperature rises,
The optical transmission attenuation of the PCF optical fiber 2 increases, and the detection circuit 5 detects the increase in the optical transmission attenuation amount and sends a signal to the alarm circuit 6 to issue an alarm to notify the occurrence of fire.

The PCF optical fiber 2 also needs to have mechanical strength, so that it is possible to use an optical fiber cord or to bundle several PCF fibers together into a cable.

<Effect> As described above, according to the present invention, the PCF optical fibers are arranged in a loop along the longitudinal direction of the long object, and the occurrence of fire is detected by utilizing the temperature characteristics of the PCF optical fibers. Therefore, the fire can be detected without receiving electrical and magnetic induction, and the optical transmission loss is small even if the PCF optical fiber is elongated, so that the fire of a long object such as an electric wire cable can be easily generated. It can be detected accurately and effectively.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a fire detection method according to the present invention, FIG. 2 is a graph showing a heating curve by a fire resistance test, FIGS. 3 and 4 and 5 are graphs showing a combustion test of an optical fiber, FIG. 6 is a graph showing various fire resistance curves for a PCF optical fiber. 1 ... Electric wire cable, 2 ... PCF optical fiber 3 ... Emitter, 4 ... Light receiver 5 ... Optical received light quantity change amount detection circuit 6 ... Alarm circuit

Claims (1)

[Claims] 1. An optical fiber whose core is made of quartz glass and whose clad is made of plastic is arranged along a long object in a loop shape, and light is projected from one end of the optical fiber and received at the other end. Fire detection method for long objects that detects a fire by increasing the amount of light intensity attenuation due to the temperature characteristics of.