JPH0157300B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fluid detection device used for detecting fluid leaks in tanks and pipelines.

Conventionally, this type of fluid detection device has been known to be based on various methods such as the flow rate difference method, the differential pressure method, the gas detection method, the ultrasonic method, the capacitance measurement method, the electric circuit disconnection method, and the oil-soluble tube method. However, both devices use electricity for detection. For this reason, there are problems in that the signal transmission path is guided by external power cables, lightning, etc., explosion-proof measures must be taken, and transmission loss is large, making it impossible to extend the transmission distance.
Therefore, recently, devices have been devised that use light instead of electricity. This uses an optical fiber whose core is covered with a cladding that is attacked by the fluid to be detected. When leaked fluid adheres to the cladding, the reflectance of light decreases at the interface between the cladding and the core, which detects fluid leakage. Or, if fluid is present between the emitter and the light receiver, the transmittance of light between them changes, so that leakage of the fluid is detected. However, in the former method, it takes time to detect leakage of fluid, and the latter method has the limitation that it can only be applied to liquids that block light.

The present invention provides a first optical fiber and a second optical fiber that are provided apart from each other so that their end surfaces face each other, and
The optical signal sent to the optical fiber is refracted in the separated space and is received by the second optical fiber only when there is no fluid to be detected in this space, thereby solving the above conventional problems. Since it uses optical fiber, it is not subject to external guidance, is explosion-proof and safe, allows long-distance transmission of signals, and is easy to install, and is also similar to conventional optical fibers. It is an object of the present invention to provide a fluid detection device that has a faster response time for fluid detection than the previous one and can be applied to any fluid.

Hereinafter, the present invention will be explained in detail based on the drawings.

1 to 3 show an embodiment of the fluid detection device of the present invention, in which a light emitting means 1 for generating an optical signal is shown.
and a first transmitting optical signal from the light emitting means 1.
It mainly consists of an optical fiber 2, a second optical fiber 3 that receives and transmits the optical signal from the first optical fiber 2, and a receiving means 4 that receives the optical signal from the second optical fiber 3. ing. The light emitting means 1 is composed of an electric signal output path 1a that outputs a required electric signal, and an electro-optical converter 1b that converts the electric signal outputted by the electric signal output circuit 1a into a required optical signal. be. The first optical fiber 2 is formed by covering a core 2a with a high refractive index with a cladding 2b with a low refractive index, and transmits the optical signal generated by the light emitting means 1 at the interface between the cladding 2b and the core 2a. This is transmitted while being totally reflected within the core 2a,
The terminal end surface 2c is cut diagonally at a predetermined angle. Like the first optical fiber 2, the second optical fiber 3 is composed of a core 3a with a large refractive index and a cladding 3b with a small refractive index.
A starting end face 3 is arranged approximately parallel to the optical fiber 2 with an appropriate distance from the optical fiber 2 in the axial direction thereof, and is offset from the axial center, and is opposite to the terminal end face 2c of the first optical fiber 2.
c is formed obliquely so as to be parallel to the end surface 2c. Further, the terminal end of the first optical fiber 2 and the starting end of the second optical fiber 3 are fixed to penetrate through the side wall 5b of the fluid detection section 5, which has a filter 5a on one side, and the end surfaces 2c and 3c of the first optical fiber 2 are fixed to each other. is located inside this fluid detection section 5. This fluid detection unit 5 is installed in advance at a place where fluid leakage is likely to occur, such as a tank or pipeline, and when fluid leaks from a tank or pipeline, the fluid passes through the filter 5a and is detected. It flows into the inside of the section 5 and accumulates therein. The optical signal transmitted through the core 2a of the first optical fiber 2 is refracted at the termination surface 2c of the first optical fiber 2, and then is exposed between the first optical fiber 2 and the second optical fiber 3. When there is no detection fluid present, the second optical fiber 3 is refracted at an appropriate angle without being totally reflected at the end surface 3c, enters the core 3a, and is transmitted through the core 3a. In a state where the fluid to be detected is accumulated in the detection unit 5, due to the difference in refractive index between the fluid to be detected and air or the light emission or discontinuity of the fluid to be detected,
The structure is such that most of it does not reach into the core 3a of the second optical fiber 3.

Further, the receiving means 4 includes a photoelectric converter 4a that converts the optical signal sent from the second optical fiber 3 into an electrical signal according to the amount of light, and an alarm setting reference circuit 4b that issues a predetermined alarm setting signal. and a comparison circuit 4c which compares the electrical signal sent from the opto-electrical converter 4a with the alarm setting signal generated by the alarm setting reference circuit 4b and outputs a contact output signal if the electrical signal is lower than the alarm setting signal level. , and an alarm circuit 4f that issues an alarm with a lamp 4d and a buzzer 4e based on the contact output signal from the comparison circuit 4c.

Note that when this fluid detection device is used to detect oil leakage, it must detect oil but not water. It is convenient to seal it with resin or the like.

Next, the operation of the present invention will be explained. When detecting fluid leakage from a tank or pipeline using the fluid detection device of the present invention, the fluid detection section 5 is installed in advance at a location where fluid is likely to leak.
Then, an electrical signal of, for example, 20 mADC or 5 VDC is outputted from the electrical signal output circuit 1a of the light emitting means 1, which is converted into an optical signal by the electro-optic converter 1b and sent to the first optical fiber 2. This optical signal is the core 2a
The fluid advances through the core 2a while being totally reflected at the interface between the fiber and the clad 2b, and when it reaches the terminal end surface 2c of the first optical fiber 2, if there is no fluid leakage, the refractive index of the core 2a and the air changes. Due to the difference, it is refracted at the terminal end face 2c as shown in FIG. 2, and just reaches the terminal end face 3c of the second optical fiber 3. And the starting surface 3c
It is bent again and enters the core 3a. On the other hand, if the fluid leaks and accumulates in the fluid detection unit 5, the refractive index of the fluid and air is different, so the optical signal is
The optical fiber 2 is refracted at a different refraction angle from the above case at the terminal end surface 2c, and most of the refraction is refracted by the core 3a of the starting end surface 3c of the second optical fiber 3, as shown in FIG.
spreads without reaching the area. Additionally, if the fluid is colored, the color will prevent the optical signal from passing through.

Furthermore, the optical signal entering the core 3a of the second optical fiber 3 from the starting end surface 3c is transmitted through the second optical fiber 3.
The signal passes through the receiving means 4, and is converted into an electrical signal by a photoelectric converter 4a. If the amount of light transmitted from the first optical fiber 2 to the second optical fiber 3 is not reduced, this electrical signal will be the original 20mADC or
The signal will be 5VDC, but even if there is no fluid leakage, the light will be somewhat diffused to the outside in the space between the first optical fiber 2 and the second optical fiber 3, and the amount of transmitted light will decrease. Therefore, depending on this, e.g.
It is as low as 12mADC or 3VDC. This electrical signal then enters the comparison circuit 4c and is compared with the alarm setting signal of the alarm setting reference circuit 4b. Only when the level is lower than the alarm setting signal level, a contact output signal is issued to the alarm circuit 4f, and the lamp 4d and buzzer 4e are activated. For example, set the alarm setting signal to 10
When mADC or 2.5VDC is used, the electric signal when there is no leakage of the fluid is higher than this, so the alarm circuit 4f will not be activated. However, fluid leaks from the first optical fiber 2 to the second optical fiber 3.
When the amount of transmitted light further decreases, the electrical signal at the opto-electrical converter 4a becomes lower than the alarm setting signal level, and as a result, a contact output signal is output from the comparison circuit 4c to drive the alarm circuit 4f, and the lamp 4d and buzzer Activate 4e. The operator can be informed of the occurrence of an abnormality by this alarm.

As described above, since the fluid detection device of the present invention uses optical fibers in the fluid detection section and the signal transmission path, it has the following advantages over electrical devices.

(1) Since optical fiber is an insulator, it is highly reliable as it does not receive any induction from power cables or lightning.

(2) Since the detection part does not require any power supply, it is safe from an explosion-proof point of view.

(3) Long-distance transmission is possible because there is little signal loss in the signal transmission path.

(4) Optical fiber has a thin core and is lightweight, making it easy to install.

In addition, compared to conventional detection devices that use light, (5) there is no need to prevent leakage fluid from damaging the cladding, so the detection response time is faster (6) by utilizing the difference in refractive index. Therefore, it can be applied regardless of the type of liquid.

It has the advantage of

[Brief explanation of drawings]

The figures show one embodiment of the present invention, in which Fig. 1 is a system diagram showing the configuration of a fluid detection device, Fig. 2 is a sectional view of the fluid detection part when no fluid is leaking, and Fig. 3 is a sectional view of the fluid detection section when no fluid is leaking. It is the same cross-sectional view when fluid leaks. 1... Light emitting means, 2... First optical fiber, 3...
...Second optical fiber, 2a, 3a...Core, 2b,
3b... Clad, 4... Receiving means.

Claims (1)

[Claims] 1. A light emitting means for generating an optical signal, a first optical fiber having an oblique termination face and transmitting an optical signal from the light emitting means, and a first optical fiber disposed at a distance from the first optical fiber, and a second optical fiber that receives and transmits most of the optical signal refracted by the end surface of the first optical fiber without the presence of a fluid to be detected; and a receiver that receives the optical signal from the second optical fiber. A fluid detection device comprising: means.