JP7370827B2 - Piping and its construction method - Google Patents

Description

The present invention relates to piping and a method of constructing the same, and particularly to a method of constructing a piping for absorbing thermal expansion and contraction of the piping.

One way to absorb the thermal expansion and contraction of piping is to construct the piping using elbows or bends. This method has the advantage that liquid stagnation is less likely to occur. Another option is to install expansion joints in the piping. Expansion joints do not require a large installation space, so they are advantageous when space is limited. As expansion joints, there are known types that use bellows and types that use slide members that slide in the length direction of piping (Patent Document 1).

Japanese Patent Application Publication No. 2011-127738

In the method of constructing piping using elbows and bends, because the elbows and bends are made of the same material as the piping components (for example, the pipes that make up the piping), they may not be able to absorb the thermal expansion and contraction of the piping. , gaps may occur in the piping or the piping may be damaged. On the other hand, in order to improve the ability of piping to absorb thermal expansion and contraction, a large installation space is required.

The method of providing expansion joints in piping tends to cause fluid stagnation. Furthermore, when a bellows type expansion joint is applied to piping subject to internal pressure, the deformation of the bellows is restricted and the desired performance may not be achieved. In addition, bellows type expansion joints produce a side effect of reaction force due to internal pressure, which may cause damage to the piping. Furthermore, members having movable parts such as bellows and sliding parts such as slide members tend to deteriorate easily and require frequent maintenance and replacement.

An object of the present invention is to provide piping and its construction method that can absorb thermal expansion and contraction in a narrow installation space and suppress the frequency of maintenance and replacement.

The present invention relates to piping that connects two piping members via a bent portion , and a method for constructing the piping. The pipe is an outdoor pipe through which ultrapure water or pure water flows, and the difference between the environmental temperature at the time of construction of the pipe and the temperature of the ultrapure water or pure water flowing through the pipe exceeds a predetermined temperature. The bent portion has a joint that constitutes the bent portion, and the elastic modulus of the joint is smaller than the elastic modulus of the piping member.

According to the present invention, it is possible to provide piping and its construction method that can absorb thermal expansion and contraction in a narrow installation space and can suppress the frequency of maintenance and replacement.

FIG. 1 is a schematic diagram of piping according to the first embodiment of the present invention. FIG. 3 is a detailed view of a bent part of the pipe. FIG. 3 is a schematic diagram showing the effect of using a joint that is easily deformed. It is a figure explaining the deflection of a 90 degree elbow. FIG. 3 is a schematic diagram of piping according to a second embodiment of the present invention.

Some embodiments of the piping construction method of the present invention will be described with reference to the drawings. In each figure, the X-axis and the Y-axis are horizontal axes that are orthogonal to each other, and the Z-axis is a vertical axis that is orthogonal to the X- and Y-axes. Regarding the X-axis, the direction from the first equipment 2 to the second equipment 3 is called the +X direction, and the opposite direction is called the -X direction. To distinguish the direction of the Y-axis, it is sometimes referred to as +Y direction and -Y direction. FIG. 1 is a schematic diagram (isometric diagram) of a piping 1 according to a first embodiment of the present invention. Piping 1 is installed outdoors and connects first equipment 2, such as a tank, pump, or processing device, and second equipment 3, such as a tank, pump, or processing device. The fluid flows from the first installation 2 towards the second installation 3.

The piping 1 of this embodiment extends linearly in the X direction between the first equipment 2 and the second equipment 3, which are two points apart from each other, and is partially provided with a bent portion 6 that bulges in the +Y direction. It is something. That is, the piping 1 includes a first piping (first piping member) 4 that extends linearly in the + A second pipe (second pipe) is provided on the same straight line as the first pipe 4 and extends linearly in the + A bent portion 6 is provided between the first pipe 4 and the second pipe 5. The fluid flowing through the pipe 1 is not limited, and examples thereof include water (including ultrapure water and pure water), oil, gas, and the like. The temperature of the fluid flowing through the pipe 1 is set to a predetermined temperature. The temperature of the fluid may vary and may vary along the piping path.

The bent portion 6 is provided along a substantially U-shaped path in the XY plane. The bent portion 6 is a combination of a joint 7, a short pipe 8, and a connecting pipe 9. The bent part 6 has one end connected to the first pipe 4, is bent in the +Y direction and extends in the +Y direction, is bent in the +X direction and extends in the +X direction, and is bent in the -Y direction and extends in the -Y direction. , is bent again in the +X direction and extends in the +X direction, and the other end side is connected to the second pipe 5. The bent portion of the bent portion 6 is constituted by a joint 7. A short pipe 8 and a connecting pipe 9 are provided between the joints 7 . As shown in more detail in FIG. 2, short pipes 8 connected to flanges 81 are provided on both sides of the joint 7, and the flanges 81 are connected to the flange 91 of the adjacent connecting pipe 9 and the first pipe 4 or the second pipe 4. It is connected to the flange of the pipe 5 (FIG. 2 shows the flange 41 of the first pipe 4) with bolts (not shown). Gaskets 11 are provided between the flanges 81 and 91 and between the flanges 81 and 41. The short tube 8 can also be omitted. The short pipe 8 and the joint 7 are joined by thermocompression bonding, heat fusion bonding, thermal welding, electric fusion bonding, or the like. The joint 7 is an elbow or bend that connects two orthogonal pipes (the connecting pipes 9, the connecting pipe 9 and the first pipe 4, or the connecting pipe 9 and the second pipe 5). The two pipes may form an angle other than 90 degrees (for example, 45 degrees or 60 degrees) as long as they are not parallel to each other. Since the bent portion 6 is provided to absorb thermal expansion and contraction of the piping 1, the bent portion 6 is not provided with a piping support for restraining displacement of the piping. However, it is possible to provide a minimum amount of support to support its own weight (downward load in the Z direction).

Incidentally, piping through which high-temperature fluid flows has conventionally been designed in consideration of thermal expansion and contraction, and bent portions including the above-mentioned elbows and bends are provided as necessary. However, thermal expansion and contraction usually does not pose a problem for piping through which a fluid close to room temperature flows, and thermal deformation of the piping due to thermal expansion and contraction is not taken into account. On the other hand, the inventor of the present application has found that even in such a case, thermal expansion and contraction becomes a problem under specific conditions. As an example, consider the case where a very long straight pipe is installed outdoors. Here, it is assumed that piping is installed in a straight line between facilities 500 m apart (in FIG. 1, it is assumed that the bent portion 6 is replaced with a straight piping 106). When construction is carried out in a high-temperature environment such as in the summer, the outside temperature can reach 30 to 40 degrees Celsius, and the pipes themselves can become even hotter. However, since the 500m distance between the facilities remains unchanged, the piping will be installed "to have a length of 500m in a high-temperature environment." Normally, a 500 m long pipe is constructed by dividing it into multiple sections, so the length of the pipe in the last section to be installed is adjusted to prevent axial stress from occurring in the pipe. This allows appropriate flange connection and welding between adjacent pipes. On the other hand, when fluid at room temperature flows after the start of operation, the temperature of the piping becomes approximately the same as the temperature of the fluid. However, because there is a large difference between the temperature of the piping during construction and the temperature of the piping when fluid is flowing, there is a possibility that a very large thermal deformation will occur. For example, if the temperature of the piping during construction is 60°C and the temperature of the piping when fluid is flowing is 20°C, the temperature difference is 40°C. If the piping is PVC pipe, the coefficient of linear expansion of PVC (polyvinyl chloride) is about 6 to 8 x 10 ^-5 /K, so 6 to 8 x 10 ^-5 /K x 40K x 500m = 1.2 Thermal expansion and contraction of ~1.4 m occurs in the axial direction of the pipe. In this way, depending on the difference between the environmental temperature at the time of construction (more precisely, the temperature of the piping) and the fluid temperature, and the straight length of the piping, extremely large thermal deformation can occur even if the fluid temperature is room temperature. There is sex.

For the above reasons, in this embodiment, the bent portion 6 is provided in the pipe 1 to absorb thermal expansion and contraction of the pipe 1. However, since the bent portion 6 requires space, it is desirable to configure the bent portion 6 as compactly as possible. Therefore, in this embodiment, the joint 7 is made of a material that is easily deformed to improve the bending deformation performance of the joint 7 itself. Specifically, the elastic modulus of the joint 7 is made smaller than the elastic modulus of the piping member, and more specifically, the Young's modulus of the joint 7 is made smaller than the Young's modulus of the piping member. Examples of the material for the joint 7 include polyethylene, but other materials such as polypropylene and reinforced polypropylene can also be used. In particular, polyethylene has a high ability to absorb unexpected thermal stress and external force even in the range of plastic deformation.

FIG. 3 is a schematic diagram showing the effect of using the easily deformable joint 7. The first pipe 4 is a very long straight pipe, and a first elbow 7A is connected to the end thereof, a first connection pipe 9A is connected to the first elbow 7A, and a first connection pipe 9A is connected to the first elbow 7A. A second connection pipe 9B is connected via the second elbow 7B. The elbow 107A of the comparative example is made of the same material (for example, PVC) as the first pipe 4 and the first and second connection pipes 9A, 9B, and has the same center line C as the first elbow 7A of the present embodiment. They have the same wall thickness t (see FIG. 2). A first connecting pipe 109A is connected to the elbow 107A of the comparative example, and a second connecting pipe 109B is connected to the first connecting pipe 109A via a second elbow 107B. The first elbow 7A of this embodiment is made of polyethylene having a smaller Young's modulus than the elbow 107A of the comparative example. The broken line indicates the first elbow 7A and the first connection pipe 9A during construction (the same applies to the comparative example). Here, a case will be described in which the first pipe 4 contracts significantly in the -X direction (the amount of thermal contraction in the -X direction is assumed to be ΔX). Since the amount of thermal expansion and contraction of the first connection pipe 9A and the second connection pipe 9B is small, the position of the second elbow 7B is left unchanged. As a result, the first elbow 7A is deformed to expand in the X direction. This deformation occurs when the first pipe 4 of the first elbow 7A does not expand or contract (that is, the position of the end of the first elbow 7A on the first pipe 4 side remains unchanged). It is thought that the deformation is similar to that when a tensile force in the radial direction (+X direction) is applied to the end connected to the connecting pipe 9A.

Figure 4 shows a 90 degree elbow with one end fixed and the other end subjected to a radial force W. This means that in FIG. 3, the end of the first elbow 7A on the first pipe 4 side is the fixed end in FIG. 4, and the end of the first elbow 7A connected to the first connection pipe 9A is the fixed end in FIG. 4, the first pipe 4 does not expand or contract, and a tensile force W in the radial direction (+X direction) is applied to the end of the first elbow 7A that is connected to the first connection pipe 9A. It is thought that this is simulating a situation similar to the one in question. The displacement δ in the load direction at this time is (π+1)WR ³ /4EI. Here, R is the radius of curvature of the elbow, E is the Young's modulus of the elbow, and I is the second moment of area of the elbow. The displacement δ is inversely proportional to E, and becomes larger as E becomes smaller. Furthermore, as the displacement δ increases, the opening angle θ of the end portion also increases. Since the displacement δ and the opening angle θ are large, the rotation angle of the first connecting pipe 9A around the Z axis due to thermal deformation becomes large, and the amount of thermal contraction ΔX in the -X direction is easily absorbed. As a result, the first connection pipe 9A can be made shorter than the first connection pipe 109A of the comparative example, and the second connection pipe 9B can be brought closer to the first pipe 4 than the second connection pipe 109B of the comparative example. I can do it. That is, the bent portion 6 can be configured compactly. The above effect can also be said to be the effect of making the bending stiffness (EI) of the first elbow 7A of the present embodiment smaller than the bending stiffness (EI) of the elbow 107A of the comparative example.

FIG. 5 shows an example in which the bent portion 6 is configured three-dimensionally. In this embodiment, the first pipe 4 and the second pipe 5 are parallel to each other. The second pipe 5 is offset from the first pipe 4 in the +Y direction. The flow direction of the fluid flowing inside the first pipe 4 and the flow direction of the fluid flowing inside the second pipe 5 are the same direction (+X direction). In this embodiment, in order to prevent interference between the second pipe 5 and another pipe 10 disposed at the same height as the first pipe 4 in the Z-axis direction, a pipe is provided at the bent portion 6 extending in the Z-axis direction. A connecting pipe 99 is provided. Here, among the connection pipes 99 of the bent portion 6, the length in the Z-axis direction of the connection pipe 99 provided on the second pipe 5 side is the Z-axis direction length of the connection pipe 99 provided on the first pipe 4 side. It is longer than the axial length. Thereby, interference with other pipes 10 can be avoided, and the ability to absorb thermal expansion and contraction can be further increased.

As explained above, in this embodiment, the bending deformation performance of the joint 7 itself is improved by using a material that easily deforms for the joint 7 (specifically, the Young's modulus of the joint 7 is made smaller than the Young's modulus of the piping). It is characterized by:

Further, this embodiment is characterized in that the bent portion 6 is provided in the pipe 1 when the difference between the environmental temperature at the time of construction and the temperature of the fluid flowing through the pipe 1 exceeds a predetermined temperature. Although the present invention is preferably applied to newly installed piping, it can also be applied as a modification of existing piping when a problem of thermal deformation occurs in existing piping. It should be noted that for the present invention the absolute temperature of the fluid flowing through the pipe 1 is not critical. Therefore, it is preferable to provide the bent portion 6 in the pipe 1 even when construction is performed in a low-temperature environment such as in winter or in a cold region, and a fluid at room temperature flows through the pipe 1. Conversely, if the temperature at the time of construction is room temperature and the temperature of the fluid flowing through the pipe 1 is also room temperature, the advantage of providing the bent portion 6 cannot be obtained. Although the predetermined temperature is not particularly limited, it can be set to about 20 degrees, for example.

The present invention can be suitably applied to plastic materials with a high linear expansion coefficient (as mentioned above, the linear expansion coefficient of PVC is about 6 to 8 x 10 ^-5 /K, and the linear expansion coefficient of iron is about 1.2 x 10 ^-5 /K), but can also be applied to metal piping such as iron.

In this embodiment, the case where the pipe 1 is installed outdoors has been described, but the same applies to the case where the pipe 1 is installed underground.

1 Piping 4 First piping 5 Second piping 6 Bent part 7 Joint (elbow, bend)
8 Short pipe 9 Connection pipe

Claims (9)

A piping construction method for connecting two piping members via a bent part , the method comprising:
The piping is an outdoor piping through which ultrapure water or pure water flows,
The difference between the environmental temperature at the time of construction of the piping and the temperature of the ultrapure water or the pure water flowing through the piping exceeds a predetermined temperature,
The method for constructing piping, wherein the bent portion has a joint that constitutes the bent portion, and the elastic modulus of the joint is smaller than the elastic modulus of the piping member. The piping construction method according to claim 1, wherein the Young's modulus of the joint is smaller than the Young's modulus of the piping member. The method for constructing piping according to claim 1 or 2, wherein the bending rigidity of the joint is smaller than the bending rigidity of a joint made of the same material as the piping member and having the same center line and the same wall thickness as the joint. . The piping construction method according to any one of claims 1 to 3, wherein the piping member is made of vinyl chloride and the joint is made of polyethylene. One end of the piping is connected to a first piping member, and the other end of the piping is installed on the same straight line as the first piping member or parallel to the first piping member. The piping construction method according to any one of claims 1 to 4, further comprising connecting to a second piping member to connect the first piping member and the second piping member. The piping construction method according to any one of claims 1 to 5, wherein at least one of the outside and inside temperatures of the piping member changes. A pipe having two piping members and a bent part connecting the two piping members,
The piping is an outdoor piping through which ultrapure water or pure water flows,
The difference between the environmental temperature at the time of construction of the piping and the temperature of the ultrapure water or the pure water flowing through the piping exceeds a predetermined temperature,
The bent portion has a joint that constitutes the bent portion, and the elastic modulus of the joint is smaller than the elastic modulus of the piping member. The piping according to claim 7 , wherein the Young's modulus of the joint is smaller than the Young's modulus of the piping member. The piping according to claim 7 or 8 , wherein the bending rigidity of the joint is smaller than that of a joint made of the same material as the piping member and having the same center line and the same wall thickness as the joint.

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