JPH0565757B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention provides two pressure conduits such as pressure iron pipes for hydroelectric power generation.
This relates to a branch pipe that branches into three or three prongs.

[Conventional technology]

As a branch pipe of a pressure conduit such as a pressure iron pipe for hydroelectric power generation, a spherical branch pipe or a branch pipe in which a main pipe and a branch pipe are directly connected are used as shown in Japanese Patent Publication No. 11800/1983. Spherical branch pipes have a high pressure resistance and are suitable for high head power generation, but the structure and processing of the spherical shell are complicated and expensive, so in the case of pressure iron pipes for medium and low head power plants, the method shown in Figure 2 and Branch pipes as shown in Figure 3 have a simple structure, are easy to construct, are economical, and are widely used. In this branch pipe, it is necessary to reinforce the joint 3 between the main pipe 1 and the branch pipe 2, and a C-shaped reinforcing girder 4 is installed along the outside of the joint between the main pipe 1 and the branch pipe 2. A U-shaped reinforcing beam 5 is provided along the outside of the section.

If the pipe diameter is large or the internal pressure applied is high, this reinforcing girder will be large (the plate thickness is extremely thick and the height is high), making construction difficult. A branch pipe as shown is used (Special Publication No. 36-10880).

The branch pipe in Figure 4 connects a conical pipe 6 to the main pipe to expand the pipe diameter, and then connects it to a branch pipe 2 made of a conical pipe, and provides crescent-shaped reinforcement inside the joint 3 between the branch pipes 2. A digit 7 is provided. This reinforcing girder that protrudes into the interior not only reinforces the joint, but also has a rectifying effect on the water flow that branches into two. In addition, JP-A No. 57-1894 discloses that along the joints between the main pipe and branch pipes or the branch pipes of a branch pipe for a pressure conduit, a U-shape with a T-shaped cross section is provided on the outside and inside of the branch pipe, respectively. A branch pipe reinforced by welding a reinforcing girder so as to protrude is disclosed.

[Problem that the invention seeks to solve]

In the conventional branch pipes shown in Figures 2 and 3, if the bending angle between the main pipe and the branch pipe is large, the turbulence of water flow at the joint of the branch pipe on the extension of the center line of the main pipe is large, resulting in pressure loss. is large. Also, U-shaped reinforcing girder 5 at the junction of branch pipes
Since a large bending moment acts on the reinforcing girder, it is necessary to increase the thickness and height of the reinforcing girder.

On the other hand, in the branch pipes shown in Figures 4 and 5, the entire reinforcing girder between the branch pipes protrudes into the inside of the branch pipe, so that the center of gravity of the reinforcing girder coincides with the point of action of the resultant force of the load.
Since only tensile force acts on the reinforcement and almost no bending moment acts on it, the cross section can be made smaller, and C-shaped reinforcing girders at the joints between the main pipe and the branch pipes are not required. However, since the amount of protrusion of the reinforcing girder at the joint of the branch pipe into the inside of the branch pipe is large, the hydraulic loss coefficient increases. Therefore, a conical pipe 6 is joined to the main pipe 1, and the pipe diameter is increased from 15 to 15 mm near the branch point. It needs to be expanded by 20%. For this reason, the total length of the branch pipe increases, the pipe body becomes thicker, the overall weight increases compared to the branch pipe shown in Figure 2, the number of divisions of the pipe body increases, the manufacturing cost increases, and the branch pipe becomes thicker. The amount of excavation required to bury it underground increases the construction cost.

Furthermore, since the branch pipe shown in Figure 4 has a large internal protrusion of the reinforcing girder, vibrations are likely to occur due to water flow, and in addition,
Since the reinforcing girder is fixed by a tube body with low rigidity, it is difficult to prevent vibration. Therefore, there is a risk that the mounting portion of the reinforcing girder may be fatigued and damaged due to vibration caused by the water flow.

Furthermore, since the U-shaped reinforcing girder shown in FIG. 2 and the reinforcing girder shown in FIG. 4 are welded to the joint of the branch pipe at one end, lamellar tear-like weld cracks are likely to occur on the end surfaces of the plates used for the reinforcing girder. The connection between this reinforcing girder and the pipe body of the main pipe or branch pipe is as shown in FIG. 9a. Such a structure exists in the entire joint between each reinforcing girder and the tube body, but in actual use, the highest stress occurs in the A part of the U-shaped reinforcing girder in Figure 3, so this part is particularly It is important that there are no defects such as weld cracks. As shown in Japanese Unexamined Patent Publication No. 57-1894, when welding a U-shaped reinforcing girder with a T-shaped cross section so that it protrudes from the inside and outside of the joint between branch pipes of a branch pipe, the reinforcement strength is However, the reinforcing girder with a T-shaped cross section that protrudes into the inside of the branch pipe greatly disturbs the water flow following the Y-shaped branch point, resulting in a large pressure loss. In addition, the reinforcing girder protruding into the branch pipe is subjected to vibration due to the vibration caused by the flowing water at the branch part. If the reinforcing girder protruding inside the branch pipe is welded at its base end, it will be difficult to detect any defects in the welded part during non-destructive inspection using X-rays, etc. during the manufacture of the branch pipe. Therefore, during use of the branch pipe, there is a risk that the welded part of the reinforcing girder may suffer fatigue failure due to minute weld defects, resulting in a major accident.

Therefore, the present invention has a simple shape, small overall size, low pressure loss, no risk of reinforcing girders being damaged by vibrations caused by water flow, and no risk of weld cracks occurring in highly stressed parts of the reinforcing girders. It is an object of the present invention to provide a branch pipe for a pressure conduit with a small number of branches.

[Means for solving problems]

In order to achieve the above object, as a result of intensive research by the present inventors, a reinforcing girder protruding inward by making a part of the reinforcing girder provided at the junction of the branch pipes of the branch pipe protrude into the inside of the branch pipe. It was discovered that this part exerts a water flow rectification effect, and the amount of protrusion of the reinforcing girder into the inside of the reinforcing girder is small, so hydraulic loss is small and vibration of the reinforcing girder can be prevented, and the present invention was completed. It came to this.

That is, the gist of the present invention is to provide a pressure conduit branch pipe in which a cylindrical main pipe and a plurality of conical branch pipes are joined together such that their axes intersect with each other at a predetermined angle at one point. , a reinforcing girder made of a U-shaped flat plate is placed along the joint between each conical tube, and at the center of the reinforcing girder, 20 to 40% of the height of the reinforcing girder protrudes inside the joint, and the rest is attached to the joint. A pressure conduit characterized in that the proximal ends of the conical pipes of the branch pipes are joined by welding so that the intermediate part of the single plate-shaped reinforcing girder is sandwiched from both sides of the reinforcing girder so as to protrude outside. Located in the branch pipe.

Next, the contents of the present invention will be explained in detail with reference to the drawings. FIG. 1 is a sectional view of an example of a branch pipe for a pressure conduit according to the present invention, and FIG. 6 is a sectional view taken along line CC of the same.
1 is the main pipe made of a cylinder, and 2 is made of a conical pipe.
The main branch pipes 2, 2 and three axes are joined in a Y-shape so that they intersect at one point. A C-shaped reinforcing girder 4 made of a C-shaped flat plate is joined along the outside of the joint between the main pipe 1 and the branch pipe 2, and a U-shaped reinforcing girder 5 made of a U-shaped flat plate is connected at the joint between the branch pipes. A part of the reinforcing girder is joined at the center so as to protrude inside the branch pipe 8.

The amount h of the reinforcing girder protruding into the branch pipe 8 at the center of the reinforcing girder 5 is preferably 20 to 40% of the height H of the reinforcing girder. The amount of protrusion into the branch pipe decreases toward both ends of the reinforcing girder, and the amount of protrusion becomes 0 at both ends. The amount of protrusion in this central part is 20%
If it is less than that, the rectifying effect of the protruding reinforcing girder will be small and the hydraulic loss will be large. If the amount of protrusion exceeds 40%, the large protruding reinforcing girder narrows the cross section of the waterway and obstructs the water flow, increasing hydraulic loss, and the vibration of the reinforcing girder due to the water flow increases, which may damage the reinforcing girder. There is.

FIG. 7 shows a sectional view of the branch pipe of the present invention in the case of asymmetrically branching into two branches. The center line of one branch pipe 2a coincides with the center line of the main pipe 1, and the other branch pipe 2b branches laterally. Also in this case, a part of the reinforcing girder 5 at the junction of the branch pipes 2a and 2b protrudes into the branch pipe.

FIG. 8 shows a cross-sectional view of the branch pipe of the present invention in the case of branching into three prongs. The center line of one branch pipe 2a coincides with the center line of the main pipe 1, and the other two branch pipes 2b, 2b
branches laterally in a symmetrical manner. A C-shaped reinforcing girder 4 is connected to the outside of the joint between the main pipe 1 and the two branch pipes 2b, 2b, and a U-shaped reinforcing girder 5 is partially connected to the joint between the branch pipe 2a and the branch pipes 2b, 2b. is provided to protrude into the branch pipe.

In the pressure conduit branch pipe of the present invention, when the head is low and the pressure is low, the C-shaped reinforcing girder 4 between the main pipe and the branch pipe is not necessarily necessary and can be omitted.

[Effect]

In the pressure conduit branch pipe of the present invention, the water flow flows along the part of the reinforcing girder provided at the joint between the branch pipes that protrudes into the branch pipe, preventing disturbance of the water flow and exhibiting a rectifying effect.

If the branch pipe of the present invention is buried in concrete,
Since the externally protruding portion of the U-shaped reinforcing girder is buried and fixed in concrete, even if pressure pulsations occur in the water flow, the vibration of the reinforcing girder is suppressed and damage to the reinforcing girder due to vibration is prevented. In particular, the entire reinforcing girder that protrudes into and out of the branch pipe is composed of a single flat plate.
Since there are no welded parts on the reinforcing girder itself, even if vibration force from running water acts on the part of the reinforcing girder that protrudes inside the branch pipe, if the part of the reinforcing girder that protrudes outside the branch pipe is fixed with concrete, etc. The vibration of the reinforcing girder made of a single steel plate is suppressed, and since the reinforcing girder itself has no welded parts, there is no risk of fatigue failure progressing from minute defects in the welded parts. Making the entire reinforcing girder that protrudes inward and outward from a single sheet of steel is extremely effective in preventing fatigue failure caused by vibrations from flowing water.

The connection between the U-shaped reinforcing girder 5 of the branch pipe of the present invention and the welded portion of the pipe body of the branch pipe is as shown in FIG. 9b. It is well known that one way to prevent lamellar tear-like weld cracks is to avoid joining at the edges of the plates, and the structure shown in Figure 9b is better in this respect than the structure shown in Figure 9a. Excellent.

In the branch pipe of the present invention, the flow may be divided from the main pipe to the branch pipe, or conversely, the flow from the branch pipe may be combined and flowed to the main pipe.

〔Effect of the invention〕

According to the branch pipe for a pressure conduit of the present invention, the branch pipe is compact, has a simple structure, and is easy to operate, so it can be manufactured at low cost.

The reinforcing girder that partially protrudes into the branch pipe exerts a rectifying effect without interfering with the water flow, so the pressure loss of the fluid in the branch pipe is small.

Since the U-shaped reinforcing girder provided at the junction of the branch pipes approaches a circular shape from an ellipse, the bending moment acting on the reinforcing girder becomes smaller, and the thickness and height of the reinforcing girder can be reduced.

Since the overall length of the branch pipe is small and the reinforcing girder is also small, the amount of excavation can be reduced when laying it in a tunnel.

The amount of protrusion of the reinforcing girder into the branch pipe is small, and the part of the reinforcing girder that protrudes outside the branch pipe can be fixed with concrete, making it possible to prevent the reinforcing girder from vibrating due to water flow. There is no risk of damage.

Since the U-shaped reinforcing girder is not welded to the joint of the branch pipe at the end of the reinforcing girder, but at the middle part, there is less risk of lamellar tear-like weld cracks occurring, and welding becomes easy.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an example of a branch pipe for a pressure conduit according to the present invention. FIG. 2 is a cross-sectional view of a conventional Y-shaped branch pipe, and FIG. 3 is a cross-sectional view taken along line AA of the same. FIG. 4 is a sectional view of another conventional branch pipe, and FIG. 5 is a sectional view taken along line BB. FIG. 6 is a cross-sectional view of the branch pipe of the present invention taken along the line C-C in FIG. 1, and FIG.
FIG. 8 is a sectional view of a three-pronged branch pipe of the present invention. FIG. 9 is a sectional view showing the structure of the welded portion of the reinforcing girder. Explanation of the sign, 1... Honest, 2, 2a, 2b...
Branch pipe, 3... Joint, 4... C-shaped reinforcement girder, 5...
U-shaped reinforcing girder, 6... Conical pipe, 7... Crescent-shaped reinforcing girder, 8... Branch pipe.

Claims (1)

[Scope of Claims] 1. In a pressure conduit branch pipe in which a cylindrical main pipe and a plurality of conical branch pipes are joined together such that their respective axes intersect with each other at a predetermined angle at one point, each cone Along the joint between the pipes, a reinforcing girder made of a U-shaped flat plate is placed at the center of the reinforcing girder, with 20 to 40% of the height of the reinforcing girder protruding inside the joint, and the rest protruding outside the joint. A branch pipe for a pressure conduit, characterized in that the proximal ends of the conical pipes of the branch pipe are joined by welding so that the middle part of the reinforcing girder, which is a flat plate, is sandwiched from both sides of the reinforcing girder, so that the conical pipe extends from the reinforcing girder. . 2. A branch pipe for a pressure conduit according to claim 1, wherein a reinforcing girder made of a U-shaped flat plate is joined to the outside of the joint portion along the joint portion between the reinforcing girder and each conical tube. 3. A pressure conduit branch pipe according to claim 1 or 2 for a Y-shaped symmetrical two-pronged branch pipe. 4. A pressure conduit branch pipe according to claim 1 or 2, which is for a T-shaped asymmetric two-pronged branch pipe. 5. A pressure conduit branch pipe according to claim 1 or 2 for a three-pronged branch pipe.