JP2006170691A - Capture mechanism of leakage gas and gas sensing system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely capture gas leaked from a gas conduit pipe. <P>SOLUTION: The capture mechanism R for the leakage gas G is provided with a support member 13 with air permeability formed on the buried gas conduit pipe 1, a collection pipe 5 laid parallel to the gas conduit pipe 1 supported by the support member 13, and a filler material 14, without air and water permeability, for blocking the space T surrounding the gas conduit pipe 1, the support member 13 and the collection pipe 5. At the bottom of the collection pipe 5, a through hole 5a is provided for capturing the leakage gas G in contact with the support member 13. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a leakage gas trapping mechanism and a gas detection system in a basement in which a gas conduit is embedded.

Currently, when a high-pressure gas conduit is buried underground, installation of a device that detects leaked gas is required by related laws and regulations to ensure safety.
As a method for detecting the leaked gas in the gas conduit buried in the underground, there is a method for detecting the leaked gas by using a collecting pipe provided together with the gas conduit laid in the tunnel mine, for example. According to this method, a collection pipe formed of a PVC pipe or the like and having a through hole is laid above the gas conduit, and air mortar (filler) having air permeability is filled around the collection pipe. Then, the gas leaked from the gas conduit passes through the filler and flows into the collecting pipe, and the gas components dissolved in the leaked gas and the permeated water inside the collecting pipe are periodically collected at the end of the collecting pipe. Collect and measure at the same time.
Moreover, in patent document 1, the pit which connects a gas conduit and the ground is provided in the embedding direction of a gas conduit by the predetermined space | interval, a collection pipe is laid between adjacent pits, and it is in the collection pipe end part in a pit. A method for detecting leaked gas has been proposed.
JP 2000-180288 A

However, when the gas conduit is buried underground, the conventional leakage gas capturing mechanism and gas detection method have the following problems.
The air mortar normally used for the filler around the gas conduit has air permeability, but the air permeability is low and the leakage gas capturing rate is not good. Furthermore, air mortar with a skeletal structure with a hollow inside has a high possibility of being destroyed in the skeleton structure for a long period of time and becoming a mud, which deteriorates the air permeability and reduces the durability of the gas conduit itself. End up.
On the other hand, because the filler such as air mortar has air permeability, the leaked gas diffuses into the filler and flows out to the outside of the filler, and is leaked by the collecting tube. The gas amount decreases and the gas detection performance decreases. As described above, there is a problem that it is difficult to specify the leaked portion of the gas conduit due to the diffusion of the leaked gas.
In addition, the filler such as air mortar has water permeability, and there is a problem that the groundwater present in the surrounding area penetrates to the inside of the collection pipe through the filler.
In addition, when the gas conduit slope is mountain-shaped, gas stays at the peak of the mountain-shaped collection pipe, and when it exceeds the volume of the collection pipe, it dissipates from the through hole to the surrounding ground. There is a problem that it is difficult to detect gas with high reliability due to diffusion. Furthermore, if there is a providence or fault in the ground, the diffused leaked gas becomes a passage for the leaked gas, and high-concentration gas concentrates on the ground, which may lead to dangers such as poisoning and fire. is there.
Furthermore, in the method proposed in Patent Document 1, it is possible to detect the leaked gas generated between the pits, but it is difficult to narrow down and specify the leaked portion of the gas conduit.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a leakage gas capturing mechanism that reliably captures gas leaked from a gas conduit and a gas detection system including the same.

In order to achieve the above object, the leakage gas trapping mechanism according to the present invention is a trapping mechanism for leaking gas underground in which a gas conduit is embedded, and a support member formed at the top of the gas conduit and having air permeability, and a support A collecting pipe supported by the member and provided with a through hole for capturing the leaked gas flowing out from the gas conduit; and a breathable and water-permeable structure that closes a space around the gas conduit, the supporting member, and the collecting pipe. It is characterized by comprising no filler.
In the present invention, the leakage gas trapping mechanism uses a non-permeable and water-permeable material for the filler that closes the periphery of the gas conduit, so that the leaked gas does not diffuse into the filler and supports the breathable gas. Only the member can be passed. And since leaked gas is reliably guide | induced to the through-hole of a collection pipe, the capture rate of leaked gas can be improved and reliable gas detection can be implement | achieved at an early stage.

In the leakage gas capturing mechanism according to the present invention, it is preferable that the through hole of the collecting tube is provided in close contact with the support member.
In the present invention, the leaked gas that has permeated into the support member from the gas conduit easily flows into the through hole.

In the leakage gas capturing mechanism according to the present invention, it is preferable that a coating layer having no water permeability is provided at the boundary between the outer peripheral surface of the support member and the filler.
In this invention, since a filler and groundwater do not osmose | permeate in a support member, a support member can maintain air permeability and can improve the capture rate of the leakage gas in a collection pipe.

The gas detection system according to the present invention is a leakage gas detection system having the above-described leakage gas capturing mechanism, wherein gas inspection vertical shafts formed toward the ground are provided at appropriate intervals, and a collection pipe Is branched to the vertical shaft to form a branch collection pipe, which is arranged to the ground, and is equipped with a gas detector at or near the end of the branch collection pipe to detect leaked gas flowing in from the gas conduit It is characterized by that.
In the present invention, since the leaked gas captured by the collection pipe and the branch collection pipe can be efficiently detected at the ground portion of the vertical shaft, the running cost can be reduced in the management work of the gas conduit. . Moreover, there is a low possibility of gas leaking to the ground part other than the vertical shaft, and safety can be ensured.

Further, in the gas detection system according to the present invention, the detection means for calculating the distance between the gas detector and the gas leak location from the time difference when the gas was detected by each gas detector and identifying the gas leak location of the gas conduit It is preferable to provide.
In the present invention, information on leaked gas detected by each gas detector can be collectively managed, and there is a difference in time detected by each gas detector when leaked gas is generated. Since the distance to the leaked part of the gas conduit can be calculated and specified within a certain range, the time required for narrowing the leaked part can be shortened.

Further, in the gas detection system according to the present invention, the branch collection pipe is provided with an on-off valve, and when the gas detector detects leak gas, the on-off valve is opened and leaked at at least one point of the branch collection pipe. It is preferable that a recovery tank for recovering the gas is provided.
In the present invention, the leaked gas that has flowed into the collection tube and the branch collection tube from the gas conduit can be guided only to the branch collection tube to be recovered. And by providing a collection tank at the tip of a branch collection pipe and collecting, leakage gas does not flow out from a shaft without a collection tank, and safety can be improved.

According to the leakage gas trapping mechanism of the present invention, the filler that closes the periphery of the gas conduit is not breathable and water permeable, so that the leakage gas does not diffuse into the filler, and the support member has a breathability. Leakage gas can pass reliably and can be guide | induced to the through-hole of a collection pipe. For this reason, the capture rate of leaked gas can be improved, and highly reliable gas detection can be realized at an early stage as compared with a conventional method in which an inspector separately detects leaked gas.
Further, according to the gas detection system of the present invention, in addition to the above-described effects, the leakage gas captured by the collection pipe by the leakage gas capture mechanism is efficiently generated in the ground portion of the vertical shaft through the branch collection pipe. Gas can be detected well. For this reason, it is possible to reduce the running cost in the management work of the gas conduit, and it is unlikely that gas leaks to the ground part other than the vertical shaft, so that safety can be ensured.

Hereinafter, a leakage gas capturing mechanism and a gas detection system according to an embodiment of the present invention will be described with reference to FIGS. 1 to 4.
FIG. 1 is a schematic diagram showing a gas detection system having a leak gas trapping mechanism according to the first embodiment, FIG. 2 is a cross-sectional view inside a tunnel showing a leak gas trapping mechanism, and FIG. 3 is a leak shown in FIG. FIG. 4 is an explanatory view showing a gas detection system having a leakage gas capturing mechanism.
The first embodiment is a case where construction is performed by a tunnel. As shown in FIG. 1, a tunnel 2 in which a gas conduit 1 is buried in the ground has a plurality of positions that communicate with the ground 3 at a predetermined position of the tunnel 2. A vertical shaft 4 (indicated by reference numerals 4a, 4b, 4c, and 4d in the figure) is provided substantially vertically. The cross-sectional area of the tunnel 2 is, for example, about 7 m ² and is a cross-section in which the gas conduit 1 can be embedded.

In the tunnel 2, in order to capture the gas G leaking from the gas conduit 1, a collecting pipe 5 is installed in parallel directly above the gas conduit 1. This collection pipe 5 is branched at the position of each vertical shaft 4a, 4b, 4c, 4d to form a branch collection pipe 6 (in the figure, distinguished by using reference numerals 6a, 6b, 6c, 6d), It is arranged along the vertical shaft 4 to the ground 3.
Each branch collection pipe 6 is provided with an on-off valve 7 (indicated by reference numerals 7a, 7b, 7c and 7d in the figure).
Among the vertical shafts 4, 4 b, 4 c function as gas detection vertical shafts, and gas detectors 8 a, 8 b, 8 c are provided at or near the ends of the branch collection pipes 6 a, 6 b, 6 c. ing.
As shown in FIG. 4, these gas detectors 8 have a function of transmitting leakage gas G detection information 9 (identified by reference numerals 9 a, 9 b, and 9 c in the figure). A central control room 10 for centrally managing the detection information 9 is installed on the ground 3, and an instruction signal 9d for operating the on-off valve 7 of each branch collection pipe 6 is sent from the central control room 10 (detection means). Is transmitted.
The vertical shaft 4d functions as a vertical shaft for collecting the leaked gas G, and a recovery tank 11 having a volume enough to collect the leaked gas G is provided at the tip of the branch collection pipe 6d (FIG. 1). reference).

As shown in FIGS. 1 and 2, a gantry 12 is provided at substantially the center of the bottom of the tunnel 2, and the gas conduit 1 is placed on the gantry 12 and laid in the tunnel traveling direction.
The trapping mechanism R for the leaked gas G including the collecting pipe 5 configured in the tunnel 2 includes a support member 13 formed in a region S above the gas conduit 1 shown in FIG. It is comprised from the collection pipe | tube 5 currently formed from the pipe | tube etc., and the filler 14 which obstruct | occludes the space T around the gas conduit 1, the supporting member 13, and the collection pipe | tube 5. As shown in FIG.

  And as shown in FIG. 3, the through-hole 5a is provided in the bottom part of the collection pipe 5, and this through-hole 5a is provided in the laying direction of the collection pipe 5 at predetermined intervals. For example, the through hole 5a has a diameter of 7 mm, and the interval between the through holes 5a adjacent to each other in the laying direction of the collection tube 5 is 200 mm.

The support member 13 is formed from a material having air permeability, for example, high-density urethane foam or the like, has a large number of voids, and has a strength such that it is not crushed by the injection pressure of the filler 14. Material is suitable.
As shown in FIG. 3, the lower end surface of the support member 13 is formed with an end surface 13 a having the same diameter as the gas conduit 1, and the upper end surface of the support member 13 has the same diameter as the collecting tube 5. A notch surface 13b is formed. The collection tube 5 is provided with the through-hole 5a in close contact with the notch surface 13b.
Moreover, as shown in FIG. 3, the outer peripheral surface except the end surface 13a and the notch surface 13b of the supporting member 13 is covered with the coating layer 15 which does not have air permeability and water permeability. The covering layer 15 can prevent the filler 14 from penetrating into the support member 13 when the filler 14 is filled into the tunnel 2.
And the supporting member 13 and the collection pipe | tube 5 are being fixed to the gas conduit 1 by the fixing member 16 (refer FIG. 3).

The filler 14 filled so as to close the inside of the tunnel 2 is made of a low-strength material that has no air permeability and water permeability and can be re-excavated. For example, the compressive strength is preferably about 0.5 KN / m ² , and a fluidized soil material generated by a slurry stabilization method in which water generated by construction and the solidified material is mixed is used. Thereby, since the amount of waste processing can be reduced, the tunnel structure of the gas conduit 1 in consideration of environmental problems can be realized.

Next, the operation of the leakage gas G capturing mechanism R will be described with reference to FIGS.
As shown in FIG. 2, when the gas conduit 1 is damaged or the like, the steel gas conduit 1 and the filler 14 are made of different materials and have low adhesion, so that there is a slight gap M at the boundary surface between them. It is formed. The gas G leaking from the gas conduit 1 does not permeate the filler 14 but permeates along the outer peripheral surface of the gas conduit 1 or directly into the air-permeable support member 13 and further collects the collecting tube 5. It penetrates into the inside of the through hole 5a.
In addition, since the filler 14 according to the first embodiment has low air permeability in addition to low air permeability, the filler in the tunnel 2 even when the groundwater level is higher than the height at which the tunnel 2 is located. The amount of groundwater entering 14 is extremely small.

Moreover, the high-pressure gas G leaking from the gas conduit 1 can pass through the support member 13 by penetrating through the fragile portion of the wall of the gap in the support member 13 made of foamed urethane or the like.
Since the through hole 5 a of the collection tube 5 is in contact with the support member 13, the leakage gas G is guided into the collection tube 5.

Next, the leakage gas G detection system will be described with reference to FIG.
For example, the gas G leaked from the leaking part X shown in FIG. 4 enters the inside of the collecting pipe 5 from the vicinity of the leaking part X by the above-described trapping mechanism R, and sequentially spreads in the pipe, and each vertical shaft 4a, 4b. It flows toward the end of the branch collection pipe 6 disposed up to the ground surfaces 4c and 4d.
The leaked gas G is detected by the gas detector 8a of the vertical shaft 4a located at the closest distance La from the leaked location X, and the detection information 9a is transmitted to the central control room 10.
Subsequently, the leaked gas G is detected by the gas detector 8b of the shaft 4b located at the second closest distance Lb from the leaked point X. Thus, the central control chamber 10 is detected by the gas detectors 8a, 8b, and 8c in the order of the short distance from the leakage point X (for example, in the order of La, Lb, and Lc in the first embodiment). Is transmitted.

Further, when the central control room 10 receives the detection information 9 of the leaked gas G, the central control room 10 transmits an instruction signal 9d to each of the on-off valves 7a, 7b, 7c, and operates the switch 7 to branch the collecting pipe. Block 6 As described above, when the leaked gas G is confirmed at at least one of the gas detectors 8, the on-off valve 7 of each shaft 4 can be operated and shut off.
Next, the leaked gas G flows into the branch collecting pipe 6d of the vertical shaft 4d provided with the recovery tank 11 and the on-off valve 7d being opened, and the leaked gas G can be recovered in the recovery tank 11.
The vertical shaft 4d functions as a recovery unit for the leaked gas G and is not provided with the gas detector 8. However, the present invention is not limited thereto, and the vertical shaft 4d may be provided with the gas detector 8 for management.

  The detection information 9 transmitted from each gas detector 8 to the central control room 10 has a time difference ΔT between the first detected time T1 and the second and subsequent detected times T2, T3, T4. Since the approximate value of the diffusion speed V is known, the distance L can be calculated from the diffusion speed V and the time difference ΔT, and the position of the breakage point X of the gas conduit 1 can be roughly specified.

  As described above, the leakage gas G capturing mechanism R according to the first embodiment leaks from the gas conduit 1 by using a material having no air permeability and water permeability as the filler 14 in the tunnel 2. The gas G passes through the filler 14 in the tunnel 2 and does not diffuse to the surroundings, but is guided to the through hole 5a of the collection tube 5 and can be reliably captured. Thereby, the capture rate of the leaked gas G can be improved, and highly reliable gas detection can be realized at an early stage.

Further, in the gas detection system according to the first embodiment, since the leaked gas G can be recovered only by the recovery tank 11, the shafts 4a, 4b, 4c not provided with the recovery tank 11 are blocked and leaked to the ground 3 Gas G does not flow out, and safety can be improved.
Further, the detection information 9 from each gas detector 8 is collectively managed in the central control room 10 and the time difference ΔT at which the gas is detected is calculated, whereby the distance from the gas detector 8 to the damaged portion X of the gas conduit 1. Since L can be specified within a certain range, the time required for narrowing down the leaked portion X can be shortened. For this reason, it is possible to reduce the running cost in the management work of the gas conduit 1.
In recent years, the gas pressure in the gas conduit 1 is increasing, and therefore, highly reliable gas detection is required. In the first embodiment, the leaked gas satisfying such a requirement. G management can be realized.

Next, another embodiment of the present embodiment will be described. However, the same or similar members and parts as those of the above-described embodiment are denoted by the same reference numerals, the description thereof is omitted, and the first embodiment is omitted. Different configurations and operations will be described.
FIG. 5 is a schematic view showing a gas detection system provided with a leakage gas capturing mechanism according to the second embodiment.
As shown in FIG. 5, in the second embodiment, the gas pipe 1 is buried when the buried portion is buried by the open-cut method from the ground 3, and the excavation performed by the open-cut method The gas conduit 1 is embedded in the portion 17.
In order to capture the leakage gas G, the gas conduit 1 is provided with a supplementary mechanism R similar to that of the first embodiment. A space T around the supplementary mechanism R is closed using a filler 14 having no air permeability and water permeability similar to that of the first embodiment. The filler 14 is filled from the bottom of the excavation part 17 to the roadbed lower surface 18, and the upper part of the filler 14 is backfilled by the roadbed roadbed 19. And the road surface 20 is formed by paving the upper part.
In this capturing mechanism R, the gas G leaked from the gas conduit 1 does not penetrate and diffuse into the filler 14, and can be reliably captured by the collecting tube 5 through the support member 13.
Further, the collecting tube 5 of the supplementary mechanism R branches at a predetermined position to form a branch collecting tube 6, and the tip thereof is disposed near the road surface 20 on the ground 3. And the gas detector 8 can be installed in the front-end | tip part of this branch collection pipe 6, and leak gas G can be detected, for example, when leak gas G was detected, it was prepared in the middle of branch collection pipe 6. The on-off valve 7 is operated to shut off the branch collection pipe 6.
Further, a box-shaped member 21 that protects the tip of the branch collection pipe 6 and the gas detector 8 is provided below the road surface 20. In the present embodiment, as in the first embodiment, a gas detection system that can grasp the leak location of the gas conduit 1 from the detection information by the gas detector 8 or collect the leaked gas G is adopted. can do.
As described above, the leakage gas G supplementing mechanism and the gas detection system according to the second embodiment also have the same effects as those according to the first embodiment.

As described above, the embodiments of the leakage gas capturing mechanism and the gas detection system according to the present invention have been described. However, the present invention is not limited to the above-described embodiments, and can be appropriately changed without departing from the scope of the present invention. is there.
For example, in the leakage gas G capturing mechanism R according to the first and second embodiments, construction reclaimed soil is used for the filler 14, but this is not necessarily the case. In short, the filler 14 may be any material that has no air permeability or water permeability and does not diffuse the leaked gas G around the gas conduit 1.
Moreover, although the vertical shaft 4 by this 1st embodiment has provided 4 places, 4a, 4b, 4c, 4d, an installation location and quantity are not restricted to this. For example, corresponding to the gradient conditions of the tunnel 2, the vertical shaft 4 can be provided at an appropriate location where the leaked gas G is likely to accumulate in the collection pipe 5. And although a vertical shaft is provided substantially perpendicularly, you may provide it diagonally according to conditions.
Further, the vertical shaft 4d that collects the leaked gas G is not limited, and the position and quantity may be planned according to conditions such as the gradient of the tunnel.

1 is an overall view showing a gas detection system provided with a leakage gas capturing mechanism according to a first embodiment of the present invention. It is sectional drawing in a tunnel which shows the capture mechanism of leaking gas. FIG. 3 is an enlarged view of a leakage gas capturing mechanism shown in FIG. 2. It is a figure which shows the gas detection system by 1st embodiment of this invention. It is the schematic which shows the gas detection system provided with the capture mechanism of the leaked gas by 2nd embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Gas conduit 2 Tunnel 4a, 4b, 4c, 4d Vertical shaft 5 Collection pipe 6a, 6b, 6c, 6d Branch collection pipe 7a, 7b, 7c, 7d On-off valve 8a, 8b, 8c Gas detector 9a, 9b, 9c, 9d Detection information 10 Central control room (detection means)
11 Collection tank 13 Support member 14 Filler 15 Cover layer G Leakage gas
X Leakage location

Claims (6)

It is a trapping mechanism for leaked gas in the underground where a gas conduit is embedded,
A support member formed at the top of the gas conduit and having air permeability;
A collecting pipe supported by the support member and provided with a through hole for capturing the leaked gas flowing out from the gas conduit;
A leakage gas trapping mechanism comprising a gas permeable material and a non-permeable filler that closes a space around the gas conduit, the support member, and the collecting pipe.   The leakage gas capturing mechanism according to claim 1, wherein the through hole of the collecting tube is provided in close contact with the support member.   The leakage gas capturing mechanism according to claim 1, wherein a coating layer having no water permeability is provided at a boundary between the outer peripheral surface of the support member and the filler.   A leak gas detection system having a leak gas trapping mechanism according to any one of claims 1 to 3, wherein gas inspection vertical shafts formed toward the ground are provided at appropriate intervals, and Leakage that flows out from the gas conduit with a gas detector installed at or near the end of the branch collection pipe, the collection pipe is branched to the shaft to form a branch collection pipe and is arranged to the ground. A gas detection system characterized by detecting gas.   A detecting means for calculating a distance between the gas detector and a gas leak location from a time difference in which leak gas is detected by each of the gas detectors and identifying a gas leak location of the gas conduit is provided. The gas detection system according to claim 4. The branch collection pipe is provided with an open / close valve, and when the gas detector detects a leak gas, at least one location of the branch collection pipe, a recovery tank that opens the open / close valve and collects the leak gas The gas detection system according to claim 4, wherein the gas detection system is provided.

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