JP2001050855A - Optical fiber type liquid sensor - Google Patents

Abstract

(57) [Problem] To provide an optical fiber type liquid sensor having improved response characteristics. SOLUTION: A slot rod 13 having a groove 16 formed in a longitudinal direction, a swellable resin 12 which expands by absorbing a liquid to be monitored, which is accommodated in the bottom of the groove 16, a swellable resin 12 and a partition member An optical fiber 11 partitioned by a slot 18 and housed in a groove 16;
In the optical fiber type liquid sensor provided with the wire rod wound thereon, a gap 17 is provided between the swellable resin 12 and the side wall of the groove 16 in the depth direction of the groove 16.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber type liquid sensor for monitoring and detecting a leak from a pipe for transporting a liquid.

[0002]

2. Description of the Related Art As a sensor for detecting leakage of a liquid from a storage tank of oil or chemicals or a transportation pipe of such a liquid, an absorbent swellable resin which absorbs a liquid whose leakage is to be detected and swells, and an optical fiber. An optical fiber type liquid sensor combining the above has been proposed.

[0003] The principle of detecting the liquid leakage of this optical fiber type liquid sensor is that the resin swollen by absorbing the liquid to be detected acts on the optical fiber to generate stress, thereby causing a bend in the optical fiber and causing a transmission loss. To a backscattered light meter (OT
DR) or the like to detect liquid leakage.

Various structures have been proposed as specific structures of the optical fiber type liquid sensor. The present inventors have made the following proposals for improving the detection sensitivity and reducing the malfunction. (Japanese Patent Application No. 9-21733)
No. 0).

That is, as shown in FIGS. 5 (a) and 5 (b), this optical fiber type liquid sensor has a slot rod 13 in which a groove 16 is formed in a longitudinal direction, and a monitor housed in the bottom of the groove 16. Swellable resin 12 that absorbs the liquid to be expanded and expands
An optical fiber 11 partitioned by the swellable resin 12 and the partition member 18 and housed in the groove 16, and a wire rod 14 wound on the slot rod 13. Reference numeral 15 denotes a tension member.

In the optical fiber type liquid sensor 10, the optical fiber 11 is loosely housed in the groove 16 of the slot rod 13. Therefore, even when the optical fiber type liquid sensor 10 is used in a curved state, no bend occurs due to the wire rod 14 wound around the slot rod 13 and no loss due to liquid leakage does not occur.

When the swellable resin 12 accommodated in the bottom of the groove 16 absorbs the liquid to be monitored and swells, the optical fiber 11 is pushed up to the outside of the groove 16 through the partition member 18 and the slot 16 is formed. The optical fiber 11 is bent by being pressed against the wire rod 14 wound on the rod 13 and causes loss. As described above, in the optical fiber type liquid sensor 10, the swellable resin 12 is
The force generated when swelling outward from the center of 3 can be efficiently transmitted to the optical fiber 11 to cause the optical fiber 11 to bend.

FIG. 6 shows a state in which a liquid to be monitored (not shown) enters the groove 16 from above the groove 16 and contacts the swellable resin 12, so that the swellable resin 12 swells. The optical fiber 11 is pressed against the wire 14 wound on the slot rod 13, and the optical fiber 11 is bent at the pressed portion B. The number of locations B where the bend occurs can be adjusted by the winding pitch of the wire 14. If it is desired to increase the detection sensitivity, the winding pitch of the wire 14 may be reduced so that the bend occurs in more places of the optical fiber 11.

[0009]

However, the above-mentioned optical fiber type liquid sensor 10 has the following problems. 1) As shown in FIG. 7A, the liquid to be detected enters the groove 16 from above the groove 16 and comes into contact with the upper part of the swellable resin 12. Then, the swellable resin 12 starts swelling from above. At this time, when the fluidity of the liquid is not good, or when the absorption and swelling of the liquid into the swellable resin 12 is extremely fast,
As shown in FIG. 7B, the upper portion of the swellable resin 12 swells before the liquid reaches the bottom of the groove 16.
Then, the swollen upper portion of the swellable resin 12 hinders diffusion of the liquid to the entire groove 16.

2) As shown in FIG. 8A, when the swellable resin 12 is in the form of a tape and is accommodated in the groove 16 so as to overlap vertically, the liquid to be detected is
As shown in FIG. 8B, the tape-shaped swellable resin 12 located above the groove 16 swells and enters the groove 16 when it enters the groove 16 from above and comes into contact with the upper part of the swellable resin 12. Thus, the diffusion of the liquid to the entire groove 16 is hindered. Further, the upper swellable resin 12 presses the side wall of the groove 16 by swelling in the width direction of the groove 16, and as a result, the lower swellable resin 12
Has the effect of suppressing upward swelling.

If the swellable resin 12 in the groove 16 does not swell over the entirety due to the above-described causes, the optical fiber 1
1 was not sufficiently pushed up due to the swelling of the swellable resin 12, and did not come into contact with the wire 14, or even if it did, there was a problem that sufficient bending did not occur and the detection sensitivity was lowered.

[0012]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has a slot rod formed with a groove in a longitudinal direction and a liquid to be monitored contained in the bottom of the groove. A swellable resin that expands and expands, an optical fiber partitioned into the swellable resin and a partition member and housed in a groove, and an optical fiber type liquid sensor including a wire wound on the slot rod. A gap is provided between the swellable resin and the side wall of the groove or in the swellable resin.

As described above, if a gap is provided between the swellable resin accommodated in the groove bottom and the side wall of the groove or in the swellable resin, the liquid to be detected easily diffuses in the groove, The swellable resin inside swells all over, pushing up the optical fiber in the groove. Therefore, the optical fiber is reliably bent in contact with the wire, so that the detection sensitivity is improved and the response speed is also increased.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a sectional view of a main part of an embodiment of an optical fiber type liquid sensor according to the present invention. In FIG. 1, the same parts as those described with reference to FIGS. In this embodiment, the liquid to be detected is kerosene.

In FIG. 1, an optical fiber 11 is a single mode fiber having a cutoff wavelength of 1.1 to 1.1.
1.3 μm, coated with UV resin. The slot rod 13 is made of high-density polyethylene and has a depth of 7.0 m.
A groove 16 having a width of 5.0 mm and a width of 5.0 mm is formed.
Two tension members 15 made of 2 mm steel wire are embedded.

The swellable resin 12 is an oil-absorbing swellable resin powder (for example, a long-chain alkyl acrylate crosslinked polymer).
Nippon Shokubai Oreo Soap (trade name)), which is hardened in a tape shape with a water-soluble binder (for example, polyvinyl alcohol) and has a width of 4.0 mm, which is narrower than the width (5.0 mm) of the groove 16. It has a tape shape (600 g / m ² ), and six tapes are stacked. The swellable resin 12 is arranged close to one side of the groove 16, and approximately 1.0 m is provided between one side wall of the groove 16 and the swellable resin 12.
m gap 17 is formed in the depth direction of the groove 16.

The partition member 18 has a width of 25 mm and a thickness of 0.1 mm.
This is a perforated tape made of 08 mm polyethylene terephthalate. The wound wire 14 is 0.9 m
1.5 m diameter soft copper wire covered with foamed polyethylene
m.

With respect to the optical fiber type liquid sensor of the present embodiment, the time change of the transmission loss of the optical fiber due to kerosene drop was measured, and the response characteristic was evaluated with the time when the transmission loss reached 1.0 dB as the response time. When the measurement was performed three times, the response times were 18, 23, and 19 minutes.

As a comparative example, an optical fiber type liquid sensor was prepared in which the width of the tape-shaped swellable resin 12 was 4.9 mm and the width of the groove 16 was substantially equal. When the response time of this optical fiber type liquid sensor was measured similarly three times, the response times were 41 minutes, 35 minutes, and 55 minutes.

From the above measurement results, it can be understood that the provision of the gap 17 between the swellable resin 12 and the side wall of the groove 16 shortens the response time and reduces the variation.

FIG. 2 is a sectional view of a main part of another embodiment.
In the present embodiment, the swellable resin 12 is an oil-absorbing swellable resin powder or flake composed of a long-chain alkyl acrylate cross-linked polymer, and a plurality of swellable resins 12 that are fixed around the string 19 with a water-soluble binder. Bundling (or twisting) at 20 and binding (or twisting) the outer diameter to the groove 16
Make it narrower than width. A gap 17 is provided between both side walls of the groove 16 and the swellable resin 12 solidified in a string shape, although not uniform in the depth direction of the groove 16.

FIG. 3 is a sectional view of a main part of still another embodiment. In the present embodiment, the swellable resin 12 is an oil-absorbing swellable resin powder or flake composed of a long-chain alkyl acrylate cross-linked polymer, and is filled in a cylinder 21 having a diameter smaller than the width of the groove 16. The cylindrical body 21 is made of a material having a strength that allows kerosene (a liquid to be detected) to penetrate, is broken by the swelling pressure of the swellable resin 12, and withstands an external force applied when dropped into the groove 16. This cylinder 2
1 is formed by bonding paper or a thin cloth with a kerosene-soluble adhesive, for example. In this embodiment, a gap 17 similar to the embodiment shown in FIG. 2 is provided.

FIG. 4 is a sectional view of a main part of still another embodiment. In the present embodiment, spacers 22 made of a porous material are arranged in a U-shape along the bottom and side walls of the groove 16, and the inside thereof is filled with the powdery swellable resin 12, and the swellable resin 12 is Are spaced apart from the bottom and side walls by the thickness of the spacer 22 to provide a gap 17. The material of the spacer 22 made of a porous material is a material which allows kerosene to pass therethrough and swells the resin 1.
The deformation due to the swelling pressure of 2 is small, and specifically,
It is made of a collection of fine wires such as metal (like steel wool) or a sponge-like resin.

[0024]

As described above, according to the present invention, there are excellent effects that the detection sensitivity is improved and the response speed is increased.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of an embodiment of an optical fiber type liquid sensor according to the present invention.

FIG. 2 is a sectional view of a main part of another embodiment.

FIG. 3 is a cross-sectional view of a main part of still another embodiment.

FIG. 4 is a cross-sectional view of a main part of still another embodiment.

5A and 5B are a perspective view and a cross-sectional view of a conventional optical fiber type liquid sensor, respectively.

6 is a perspective view showing a state when the swellable resin swells in the optical fiber type liquid sensor shown in FIG.

FIGS. 7A and 7B are cross-sectional views illustrating problems of a conventional optical fiber type liquid sensor.

FIGS. 8A and 8B are other cross-sectional views each illustrating a problem of the conventional optical fiber type liquid sensor.

[Explanation of symbols]

 Reference Signs List 10 optical fiber type liquid sensor 11 optical fiber 12 swellable resin 13 slot rod 14 wire 15 tension member 16 groove 17 gap 18 partitioning member 19, 20 string 21 cylinder 22 spacer

Claims (1)

[Claims] 1. A slot rod having a groove formed in a longitudinal direction, a swellable resin which absorbs a liquid to be monitored and which is accommodated in the bottom of the groove and expands, and is partitioned by the swellable resin and a partition member. In an optical fiber type liquid sensor including an optical fiber housed in a groove and a wire wound on the slot rod, between the swellable resin and a side wall of the groove or in the swellable resin. An optical fiber type liquid sensor characterized in that a gap is provided in the liquid crystal sensor.