WO2024252532A1 - Corrosion prevention method and corrosion prevention system - Google Patents

Abstract

A corrosion prevention method according to the present disclosure comprises: a step for sealing one end (1a) of a metal conduit (1) with a closing cap (14a) and sealing another end (1b) of the metal conduit (1) with a closing cap (14b); a step for connecting a gas feed hose (11a) to a connection port (141) of the closing cap (14a), connecting a gas discharge hose (12a) to a connection port (141) of the closing cap (14b), and supplying an inert gas to the inside of the metal conduit (1) via the gas feed hose (11a); and a step for closing the connection ports (141) of the closing cap (14a) and the closing cap (14b) with a shut-off valve (142) after filling of the inert gas to the inside of the metal conduit (1) is completed.

Description

Corrosion prevention method and corrosion prevention system

This disclosure relates to a corrosion prevention method and a corrosion prevention system.

There are many facilities buried underground, such as communication tunnels, manholes, and pipelines. Of these facilities, many of the pipelines in particular have been in use for a long time.

　Approximately half of telecommunications conduits are made of carbon steel. Over time after construction, metal corrosion of carbon steel progresses due to various oxidation reactions resulting from contact with the atmosphere, water, or other metals. As corrosion progresses, rust bumps form inside the conduit, hindering the installation of inner pipes such as cables or pipelines inside the conduit, and reducing the seismic resistance of the conduit.

On the other hand, new social infrastructure is needed for the utilization of hydrogen energy to achieve carbon neutrality, for the recovery of carbon dioxide, and for the construction of microgrids to ensure a stable supply of energy, and there are hopes for the effective use of buried underground structures (manholes, pipelines, tunnels, etc.).

Non-Patent Document 1 describes a corrosion prevention method in which the outer surface of a metal pipeline is coated with polyethylene and the inner surface of the metal pipeline is painted with a synthetic resin paint or the like. Non-Patent Document 2 describes a repair method for pipelines with advanced corrosion using a lining method in which a resin-based lining material is inserted and a resin film is formed on the inner surface of the pipeline.

Corrosion rate model for the inner surface of steel pipes in an underground manhole environment, Materials and Environment 2019 Conference Paper, 68, 321-325 (2019) Inspection, diagnosis, and repair/renovation technology for pipeline equipment, NTT Technical Journal, 50 (March 2006)

It is known that the anticorrosive effect of applying synthetic resin paint decreases over time. Therefore, the method described in Non-Patent Document 1 may not provide sufficient anticorrosive effect over time after the construction of metal pipelines.

In addition, when an inner pipe is installed inside a metal pipeline, it is difficult to apply the method described in Non-Patent Document 2. In addition, in the method described in Non-Patent Document 2, the pipe diameter (inner diameter) becomes smaller due to the lining material, which may lead to a decrease in the installation performance of the inner pipe.

The purpose of this disclosure, made in consideration of the above problems, is to provide a corrosion prevention method and corrosion prevention system that can prevent corrosion of metal pipelines without changing the inside diameter.

In order to solve the above problems, the corrosion prevention method according to the present disclosure is a corrosion prevention method for a metal pipeline buried underground, and includes the steps of sealing one end of the metal pipeline with a first blocking cap having a first connection port and a first shutoff valve capable of closing the first connection port, and sealing the other end of the metal pipeline with a second blocking cap having a second connection port and a second shutoff valve capable of closing the second connection port, connecting an air supply hose to the first connection port, connecting an exhaust hose to the second connection port, and supplying an inert gas to the inside of the metal pipeline via the air supply hose, and, after the filling of the inert gas into the inside of the metal pipeline is completed, closing the first connection port with the first shutoff valve and closing the second connection port with the second shutoff valve.

In order to solve the above problem, the corrosion prevention system according to the present disclosure is a corrosion prevention system for a metal pipeline buried underground, and includes a first blocking cap having a first connection port and a first shutoff valve capable of closing the first connection port and sealing one end of the metal pipeline, a second connection port and a second shutoff valve capable of closing the second connection port and sealing the other end of the metal pipeline, a supply device that supplies an inert gas to the inside of the metal pipeline via an air supply hose connected to the first connection port, and an exhaust device that exhausts gas from the inside of the metal pipeline via an exhaust hose connected to the second connection port, and after the inside of the metal pipeline is filled with the inert gas, the first connection port is closed by the first shutoff valve and the second connection port is closed by the second shutoff valve.

The corrosion prevention method and corrosion prevention system disclosed herein can prevent corrosion of metal pipelines without changing the inner diameter.

FIG. 1 is a diagram illustrating a configuration example of a corrosion prevention system according to an embodiment of the present disclosure. FIG. 2 is a front view of the closure cap shown in FIG. 1 . FIG. 2 is a diagram showing the components constituting the closure cap shown in FIG. 1 before being connected together. FIG. 2 shows the closure cap shown in FIG. 1 secured to one end of a metal pipe. 2 is a flowchart for explaining a corrosion prevention method using the corrosion prevention system shown in FIG. 1 .

The following describes an embodiment of the present disclosure with reference to the drawings.

FIG. 1 is a diagram showing an example of the configuration of a corrosion prevention system 10 according to an embodiment of the present disclosure. The corrosion prevention system 10 according to this embodiment prevents corrosion of a metal pipeline 1, such as a communication pipeline, buried underground. As shown in FIG. 1, the metal pipeline 1 is provided to connect underground structures 3, such as manholes, handholes, or tunnels, installed underground. In the following, an example will be described in which an inner pipe 2, such as a cable or pipeline, is laid inside the metal pipeline 1 (the inner pipe 2 is inserted from one end 1a of the metal pipeline 1 and exposed from the other end 1b of the metal pipeline 1), as shown in FIG. 1.

As shown in FIG. 1, the corrosion prevention system 10 according to this embodiment includes a supply device 11, an exhaust device 12, a measuring device 13, and blocking caps 14a and 14b. The supply device 11 and the exhaust device 12 are installed, for example, on the ground.

The supply device 11 is connected to an air supply hose 11a and supplies an inert gas such as dried nitrogen through the air supply hose 11a.

The exhaust device 12 is connected to an exhaust hose 12a and exhausts gases such as air and inert gases through the exhaust hose 12a.

The measuring device 13 measures the oxygen concentration inside the metal pipe 1 or the oxygen concentration of the gas discharged from the exhaust hose 12a. In FIG. 1, the measuring device 13 shows an example in which it measures the oxygen concentration of the gas discharged from the exhaust device 12 via the exhaust hose 12a.

The blocking cap 14a, which serves as the first blocking cap, seals one end 1a of the metal pipeline 1. As shown in FIG. 1, the blocking cap 14a can seal one end 1a of the metal pipeline 1 with the inner pipe 2, which is laid inside the metal pipeline 1, passing through it.

The blocking cap 14b, which serves as the second blocking cap, seals the other end 1b of the metal pipeline 1. As shown in FIG. 1, the blocking cap 14b can seal the other end 1b of the metal pipeline 1 with the inner pipe 2 laid inside the metal pipeline 1 passing through it. Hereinafter, when there is no need to distinguish between the blocking cap 14a and the blocking cap 14b, they will be referred to as the blocking cap 14.

Figure 2 is a front view of the closure cap 14.

As shown in FIG. 2, the blocking cap 14 has a connection port 141, a shutoff valve 142, and a passage port 143.

The air supply hose 11a or the exhaust hose 12a is connected to the connection port 141. That is, the air supply hose 11a is connected to the connection port 141 (first connection port) of the blocking cap 14a, and the exhaust hose 12a is connected to the connection port 141 (second connection port) of the blocking cap 14b.

The shutoff valve 142 can close and open the connection port 141.

The inner tube 2 can pass through the passage opening 143. The inner diameter of the passage opening 143 is approximately the same size as the outer diameter of the inner tube 2. This makes it difficult for gas to flow in or out of the passage opening 143 even when the inner tube 2 has passed through the blocking cap 14.

As shown in FIG. 2, the closure cap 14 includes a first member 144 and a second member 145 that can be connected to the first member 144. As shown in FIG. 3, the first member 144 and the second member 145 are provided separately, and the closure cap 14 is formed by connecting these members. Note that the shutoff valve 142 is not shown in FIG. 3.

The first member 144 is a rectangular member in a plan view, and has a semicircular recess 144a on one side.

The second member 145 is a rectangular member in a plan view, and has a semicircular recess 145a on one side. The second member 145 is also provided with a connection port 141. The first member 144 and the second member 145 are connected, for example, by a screw 145b, so that the side on which the recess 144a is provided is in contact with the side on which the recess 145a is provided. When the first member 144 and the second member 145 are connected, the recess 144a and the recess 145a form a passage port 143.

Referring again to FIG. 2, the blocking cap 14 has a fixing portion 146 for fixing to the structure of the underground structure 3 with an anchor or a screw. FIG. 4 is a diagram showing the blocking cap 14 fixed to the structure of the underground structure 3, and is a side view of the blocking cap 14.

As shown in FIG. 4, the blocking cap 14 has an insertion portion 147 that is inserted into the metal pipeline 1. The outer diameter of the insertion portion 147 is approximately equal to the inner diameter of the metal pipeline 1. With the insertion portion 147 inserted into the metal pipeline 1, the blocking cap 14 is fixed to the structure of the underground structure 3 from the inside of the structure (side surface) of the underground structure 3. In this manner, the blocking cap 14 can seal one end 1a and the other end 1b of the metal pipeline 1. Airtightness can be further improved by wrapping security tape 148 or the like around the passage opening 143 and the inner pipe 2 for protection.

As described with reference to Figures 2 to 4, the first member 144 and the second member 145 are connected to form the blocking cap 14, so that the one end 1a and the other end 1b of the metal pipeline 1 can be sealed with the blocking cap 14 while the inner tube 2 is laid inside the metal pipeline 1.

In this embodiment, since an example is used in which the inner pipe 2 is laid inside the metal pipeline 1, the blocking cap 14 has a passage hole 143. However, if the inner pipe 2 is not laid inside the metal pipeline 1, the blocking cap 14 does not need to have a passage hole 143.

Next, the corrosion prevention method using the corrosion prevention system 10 according to this embodiment will be described with reference to the flowchart shown in FIG. 5.

First, remove moisture from inside the metal pipe 1 by spraying an adsorbent inside the metal pipe 1 or by using a suction device (step S11).

Next, a blocking cap 14a is attached to one end 1a of the metal pipeline 1, and a blocking cap 14b is attached to the other end 1b of the metal pipeline 1 (step S12).

As described above, the blocking cap 14 is attached to the metal pipeline 1 when the inner tube 2 has passed through the passage opening 143, and seals one end 1a and the other end 1b of the metal pipeline 1. The blocking cap 14 can be attached to the metal pipeline 1 in this state by connecting the first member 144 and the second member 145.

For example, by connecting the first member 144 and the second member 145 with the inner tube 2 placed in the recess 144a of the first member 144 and the recess 145a of the second member 145, the inner tube 2 can be placed through the passage opening 143. Then, by attaching the blocking cap 14 to one end 1a and the other end 1b of the metal pipeline 1, the one end 1a and the other end 1b of the metal pipeline 1 can be sealed with the inner tube 2 passing through the passage opening 143 (first passage opening) of the blocking cap 14a and the passage opening 143 (second passage opening) of the blocking cap 14b. The connecting opening 141 of the blocking cap 14 is left open.

Next, the air supply hose 11a is attached to the connection port 141 of the blocking cap 14a, and the exhaust hose 12a is attached to the connection port 141 of the blocking cap 14b (step S13).

Once the installation of the air supply hose 11a and the exhaust hose 12a is complete, the supply device 11 supplies the inert gas to the inside of the metal pipeline 1 via the air supply hose 11a (step S14). The exhaust device 12 also starts exhausting the gas inside the metal pipeline 1 via the exhaust hose 12a. By supplying the inert gas to the inside of the metal pipeline 1 using the supply device 11 and exhausting the gas inside the metal pipeline 1 using the exhaust device 12, the air inside the metal pipeline 1 can be replaced with the inert gas.

The measuring device 13 measures the oxygen concentration inside the metal pipeline 1 or the oxygen concentration of the gas discharged from the exhaust hose 12a. The measuring device 13 determines whether the measured oxygen concentration is below a predetermined value (step S15). By determining whether the oxygen concentration is below a predetermined value, it is possible to determine whether the gas inside the metal pipeline 1 is being replaced from air to inert gas, i.e., whether the filling of the inside of the metal pipeline 1 with inert gas has been completed.

If it is determined that the measured oxygen concentration is not equal to or lower than the predetermined value (step S15: No), the process returns to step S14, and the supply device 11 continues to supply the inert gas.

If it is determined that the measured oxygen concentration is equal to or lower than the predetermined value (step S15: Yes), the supply device 11 stops the supply of the inert gas (step S16). In addition, the exhaust device 12 stops exhausting the gas inside the metal pipe 1. In other words, when the filling of the inside of the metal pipe 1 with the inert gas is completed, the supply of the inert gas is stopped.

When filling of the interior of the metal pipeline 1 with the inert gas is completed and the supply of the inert gas and the exhaust of the gas inside the metal pipeline 1 are stopped, the connection port 141 (first connection port) of the blocking cap 14a is blocked by the shutoff valve 142 (first shutoff valve), and the connection port 141 (second connection port) of the blocking cap 14b is blocked by the shutoff valve 142 (second shutoff valve) (step S17). In this way, the interior of the metal pipeline 1 can be filled with the inert gas.

After the shutoff valve 142 closes the connection port 141, the air supply hose 11a and the exhaust hose 12a are removed (step S18).

The corrosion prevention method using the corrosion prevention system 10 according to this embodiment thus includes the steps of sealing one end 1a of the metal pipeline 1 with a blocking cap 14a and sealing the other end 1b of the metal pipeline 1 with a blocking cap 14b (step S12), connecting the air supply hose 11a to the connection port 141 of the blocking cap 14a, connecting the exhaust hose 12a to the connection port 141 of the blocking cap 14b, and supplying inert gas to the inside of the metal pipeline 1 via the air supply hose 11a (steps S13 and S14), and, after the filling of the inside of the metal pipeline 1 with inert gas is completed, closing the connection port 141 of the blocking cap 14a with the shutoff valve 142 and closing the connection port 141 of the blocking cap 14b with the shutoff valve 142 (step S17).

The inside of the metal pipeline 1 can be filled with inert gas by sealing one end 1a and the other end 1b of the metal pipeline 1 with a blocking cap 14, supplying inert gas to the inside of the metal pipeline 1 via the air supply hose 11a, and then blocking the connection port 141 of the blocking cap 14. In this manner, in this embodiment, the progress of corrosion due to various oxidation reactions caused by contact with the atmosphere, water, or other metals can be suppressed inside the metal pipeline 1. In addition, in this embodiment, the progress of corrosion is suppressed by filling the inside of the metal pipeline 1 with inert gas, so the inner diameter of the metal pipeline 1 is not changed. Therefore, there is no effect on the performance of laying the inner pipe 2 inside the metal pipeline 1.

The following notes are further provided with respect to the above embodiment.

[Additional Note 1]
A method for preventing corrosion of a metal pipeline buried underground, comprising the steps of:
one end of the metal conduit is sealed with a first blocking cap having a first connecting port and a first shutoff valve capable of closing the first connecting port, and the other end of the metal conduit is sealed with a second blocking cap having a second connecting port and a second shutoff valve capable of closing the second connecting port;
an air supply hose is connected to the first connecting port, an exhaust hose is connected to the second connecting port, and an inert gas is supplied to the inside of the metal pipe via the air supply hose;
a first shutoff valve for closing the first connecting port and a second shutoff valve for closing the second connecting port after the inert gas has been filled into the interior of the metal pipeline;

[Additional Note 2]
In the corrosion prevention method according to claim 1,
Measure the oxygen concentration inside the metal pipe or the oxygen concentration of the gas discharged from the exhaust hose;
The corrosion prevention method further comprises stopping the supply of the inert gas when the measured oxygen concentration becomes equal to or lower than a predetermined value.

[Additional Note 3]
In the corrosion prevention method according to claim 1 or 2,
an inner pipe is laid in the metal pipeline, the inner pipe being inserted into one end of the metal pipeline and exposed from the other end of the metal pipeline;
the first closure cap has a first passage opening through which the inner tube passes,
The second closure cap has a second passage opening through which the inner tube passes.

[Additional Note 4]
In the corrosion prevention method according to claim 3,
A corrosion prevention method in which the first blocking cap and the second blocking cap each have a first member and a second member connectable to the first member, and the first passage port and the second passage port are formed by connecting the first member and the second member.

[Additional Note 5]
A corrosion protection system for an underground buried metal pipeline, comprising:
a first blocking cap having a first connecting port and a first shutoff valve capable of closing the first connecting port and configured to seal one end of the metal pipe;
a second blocking cap having a second connecting port and a second shutoff valve capable of closing the second connecting port and sealing the other end of the metal pipe;
a supply device that supplies an inert gas to the inside of the metal pipeline through an air supply hose connected to the first connection port;
an exhaust device that exhausts gas from inside the metal pipe through an exhaust hose connected to the second connection port,
a corrosion prevention system, wherein after the inert gas has been completely filled into the interior of the metal pipeline, the first connecting port is closed by the first shutoff valve and the second connecting port is closed by the second shutoff valve.

The above-mentioned embodiments have been described as representative examples, but it will be apparent to those skilled in the art that many modifications and substitutions can be made within the spirit and scope of the present disclosure. Therefore, the present invention should not be interpreted as being limited by the above-mentioned embodiments, and various modifications or changes are possible without departing from the scope of the claims. For example, it is possible to combine multiple configuration blocks shown in the configuration diagram of the embodiment into one, or to divide one configuration block.

REFERENCE SIGNS LIST 1 Metallic pipeline 2 Inner pipe 10 Corrosion prevention system 11 Supply device 11a Air supply hose 12 Exhaust device 12a Exhaust hose 13 Measuring device 14a Closure cap (first closing cap)
14b Closure cap (second closure cap)
141 Connection port 142 Shutoff valve 143 Passage port 144 First member 144a Recess 145 Second member 145a Recess 146 Fixing portion 147 Insertion portion 148 Confidentiality tape

Claims (5)

A method for preventing corrosion of a metal pipeline buried underground, comprising the steps of:
sealing one end of the metal conduit with a first blocking cap having a first connecting port and a first shutoff valve capable of closing the first connecting port, and sealing the other end of the metal conduit with a second blocking cap having a second connecting port and a second shutoff valve capable of closing the second connecting port;
connecting an air supply hose to the first connecting port, connecting an exhaust hose to the second connecting port, and supplying an inert gas into the inside of the metal pipeline through the air supply hose;
and after completion of filling the inside of the metal pipeline with the inert gas, closing the first connection port with the first shut-off valve and closing the second connection port with the second shut-off valve. The corrosion prevention method according to claim 1,
measuring the oxygen concentration inside the metal pipe or the oxygen concentration of the gas discharged from the exhaust hose;
The corrosion prevention method further comprises stopping the supply of the inert gas when the measured oxygen concentration becomes equal to or lower than a predetermined value. The corrosion prevention method according to claim 1,
an inner pipe is laid in the metal pipeline, the inner pipe being inserted into one end of the metal pipeline and exposed from the other end of the metal pipeline;
the first closure cap has a first passage opening through which the inner tube passes,
The second closure cap has a second passage opening through which the inner tube passes. The corrosion prevention method according to claim 3,
A corrosion prevention method in which the first blocking cap and the second blocking cap each have a first member and a second member connectable to the first member, and the first passage port and the second passage port are formed by connecting the first member and the second member. A corrosion protection system for an underground buried metal pipeline, comprising:
a first blocking cap having a first connecting port and a first shutoff valve capable of closing the first connecting port and configured to seal one end of the metal pipe;
a second blocking cap having a second connecting port and a second shutoff valve capable of closing the second connecting port and sealing the other end of the metal pipe;
a supply device that supplies an inert gas to the inside of the metal pipeline through an air supply hose connected to the first connection port;
an exhaust device that exhausts gas from inside the metal pipe through an exhaust hose connected to the second connection port,
a corrosion prevention system, wherein after completion of filling the inside of the metal pipeline with the inert gas, the first connection port is closed by the first shutoff valve and the second connection port is closed by the second shutoff valve.

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