JPS5920092B2 - optical oil detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical oil detector for detecting oil leaks and the like.

Due to the recent frequency of oil leak accidents from petroleum and petrochemical plants and the strengthening of legal requirements for the installation of oil leak detection devices, there is a need for highly reliable oil leak detection devices.

Conventional oil leakage detection devices are based on a capacitance variation method. For example, a float 1 as shown in Figure 1 is floated in a reservoir provided at a predetermined location relative to an oil tank. It is placed with metal studs.

That is, the electrode 3 is placed on the inner surface of the float 1 at the waterline position 2.
is arranged, and a weak high frequency current is applied to this electrode 3 from an electronic circuit 4, so that there is no oil leakage (when the electrode 3
The high-frequency current applied to the float passes through the wall (synthetic resin) of the float 1 and enters the water (* is a metal stand (not shown)).
Diffusion attenuation occurs. However, when oil flows into the empty pit, it accumulates due to oil leakage.
The relative permittivity of the vicinity changes greatly, and the attenuation of high-frequency current becomes smaller. Therefore, this change is detected by the electronic circuit 4, this detection signal is taken out via the cable 6, and an oil leak alarm (not shown) is activated. This is to align the water line of electrode 1 with the installation position of electrode 3.However, in the conventional device described above, the leaked oil must be collected (and the amount of oil leaked becomes considerably large). Because it took a long time to detect the alarm, the alarm was delayed, and there was a risk that the measures could not be taken in time.

Also, it was not possible to accurately detect which part of the oil tank was leaking.

Furthermore, in order to float the device on oil, it had to be of some kind of explosion-proof construction.The present invention was made in view of the above points, and when light is input from one end, this light is transmitted to the other end. An optical oil detector is constructed using a light guide that can transmit light with low loss, and is based on the reduction in the amount of light transmitted through the light guide that occurs when oil comes into contact with the light guide. Hereinafter, the present invention will be explained in detail based on the embodiments shown in the accompanying drawings.

FIG. 2 is a diagram showing the principle of the structure of the present invention, and shows the light guide 10 as one light guide wire.

The light guide 10 shown in longitudinal section has a guide core 11 made of glass fiber or synthetic resin fiber whose outer periphery is covered with a cladding 12. The light transmitted by the light guide 10 can be transmitted to the other end with low loss.The principle of light transmission and the principle of oil detection by this light guide 10 will be explained with reference to FIGS. 3 and 4. Guide core 11
The refractive index of the cladding 12 is n1, and the refractive index of the cladding 12 is N2.

Then, if the incident angle of light to the core 11 is smaller than the angle α corresponding to the critical angle γ between the core 11 and the cladding 12 (this is called the acceptance angle (
The light 11 incident on the cladding 12 reaches the other end with low loss while repeating total reflection at the interface with the cladding 12. From the viewpoint of principle 7 of general oil detection (more broadly liquid detection), the cladding 12 does not need to be made of glass or synthetic resin, but is an optical medium with a refractive index lower than the refractive index n1 of the core 11, such as air (N2
21) If so, then (・.

Therefore, to simplify the explanation, we will explain the case where the cladding is air.As shown in FIG. 4, the refractive index n of the core 11 is
When the optical medium 13 with a refractive index N3 greater than 1 is attached, the light 1 propagating in the core cannot be totally reflected at the interface, and a part of it exits into the optical medium 13 through the I2 path. If this optical medium 13 is a medium that easily absorbs light, such as crude oil or heavy oil, most of the light that passes through it is absorbed, and its surface 1
3'('The light 13 that is reflected and returns to the core 11,
i4 is extremely small. Therefore, if a light receiving element is placed at the light receiving end and changes in the amount of light are monitored, oil adhesion can be detected. Therefore, as shown in FIG. 2, a light emitting element 14 is arranged at one end of the light guide 10 and a light receiving element 15 is arranged at the other end, and a certain amount of light is made to enter the core 11 from the light emitting element 14.
The amount of transmitted light is converted into an electrical signal by the light receiving element 15.

The output of the light receiving element 15 is sent to the comparison circuit 1 via the amplifier circuit 16.
7 and is compared with the alarm reference value. When the detection signal becomes smaller than the alarm reference value due to a decrease in the amount of transmitted light,
The output of the comparison circuit 17 is given to an alarm circuit 18, and an alarm 19 such as a lamp or a buzzer is activated. by the way,
In principle, the cladding 12 could be made of air (as I said,
Guide core 11 may be unnecessary depending on usage conditions and environment.
Direct contact with air may cause malfunction, and air is not suitable for practical use.

Therefore, the cladding 12 must be made of a material other than air (gas).
It must not be something that can be peeled off from 1 in an unreasonable manner.
In view of this, in the present invention, the clad 12 is made of a material that is swollen by the oil that is the detection target. It should be made up of materials.

For example, if the detection target is petroleum-based oil such as crude oil, heavy oil, or gasoline, the cladding 12 may be made of silicone resin. At this time, swelling occurs in the oil-attached portion of the cladding 12. In this way, the cladding 12
If swelling occurs in the cladding 12 and guide core 11.
When the interface between the A portion of the light leaks to the outside, reducing the amount of light that passes through to the light receiving element.Furthermore, oil may penetrate into the cladding 12 due to the swelling.In such a case, the penetrated oil may become a guide. It comes into direct contact with the core 11. At this time, if the refractive index of the oil is larger than the refractive index of the cladding 12, the critical angle between this contact portion and the core 11 decreases, and this also leads to the light receiving element. The amount of transmitted light decreases.In addition, if the refractive index of the oil that has penetrated is larger than the refractive index of the guide core 11, a part of the light that passes through the core 11 is caused by this oil as described above. Of course, in this case as well, the amount of transmitted light reaching the light receiving element is reduced.However, in the present invention, the above-mentioned good detection of oil cannot be achieved simply by causing swelling in the cladding 12. The swelling of the cladding 12 is a sufficient condition for oil detection. Fig. 5 shows a side view of the specific configuration of the optical oil detector according to the present invention, and Fig. 6 shows the line - Its cross section is shown as (・ru).

As is clear from FIG. 6, a plurality of light guide wires 10 shown in FIG. ℃・ru.

The sheath 21 serves to protect the light guide 10 from damage caused by external mechanical forces and makes it easier to absorb the force shaft, and can be made of, for example, cotton, asbestos, etc. Optical connectors 23A and 24A are attached to both ends of the Tekta cable 22, and the light emitting element 1
A connector 23B that connects to the connector 23A is provided on the 4 side, and a connector 24B that connects to the connector 24A is provided on the light receiving element 15 side.

The light emitting element 14 is connected via these connectors 23A to 24B.
and the oil detector cable 2 for the light receiving element 15.
2 is removable. This is to make it convenient to replace only the cable 22, since the oil detector cable 22 will be contaminated once oil is detected. The part of the connector 23A (or 24A) attached to the end of the oil detector cable 22 will be explained.

The connector 23A (or 24A) includes a mounting fitting 25, a protective tube 26, and a female threaded portion 27. light guide 1
0 protrudes from its end by a predetermined length, and a cylindrical fitting 25 is inserted into the cable 22 and fixed. To prevent the cable 22 from being bent and damaged at the end of this metal fitting 25, attach a rubber protective tube 26 to the length of the cable 22.
The periphery of the end of the metal fitting 25 located on the side is coated. A female thread 27 is attached to the end of the fitting 25 (ie, the end of the cable 22) opposite to the protective tube 26.
This female threaded portion 27 engages with the mounting fitting 25 so as to be freely rotatable and movable only within a limited range in the axial direction. Connector 23B on the side of the light emitting element 14 and light receiving element 15
and 24B are shown in cross section.

There is a male screw 28 (28
A wide hole 29 (29○) for receiving the tip of the metal fitting 25 and a narrow hole 30 (3σ diameter) for receiving the bundle of light guides 10 are provided in stages. The narrow hole 30 (3
A collar 32 (32
is inserted. The outer diameter of collar 32 (32) is hole 31 (3
17), and its inner diameter is matched to the outer diameter of the light emitting element 14 (at a certain degree, the light receiving element 15). Then, the light emitting element 14 (or light receiving element 15) is inserted into this collar 32 (32○).
Two are made of electrically insulating material such as synthetic resin, and the element 14 (
or 15) is useful for alignment and electrical insulation during insertion. The connector 23B (24B) has a flange portion 33 (3
It is fixed to a case 34 for housing an electric circuit with screws or the like at a point 3'). In addition to the light emitting element 14 and the light receiving element 15, the case 34 houses a power supply circuit (not shown) that supplies power to the light emitting element 14 and an amplifier circuit 16 that amplifies the output of the light receiving element 15.

The oil detector cable 22 and the case 34 to which it is connected are installed at the location where oil leakage or oil contamination should be detected, and the output of the amplifier circuit 16 is connected to the case 34 by wire or wirelessly.
4 and transmits it to a comparison circuit 17, an alarm circuit 18, etc. installed in a remote oil leak monitoring center. In the case of wireless transmission, a wireless transmitter is housed within the case 34. Of course, all the blocks from the comparator circuit 17 to the alarm 19 can be housed in the case 34. Pixel element 14,1
5 are used separately, each case 34 becomes a separate case. Connector 23A (
24A), insert the bundle of light guides 10 at the tip of the cable 22 into the narrow hole 30 (3
0, screw the male screw part 27 onto the male screw 28 (28'), and tighten until the tip of the mounting bracket 25 hits the bottom of the wide hole 29 (29○).

Then, the distance x between the tip of the light guide 10 and the tip of the light emitting element 14 (or light receiving element 15) in the narrow holes 30 (30) is set to an ideal distance. In order for the light from 14 to enter the light guide 10 effectively, the distance x should not be too wide. For example, if the diameter of the bundle of light guides 10 is 1.2 wm, the distance X should be 0.27 m to 0.27 m. Connectors 23A, 23B (24A, 24
B) is composed of ℃・. One light guide wire 10
It was confirmed through trial production that when a bundle of light guides 10 was made by bundling 19 light guides with a diameter of 180 μm, the diameter of the bundle was 1.2 m (Fig. 7 and FIG. 8 shows an example in which the oil detector of the present invention is applied to detect oil leakage from an oil tank 35.

Immediately below the bottom of the oil tank 35, as shown in FIGS. 7 and 8, a grid-like cable pit 36 in the XY direction is formed, and there are two oil detectors in the XY direction having the configuration shown in FIG. Lay the cables 22X and 22Y.
Both cables are connected to the light emitting element 14X (14Y) and the light receiving element 15 via connectors (not shown) as shown in FIG.
Connected to X(15Y). This light receiving element 15X (15
The output of Y) is amplified by an amplifier 37 and then compared with a reference signal by a comparator 38. Therefore, if an oil leak occurs at either position of the oil detector cables 22X or 22Y, this oil will adhere to the oil detector cable and the amount of light received by the light receiving element 15X (15Y) will be reduced, so that the signal applied to the comparator 38 will be reduced. decreases beyond a predetermined value. As a result, the comparator 38 generates an alarm signal to the alarm 39 indicating an abnormality. In addition, oil detector cable 22
If the cable 22 is sufficiently protected, the cable 22 should be placed inside an appropriate liquid-permeable flexible protective tube.

This flexible protective tube is, for example, a liquid-permeable type in which a coil spring is used as an aggregate and a flexible tube is formed by braiding and winding a braid made of a flexible thin wire member on the outside of the coil spring. A flexible 4-cable protection tube can be used. In the above explanation, we have described an example in which a multicore oil detector cable is constructed by bundling a large number of light guides, but it is possible to bundle a small number or a single light guide as long as the mechanical protection and quality stability are sufficient. Even if it's a light guide (・.

In addition, oil leak detection can of course be carried out not only at the bottom of the tank but also at any desired location. In addition, the detection target of the present invention is not limited to oil (in this case, clad 12
As explained above, according to the present invention, it is possible to use a material that swells with the liquid to be detected. By doing so, the detection location can be set linearly, expanding the detection range.

In addition, the material of the cladding is specially designed so that it reacts quickly to only the liquid to be detected, ensuring rapid and reliable detection. Furthermore,
Since the oil detector cable part is detachable using a connector, it has the advantage of being easy to replace.Also, if the oil detector cable is installed at the bottom of the oil tank in the X and Y directions, If an oil leak occurs anywhere near the cable installation path, a decrease in the amount of light received is automatically detected and an alarm is issued immediately, so oil leak detection is quick and reliable. If the number is increased, oil leaks can be detected more precisely, and the oil leak position can be more accurately specified.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway side view illustrating a conventional oil leak detection device, and FIG. 2 is a schematic diagram including a partially vertical sectional view showing the principle of the configuration of an optical oil detector according to the present invention. , Figure 3 is a cross-sectional view for explaining the principle of light transmission by a light guide.
Fig. 4 is a sectional view for explaining the principle of general oil detection using a light guide, Fig. 5 is a partially sectional side view showing a specific example of the optical oil detector according to the present invention, and Fig. 6 5 is a cross-sectional view indicated by the line - in FIG. 5, FIG. 7 is a side view when the present invention is applied to leak detection of an oil tank, and FIG. 8 is a bottom view of the tank in FIG. 7. DESCRIPTION OF SYMBOLS 10... Light guide, 11... Light guide core, 12... Clad, 13,20... Oil, 14,1
4X...Light emitting element, 15,15X...Light receiving element, 1
9,30...alarm, 21. ．． ．． Sheath, 22...
Oil detector cable, 23A, 23B, 24A,
24B... Connector, 25... Mounting bracket, 26.
...Protection tube, 27...Female thread, 28...Male thread, 32...Collar, 34...Electric circuit storage case 35...Oil tank, 36...Cable pit.

Claims (1)

[Claims] 1 The outer periphery of a linear guide core with a predetermined refractive index is covered with a cladding material that has a smaller refractive index than the core and has the property of being swollen by the liquid to be detected such as oil. a light guide configured to transmit light with low loss from one end of the core to the other end; a liquid-impregnable protective coating covering the outer periphery of a bundle of one or more of the light guides; a light emitting element disposed at one end of the light guide; a light receiving element disposed at the other end of the light guide;
The detection device includes a connector for removably connecting the light emitting element and the light receiving element to each end of the light guide in a predetermined positional relationship, and an electric circuit for extracting a signal according to the amount of light received by the light receiving element. An optical oil detector that detects the liquid to be detected based on a decrease in the amount of received light that occurs when the liquid to be detected swells the cladding material.