JP3825345B2 - Welding method for piping - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a welding method for metal pipes in which the ends of both metal pipes to be welded are butted.
[0002]
[Prior art]
Welding between pipes is performed by arranging the connecting ends of the pipes to face each other with a predetermined gap, and placing a weld metal in the gap. At that time, in order to prevent oxidation of the weld metal and the inner surface of the pipe, it is customary to perform welding in a state where the welded portion of the steel pipe is shielded from the atmosphere by an inert gas backshield gas such as argon gas.
[0003]
As a filling operation of the inert gas, a method of closing the outer ends (ends on the side not facing each other) of the two pipes and injecting the inert gas from the inlet provided at the ends is performed. It was. However, in this method, the entire inside of the pipe is filled with an inert gas. Especially, when the pipe to be welded is as long as several tens of meters, and further toward the final welding, the pipe becomes close to the pipe of the entire plant. There are cases where the distance is several kilometers. For this reason, since the usage-amount of an inert gas becomes large, the method which inject | pours an inert gas only between both the closure plugs which provide a closure plug in the both sides of the welding part vicinity is employ | adopted. (See Figure 1)
[0004]
As such a closure plug, a balloon is attached to the tip of the guide cable, the balloon is inserted into a predetermined position, the balloon is inflated to seal the piping, and after welding is completed, the balloon plug method is used to squeeze the balloon and remove it. There is a water-soluble plug method in which a plug formed by molding an active substance is inserted into a pipe and fixed with an adhesive, and after welding is completed, water is poured into the pipe to dissolve and remove the water-soluble plug.
[0005]
[Problems to be solved by the invention]
However, with the balloon plug method, it is difficult to insert balloons with long pipes of several kilometers, and there are many bent parts in the pipes. It is difficult to insert balloons with such pipes. Are uncertain, and there may be a case where the piping is blocked due to the dropping of the balloon.
In addition, in the water-soluble plug method, it is necessary to flow a large amount of water in order to dissolve and remove the water-soluble plug, and a large amount of time, labor, and cost are required. If the adhesive strength is weak, or if the adhesive strength is increased, water-soluble plugs and adhesives remain even after water has been melted. If the water-soluble plug does not dissolve, blockage of the piping will occur, and water will be disliked. There are problems such as being unsuitable for piping and storage tanks that handle hazardous materials.
[0006]
The object of the present invention is to maintain the advantages of the balloon plug method and the water-soluble plug method, which consumes a small amount of inert gas, without leaving any residue in the pipe, without worrying about blockage of the pipe, and closing the pipe line It is an object of the present invention to provide a welding method that can shorten the time, has a simple apparatus, can close a vertical pipe, and can be applied to a pipe that handles dangerous materials.
[0007]
[Means for Solving the Problems]
In order to solve such a problem, the present invention provides a metal pipe welding method in which a welded portion of a metal pipe is welded in a state shielded from the atmosphere with a back shield gas, and at least one of the closing plugs for closing the pipe is cooled. A closure plug comprising a solidified liquid or gas solidified,
When the plug is inserted into the metal pipe, the plug body is sized so that a minute gap exists between the inner wall of the metal pipe and the liquid or gas solidified from the same material as the plug body. A seal portion that seals the gap, and a handling rod that is embedded in the plug body and can be gripped when the plug body is inserted into the metal pipe,
(1) Insert the plug body from the opening of at least one of the two metal pipes to be welded,
(2) A sealing portion that seals the minute gap with a liquid or gas solidified material of the same material as that of the plug body is formed by cooling means from the outside of the pipe, and a closing plug constituted by the plug body and the sealing portion is formed in the metal pipe. Formed in place,
(3) The two metal pipes are arranged to face each other, and both the metal pipes are welded in a state of being cut off from the atmosphere while supplying a back shield gas from a gap between the two metal pipes arranged to face each other.
Hereinafter, the “closed plug made of a solidified liquid or gas that solidifies upon cooling” is referred to as an “ice plug”.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the welding method of the present invention will be described with reference to the drawings.
Oite to this example, as shown in FIG. 1, provided ice plug 2 closing the metal pipe on both sides of the metal pipe 1 across the welded portion of the metal pipe 1.
As shown in FIG. 1, when the metal pipes 1 to be welded are arranged to face each other with a predetermined interval, the ice plug 2 can be formed by an operation from the opening end 3 of the metal pipe 1 arranged to face each other. Becomes easy.
Moreover, the cooling device 4 is provided in the metal piping outer wall of the position which installs the ice plug of the metal piping 1 , and this is cooled . Any cooling device can be used as long as it can cool a liquid or gas to its solidification temperature, but it can be a cooling jacket using a refrigerant such as freon gas or liquid nitrogen, or cooling using the Peltier effect. An instrument can be illustrated. It is preferable that the cooling device is detachable from the metal pipe because the cooling position can be set and the location can be cooled as the welding position moves.
When a cooling jacket is used, it is preferable to apply a silicon-based heat conductive caulking putty to the gap between the metal pipe and the cooling jacket to close the gap, since the heat transfer is increased and the cooling efficiency is improved.
[0009]
When the ice plug installation position is cooled , the ice plug 2 is formed at a predetermined position in the metal pipe 1.
The material of the ice plug 2 is a solidified liquid or gas that solidifies upon cooling. Specifically, the ice is obtained by cooling water, preferably pure water, and is obtained by cooling carbon dioxide. Ice is preferably used. Dry piping is preferably used when the piping is a hazardous material that dislikes water, and when piping that can use water is preferable, water is preferable because it is easy to solidify and inexpensive. It is preferable to use pure water so as not to cause contamination.
The ice plug 2 includes a plug body having a size in which a minute gap exists between the inner wall of the metal pipe 1 and a seal portion that seals the minute gap in a subsequent process, The handling rod is embedded in the main body and can be gripped when the plug main body is inserted into the metal pipe. This handling bar facilitates insertion and installation of the plug body . For example, the plug body can be extracted by using a heated block of ice or dry ice, or water is poured into a metal tube of the same diameter, and the whole is cooled to form an ice column. it is obtained Rukoto by extracting it from in the atmosphere.
FIG. 2 shows an example in which the handling bar 5 is embedded in the plug body 2a. Further, if the handling bar 5 is provided with a heating mechanism, a gas vent hole can be easily formed in the ice plug 2 by installing and fixing the ice plug 2 and then heating and removing the handling bar . The handling rod 5 may be embedded by solidifying it with the handling rod inserted when water, carbon dioxide gas, or liquefied carbon dioxide gas is solidified in a block shape.
As this heating mechanism, for example, a mechanism in which a heating element such as an electric heating coil is embedded in a handling rod and heated by energization can be employed.
Then, the plug body is inserted into a predetermined position inside the metal pipe 1.
[0010]
After inserting the plug body in place, the same liquid or gas and the material of the plug body is sprayed toward the open end thereof 3 by mists nozzle 6 in the interior of the metal pipe 1 to the plug body.
Since the arrangement part of the plug body of the metal pipe 1 is cooled by the cooling device 4, the sprayed liquid or gas is solidified there to form a seal portion, whereby the ice plug 2 is formed and fixed to the metal pipe . And gas sealing becomes possible. Stop liquid or gas spraying after fixing and sealing.
[0011]
Next, the handling bar is extracted from the plug body to form a gas vent hole. By forming the gas vent hole, it becomes easy to replace the air in the pipe with the back shield gas when the back shield gas is supplied into the pipe sandwiched between the ice plugs 2.
In addition, by providing a handling bar, a liquid or gas can be sprayed while supporting the plug body with the handling bar so that the plug body is in a predetermined position to form a seal, and an ice plug can be installed in the metal pipe. Can also be closed.
[0012]
In the construction method of the present invention, as described above, when the plug body is inserted into the metal pipe, the plug body having a size with a minute gap between the inner wall of the metal pipe is inserted into the metal pipe, and the plug body is installed in the position. An ice plug is formed by providing a cooling device outside of the metal pipe in order to spray the liquid or gas into the metal pipe while cooling it, and cooling and solidifying the sprayed liquid or gas at a predetermined position to form a seal portion. Since the method of arranging airtightly on the inner wall of the metal pipe is adopted, the plug body can be easily and reliably inserted, and the ice plug can be fixed and sealed easily and reliably.
Moreover, in the case of piping that dislikes water that contains dangerous materials, such piping can be safely welded by using dry ice.
[0013]
Next, as shown in FIG. 3, a short pipe 7 having the same diameter as or slightly shorter than the gap between the metal pipes 1 and 1 and having the same diameter as the metal pipe 1 to be welded is placed between the metal pipes 1 and 1. The tip of the back shield gas supply hose 8 is inserted into the pipe through the gap between the short pipe 7 and one metal pipe 1. Then, with the insertion position as a base point, the gas temporary fixing tape 9 is made to make a round around the gap to seal the gap from the outside. Between the short pipe 7 and the other metal pipe 1, the gas temporary fixing tape 9 is rounded around the gap and sealed from the outside.
The length of the short tube 7 is preferably 300 cm or less, and more preferably 20 to 100 cm. If the length of the short tube is shorter than this lower limit, the ice plug insertion operation tends to be difficult. If the length of the short pipe is longer than this upper limit, the amount of the inert gas filled increases.
Next, the back shield gas is supplied to the space in the tube sealed from the tip of the back shield gas supply hose 8.
As the back shield gas used in the present invention, an inert gas is used. As this inert gas, argon gas, helium gas, or carbon dioxide gas is preferably used.
[0014]
Next, while peeling off the temporary fixing tape 9 of the gas from the gap where the tip of the back shield gas supply hose 8 is not inserted, the gaps of the peeled portions are sequentially welded and the entire circumference is welded. Next, the one where the tip of the supply hose is inserted is similarly welded while peeling off the temporary fixing tape 9, and the back shield gas supply hose 8 is extracted from the gap immediately before the welded part goes around, and filled with the back shield gas. Weld the final welded part in the finished state.
When the welding is completed, the cooling is stopped and the cooling device is removed, so that the ice plug is vaporized or melted, and the ice plug can be surely removed.
[0015]
Providing a heat dissipation mechanism (not shown) on the outer tube wall between the welding location and the ice plug 2 can prevent the propagation of cold heat to the welded portion and the propagation of welding heat to the ice plug, improving the thermal efficiency. Therefore, it is preferable. Examples of the heat dissipation mechanism include a heat dissipation fin made of a metal having good heat conductivity and a mechanism utilizing the Peltier effect. It is preferable to provide two or more heat dissipation mechanisms, one for preventing the propagation of cold heat and the other for preventing the propagation of welding heat. It is preferable that the heat dissipating mechanism is detachably provided on the metal piping wall because the heat propagation preventing position can be appropriately set as the welding position moves.
[0016]
In FIG. 1 and FIG. 3, an example in which a short pipe is installed between metal pipes is shown. However, when welding a metal pipe, one of the pipes to be welded may not be fixed in cases other than the final welded part. it is not necessary to install a short tube between the case, the metal pipe which is not fixed to the fixed metal tubing ice plug from installed oppositely disposed in both the metal pipe, the clearance of both metal pipes disposed opposite Both metal pipes may be welded while supplying the back shield gas from.
In addition, the end of the pipe that is not fixed may be open at the end opposite to the welded portion. In such a case, even if a conventionally known closing plug is used, the opening portion after pipe welding is used. Therefore, an ice plug may be used only on one side and a conventionally known closing plug may be used on the other side. In this case, a conductive pipe may be provided on the closed plug, and both metal pipes may be welded while supplying the back shield gas through the conductive pipe.
[0017]
【The invention's effect】
As described above, in the present invention, since a solidified liquid or gas is used as the closing plug, only the liquid or gas remains in the pipe after the welding is completed. Therefore, there is a risk of clogging in the pipe. Never leave.
Also, when the plug body is inserted from the opening before welding, it is inserted using a handling rod, and then a sealing part is formed to form a closing plug, so that the closing plug can be inserted and fixed easily. This can be done and the back shield gas can be reliably sealed.
For this reason, there is no need to insert / remove from a distant opening other than the welded part like a balloon plug, and there is no need to dissolve and wash with a large amount of water after welding like a water-soluble plug, so the pipeline is closed. The pipeline closure can be easily released and the pipeline closure time can be shortened.
In addition, by using the handling rod, the vertical pipe can be easily closed.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram illustrating an embodiment of the present invention.
FIG. 2 is a view showing a plug body in which a handling rod is embedded.
FIG. 3 is a schematic configuration diagram illustrating another embodiment of the present invention.
[Explanation of symbols]
1: Metal piping, 2: Ice plug, 2a: Plug body, 3: Metal piping opening, 4: Cooling device, 5: Handling rod, 6: Spray nozzle, 7: Short pipe, 8: Back shield gas supply hose, 9: Gas temporary fixing tape

Claims (4)

In the welding method for metal piping, where the welded portion of the metal piping is shielded from the atmosphere with back shield gas,
At least one of the closing plugs for closing the inside of the metal pipe is a closing plug made of a solidified liquid or gas that solidifies by cooling ,
When the plug is inserted into the metal pipe, the plug body is sized so that a minute gap exists between the inner wall of the metal pipe and the liquid or gas solidified from the same material as the plug body. A seal portion that seals the gap, and a handling rod that is embedded in the plug body and can be gripped when the plug body is inserted into the metal pipe,
(1) Insert the plug body from the opening of at least one of the two metal pipes to be welded,
(2) A sealing portion that seals the minute gap with a liquid or gas solidified material of the same material as that of the plug body is formed by cooling means from the outside of the pipe, and a closing plug constituted by the plug body and the sealing portion is formed in the metal pipe. Formed in place,
(3) A welding method characterized in that the two metal pipes are opposed to each other, and the two metal pipes are welded in a state where the metal is cut off from the atmosphere while supplying a back shield gas from the gap between the two metal pipes arranged opposite to each other . In the step (2), the seal portion is formed by spraying a liquid or a gas into a minute gap in the metal pipe and cooling and solidifying the sprayed liquid or gas at a predetermined position. The welding method according to 1. Instead of the step (3), the step (3 ′) the two metal pipes are arranged to face each other, a short pipe having the same diameter is arranged between the metal pipes arranged to face each other, and between the metal pipe and the short pipe The welding method according to claim 1 or 2, wherein the short pipe and both metal pipes are welded in a state of being cut off from the atmosphere while supplying the back shield gas . The welding method according to any one of claims 1 to 3, wherein the closing plug is ice obtained by cooling water .

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