JPS62147336A - Method for detecting leakage of sea bottom gas pipeline - Google Patents

Abstract

PURPOSE:To make it possible to detect the leakage of a sea bottom gas pipeline, by feeding tracer gas to the sea bottom gas pipeline along with carrier gas. CONSTITUTION:Tracer gas 4 can safely coexist along with carrier gas 3 and is water soluble one. If it is assumed that leak hole 5 is generated in a sea bottom gas pipeline 2 and the leaked jet stream 6 is generated from said leak hole 5, the gas 4 is contained in the jet stream 6 along with the gas 3 and dissolved in seawater 7. A mother ship 9 is navigating along the pipeline 2 on the sea 8. The mother ship 9 is equipped with a minute amount gas detector 11 and a sampling apparatus 12 is connected to the apparatus 11. The apparatus 12 is suspended toward the line 2 and samples seawater 7 in the vicinity of the pipeline 2 while runs along the vicinity of the pipeline 2 along with the navigation of the mother ship 9. This seawater 7 is analyzed and, if the gas 4 can be detected by the apparatus 11, it is judged that leakage is generated. The detection of a minute amount of the gas 4 is performed by evaporating the sample and further adapting a difference absorption method to the evaporated sample by utilizing laser beam.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for detecting leaks in gas pipelines laid under the sea.

[Conventional technology]

A method using a submersible (submersible robot) is already known as a method for detecting leaks in submarine gas pipelines. This submersible method involves lowering the submersible into the sea, which is connected by a cable from the mother ship, and placing it on top of a gas pipeline laid on the ocean floor. The system obtains sound or video signals along the lines, sends them to the mother ship via the signal transmission line in the cable, processes the signals on the mother ship, and detects leaks in the submarine gas pipeline. .

However, in this method using a submersible, it is not always easy to place the submersible precisely on the undersea gas pipeline, and it is difficult to place the submersible precisely on the undersea gas pipeline. In addition to the above-mentioned hearing devices and imaging devices, a reasonable amount of equipment for operating the submersible is required.
Submersibles had become extremely expensive.

Furthermore, as a leakage detection method other than the method using a submersible, a method using a listening pig is being researched. This method attempts to detect a leak hole in an undersea gas pipeline by detecting high-frequency sound emitted by the leak hole using a listening pig equipped with a high-frequency sensor.

However, in this method using a listening pig, it is difficult to distinguish between the noise emitted by the listening pig itself while driving and the noise before detection from the leak hole, and it has not been put into practical use at this stage.

Additionally, some current piping does not allow the use of listening pigs due to valves, etc.

[Problems that the invention attempts to solve]

The present invention has been made in view of the above-mentioned current state of the prior art, and an object thereof is to provide a method for detecting leaks in submarine gas pipelines that is less expensive than that of submersibles, etc., and has sufficient accuracy for practical use.

[Summary of the invention]

Therefore, in the present invention, a water-soluble tracer gas that can safely coexist with the transport gas is pumped to the submarine gas pipeline together with the transport gas, and a sample obtained by sampling seawater near the submarine gas pipeline is appropriately collected. The leakage of the submarine gas pipeline is detected by analyzing the tracer gas component in the sample by a method. [Embodiments] Hereinafter, embodiments of the present invention will be described based on the drawings. .

FIG. 1 shows an embodiment of the leakage detection method for a submarine gas pipeline according to the present invention. In the figure, a submarine gas pipeline (2) is laid on the seabed (1), and this submarine gas pipeline (2) The transport gas (3) and the tracer gas (4) are pumped.

The transport gas (3) is, for example, natural gas, and the submarine gas pipeline (2) is originally intended to transport this transport gas (3). In addition, tracer gas (
4) can coexist safely with the transport gas (37) and is water-soluble.Here, being able to coexist safely with the transport gas (3) means that there is no reactivity with the transport gas (3). death,
In particular, it means that there will be no reaction that would cause an explosion, ignition, or the production of strongly corrosive gases.

Further, a tracer gas (which itself is less corrosive and preferably inexpensive) is used. Examples of the tracer gas include NH3.

Further, the ratio of the tracer gas (4) to the transport gas (3) is 1. For example, it is appropriate that the partial pressure of the tracer gas (4) is about less than the volumetric ratio corresponding to the liquefaction pressure.

A leakage hole (5) has occurred in the submarine gas pipeline (2), and if a leakage spout (6) is generated from this leakage hole (5), the leakage spout (6) is caused by the above-mentioned transportation. A tracer gas (4) is included together with the gas (31), and the water-soluble tracer gas (4) dissolves in the seawater (7).

Meanwhile, on the sea (8), a mother ship (9) is sailing along an undersea gas pipeline (2). The mother ship (9) is equipped with a trace gas detection device αυ, and a sampling device (2) is connected to this trace gas detection device αη. The sampling device α2 is suspended toward the submarine gas pipeline (2), and the mother ship is traveling along the submarine gas pipeline (2).
) while running along the vicinity of the submarine gas pipeline (
2) It is designed to sample the seawater (force) in the vicinity.

If the sampled seawater (7) is analyzed by the sampling device (6) and tracer gas (4) is detected by the trace gas detection device (11), it means that a leak has occurred.

There are various methods for detecting trace gases, but in this example, the sample was vaporized.

Furthermore, a differential absorption method using laser light is used.

FIG. 2 shows an example of a different configuration of this trace gas detection device CLI.

In the figure, the laser oscillator Q directs the laser oscillator Q through the guide (A) into the laser multiple reflection chamber (E) at the absorption wavelength λ.

It is designed to oscillate laser beams of two types of wavelengths: λ7 and reference λ7. Absorption wavelength λ. The laser beam has a wavelength in the band absorbed by the tracer gas (4). For example, if the tracer gas (4) is NH3, λo=9.2
It is 17 μm. Further, the reference wavelength λ is a wavelength slightly shifted from the absorption band of the tracer gas (4).

In this way, by introducing the reference wavelength λr in addition to the absorption wavelength λG, these two wavelengths can be separated. , λ1 at the same time, it is possible to eliminate from the measurement results errors caused by absorption of laser light due to factors other than absorption of laser light by the tracer gas (<4). ) is equipped with a calibrator (c) to compensate for the accuracy of the oscillation wavelength.

A plurality of reflecting mirrors (E) are provided in the laser multiplex reflection chamber (1), and the laser light (λ0, λr) introduced into the chamber top.

After being reflected many times between these reflecting mirrors, the light is guided out of the chamber from the other guide rod. Further, the sample sampled by the sampling device (2) is introduced into the laser multiplex reflection chamber (4) after being vaporized by the vaporizer, and the sample gas in the gaseous state is introduced between the reflecting mirrors (c). Absorption wavelength λ that is repeatedly reflected at . of laser light will be absorbed. At this time, due to repeated reflections, a sufficiently long optical path is formed in the chamber (2).
Since the laser beam is secured within the range, sufficient absorption of laser light is achieved. Note that the laser beam having the reference wavelength λr is not absorbed by the sample gas.

The laser beam guided from the laser multiplex reflection chamber (to the guide) is separated by a filter into a component with an absorption wavelength λ0 and a component with a reference wavelength λr, and then separated into a component with an absorption wavelength λ0 and a component with a reference wavelength λr. Each wavelength λ. , the intensity of λr is detected.

These detection results are input to the divider (33) via the amplifier (al) (32).

The absorbing wavelength λ with respect to the reference wavelength λr is determined by this divider (33). The intensity ratio of is determined, and from that value, it is determined whether or not the sample gas, that is, the tracer gas (4) absorbs the absorption wavelength λ0, and therefore, it is determined whether or not there is a leak in the submarine gas pipeline (2). This kind of judgment process.

A processor (34) connected to the divider (33).
), and the detection results are sent to the printer (35).
While the necessary data is printed out on Memo'J (36
)J is now memorized.

According to this embodiment 1, it is possible to detect a leak in a submarine gas pipeline (2) at a relatively low cost without using an expensive submersible, and to perform detection with sufficient accuracy for practical use. I can do it.

In addition, it is easy to operate because it does not require a precise positioning along the undersea gas pipeline (2) as in the case of using a submersible.

In addition, in the above embodiment, the absorption wavelength λ. =9.217
μm, but NH3 has a strong absorption band at a wavelength of 1.25 pm or about 1.50 μm, and the absorption wavelength λ0
These values may be used as the reference wavelength λr, and a wavelength close to these values may be used as the reference wavelength λr. In such a case, the guides (a) and (e) can be made of optical fiber, and the sampling device (6), vaporizer @ji, and laser multiplex reflection chamber) can be integrated into the mother ship. It hangs down from (9) towards the submarine gas pipeline (2), and equipment such as a laser oscillator (9) and a detector (on the top) are installed inside the mother ship (9), and the transmission of laser light in both calculations is carried out. This can be done via the optical fiber guide (a).

Further, in the above embodiment, N is used as the tracer gas.
Although H is used as an example, any other type of gas that can safely coexist with the transport gas and is water-soluble may be used.

Furthermore, the detection of tracer gas components in a sample is not limited to the case where the absorption phenomenon of a specific wavelength by the tracer gas component of laser light is used. A semiconductor gas detection method using a semiconductor that changes may be used, or a water-soluble tracer gas component may be detected while the sample is in an aqueous solution state without being vaporized.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to detect a leak in a submarine gas pipeline at a relatively low cost and with sufficient accuracy for practical use.

[Brief explanation of drawings]

Figure 1 is a sectional view showing an embodiment of the method for detecting a leak in a submarine gas pipeline according to the present invention, and Figure 2 is a block diagram showing the configuration of a trace gas detection device used in the embodiment. (2)...Undersea gas pipeline, (3)...Transportation gas, (4)...Tracer gas, (5)...Leak hole, (6)...Leakage ejection % (7)・・Seawater, (9
)... Mother ship, C1η... Trace gas detection device, @...
・Sampling device, Qη...laser oscillator, (a)
Hanging...guide, tilting...laser multiple reflection chamber,
Gradient... vaporizer, wire (to)... detector% (33
)...Dipipe, (34)...Processor, (3
5)...Printer, (36)...Memory. Patent applicant: Nippon Kokan Co., Ltd. Inventor: Koji Ishihara Patent attorney: Sho Yoshihara Figure 2

Claims (3)

[Claims] (1) A water-soluble tracer gas that can safely coexist with the transport gas is pumped together with the transport gas to a submarine gas pipeline, and seawater near the submarine gas pipeline is sampled, and the tracer gas components in the obtained sample are A method for detecting a leak in a submarine gas pipeline, comprising: detecting a leak in the submarine gas pipeline. (2) The leak detection method for a submarine gas pipeline according to claim 1, wherein the tracer gas in the sample is detected after the sample is vaporized. (3) A method for detecting a leak in a submarine gas pipeline according to claim 2, characterized in that the detection of the tracer gas after vaporizing the sample is performed by a differential absorption method using laser light.