JP2003028375A - Pipe base attaching method, branched pipe connecting method, and dust antiscattering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pipe base and a branched pipe in a pipe without contaminating an inside of a pipe. SOLUTION: This dust antiscattering device 7 for preventing scattering of cut power inside the pipe 1 when forming an opening 19 in an attaching position of the pipe base of the pipe 1 comprises a plurality of opening and closing arms 13 arranged in a longitudinal middle portion of a pipe axis 11 shorter than the inner diameter of the pipe 1 to be foldable; a seal cover 14 which has an approximate cone shape, attached to the opening and closing arm 13, and can be diametrically contracted through a link 16 by an opening and closing block 15 arranged at one end of the pipe axis 11, and is adapted to be inserted from a lower hole 5 in a contracted state into the inside of the pipe 1 and is enlarged so as to cover the lower hole 5; and a fixing screw shaft 17 which protrudes from the other end of the pipe shaft 11 to be pushed to the other side of an inner surface of the pipe 1 so that end portions of the enlarged opening and closing arms 13 are pushed at one side surrounding the lower hole 5 of the inner surface of the pipe 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nozzle base mounting method, a branch pipe connecting method, and a dust scattering prevention device for mounting a nozzle base and a branch pipe on a pipe without contaminating the inside of the pipe.

[0002]

2. Description of the Related Art There is a case where a remodeling work is required such that a branch pipe is added by attaching a nozzle to a pipe through which an active fluid flows, such as sodium pipe in a nuclear facility. When performing such work, for example, in the case of sodium piping, when sodium comes into contact with air, foreign matter is generated and post-treatment becomes difficult, and when sodium reacts with moisture in the air, etc. It is also possible that a sodium fire will occur.

[0003]

Therefore, when performing work such as attaching a nozzle or branch pipe to a pipe containing an active fluid as described above, when the nozzle is attached, the air outside the pipe or It is necessary to reduce the problem that the inside of the pipe is contaminated by the working gas, etc., and further, the problem that the inside of the pipe is contaminated by the chips generated during the drilling work for mounting the nozzle base. .

The present invention has been made in response to the above problems, and a nozzle mounting method and a branch pipe connecting method capable of mounting a nozzle and a branch pipe on the pipe without contaminating the inside of the pipe. Another object is to provide a dust scattering prevention device.

[0005]

The invention according to claim 1 is
Welding and fixing the nozzle to the outer peripheral surface of the pipe, drilling a lower hole through the inside of the nozzle to just before the inner surface of the pipe by the hole making tool provided in the cutting device, and then enclosing the entire installation part of the cutting device The seal cover is equipped with a dust scattering prevention device that can be expanded and contracted in an umbrella shape, an outside air isolation device that houses a closing lid that closes the end of the nozzle and a cutting tool, and the inert gas is supplied into the outside air isolation device. , While maintaining an inert gas atmosphere,
After the lower hole is penetrated into the inner surface of the pipe by the hole making tool of the cutting device and the inside of the root of the pipe stand is cleaned, the dust scattering prevention device is reduced and inserted into the pipe from the lower hole inside the pipe. To cover the lower hole from the inside of the pipe by expanding with the seal cover, and then, by attaching a cutting tool to the cutting device to process the inner surface of the lower hole and further finish processing to form the opening, In this method, the dust scattering prevention device is removed from the opening by cleaning, the end of the nozzle is closed by the closing lid, and then the outside air separator is removed.

The invention according to claim 2 is the nozzle mounting method according to claim 1, characterized in that a U-drill or a hole saw having a flat tip is used as a hole forming tool for forming a pilot hole.

According to a third aspect of the present invention, when the branch pipe is connected to the nozzle that is formed with the opening according to the first or second aspect and is closed by the closing lid, the end of the branch pipe is separated from the nozzle. Separately, prepare the connecting pipe that connects the end of the branch pipe and the nozzle, and remove the closing lid, and at the same time connect the connecting pipe between the end of the pipe and the nozzle. Insert and seal the pipes between the connecting pipe and the branch pipe and between the connecting pipe and the nozzle with the airtight tape, and then remove the airtight tape and weld them together. Between the joint pipe and the branch pipe,
And a branch pipe connecting method characterized in that the connection pipe and the pipe base are sequentially connected.

According to a fourth aspect of the present invention, there is provided a dust scattering prevention device for preventing cutting chips from scattering inside a pipe when an opening is formed at a mounting position of a pipe base, and an inner diameter of the pipe. A shorter tube shaft, a plurality of openable and closable arms that are bendable in the longitudinal middle portion of the tube shaft, a seal cover that has a substantially conical shape and is attached to the plurality of open and close arms, and one end side of the tube shaft. An opening / closing piece that is slidably provided and expands / contracts the seal cover via a link provided between each opening / closing arm and an end of the expanded opening / closing arm provided inside the pipe shaft and surrounds a pilot hole on the inner surface of the pipe. A dust scattering prevention device, comprising: a fixing screw shaft that protrudes from the other end of the pipe shaft so as to be pressed to one side and can be pressed to the other side of the inner surface of the pipe.

According to the present invention, it operates as follows.

According to the first aspect of the present invention, the nozzle is welded and fixed to the outer peripheral surface of the pipe, the lower hole is drilled through the inside of the nozzle to just before the inner surface of the pipe by the hole making tool provided in the cutting device, and then the cutting device. The outside air isolation device surrounding the entire installation portion of the device is installed, an inert gas is supplied to the inside of the outside air isolation device, and the inert gas atmosphere is maintained. After cleaning the inside of the base of the pipe stand, insert the dust scattering prevention device into the inside of the pipe from the pilot hole with the dust scattering prevention device in a contracted state and expand inside the pipe to seal the pilot hole inside the pipe. Cover from
Then, a cutting tool is attached to the cutting device to form an opening by finishing the inner surface of the pilot hole, and then the end of the nozzle is closed by the closing lid, and then the outside air isolation device is removed. Since the inside of the pipe is not contaminated with outside air or cutting chips, the work of installing the nozzle on the pipe can be efficiently performed.

According to the second aspect of the present invention, by using a U-drill or a hole saw with a flat tip for the hole forming tool that forms the pilot hole, it is possible to minimize the scattering of cutting chips inside the pipe.

According to the third aspect of the present invention, the end portion of the branch pipe is arranged at a distance from the nozzle base, and the connecting pipe for connecting the end portion of the branch pipe and the nozzle base is prepared, and the closing lid is provided. At the same time when removing the pipe, insert a joint pipe between the end of the branch pipe and the nozzle, and attach airtight tape between the joint pipe and the branch pipe and between the joint pipe and the nozzle. The branch pipes are connected by sequentially closing the pipes and welding the pipes while removing the airtight tape, and then between the pipes and the pipes. , The inside of the pipe is not contaminated by the outside air, and the work of connecting the branch pipe to the nozzle can be efficiently performed.

In the invention according to claim 4, the dust scattering prevention device for preventing the scattering of cutting chips inside the pipe when forming the opening for mounting the nozzle on the outer peripheral surface of the pipe is an umbrella shape. Since it has a structure that can be expanded and contracted and it can be expanded inside the pipe to surround the pilot hole, with a simple structure and simple operation, cutting chips etc. will be scattered inside the pipe when forming the opening. Can be reliably prevented.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described below with reference to the drawings.

1 to 8 are working process diagrams showing the form of a nozzle mounting method according to the present invention in accordance with a work procedure. The form of the present invention will be described below in accordance with the work procedure.

In order to install a new nozzle on the pipe, first,
As shown in FIG. 1, a tubular nozzle 2 is fixed to a required position on the outer peripheral surface of the pipe 1 by welding.

Next, as shown in FIG. 2, the cutting device 3 is fixed to the pipe 1, and the hole making tool 4 provided in the cutting device 3 makes a pilot hole through the inside of the nozzle base 2. At this time, as shown in FIG. 9, so that the pilot hole 5 does not penetrate the inner surface of the pipe 1,
Perforation is performed until just before the penetration while leaving a predetermined thickness t.
The hole making tool 4 at this time may be a normal drill, or a U drill or a hole saw with a flat tip.

Next, as shown in FIG. 3, an outside air isolation device 6 that surrounds the entire installation portion of the cutting device 3 is attached to the pipe 1. At this time, a dust scattering prevention device 7 in which a seal cover, which will be described later, can expand and contract like an umbrella is provided inside the outside air isolation device 6.
(FIG. 4, FIG. 11, FIG. 12), cutting tool 8 (FIG. 4, FIG. 1)
3) and the closing lid 9 (FIG. 5) for closing the end of the nozzle 2 are housed in advance. Further, although not shown, the outside air isolation device 6 is provided with flexible work gloves that allow various work inside the outside air isolation device 6 to be performed by inserting a hand from the outside with the outside air shut off. There is.

Further, for example, an inert gas such as argon gas is supplied from the gas cylinder 10 or the like into the outside air isolation device 6 to replace the inside of the outside air isolation device 6. In this inert gas atmosphere, the punching tool 4 provided in the cutting device 3 penetrates the pilot hole 5 as shown in FIG. This pilot hole 5
It is preferable to use a U-drill or a hole saw with a flat tip for the through processing. This is to reduce as much as possible the scattering of cutting powder inside the pipe 1 when penetrating the pilot hole 5, and when a U-drill or a hole saw with a flat tip is used for opening, it is shown in FIG. As described above, the cutting pieces S having a substantially disc shape are removed, and scattering of cutting chips is prevented. When the lower hole 5 is opened, a cleaning work for removing the cutting pieces S, the cutting chips and the like shown in FIG. 10 inside the root portion of the nozzle 2 is performed with the work gloves provided in the outside air isolation device 6.

Next, as shown in FIG. 4, the outside air isolation device 6
The dust scattering prevention device 7 previously accommodated in the inside is inserted into the pipe 1 from the lower hole 5 in a reduced state, and expanded inside the pipe 1 to cover the lower hole 5 from the inside of the pipe 1 with a seal cover. To do so.

FIG. 11 and FIG. 12 show an example of the dust scattering prevention device 7, and the dust scattering prevention device 7 is shown.
Is a pipe shaft 11 shorter than the inner diameter of the pipe 1, a plurality of opening / closing arms 13 provided at a middle portion in the longitudinal direction of the pipe shaft 11 so as to be bendable by a fulcrum 12, and a plurality of opening / closing arms having a substantially conical shape. And a seal cover 14 attached to the opening / closing arm 13 so as to cover 13. The seal cover 14 has an elliptical plan shape as shown in FIG. 12 so as to match the curved inner surface of the pipe 1 and surround the pilot hole 5.

Further, a slide opening / closing piece 15 is attached to one end side of the tube shaft 11, and the opening / closing piece 1 is attached.
5 and each of the opening / closing arms 13 are connected by a link 16, and when the opening / closing piece 15 is slid up and down along the tube axis 11, the seal cover 14 is folded and expanded into a substantially conical shape. It can be scaled up and down.

Further, a fixing screw shaft 17 is provided inside the pipe shaft 11, and a rotating rod 18 is inserted into the pipe shaft 11 from the lower end side of FIG. 11 to rotate the fixing screw shaft 17. Then, the upper end of the fixing screw shaft 17 projects from the pipe shaft 11, and the end (lower end) of the expanded opening / closing arm 13 is connected to the pipe 1
The upper end of the fixing screw shaft 17 is pressed against the other side (upper side) of the inner surface of the pipe 1 so as to be pressed against the inner surface on one side (lower side) surrounding the lower hole 5 of the inner surface.

Therefore, the dust scattering prevention device 7 in the folded state is inserted into the pipe 1 from the lower hole 5 and the opening / closing piece 15 is raised to open the opening / closing arm 13 and the seal cover 14.
Is expanded like an umbrella, and further, the rotating rod 18 is inserted into the tube shaft 11 and the fixing screw shaft 17 is rotated, and the upper end of the fixing screw shaft 17 projects and is pressed against the inner surface of the pipe 1. As a result, the dust scattering prevention device 7 is fixed inside the pipe 1 in an expanded state so as to surround the lower hole 5.

In this state, as shown in FIGS. 4 and 13,
A cutting tool 8 is attached to the cutting device 3, and the inner surface of the lower hole 5 is cut by the cutting tool 8 to form an opening 19 inside the nozzle 2 as shown in FIG. At this time, the cutting powder scattered by the cutting of the cutting tool 8 is prevented from scattering inside the pipe 1 by the surrounding of the dust scattering prevention device 7.

Subsequently, a closing lid 9 (FIG. 5) is attached to the lower end of the nozzle stub 2 to shut off the outside air, and then the outside air separating device 6 and the cutting device 3 are removed to obtain the state shown in FIG.

Next, as shown in FIG. 6, the outside air separating device 6 in which the grinder 20 is housed in advance inside the outside air separating device 6 is attached again to the outer periphery of the pipe 1 in FIG. Then, after removing the closing lid 9 attached to the nozzle stub 2 in a state where an inert gas is supplied into the outside air isolation device 6, FIG.
As shown in FIG. 5, finish processing such as R processing on the inner side of the base portion of the nozzle stub 2 is performed by the grinder 20. Then, a cleaning operation is performed to remove the cutting chips scattered inside the dust scattering prevention device 7. After that, the dust scattering prevention device 7 is contracted by the reverse operation to the above and taken out from the opening 19 into the outside air isolation device 6. Subsequently, as shown in FIG. 7, the lower end of the nozzle 2 is closed by the closing lid 9.

After that, when the outside air isolator 6 is removed, the state shown in FIG. 8 is obtained and the installation of the nozzle 2 is completed. If the grinder 20 is housed in the outside air isolation device 6 of FIG. 3 in advance, the grinder of FIG. 6 can be processed without the step of FIG. 5 after processing the opening 19 of FIG. A finishing process according to 20 can be performed.

As shown in FIG. 1 to FIG. 8 and FIG. 9 to FIG. 15, the nozzle 2 is welded and fixed to the outer peripheral surface of the pipe 1, and the inside of the nozzle 2 is opened by the boring tool 4 provided in the cutting device 3. The lower hole 5 is drilled up to just before the inner surface of the pipe 1 through which the outside air separator 6 surrounding the entire installation portion of the cutting device 3 is installed, and an inert gas is supplied into the outside air separator 6 to supply the inert gas. In a state where the atmosphere is maintained, the lower hole 5 is made to penetrate the inner surface of the pipe 1 by the hole making tool 4 of the cutting device 3, the inside of the base portion of the nozzle base 2 is cleaned, and then the dust scattering prevention device 7 is reduced. Then, the pilot hole 5 is inserted into the pipe 1 through the pilot hole 5 and expanded inside the pipe 1 to cover the pilot hole 5 from the inside of the pipe 1 by the seal cover 14, and then the cutting tool 3 is cut by the cutting tool 8.
Is attached to finish the inner surface of the pilot hole 5 to form the opening 19, and subsequently the end of the nozzle 2 is closed by the closing lid 9, and then the outside air isolator 6 is removed. The work of installing the nozzle base 2 on the pipe 1 can be efficiently performed without contaminating the inside of the pipe 1 with outside air, cutting chips, or the like.

Further, since the dust scattering prevention device 7 can be expanded and contracted with a simple structure and expanded inside the pipe 1 so as to surround the pilot hole 5, the opening 19 is formed.
It is possible to reliably prevent chips and the like from scattering inside the pipe 1 when forming the.

FIGS. 16 to 18 are work process diagrams showing, in accordance with the work procedure, a form in which a branch pipe is connected to a nozzle installed on the pipe in the procedure of FIGS. 1 to 8. The form of the present invention will be described below. It will be explained according to the work procedure.

As shown in FIG. 8, the closing lid 9 is installed on the pipe 1.
In order to connect the branch pipe to the nozzle block 2 closed by
As shown in FIG. 6, a branch pipe 21 having the same diameter as the nozzle base 2 having one end 21a opened and the other end 21b closed is prepared by performing a pressure resistance test, and the open end 21a of the branch pipe 21 is prepared.
Are spaced apart from the nozzle base 2. Furthermore, the branch pipe 2
A short connecting pipe 22 for connecting between the open end 21a of No. 1 and the nozzle 2 is prepared.

At the same time when the closing lid 9 of FIG. 8 is removed from the nozzle base 2, as shown in FIG. 16, a connecting pipe 22 is provided between the open end 21a of the branch pipe 21 and the nozzle base 2. After the insertion, as shown in FIG. 17, the joining pipe 22 and the branch pipe 21 and the joining pipe 22 and the nozzle base 2 are closed with airtight tapes 23, respectively. As a result, the branch pipe 21 is hardly polluted by the outside air inside the pipe 1.
And the connecting pipe 22 can be arranged.

Then, as shown in FIG. 18, the work of welding the airtight tape 23 while peeling off the airtight tape 23 is performed between the joining pipe 22 and the branch pipe 21, and between the joining pipe 22 and the nozzle base 2. In sequence. As a result, the work of connecting the branch pipe 21 to the nozzle base 2 is completed.

As shown in FIGS. 16 to 18, the open end 21a of the branch pipe 21 is arranged at a distance from the nozzle base 2, and the end 21a of the branch pipe 21 and the nozzle base 2 are arranged. The connecting pipe 22 to be connected is prepared, and at the same time when the closing lid 9 is removed, the connecting pipe 22 is inserted between the end 21a of the branch pipe 21 and the nozzle base 2 to connect the connecting pipe 22 and the branch pipe 21. The work of welding the mutual pipes 22 and the branch pipes 21 with each other and the pipes 2 and the nozzle base 2 are closed by airtight tapes 23 and then the airtight tapes 23 are peeled off and welded to each other. Since the branch pipe 21 is connected by sequentially performing the connection pipe 22 and the nozzle pipe 2, the branch pipe 21 is connected to the pipe nozzle 2 without contaminating the inside of the pipe 1 with outside air. The work of connecting the pipe 21 can be efficiently performed.

It should be noted that the present invention is not limited to the above embodiment, and various modifications can be made without departing from the scope of the present invention.

[0037]

According to the first aspect of the present invention, the nozzle is welded and fixed to the outer peripheral surface of the pipe, and the lower hole is drilled through the inside of the nozzle to just before the inner surface of the pipe by the hole making tool provided in the cutting device. After that, an outside air isolation device that surrounds the entire installation portion of the cutting device is installed, and an inert gas is supplied into the outside air isolation device. After the hole penetrates the inner surface of the pipe and the inside of the base of the pipe stand is cleaned, the dust scattering prevention device is reduced and inserted into the pipe through the pilot hole to expand inside the pipe, and The hole is covered from the inside of the pipe, and subsequently, a cutting tool is attached to the cutting device to finish the inner surface of the pilot hole to form the opening,
Then, after closing the end of the nozzle with the closing lid, the outside air isolation device is removed, so that the nozzle is installed on the pipe without contaminating the inside of the pipe with outside air or cutting chips. There is an effect that work can be done efficiently.

According to the second aspect of the invention, by using a U drill or a hole saw having a flat tip for the hole forming tool for forming the pilot hole, it is possible to minimize the scattering of the cutting chips into the inside of the pipe. There is.

According to the invention of claim 3, an end portion of the branch pipe is arranged at a distance from the nozzle, and a joint pipe for connecting the end of the branch pipe and the nozzle is prepared, At the same time as removing the closure lid, insert a joint pipe between the end of the branch pipe and the nozzle to make the joint pipe and the branch pipe and between the joint pipe and the nozzle airtight. The branch pipes are connected by closing them with tape and then peeling off the airtight tape and welding them together in order between the joining pipe and the branch pipe and between the joining pipe and the nozzle. Therefore, there is an effect that the inside of the pipe is not contaminated with the outside air and the work of connecting the branch pipe to the nozzle can be efficiently performed.

According to the fourth aspect of the present invention, there is provided a dust scattering prevention device for preventing cutting chips from scattering inside a pipe when forming an opening for mounting a nozzle on the outer peripheral surface of the pipe, Since it can be expanded and contracted like an umbrella and can be expanded inside the pipe to enclose the pilot hole, chips and the like are scattered inside the pipe when the opening is formed with a simple structure and simple operation. There is an effect that it can be surely prevented.

[Brief description of drawings]

FIG. 1 is a process diagram showing a state in which a nozzle is attached to a pipe.

FIG. 2 is a process diagram showing a state in which a cutting device is installed in a pipe and a pilot hole is bored inside a nozzle by a hole punching tool.

FIG. 3 is a process diagram showing a state in which an outside air isolation device that surrounds a cutting device is installed in a pipe, and a pilot hole is made to penetrate inside the nozzle by a hole punching tool.

FIG. 4 is a process diagram showing a state in which a dust scattering prevention device is installed inside a pipe and an opening is formed by cutting a lower hole with a cutting tool.

FIG. 5 is a process diagram showing a state in which a nozzle is surrounded by a closing lid and an outside air isolator and a cutting device are removed.

FIG. 6 is a process diagram showing a state in which the outside air isolation device is installed again in the pipe, the closing lid is removed, and the inside of the root of the pipe stand is finished by a grinder.

FIG. 7 is a process diagram showing a state in which a closing lid is attached to the nozzle base after cleaning the inside of the nozzle base portion and the like.

FIG. 8 is a process diagram showing a state in which the outside air isolation device has been removed and the installation of the nozzle on the pipe has been completed.

FIG. 9 is a cross-sectional view showing a state in which a pilot hole is drilled just before the inner surface of the pipe.

FIG. 10 is a cross-sectional view showing a state in which a pilot hole is formed by penetrating the inner surface of the pipe.

FIG. 11 is a partially cut side view showing the structure of the dust scattering prevention device.

FIG. 12 is a plan view of FIG. 11.

FIG. 13 is a cut side view showing a state in which an opening is formed by a cutting tool.

FIG. 14 is a cut side view showing a state in which an opening is formed.

FIG. 15 is a cut side view showing a state in which the inside of the base of the tube base is finished by a grinder.

FIG. 16 is a process diagram showing a state in which a branch pipe and a coupling pipe are arranged in order to connect a nozzle branch pipe.

FIG. 17 is a view showing that a connecting pipe is arranged between a nozzle and a branch pipe,
FIG. 6 is a process diagram showing a state in which the joining pipe and the branch pipe, and the joining pipe and the nozzle base are closed by an airtight tape.

FIG. 18 is a process diagram showing a state in which the joining pipe and the branch pipe and the joining pipe and the nozzle base are welded while the airtight tape is peeled off.

[Explanation of symbols]

1 piping 2 tubes 3 cutting equipment 4 punching tools 5 pilot holes 6 Outside air isolation device 7 Dust scattering prevention device 8 cutting tools 9 Closing lid 11 tube axis 13 open / close arm 14 seal cover 15 Opening and closing pieces 16 links 17 Screw shaft for fixing 19 opening 21 Branch pipe 21a One end (end) 21b The other end (end) 22 Joint piping 23 Airtight tape

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yosuke Takahashi             Stone, Shin-Nakahara-cho, Isogo-ku, Yokohama-shi, Kanagawa             Kawashima Harima Heavy Industries, Ltd. Yokohama Engineer             Inside the center F term (reference) 3H019 CB05

Claims (4)

[Claims] 1. A pipe nozzle is welded and fixed to the outer peripheral surface of a pipe, a lower hole is drilled through the inside of the nozzle to a position just before the inner surface of the pipe by a hole making tool provided in the cutting device, and then the entire installation portion of the cutting device. A dust scattering prevention device capable of enclosing the inside of the device and having a seal cover capable of expanding and contracting like an umbrella, an outside air isolation device accommodating a closing lid for closing the end of the nozzle and a cutting tool are installed inside the outside air isolation device. After supplying the inert gas and maintaining the inert gas atmosphere, the lower hole is made to penetrate the inner surface of the pipe by the hole making tool of the cutting device, and after cleaning the inside of the base of the pipe stand, the dust scattering prevention device Is inserted into the pipe from the lower hole in a reduced state and expanded inside the pipe to cover the lower hole from the inside of the pipe with the seal cover, and then a cutting tool is attached to the cutting device to clean the inner surface of the lower hole. Processing and further finishing To form an opening, clean the interior of the nozzle, remove the dust scattering prevention device from the opening, close the end of the nozzle with the closing lid, and then remove the outside air isolation device. . 2. The nozzle mounting method according to claim 1, wherein a U-drill or a hole saw having a flat tip is used as a hole forming tool for forming the prepared hole. 3. When connecting a branch pipe to a nozzle base having an opening formed according to claim 1 or 2 and closed by a closing lid,
The end portion of the branch pipe is arranged at a distance from the nozzle stub, and the connecting pipe for connecting the end portion of the branch pipe and the nozzle stub is prepared. Insert the connecting pipe between the pipe and the nozzle to block the connecting pipe and the branch pipe with each other, and between the connecting pipe and the nozzle with the airtight tape, and then remove the airtight tape. A branch pipe connecting method is characterized in that the welding work between them is sequentially performed between the joining pipe and the branch pipe and between the joining pipe and the nozzle. 4. A dust scattering prevention device for preventing cutting chips from scattering inside a pipe when forming an opening at a mounting position of a pipe nozzle, the pipe shaft being shorter than an inner diameter of the pipe. A plurality of openable and closable arms that are bendable in the middle of the pipe shaft in the lengthwise direction, a seal cover that has a substantially conical shape and is attached to the plurality of openable and closable arms, and is provided slidably on one end side of the pipe shaft. An opening and closing piece that expands and contracts the seal cover via a link provided between each opening and closing arm, and the end of the expanded opening and closing arm provided inside the pipe shaft is pressed against one side surrounding the pilot hole inside the pipe. A dust scattering prevention device comprising: a fixing screw shaft that projects from the other end of the pipe shaft and can be pressed against the other side of the inner surface of the pipe.