JP5232633B2 - Pipe welding method - Google Patents

Description

  The present invention relates to a pipe welding method used when butt welding pipes such as stainless steel pipes and chrome steel pipes.

  In general, when performing arc welding, an inert gas that does not react with metals even at high temperatures (Inert) to prevent the occurrence of defects such as cracks in the weld due to the influence of oxygen and nitrogen in the air. Gas) is supplied to the periphery of the weld and welding is performed in an inert gas atmosphere. As the inert gas, for example, argon gas is preferably used.

  Accordingly, welding of pipes such as stainless steel pipes and chrome steel pipes is similarly performed in an inert gas atmosphere. In particular, when this type of pipe is butt-welded, it is necessary to keep not only the outside of the pipe but also the inside, that is, the internal space, in an inert gas atmosphere. Therefore, it is necessary to supply the inert gas into the pipe before the welding and replace the inside of the pipe with the inert gas.

  However, pipes such as stainless steel pipes and chrome steel pipes are long and used in a complicated and complicated manner as components of equipment such as nuclear power plants and thermal power plants. It is installed. Therefore, when exchanging a part of the pipes that are already arranged, the internal space of the entire pipe including the equipment may be replaced with an inert gas. In such a case, a large number of man-hours and work periods are often required for advance preparation for replacement with an inert gas.

Therefore, instead of replacing the internal space of the entire pipe with inert gas, temporarily install a temporary stopper as a seal in the pipe so that only the internal space around the welded area is an inert gas atmosphere. The technique to do is considered.
As a specific procedure in this case, after temporarily installing a temporary stopper in the pipe, the pipes are butted together. Then, an inert gas is supplied to the inside of the butted pipes. As a result, the inside of the pipe sealed on both sides with a temporary stopper can be made an inert gas atmosphere. That is, only the internal space around the welded portion can be made an inert gas atmosphere. As described above, since only a necessary region in the pipe can be replaced with the inert gas, it is more efficient than the above-described method in which the internal space of the entire pipe is replaced with the inert gas.

However, this method inevitably requires the trouble of collecting the temporary stopper installed after the end of welding. In particular, in order to reliably recover the temporary stopper, it must be installed near a point that is easy to recover later, for example, near the end of the pipe or a valve element interposed in the middle of the pipe. It will be limited. For this reason, it is difficult to install a temporary stopper near the welding location, and in most cases, the temporary stopper must be installed at a position far from the welding location.
Therefore, a large amount of inert gas is used, and a lot of time is required for the replacement work, and it is still impossible to efficiently prepare in advance.

Therefore, as a new method, a method of confining the inert gas only around the welded part by using a temporary stopper made of a water-soluble film (for example, polyvinyl alcohol film) in a bag shape is considered. (See Patent Document 1).
In this method, since a temporary stopper that dissolves in water is used, it is possible to save the trouble of collecting the temporary stopper after welding. As a specific procedure, after installing a temporary stopper inflated at a position pushed into the pipe from a joint end which is a welded place, the pipes are brought into contact with each other. Then, an inert gas is supplied to the inside of the pipe, and the inside of the pipe sealed on both sides with a temporary stopper, that is, the inner space around the welded place is replaced with an inert gas atmosphere (when argon gas is used for replacement) (Referred to as argon back). After welding in this state, a fluid such as warm water is allowed to flow through the pipe. Then, the temporary stopper installed in the pipe is dissolved by this fluid. Thereby, a temporary stopper can be easily discharged | emitted out of piping with a fluid.

As described above, since the sealing material is not recovered but can be easily removed using the fluid, the temporary stopper can be freely installed in the pipe without being restricted. Therefore, the temporary stopper can be installed near the welding location. As a result, the amount of inert gas used can be reduced, and the time required for the replacement work can be shortened.
JP-A-5-245633

  By the way, a temporary stopper made of a water-soluble film is easily affected by temperature and humidity. Therefore, when installing a temporary stopper, it is preferable to install it as close as possible to the welding point in terms of reducing the amount of inert gas used. However, in practice, it should not be affected by heat during welding. It must be installed at a position away from the welding point. That is, it is necessary to install in a state where it is pushed from the joint end of the pipe, which is a welding location, to a position where it is not affected by heat during welding. Moreover, it is necessary to maintain the temporary stopper in a state where it is inflated reliably at that position, and to keep it in close contact with the inner surface of the pipe.

In this regard, in the method described in Patent Document 1, the step of pushing into the pipe with the air blowing nozzle inserted into the temporary plug, the step of blowing the air from the air blowing nozzle and then inflating the temporary plug after being pushed, After inflating, a step of extracting the air blowing nozzle is performed.
However, since the temporary stopper is pushed in with the air blowing nozzle inserted, the temporary stopper may be damaged by the nozzle. Further, there is a possibility that the air blowing nozzle may come off midway. Therefore, it is a work to be performed with caution, and is not time-consuming and efficient. In addition, after extracting the air blowing nozzle, air may leak from the temporary stopper, and it is difficult to expect reliable adhesion over a long period of time. Therefore, it has a bad influence on welding, and in severe cases, it may be difficult to perform the welding itself.

  The present invention has been made in view of such circumstances, and its purpose is to allow a balloon, which is a temporary stopper, to be set for a long time without being easily damaged by anyone inside the pipe at a position away from the welding point. A pipe welding method is provided in which the balloon can be brought into close contact with the pipe and the butt welding of the pipe can be reliably performed.

The present invention provides the following means in order to solve the problems and achieve the object.
A pipe welding method according to the present invention is a pipe welding method in which two pipes are butt-welded in an inert gas environment using an inflatable water-soluble balloon, and vaporization is caused by evaporation or sublimation. A storage step of storing the volatile material in the deflated balloon through the introduction tube and then sealing the vaporizable material by closing the introduction tube; and the balloon in which the volatile material is stored 2 A set step of pushing into each of the pipes of the book and moving it to a position separated from the joint end by a specified value or more and setting it outside the high temperature region during welding; after setting the balloon, the vaporizable material Inflating the balloon with the gas generated by vaporization of the gas, and inflating the balloon to the inner surface of the pipe, butting the joint ends of the two pipes together, A replacement step of replacing the internal spaces of both pipes surrounded by balloons in the environment of the inert gas, and after the replacement is completed, the butted portions of the two pipes from the outer surface side while supplying the inert gas A welding process for welding, and a flushing process for supplying a fluid into both the pipes after the welding is completed to dissolve the balloon and discharging the fluid from the pipes together with the fluid.

In the pipe welding method according to the present invention, first, a storing step of storing the vaporizable material in the balloon in a deflated state via the introduction tube is performed. After the storage, the balloon introduction tube is closed to seal the vaporizable material inside.
Subsequently, the deflated balloons containing the vaporizable material are respectively pushed into the two pipes and are moved away from the joint end by a predetermined value or more so as not to be affected by heat during welding. A setting process of setting outside the high temperature region is performed. Then, the vaporizable material spontaneously volatilizes or sublimates and vaporizes to generate gas, so that the balloon is expanded by the gas. By this expansion step, the balloon can be brought into close contact with the inner surface of the pipe, and the pipe can be closed on the way.

After setting the balloons on the two pipes, the joint ends of both pipes are butted together. Under the present circumstances, the internal space of both piping around a welding location becomes the obstruction | occlusion space enclosed with the balloon. Then, a replacement process is performed in which an inert gas is supplied to the closed internal space and replaced in an environment of the inert gas. That is, the back side of the welded portion can be placed in an inert gas environment.
And after substitution is complete | finished, the welding process which welds the butt | matching part of both piping from an outer surface side is performed, supplying an inert gas. Thereby, the butted joint ends can be integrally coupled, and both pipes can be connected to one. In particular, not only the outside but also the inside of the welded part is in an inert gas environment, so it can be welded without being affected by oxygen, nitrogen, etc. in the air, and does not have cracks. It can be performed.
Then, after the end of welding, a flushing process is performed in which a fluid is supplied into both pipes to dissolve the water-soluble balloon, and the balloon components dissolved together with the fluid are discharged from both pipes. As a result, the balloon that has blocked the inside of the pipe can be surely removed, and both pipes can be used immediately thereafter.

In particular, according to the method of the present invention, the balloon body can be pushed into a position away from the joint end, which is a welding location, in a deflated state, so that the balloon body can be easily set and reliably set at a desired position. Moreover, since there is no need to use an air blowing nozzle or the like as in the prior art, there is no risk of damaging the balloon. Further, since the vaporizable material is used, the balloon can be inflated naturally and reliably. Therefore, efficient work can be performed.
Furthermore, since the vaporizable material is used, the balloon can be inflated after the introduction tube is reliably closed. Therefore, it is possible to reliably prevent the gas from leaking and to keep the balloon in close contact with the inner surface of the pipe for a long time. Therefore, high gas sealing performance can be expected, and high-quality welding work can be performed.

  The pipe welding method according to the present invention is characterized in that, in the pipe welding method of the present invention, the vaporizing material is stored in the balloon while being held by a holding tray during the storing step. .

In the pipe welding method according to the present invention, the vaporizable material is not stored directly in the balloon, but is stored in a state of being held by a holding tray. Therefore, it is possible to prevent the vaporizable material from coming into direct contact with the balloon until it is vaporized after being stored. Therefore, it is possible to prevent the balloon temperature from being suddenly lowered locally due to the endothermic reaction that occurs during vaporization of the vaporizable material. Therefore, it is possible to reduce the possibility that the balloon is torn due to a rapid temperature drop.
Furthermore, it is possible to prevent the piping from being locally cooled by the endothermic reaction and causing condensation. Therefore, the possibility of balloon breakage due to condensation can be reduced.

  The pipe welding method according to the present invention is the pipe welding method according to the present invention, wherein a water-soluble adhesive liquid having a viscosity is applied to the entire surface of the balloon in the setting step, and then the inside of the pipe. It is characterized by pushing.

In the pipe welding method according to the present invention, since the adhesive liquid is applied to the surface of the balloon, the balloon can be kept in close contact with the inner surface of the pipe using the surface tension of the adhesive liquid. Therefore, more reliable gas sealing performance can be expected over a long period of time. Further, even when the balloon has lost some tension for some reason, the adhesive liquid enters the lost tension portion, so that the close contact state can be maintained. Also in this respect, a more reliable gas sealing property can be expected.
In addition, since the adhesive liquid is water-soluble, it can be removed from the pipe by the flushing process, and there is no fear of remaining in the pipe.

  Further, the pipe welding method according to the present invention is the above pipe welding method according to the present invention, wherein in the flushing step, a dissolved component of the balloon is removed from the fluid after flushing using a filter that adsorbs organic matter. The removing step is performed.

  In the pipe welding method according to the present invention, since the removal process using a filter is performed during flushing, the dissolved balloon components can be removed from the fluid with high accuracy. Therefore, it is possible to prevent balloon components from remaining in the pipe. Therefore, it is possible to prevent the balloon component from running around to the equipment device connected to the pipe, and to prevent adverse effects such as malfunctions from occurring on the equipment device side.

  Further, the pipe welding method according to the present invention is characterized in that, in the pipe welding method of the present invention, a confirmation step is performed to confirm whether or not the balloon is in close contact with the inner surface of the pipe in the expansion step. To do.

  In the pipe welding method according to the present invention, after the balloon is inflated, a confirmation step is performed to confirm whether or not the balloon is securely adhered to the inner surface of the pipe from the elasticity of the balloon. Therefore, a more reliable gas sealing property can be expected. In particular, since the confirmation is performed before the replacement step, it is possible to prevent the inert gas from being wasted.

  According to the pipe welding method according to the present invention, a balloon can be set in the pipe at a position away from the welding location without being easily damaged by anyone, and the balloon can be brought into close contact with the pipe for a long time. Therefore, high gas sealing performance can be expected, butt welding of pipes can be reliably performed under an inert gas environment, and high-quality welding work can be performed.

(First embodiment)
A first embodiment according to the present invention will be described below with reference to FIGS.
As shown in FIG. 1 (a), the pipe welding method of the present embodiment uses two water-soluble balloons (pipe welding balloons) 1 in an argon gas (inert gas) G environment. This is a method of butt welding the pipe 2. In FIG. 1, the balloon 1 is illustrated in a simplified manner.

In this pipe welding method, as shown in FIG. 2, the storing step (S1) for storing the dry ice D, which is a vaporizable material, in the balloon 1 in a deflated state, and the balloon 1 storing the dry ice D in the pipe 2 A setting step (S2) for setting the inside of the balloon, an inflating step (S3) for inflating the balloon 1, a replacing step (S4) for replacing the inside of the piping 2 under the environment of the argon gas G, and the piping 2 for two. A welding process (S5) for butt welding and a flushing process (S6) for discharging the balloon 1 from the pipe 2 are provided.
In the present embodiment, the case where dry ice D that is vaporized by sublimation is used as the vaporizable material will be described as an example. Hereinafter, each of these steps will be described in detail.

First, the balloon 1 will be described before describing each process.
As shown in FIG. 3, the balloon 1 used in this embodiment includes an inflatable balloon main body 10 and an introduction cylinder 11 that is formed integrally with the balloon main body 10 and that contains dry ice D into the balloon main body 10. And is composed of.
The balloon 1 is made of PVA (polyvinyl alcohol), which is one of water-soluble materials, specifically, vinylon VF-L (manufactured by Kuraray). It is a water-soluble balloon that dissolves. A method for manufacturing the balloon 1 will be described later.

The balloon body 10 is formed to be cylindrical when inflated, and is adapted to fit the inner surface of the pipe 2. One end side of the balloon body 10 is completely closed and closed. On the other hand, the other end side of the balloon body 10 is closed in a partially opened state, and is formed in a state in which the introduction tube 11 is connected to the partially opened portion.
The outer diameter φ of the balloon body 10 is preferably larger than the inner diameter of the pipe 2, and the length L is preferably at least twice as long as the inner diameter of the pipe 2. For example, in the case of the pipe 2 having a nominal diameter B of 2B and a nominal diameter, it may be about 150 mm, about 375 mm in the case of 6B, about 625 mm in the case of 10B, and about 900 mm in the case of 14B. However, it is not limited to these numerical values, and it may be formed longer, or may be a length not more than twice the inner diameter of the pipe 2.
The introduction tube 11 is formed in a cylindrical shape having an outer diameter much smaller than that of the balloon body 10 and can be closed by welding.

  By the way, the piping 2 of this embodiment is, for example, a stainless steel pipe or a chrome steel pipe used as a nuclear power pipe, a boiler tube or the like, and each end is connected to a plant facility (equipment equipment) P as shown in FIG. Yes.

Next, the case where the pipe 2 is welded using the balloon 1 will be described while explaining each process described above in detail.
First, a storage step (S1) for storing the dry ice D in the balloon 1 is performed. Specifically, as shown in FIG. 4, after the dry ice D is stored in the balloon 1 in a deflated state via the introduction cylinder 11, the introduction cylinder 11 is closed by welding as shown in FIG. D is sealed inside. At this time, the dry ice D is fixed and easy to handle.

After this process is completed, a setting process (S2) is performed. That is, as shown in FIG. 6, the deflated balloon 1 containing the dry ice D is pushed into the pipe 2 and moved so as to be separated from the joint end 2 a by a predetermined value H or more. Set it outside the high temperature range that is not affected by heat.
The specified value H is a numerical value that varies depending on the material and size of the pipe 2, the welding conditions, and the like, but is empirically about 100 mm.

  Then, since the dry ice D naturally sublimates and vaporizes to generate gas, the balloon 1 is inflated by this gas as shown in FIG. Thereby, the balloon 1 can be closely adhered to the inner surface of the pipe 2, and the pipe 2 can be closed on the way. This process is an expansion process (S3).

  After the inflation, a confirmation step (S3a) for confirming whether or not the balloon 1 is securely adhered to the inner surface of the pipe 2 is performed. As a method for confirming, for example, the contact condition is confirmed by visually observing whether there is a gap between the inner surface of the pipe 2 and the balloon body 10. Moreover, the balloon main body 10 is pushed and the contact condition is confirmed by the feel of the elasticity at that time. In any method, the tightness of the balloon body 10 can be confirmed. At this point, the expansion step (S3) ends.

After performing each process mentioned above with respect to the two piping 2, respectively, it transfers to a substitution process (S4). First, as shown in FIG. 8, the joining ends 2a of the two pipes 2 are butted together. At this time, the internal space of both pipes 2 around the welded portion is a closed space surrounded by the balloon 1. Then, the argon gas G is supplied to the closed internal space and replaced with the environment of the argon gas G. That is, the back side of the welded portion is placed in an argon gas G environment.
In addition, when supplying argon gas G, you may supply from the clearance gap between the joining ends 2a. Alternatively, a recess may be formed in the pipe 2 in the vicinity of the joint end 2a, and a hole that can be filled later is formed in the recess, and the argon gas G may be supplied through the hole.

  After the replacement with the argon gas G is completed, as shown in FIG. 1A, a welding step of welding the butted portions of both pipes 2 from the outer surface side while supplying the argon gas G with the welding torch T (S5). I do. Thereby, the joined joint ends 2a can be integrally coupled, and both the pipes 2 can be connected to one. Especially, not only the outside but also the inside of the welded part is under the atmosphere of argon gas G, so it can be welded without being affected by oxygen, nitrogen, etc. in the air, and high quality welding work without cracks etc. It can be performed.

After the welding is completed, a flushing step (S6) is performed. That is, as shown in FIG. 9, hot water W is supplied into both pipes 2. Thereby, the water-soluble balloon 1 can be dissolved, and the components of the balloon 1 dissolved together with the hot water W can be discharged from both the pipes 2.
As a result, as shown in FIG. 1 (b), the balloon 1 that has blocked the inside of the pipe 2 on the way can be surely removed, and both pipes 2 can be used immediately thereafter.

As described above, according to the pipe welding method of the present embodiment, the balloon body 10 is pushed into a position away from the joint end 2a that is a welding position in a deflated state, so that the balloon body 10 can be easily set and reliably set at a desired position. can do. In addition, since there is no need to use an air blowing nozzle or the like as in the prior art, there is no risk of damaging the balloon 1.
Further, since the dry ice D is used, the balloon 1 can be inflated naturally and reliably. Therefore, efficient work can be performed.
Furthermore, since the dry ice D is used, the balloon 1 can be inflated after the introduction tube 11 is completely closed. Therefore, the gas sublimated by the dry ice D can be reliably prevented from leaking, and the balloon 1 can be kept in close contact with the inner surface of the pipe 2 for a long time. Therefore, high gas sealing performance can be expected, and high-quality welding work can be performed.

  Moreover, in this embodiment, after inflating the balloon 1, the confirmation process (S3a) which confirms whether it is closely_contact | adhered to the inner surface of the piping 2 is performed. Therefore, a more reliable gas sealing property can be expected. In particular, since the confirmation is performed before the substitution step (S4) for substitution with the argon gas G, it is possible to prevent the argon gas G from being wasted.

Next, a method for manufacturing the balloon 1 used in this embodiment will be described.
This manufacturing method is a method that can efficiently manufacture the balloon 1 at a low cost with a simple process of simply repeating welding. As shown in FIG. 10, the first welding step (S10) and the second welding are performed. In this method, the step (S11) and the third welding step (S12) are mainly performed.
Hereinafter, each of these steps will be described in detail.

  First, the first welding step (S10) is performed. Specifically, as shown in FIG. 11, a sheet body 15 having a square shape in plan view made of PVA (Vinylon VF-L: manufactured by Kuraray), which is a water-soluble material, is prepared. In addition, as thickness, in order to provide tolerance with respect to temperature, humidity, etc., what is necessary is just to use what is as thick as possible. For example, 30 μm or more. Subsequently, as shown in FIG. 12, the sheet body 15 is rounded so that the ends overlap each other, and is formed into a cylindrical shape having both ends opened. And the overlapping edge parts are continuously welded. At this time, the cylindrical diameter may be determined according to the inner diameter of the pipe 2. This completes the first welding step (S10). In addition, the code | symbol S1 shown in FIG. 12 is the welding line after welding.

  Subsequently, a second welding step (S11) is performed. Specifically, as shown in FIG. 13, one end side of a cylindrical sheet body 15 having both ends opened is further welded, and the one end side that has been opened is completely closed and closed. Thereby, the sheet | seat body 15 will be in the state which opened only the other end side. In addition, when performing this process, it welds so that welding line S2 may draw a substantially C type | mold. And as shown in FIG. 14, after welding, the excess part located in the outer side of welding line S2 is cut off.

  Subsequently, the reverse process (S13) is performed before the third welding process (S12). That is, the sheet body 15 shown in FIG. 14 whose one end side is closed in a substantially C shape is turned over so that the front and back sides thereof are reversed. Thereby, as shown in FIG. 15, the welding lines S1 and S2 welded in the first welding step (S10) and the second welding step (S11) can be reversed and concealed to the inner surface side.

After performing this reversing step (S13), a third welding step (S12) is performed. Specifically, as shown in FIG. 16, the introduction tube 11 is welded integrally with the other end of the cylindrical sheet 15 being welded in a state in which the other end is left open, and the tip being open at the part that is partially open. It is welded so as to be formed in a connected state.
At this time, welding is performed so as to form the introduction cylinder 11 using the region excluding the welding line S1 welded in the first welding step (S10). That is, welding is performed so that only the welding line S3 welded in the third welding step (S12) remains on the introduction cylinder 11.

  As a result, the balloon 1 shown in FIG. 3 having the balloon body 10 and the introduction tube 11 can be manufactured. In particular, the balloon 1 swells in a cylindrical shape when inflated. Accordingly, since the outer peripheral surface is in a state along the inner surface of the pipe 2 when it is set inside the pipe 2, it naturally fits into the inner surface of the pipe 2 and adheres closely without any gap. Therefore, the pipe 2 can be tightly closed in the middle, high gas sealing performance can be exhibited, and it can be kept in close contact for a long time. Therefore, as described above, it is possible to perform a high-quality welding operation without cracks.

And according to the said manufacturing method, the balloon 1 can be produced in the simple process of only repeating a welding from the sheet | seat body 15 of 1 sheet. Therefore, the balloon 1 can be produced efficiently at low cost.
Further, since the welding lines S1 and S2 in the first welding process (S10) and the second welding process (S11) are hidden on the inner surface side by the turning over process (S13), the welding lines S1 and S2 are The outer surface can be made smooth without appearing on the outer surface. Therefore, the balloon 1 can be brought into close contact with the inner surface of the pipe 2 without any gap, and higher gas sealing performance can be expected.

In the second welding step (S11), the welding line S2 is welded so as to draw a substantially C-shaped trajectory. Thereby, when the balloon 1 is inflated, one end side can be inflated without making it as square as possible. If the angle is excessively large, the argon gas G is locally concentrated, and there is a possibility that the pressure is increased more than other portions, leading to leakage. However, since it is inflated in a state where cornering is eliminated as much as possible, the possibility of leakage can be reduced, and the reliability can be further improved.
Further, during the third welding step (S12), welding is performed using a region excluding the welding line S1 generated during the first welding step (S10). Therefore, the two welding lines S1 and S3 generated in the two steps of the first welding step (S10) and the third welding step (S12) do not remain in the introduction cylinder 11, but the third welding step. Only the welding line S3 generated in (S12) remains. Therefore, the outer peripheral surface of the introduction cylinder 11 can be made as smooth as possible with as few seams as possible, and the possibility of leakage can be reduced.

  In addition, in the above-described manufacturing method, it is preferable to perform welding in such a manner that the welding lines are doubled on the inner side and the outer side in the welding process. By doing so, the possibility of leakage from the welding line can be reduced, and the balloon 1 can be made more reliable.

(Second Embodiment)
Next, a second embodiment according to the present invention will be described with reference to FIGS. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.
The difference between the second embodiment and the first embodiment is that the dry ice D and the balloon 1 are in direct contact with each other in the first embodiment, but the dry ice D and the balloon 1 are directly in the second embodiment. It is a point which prevents a special contact.

That is, in the pipe welding method of the present embodiment, as shown in FIG. 17, the dry ice D is stored in the balloon 1 while being held by the holding tray 21 in the storing step (S1). Therefore, as shown in FIG. 18, it is possible to prevent the dry ice D from coming into direct contact with the balloon 1 from when it is stored until it is vaporized by sublimation. Therefore, it is possible to prevent the temperature of the balloon 1 from being suddenly lowered locally by the endothermic reaction that occurs during the sublimation of the dry ice D. Therefore, possibility that the balloon 1 will be torn by rapid temperature fall can be reduced.
Furthermore, it is possible to prevent the pipe 2 from being locally cooled by the endothermic reaction and causing condensation. Therefore, the possibility of the balloon 1 being broken due to condensation can be reduced.

  In addition, as a method of manufacturing the balloon 1 in this case, as shown in FIG. 19, a holding plate 21 is formed in a cylindrical shape between the second welding step (S11) and the third welding step (S12). What is necessary is just to perform the fixing process (S14) which fixes to the inner side of the sheet | seat body 15. FIG.

  The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

  For example, in each of the above embodiments, the balloon 1 is inflated using the dry ice D, but is not limited to the dry ice D, and any vaporizable material that vaporizes by sublimation or volatilization may be used. However, it is preferable to use a sublimable material that vaporizes by sublimation, such as dry ice D, as the vaporizable material. This is preferable because it can be handled in a solid state. Note that naphthalene may be used when a sublimable material is used as the vaporizable material.

Moreover, in each said embodiment, as shown in FIG. 20, after apply | coating the water-soluble adhesive liquid M which has a fixed viscosity to the whole surface of the balloon 1 in the case of a setting process (S2), inside the piping 2 is carried out. You can push in.
In this case, since the adhesive liquid M is applied to the surface of the balloon 1, the balloon body 10 can be kept in close contact with the inner surface of the pipe 2 using the surface tension of the adhesive liquid M. Therefore, more reliable gas sealing performance can be expected over a long period of time. Even if the balloon body 10 has lost some tension for some reason, the adhesive liquid M enters the lost tension portion, so that the contact state can be maintained. Also in this respect, a more reliable gas sealing property can be expected.

In addition, since the adhesive liquid M is water-soluble, it can be removed from the pipe 2 by the flushing step (S6), and there is no possibility of remaining in the pipe 2. Examples of such an adhesive liquid M include glycerin, paste, and glue.
In this case, when the balloon 1 is manufactured, as shown in FIG. 21, after the third welding step (S12), an application step (S15) for applying the adhesive liquid M to the entire surface of the balloon 1 is performed. Just do it.

Moreover, in each said embodiment, as shown in FIG.22 and FIG.23, after flushing the component of the melt | dissolved balloon 1 using the absorption filter (filter) 20 which adsorb | sucks organic substance in the flushing process (S6). The removal step (S6a) for removing from the hot water W may be performed.
By performing this step, the dissolved components of the balloon 1 can be removed from the warm water W with high accuracy. Therefore, it is possible to prevent the components of the balloon 1 from remaining in the pipe 2. Therefore, it can prevent that the component of the balloon 1 wraps around to the plant equipment P side connected to the piping 2, and can prevent that bad influences, such as malfunctioning, arise on the plant equipment P side beforehand. .
An activated carbon filter may be used as the filter. In this case, carbon can be mainly removed and no carbon remains in the pipe 2.

Moreover, in each said embodiment, although the case where the balloon 1 was produced using PVA, specifically, vinylon VF-L (made by Kuraray) was mentioned as an example, it produced with PVA other than vinylon VF-L. Alternatively, it may be made of a material other than PVA. However, PVA is suitable as a water-soluble material because it has many hydroxy groups (—OH) in the molecule.
In particular, the property required of the balloon 1 is required to be resistant to humidity but easily dissolved in hot water W. Therefore, when the balloon 1 is produced using PVA, it is possible to bring the melting temperature and high-temperature and high-humidity resistance closer to desired states by selecting the grade of saponification degree and molecular weight. For example, when the degree of saponification is increased, the number of hydroxy groups decreases, so that it becomes difficult to dissolve in warm water W and water resistance increases, but moisture permeability decreases and it becomes difficult to pass moisture. On the other hand, when the degree of saponification is lowered, it is easy to dissolve in the warm water W and the water resistance becomes low, but on the other hand, the moisture permeability increases and the moisture can be easily passed.

  Thus, it is necessary to reduce the saponification degree if attention is paid to the point that it is easily dissolved in the hot water W, but it is necessary to increase the saponification degree if attention is paid to the point that it is difficult to pass moisture. Therefore, in order to achieve the above contradictory properties, that is, the property of being strong against humidity but being easily soluble in hot water W, it is necessary to adjust the saponification degree with an optimal balance. In this respect, it is preferable to adjust the saponification degree to 96 to 98. By doing so, the balloon 1 can be set even in a high-temperature and high-humidity environment of a temperature of 40 ° C. and a humidity of 90%, and the balloon 1 can be dissolved with warm water W of about 70 ° C. .

It is a figure which shows one Embodiment which concerns on this invention, Comprising: (a) is a figure of the state which has welded the butt | matching part of two piping with which the balloon was set, (b) is a balloon after completion | finish of welding. It is a figure of the state which removed. It is a flowchart at the time of performing butt welding of piping shown in FIG. It is an expansion perspective view of the balloon shown in FIG. It is a process figure at the time of performing butt welding of piping along the flowchart shown in FIG. 2, Comprising: It is a figure which shows the state which set the dry ice in the deflated balloon. It is a figure which shows the state which welded and closed the front-end | tip of the introduction cylinder of the balloon after the state shown in FIG. It is a figure which shows the state which set the balloon inside the piping after the state shown in FIG. It is a figure which shows the state which two balloons expanded by the sublimation of dry ice after the state shown in FIG. It is a figure which shows the state which butted two piping after the state shown in FIG. 7, and is supplying argon gas inside. It is a figure which shows the state just before supplying warm water in piping after the state shown to Fig.1 (a), and dissolving a balloon. It is a flowchart at the time of manufacturing the balloon shown in FIG. It is a process figure at the time of manufacturing a balloon along the flowchart shown in FIG. 10, Comprising: It is a figure which shows the state which prepared the water-soluble sheet | seat body. It is a figure which shows the state which welded the edge part of the sheet | seat body, after rounding a sheet | seat body and making it cylindrical shape after the state shown in FIG. It is a figure which shows the state which welded the end side of the sheet | seat body formed in the cylindrical shape after the state shown in FIG. 12, and was completely plugged up. It is a figure which shows the state which cut | disconnected the welded extra part after the state shown in FIG. It is a figure which shows the state which turned the sheet body upside down so that the front and back might reverse after the state shown in FIG. FIG. 16 is a view showing a state in which, after the state shown in FIG. 15, the other end side of the sheet body is welded to form a balloon body and an introduction tube. It is a figure which shows 2nd Embodiment which concerns on this invention, Comprising: It is a figure which shows the balloon to which the holding tray holding dry ice was fixed. It is a figure which shows the state which the balloon expanded by the sublimation of the dry ice hold | maintained at the holding plate after the state shown in FIG. It is a flowchart at the time of manufacturing the balloon which has a holding tray. It is a figure which shows the modification which concerns on this invention, Comprising: It is a figure which shows the state which apply | coated the adhesive liquid to the outer surface of a balloon. It is a flowchart at the time of manufacturing the balloon which apply | coated the adhesive liquid. It is a figure which shows the modification which concerns on this invention, Comprising: When melt | dissolving a balloon using warm water, it is a figure which shows the state which set the absorption filter which removes the dissolved component of a balloon to piping. It is a flowchart at the time of performing butt welding of piping, utilizing an absorption filter.

Explanation of symbols

D ... Dry ice (vaporizable material)
G: Argon gas (inert gas)
M ... Adhesive liquid H ... Specified value W ... Hot water (fluid)
1 ... Balloon (balloon for pipe welding)
DESCRIPTION OF SYMBOLS 2 ... Piping 2a ... Joint end of piping 10 ... Balloon body 11 ... Introducing tube 20 ... Absorption filter 21 ... Holding plate S1 ... Storage process S2 ... Setting process S3 ... Expansion process S3a ... Confirmation process S4 ... Replacement process S5 ... Welding process S6 ... Flushing process S6a ... Removal process

Claims (5)

A pipe welding method in which two pipes are butt-welded in an inert gas environment using an inflatable water-soluble balloon,
After storing the vaporizable material vaporized by volatilization or sublimation through the introduction tube in the deflated state of the balloon, the storage step of closing the introduction tube and sealing the vaporizable material inside,
A setting step of pushing the balloons containing the vaporizable material into the two pipes and moving the balloons to a position separated from the joint end by a predetermined value or more to set the area outside the high temperature area during welding. When,
After the balloon is set, an inflating step of inflating the balloon with a gas generated by vaporization of the vaporizable material and bringing the balloon into close contact with the inner surface of the pipe;
A replacement step of abutting the joint ends of the two pipes and replacing the internal spaces of both pipes surrounded by the balloon under the inert gas environment;
After the replacement is completed, a welding process of welding the butted portions of both the pipes from the outer surface side while supplying the inert gas;
And a flushing step of supplying a fluid into the two pipes after the end of the welding to dissolve the balloon and discharging the two balloons together with the fluid. In the pipe welding method according to claim 1,
A pipe welding method characterized in that, in the storing step, the vaporizable material is stored in the balloon while being held by a holding tray. In the pipe welding method according to claim 1 or 2,
A pipe welding method, wherein a water-soluble adhesive liquid having viscosity is applied to the entire surface of the balloon and then pushed into the pipe during the setting step. In the pipe welding method according to any one of claims 1 to 3,
In the flushing step, a pipe welding method is characterized in that a removal step of removing dissolved components of the balloon from the fluid after flushing is performed using a filter that adsorbs organic matter. In the pipe welding method according to any one of claims 1 to 4,
A pipe welding method comprising performing a confirmation step of confirming whether or not the balloon is in close contact with the inner surface of the pipe during the expansion step.

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