JPH09280463A - Piping with branch pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate such necessity that a branch pipe is welded to a main pipe, and diminish remaining stress generated in a branch pipe mounting welding part by arranging a parallel piping for a branch pipe, having smaller diameter than a main pipe in parallel to the main pipe at both ends of the main pipe in parallel, and welding the branch pipe in the middle of this parallel piping for the branch pipe. SOLUTION: A steam main pipe (main piping) 1 in a thermal electric power plant is piped from a boiler outlet side 2 to a turbine 3, and a parallel piping 4 for a branch pipe, whose both ends are connected to the neighborhood of both ends of the main piping 1 is arranged in parallel to the main piping 1. In this parallel piping 4 for the branch pipe, upstream and downstream side opening/closing valves 5a, 5b are arranged at both ends, and a branch pipe 6 such as upstream and downstream side pressure detecting pipes 6a, 6c and a steam sampling pipe 6b is connected to the middle of the parallel piping 4. When the branch pipe 6 is attached to the parallel piping 4, a pipe mounting seat 7 is welded after a hole is opened in the parallel piping 4, and the branch pipe 6 is welded to the pipe mounting seat 7. Hereby, heat treatment after welding can be eliminated, and the reliability of the piping can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to, for example, the detection or sampling of the pressure of a fluid flowing in a high-pressure or large-diameter pipe in a steam main in a nuclear or thermal power plant or in various plants. The present invention relates to a pipe with a branch pipe in which a plurality of branch pipes are connected in the middle of the pipe.

[0002]

2. Description of the Related Art FIG. 2 (A) is a schematic view of a conventional pipe with a branch pipe for a steam main pipe, and FIG. 2 (B) is a cross-sectional view of an attachment portion of the branch pipe in the conventional pipe with a branch pipe. As shown in FIG. 2 (A), the main pipe (steam main pipe) 1 is arranged to send a large amount of high-pressure and high-temperature steam from the boiler outlet header 2 to the turbine 3. The main pipe 1 has a large wall thickness so as to withstand high pressure, and has a large diameter. A certain number of branch pipes 6 such as an upstream pressure detection pipe 6a, a steam sampling pipe 6b, and a downstream pressure detection pipe 6c are connected and provided in the middle of the main pipe 1. As shown in FIG. 2B, the branch pipe 6 is attached to the main pipe 1 by forming a hole in the main pipe 1,
The pipe mounting seat 7 is welded to the pipe mounting seat 7, and the branch pipe 6 is welded to the pipe mounting seat 7. The holes may be formed after the pipe mounting seat 7 is attached. 8 indicates a welded portion.

[0003]

The conventional pipe with a branch pipe is as described above, and the pipe mounting seat 7 and the welded portion 8 may be repaired or replaced due to deterioration over time.
When the pipe mounting seat 7 is attached to the main pipe 1 by welding, residual heat may remain in the main pipe 1 near the attachment portion due to the heat of welding and cracks may occur, so heat treatment such as annealing should be performed. Since it was necessary to remove residual stress and there were many welding points, it took a lot of time and effort. Even if such heat treatment is performed, the heat of welding causes the main pipe 1
However, there is a problem in that the quality of the pipe 1 may deteriorate and there is a problem in terms of quality assurance and reliability of the main pipe 1.

The present invention has been made to solve the above problems, and it is not necessary or easy to perform heat treatment after welding, and there is a problem of quality assurance and reliability of the main pipe 1. The purpose is to obtain a pipe with no branch pipe.

[0005]

The pipe with branch pipe according to the present invention is provided with parallel pipes for branch pipes, which are connected to both ends of the main pipe and have a diameter smaller than the main pipe, arranged side by side on the main pipe. A branch pipe is connected by welding in the middle of the pipe.

In the pipe with branch pipe according to the present invention, the branch pipe is connected to both ends of the main pipe and is connected to the parallel pipes for branch pipes arranged in parallel. Therefore, the branch pipe is not attached to the main pipe, and the main pipe is not attached. A heat-affected zone of welding is prevented from occurring, heat treatment for removing residual stress of the main pipe is unnecessary, and problems such as deterioration of material of the main pipe and deterioration of reliability are eliminated. Although parallel pipes for branch pipes are attached to this pipe, there are only two locations at both ends, and there are few problems such as the trouble of heat treatment and deterioration of material. In addition, the above-mentioned problem that occurs in the parallel pipe for branch pipe by welding the branch pipe to the parallel pipe for branch pipe is because the parallel pipe for branch pipe has a smaller diameter than the main pipe, and the wall thickness of the pipe is thin. Is less likely to occur,
Residual stress can be easily removed.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a pipe with a branch pipe according to the present invention will be described below with reference to the drawings. In FIG. 1 (A), 1 is, for example, a steam main pipe (main pipe) in a thermal power plant, and is arranged to send a large amount of high-pressure and high-temperature steam from a boiler outlet pipe 2 to a turbine 3. Therefore, the main pipe 1 has a large diameter and a large diameter so as to withstand high pressure. Parallel pipes 4 for branch pipes are provided side by side on the main pipe 1 by connecting both ends to both ends of the main pipe 1. The diameter of the branch pipe parallel pipe 4 is smaller than that of the main pipe 1, and the pressure of steam in the branch pipe parallel pipe 4 has the same distribution as that of the main pipe 1, and is a diameter necessary for the steam to flow at a certain speed. Good. An upstream side opening / closing valve 5a and a downstream side opening / closing valve 5b are provided at both ends of the branch pipe parallel pipe 4. A certain number of branch pipes 6 such as an upstream pressure detection pipe 6a, a steam sampling pipe 6b, and a downstream pressure detection pipe 6c are connected and provided in the middle of the branch pipe parallel pipe 4.

As shown in FIG. 1B, the branch pipe 6 is attached to the branch pipe parallel pipe 4 by forming a hole in the branch pipe parallel pipe 4 and installing a pipe mounting seat 7 in the branch pipe parallel pipe 4. Welding and attaching, the branch pipe 6 is welded and attached to the pipe attachment seat 7. The holes formed in the branch pipe parallel pipe 4 may be formed after the pipe mounting seat 7 is attached. 8a and 8b show welded portions.

Next, the function or operation of the pipe with branch pipe shown in FIG. 1 will be described. As shown in FIG. 1 (A), the main pipe 1 connected to the boiler outlet header 2 and the turbine 3 and having a large diameter and a large wall thickness has a large amount of high pressure and high temperature from the boiler outlet header 2 to the turbine 3. Circulate the steam of. A part of the steam entering the main pipe 1 from the boiler outlet head 2 flows through the upstream side opening / closing valve 5a and flows in the branch pipe parallel pipe 4, passes through the downstream side opening / closing valve 5b, and flows in front of the turbine 3. Join the main pipe 1. The on-off valves 5a and 5b are normally open, and are closed when the pressure detection pipe 6a or the like is repaired or when necessary. The pressure detection pipes 6a and 6c are branch pipes for detecting the pressure of steam at each position during operation. The steam sampling pipe 6b is a branch pipe for collecting the steam during operation and checking whether or not there is salt in the steam.

As shown in FIG. 1B, the branch pipe 6 is attached to the parallel pipe 4 for the branch pipe by welding through the pipe mounting seat 7, but the welded portion 8a is parallel to the branch pipe. Between the pipe 4 and the pipe mounting seat 7, the welded portion 8b is the pipe mounting seat 7.
Between the pipe and the branch pipe 6 is constructed so that steam leaks and the like can be sufficiently endured and pressure and vibration of the steam can be sufficiently endured. However,
In the conventional mounting structure shown in FIG. 2 (B), the branch pipe 6 is mounted on the main pipe 1, and since the main pipe 1 has a large diameter and a large pipe wall thickness, the residual stress after welding the welded portion 8a is large. However, the heat treatment for removing the residual stress is very time-consuming, and it is difficult to remove the residual stress even if it takes time, and the material is deteriorated.

On the other hand, in the mounting structure of the pipe with a branch pipe according to the present invention shown in FIG. 1B, the mounting partner of the branch pipe 6 is the parallel pipe 4 for the branch pipe, and the branch pipe 6 is the main pipe 1. Is not attached, and the heat affected zone of welding is prevented from occurring in the main pipe 1. As a result, the heat treatment or the like for removing the residual stress of the main pipe 1 which is conventionally required becomes unnecessary, and the problems such as the deterioration of the material of the main pipe 1 and the deterioration of reliability are solved. Although the parallel pipes 4 for branch pipes are attached to the main pipe 1, it is only at two positions at both ends, and there are few problems such as trouble of heat treatment and deterioration of material. Also, the parallel pipe for branch pipe 4
The above problem that occurs in the branch pipe parallel pipe 4 by welding the branch pipe 6 to the above is that the branch pipe parallel pipe 4 has a smaller diameter than the main pipe 1, and the pipe wall thickness is thin. It is small and heat treatment for removing residual stress can be easily performed. Further, there is little risk that the material will deteriorate.

In general, when a plate (tube) having a large plate thickness (wall thickness) is subjected to welding, there is a large temperature difference in the temperature distribution of the material to be welded during welding, and a large residual stress occurs. Moreover,
The residual stress generated in the thick one is three-dimensional, and the residual stress also occurs in the plate thickness direction. Therefore, it is necessary to heat a wide range in order to remove the residual stress, which is very troublesome. Further, it is difficult to completely remove it even with such a time and effort. On the other hand, the thin type has a small temperature difference in temperature distribution and a small residual stress. The residual stress is two-dimensional and can be easily removed.

Further, since the wall thickness of a pipe that withstands the pressure inside the pipe is proportional to the product of the pressure inside the pipe and the pipe diameter, if the pressure is the same, the wall thickness of the pipe is approximately proportional to the pipe diameter. Become. That is, the wall thickness of the branch pipe parallel pipe 4 is reduced in proportion to the ratio of the diameters of the main pipe 1 and the branch pipe parallel pipe 4. In the branch pipe parallel pipe 4, in actuality, steam may flow through the branch pipe parallel pipe 4 at a certain speed, so that the diameter of the branch pipe parallel pipe 4 is a fraction of the diameter of the main pipe 1. Diameter is good and pipe wall thickness is a fraction
Thickness. Note that FIG. 1B and FIG. 2B are shown at substantially the same scale.

In the above description of the embodiment of the pipe with a branch pipe according to the present invention, the steam pipe of a thermal power plant or the like has been described, but the branch pipe should be connected to a high-pressure or large-diameter pipe of another plant or the like. It can be applied in any case.

[0015]

As described above, according to the present invention, since the branch pipes are connected to the parallel pipes for branch pipes having small diameters, which are connected in parallel to each other at both ends, the branch pipes are welded to the main pipes. There is no need to reduce the residual stress generated in the welded pipe mounting weld,
The residual stress can be easily removed. Thereby, the quality and reliability of the pipe can be improved.
Further, the effect that the construction cost can be reduced can be obtained.

[Brief description of drawings]

FIG. 1 shows an embodiment of a pipe with a branch pipe according to the present invention, (A) is a schematic diagram of the pipe with a branch pipe, and (B) is a sectional view showing the structure of a branch pipe attachment portion.

FIG. 2 shows a conventional pipe with a branch pipe, (A) is a schematic view of the pipe with a branch pipe, and (B) is a cross-sectional view showing the structure of a branch pipe attachment portion.

[Explanation of symbols]

1: Main piping, 2: Boiler outlet heading, 3: Turbine,
4: Parallel pipe for branch pipe, 5a, 5b: Open / close valve, 6a,
6b, 6c: Branch pipe, 7: Pipe mounting seat, 8: Welded portion.

Claims (1)

[Claims] 1. In a pipe to be connected by welding a branch pipe in the middle of the main pipe, parallel pipes for branch pipes, which are connected to both ends of the main pipe and have a diameter smaller than that of the main pipe, are provided side by side in the main pipe, A pipe with a branch pipe, wherein the branch pipe is connected by welding in the middle of the parallel pipe for the branch pipe.