Composite tube, piping structure, and piping structure manufacturing method

Abstract

To provide a composite tube with further improved strength and excellent workability, in order to solve a conventional problem that there is a need of cutting an outer periphery at an end of the composite tube when inserting the composite tube in a joint, which results in deterioration of strength due to a thin wall of a cut portion, and deterioration of workability because resistance at the time of inserting the pipe into a socket becomes large due to a rough cut area.SOLUTION: In a composite tube having a fiber-reinforced resin layer, arithmetic surface roughness Ra of an outer periphery at one or both of ends at least in an axial direction is 0.4 μm or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a composite pipe, a piping structure, and a method for manufacturing a piping structure. [Background technology]

[0002] Composite pipes such as Fiberglass Reinfoced Plastic Mortar Pipes (FRPM pipes) are known as underground pipes for laying underground water pipes, power cables, etc. Composite pipes have one or more fiber reinforced plastic layers (FRP layers). Composite pipes are required to have high strength because they are laid underground. For example, Patent Document 1 proposes a composite pipe having a core material, a first outer FRP layer located on the outside of the core material, a second outer FRP layer located on the outside of the first outer FRP layer, a first inner FRP layer located on the inside of the core material, a second inner FRP layer located on the inside of the first inner FRP layer, and a third inner FRP layer located on the inside of the second inner FRP layer. According to the invention described in Patent Document 1, the bending strength against a load from the outer circumferential surface is improved.

[0003] When laying composite pipes underground, they are connected to each other via joints. When connecting composite pipes to each other, the end of the composite pipe is inserted into the socket of the joint. Because composite pipes do not have a uniform outer diameter due to the special manufacturing method, the surface of the end of the composite pipe is scraped to reduce the outer diameter and a taper is formed at the tip, and then the end of the composite pipe is inserted into the socket of the joint (for example, Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-074211 A [Patent Document 2] JP 2013-068238 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, when the end of a composite pipe is cut, the pipe becomes thinner and its strength is reduced. In addition, the cut area becomes rough, which increases the resistance when inserting the pipe into a socket, making it difficult to install. An object of the present invention is to provide a composite pipe that has increased strength and excellent workability. [Means for solving the problem]

[0006] The present invention has the following aspects. <1> In a composite pipe having a fiber-reinforced resin layer, A composite pipe, the arithmetic surface roughness Ra of the outer circumferential surface of at least one or both axial ends being 0.4 μm or less. <2> The outer peripheral surface of the end portion is formed of a cured resin. <1> The composite pipe according to claim 1.

[0007] <3> <1> or <2> and a joint having a receiving port, A piping structure, wherein an end of the composite pipe is located within the receiving port.

[0008] <4> <3> A method for manufacturing the piping structure according to the present invention, A method for manufacturing a piping structure, comprising the step of inserting an end of the composite pipe into the receiving port without cutting an outer peripheral surface of the end of the composite pipe. Effect of the Invention

[0009] The composite pipe of the present invention has increased strength and excellent workability. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a perspective view showing one embodiment of a composite pipe of the present invention. [Diagram 2] FIG. 2 is a perspective view showing a layer structure of the composite pipe of FIG. [Diagram 3] 1 is a cross-sectional view of one embodiment of a piping structure of the present invention. [Figure 4] 1A to 1C are process diagrams illustrating an example of a method for manufacturing a piping structure according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] In this specification and claims, the use of "to" indicating a range of numerical values ​​means that the numerical values ​​before and after it are included as the lower limit and upper limit.

[0012] (composite pipe) The composite pipe of the present invention has a fiber reinforced resin layer. 1 is a cylindrical fiber reinforced plastic composite pipe (FRPM pipe). The composite pipe 10 is open at both ends in the axial direction O. 2 is a diagram showing the layer structure of the pipe wall 11 of the compound pipe 10. In Fig. 2, X indicates the direction of the axis O, and Y indicates the circumferential direction of the compound pipe 10.

[0013] The composite pipe 10 has a cylindrical core material 4. The pipe wall 11 of the composite pipe 10 has the core material 4, a first fiber reinforced resin layer (FRP layer) 3 located on the outer peripheral surface (radially outer surface) of the core material 4, a second FRP layer 2 located on the outer peripheral surface of the first FRP layer, an outer layer 1 located on the outer peripheral surface of the second FRP layer 2, a third FRP layer 5 located on the inner peripheral surface (radially inner surface) of the core material 4, a fourth FRP layer 6 located on the inner peripheral surface of the third FRP layer 5, a fifth FRP layer 7 located on the inner peripheral surface of the fourth FRP layer 6, and an inner layer 8 located on the inner peripheral surface of the fifth FRP layer 7. That is, the pipe wall 11 of the composite pipe 10 has, radially outward from the axis O, an inner layer 8, a fifth FRP layer 7, a fourth FRP layer 6, a third FRP layer 5, a core material 4, a first FRP layer 3, a second FRP layer 2, and an outer layer 1, in this order. The compound pipe of the present invention is not limited to a cylindrical shape, but may be a rectangular cylindrical shape or the like.

[0014] The nominal diameter (inner diameter) of the compound pipe 10 is, for example, 200 to 3000 mm. The outer diameter R of the composite pipe 10 is, for example, 216 to 3137 mm. In addition, the outer diameter R of the composite pipe 10 is substantially the same from the thickest part of the composite pipe 10 to any end. "Substantially the same" means that the outer diameter does not change with a step. In other words, the end of the composite pipe 10 is not cut. By not cutting, the amount of waste generated can be further reduced. The outer diameter being "substantially the same" means that the outer diameter is, for example, within 10% from the thickest part of the composite pipe 10 to any end. The outer diameter at any point is the average of measurements taken at 10 arbitrary points in the Y direction. The end of the compound pipe 10 may be tapered. Tapering the end of the compound pipe 10 allows the compound pipe 10 to be inserted more smoothly in the manufacturing method of the piping structure described below. However, from the viewpoint of reducing waste, it is preferable that the tapering be performed in a short region (for example, 50 mm or less) from the end face of the compound pipe 10.

[0015] The thickness T of the pipe wall 11 is appropriately selected depending on the nominal diameter, for example, and is, for example, 7 to 67 mm. In addition, the thickness T of the pipe wall 11 is substantially the same from one end to the other end of the composite pipe 10. "Substantially the same" means that the thickness T does not change with a step. "Substantially the same" means, for example, that the difference is within a range of 10%. The thickness at any point is the average of measurements taken at 10 random points in the Y direction.

[0016] <Core material> The core material 4 is a hardened resin mortar composition containing resin mortar. The resin mortar is not particularly limited, but may be, for example, a mixture of thermosetting resin, silica sand, calcium carbonate, and chopped strands of glass fiber. An example of the thermosetting resin is an unsaturated polyester resin. The resin mortar composition may be a composition comprising resin mortar and aggregate (resin concrete). Examples of aggregates include those conventionally mixed in resin concrete, such as gravel, crushed stone, boulders, blast furnace slag aggregate, artificial lightweight aggregate, etc. The average particle size of the aggregate is, for example, 0.1 to 10 mm. In the resin concrete, the amount of aggregate per 100 parts by mass of resin mortar is, for example, 60 to 90 parts by mass. The resin mortar composition may contain additives such as a polymerization inhibitor, a hardener, and a hardening accelerator. The thickness of the core material 4 is not particularly limited, but is, for example, 2 to 55 mm. The thickness of the core material 4 is, for example, 30 to 90% of the thickness of the composite pipe.

[0017] <First FRP layer> The first FRP layer 3 is a cured resin product of an FRP resin composition containing resin, and contains fibers. In the first FRP layer 3, a plurality of fibers extending in the X direction are aligned in the Y direction. The reinforcing fibers are not particularly limited and may be either inorganic or organic fibers. Examples of inorganic fibers include glass fibers and carbon fibers. Examples of organic fibers include aramid fibers and polyethylene terephthalate fibers. The fibers may be monofilaments or rovings made of twisted monofilaments. The fiber thickness is, for example, 40 to 5000 tex.

[0018] The number of fibers in the first FRP layer is preferably 10 to 400 per 10 cm in the Y direction. When the number of fibers is equal to or more than the lower limit, the strength can be further increased. When the number of fibers is equal to or less than the upper limit, the productivity can be further increased. In the first FRP layer 3, the fibers do not have to be continuous in the X direction, and multiple fibers of a predetermined length may be aligned along the X direction. In this case, fibers adjacent in the axial direction may partially overlap in the direction of the axis O. In addition, the fibers may overlap in multiple layers in the thickness direction of the pipe wall 11. The length direction of the fibers in the first FRP layer 3 may be along the X direction or along the Y direction, or may form a spiral around the axis O. In addition, for example, the fibers in the first FRP layer 3 may be woven, knitted, or nonwoven fabric.

[0019] The resin of the FRP resin composition is preferably a thermosetting resin, such as an unsaturated polyester resin or an epoxy resin. The FRP resin composition may contain additives, such as a curing agent, a curing accelerator, an antioxidant, an ultraviolet absorbing agent, and a polymerization inhibitor.

[0020] The content of the fibers in the FRP resin composition (that is, in the first FRP layer 3) is preferably, for example, 100 to 200 parts by mass with respect to 100 parts by mass of the resin.

[0021] The thickness of the first FRP layer 3 can be determined taking into consideration the outer diameter R, the strength required for the composite pipe 10, and the like, and is, for example, 0.5 to 6.0 mm.

[0022] <Second FRP layer> The second FRP layer 2 is similar to the first FRP layer 3 . The material, length and longitudinal direction of the fibers of the second FRP layer 2 may be the same as or different from the material, length and longitudinal direction of the fibers of the first FRP layer 3 . The type of resin in the second FRP layer 2 may be the same as or different from the type of resin in the first FRP layer 3. The thickness of the second FRP layer 2 may be the same as or different from the thickness of the first FRP layer 3. However, from the viewpoint of reliably enhancing the smoothness of the outer circumferential surface of the composite pipe 10, it is preferable that the longitudinal direction of the fibers of the second FRP layer 2 is aligned along the Y direction, and that the thickness of the second FRP layer 2 is greater than the thickness of the first FRP layer 3. This makes it possible to make the winding tension of the fibers of the second FRP layer 2 more uniform, and to make the outer circumferential surface smoother.

[0023] The sum of the thickness of the first FRP layer 3 and the thickness of the second FRP layer 2 (the thickness of the outer FRP layer) can be appropriately determined taking into consideration the nominal diameter, etc., and is preferably 1.0 to 12.0 mm, for example. When the thickness of the outer FRP layer is equal to or greater than the above lower limit, the strength of the composite pipe 10 can be further increased. When the thickness of the outer FRP layer is equal to or less than the above upper limit, the productivity can be further increased and the fluctuation range of the thickness of the FRP layer can be further reduced.

[0024] <Third FRP layer> The third FRP layer 5 is similar to the first FRP layer 3 . The fiber material, length, and longitudinal direction of the third FRP layer 5 may be the same as or different from the fiber material, length, and longitudinal direction of the first FRP layer 3 . The type of resin in the third FRP layer 5 may be the same as or different from the type of resin in the first FRP layer 3. The thickness of the third FRP layer 5 may be the same as or different from the thickness of the first FRP layer 3 .

[0025] <The fourth FRP layer> The fourth FRP layer 6 is similar to the first FRP layer 3 . The fiber material, length, and longitudinal direction of the fourth FRP layer 6 may be the same as or different from the fiber material, length, and longitudinal direction of the first FRP layer 3 . The type of resin of the fourth FRP layer 6 may be the same as or different from the type of resin of the first FRP layer 3. The thickness of the fourth FRP layer 6 may be the same as or different from the thickness of the first FRP layer 3 .

[0026] <Fifth FRP layer> The fifth FRP layer 7 is similar to the first FRP layer 3 . The fiber material, length, and longitudinal direction of the fifth FRP layer 7 may be the same as or different from the fiber material, length, and longitudinal direction of the first FRP layer 3 . The type of resin of the fifth FRP layer 7 may be the same as or different from the type of resin of the first FRP layer 3. The thickness of the fifth FRP layer 7 may be the same as or different from the thickness of the first FRP layer 3 .

[0027] The sum of the thickness of the third FRP layer 5, the fourth FRP layer 6, and the fifth FRP layer 7 (the thickness of the inner FRP layer) can be determined appropriately taking into account the nominal diameter, etc., and is the same as the thickness of the outer FRP layer. The thickness of the inner FRP layer and the thickness of the outer FRP layer may be the same or different. However, from the viewpoint of improving strength, it is preferable that the thickness of the outer FRP layer is equal to the thickness of the inner FRP layer. "Equal" means that the difference between the two is within a range of ±10%.

[0028] <Outer layer> The outer layer 1 forms the outer peripheral surface of the composite pipe 10 . The outer layer 1 may be, for example, a covering sheet in which the surface of a nonwoven fabric is covered with a resin, or a cured product of an impregnated sheet in which a nonwoven fabric is impregnated with a resin. Alternatively, it may be a resin layer (not including a nonwoven fabric) in which a resin composition is cured. The resin of the outer layer 1 may be a non-foamed resin or a foamed resin, but from the viewpoint of making the outer peripheral surface of the composite pipe 10 smoother, a non-foamed resin is preferable. By having such an outer layer 1, the outer peripheral surface of the composite pipe 10 can be formed of a cured resin, making the outer peripheral surface of the composite pipe 10 smooth. In addition, by having the outer layer 1, the FRP layer of the composite pipe 10 can be protected.

[0029] Examples of the nonwoven fabric include inorganic nonwoven fabric and organic nonwoven fabric. Examples of inorganic nonwoven fabrics include glass paper, glass fiber (glass blinds), glass cloth, glass fiber, etc. Examples of organic nonwoven fabrics include polyester fiber nonwoven fabrics, etc. Examples of the resin constituting the outer layer 1 include thermoplastic resins and thermosetting resins, among which thermosetting resins are preferred. Examples of the thermoplastic resins include polyolefins such as polypropylene and polyethylene, vinyl chloride resins, vinylidene chloride resins, etc. Examples of the thermosetting resins include unsaturated polyester resins, epoxy resins, etc.

[0030] The thickness of the outer layer 1 is, for example, preferably 0.1 to 1.0 mm, and more preferably 0.3 to 0.7 mm. When the thickness is equal to or greater than the above lower limit, the influence of irregularities on the outer peripheral surface of the second FRP layer 2 can be sufficiently reduced, and the outer peripheral surface of the composite pipe 10 can be made smoother. In addition, when the thickness of the outer layer 1 is equal to or greater than the above lower limit, damage from external forces can be further reduced. When the thickness of the outer layer 1 is equal to or less than the above upper limit, productivity can be further improved.

[0031] <Inner layer> The inner layer 8 is similar to the outer layer 1. The configuration of the inner layer 8 may be the same as the configuration of the outer layer 1, or may be different. The thickness of the inner layer 8 is similar to that of the outer layer 1. The thickness of the inner layer 8 may be the same as that of the outer layer 1 or may be different. The thickness of the inner layer 8 and the thickness of the outer layer 1 may be the same or different. However, from the viewpoint of protection against external forces and liquid penetration, the thickness of the outer layer 1 is preferably equal to or greater than the thickness of the inner layer 8, and more preferably equal. When the thickness of the outer layer 1 is equal to or greater than the thickness of the inner layer 8, the external force on the composite pipe 10 can be mitigated, and the strength of the composite pipe 10 can be further increased. In addition, when the thickness of the outer layer 1 is equal to the thickness of the inner layer 8, the stress distribution when an external force is generated can be made uniform, local stress concentration can be avoided, and the strength of the composite pipe 10 can be further increased. "Equal" means that the difference between the two is within ±10%.

[0032] <Surface roughness of composite pipes> The outer peripheral surface of the composite pipe 10 is preferably smooth. The arithmetic surface roughness Ra of the outer peripheral surface of one or both of the one end 12 and the other end 13 of the composite pipe 10 is preferably 0.4 μm or less. Hereinafter, an end having an arithmetic surface roughness Ra of the outer peripheral surface of 0.4 μm or less may be referred to as a "specific roughness end". By having a specific roughness end, the end can be easily inserted into a socket of a fitting without grinding the outer peripheral surface of the end, which facilitates installation and increases the strength of the composite pipe 10 and the piping structure having the same. The arithmetic mean roughness Ra is the average value of measurements taken at any two points on the outer circumferential surface in accordance with JIS B 0601 (2013). The measurement points should avoid any areas with poor appearance such as voids, gaps, or unevenness. In this embodiment, the "specific roughness end" is an end that is inserted into a socket of a fitting (i.e., a plug) in a piping structure described later. The arithmetic surface roughness of the outer peripheral surface of the insertion hole can be adjusted by combining the composition of the outer layer 1, the manufacturing conditions, and the like.

[0033] <Manufacturing method of composite pipes> The method for manufacturing the composite pipe 10 is not particularly limited, and any conventionally known manufacturing method such as a filament winding method, a centrifugal molding method, a pultrusion method, or a hand lay-up method can be used. In the filament winding method, a core tube is rotated and fed at a constant speed, and the material of the inner layer 8 (resin, nonwoven fabric, etc.), the material of the fifth FRP layer 7 (FRP resin composition, fiber, etc.), the fourth FRP layer 6 (FRP resin composition, fiber, etc.), the third FRP layer 5 (FRP resin composition, fiber, etc.), the core material 4 (resin mortar composition, aggregate, etc.), the first FRP layer 3 (FRP resin composition, fiber, etc.), the second FRP layer 2 (FRP resin composition, fiber, etc.), and the material of the outer layer 1 (resin, nonwoven fabric, etc.) are sequentially wound around the core tube, cured in sequence, and then cut to a desired length to produce a composite pipe 10. According to these methods, composite pipes 10 of various sizes can be manufactured by changing the size of the core tube. In this embodiment, after winding the material of the outer layer 1, it is preferable to smooth the outer surface (smoothing step) while the resin of the outer layer 1 is in an uncured state. In the smoothing step, for example, a roller, a squeegee, or the like is used. By including the smoothing step, the outer peripheral surface of the composite pipe 10 can be made smoother, and the specified roughness end portion can be more reliably formed. After obtaining the desired composite pipe 10, one or both of the end portion 12 and the end portion 13 may be polished (polishing step). By including the polishing step, one or both of the end portion 12 and the end portion 13 can be more reliably brought to the desired arithmetic surface roughness. Examples of the polishing method in the polishing step include manual grinding using a grinder or the like, mechanical grinding using a rotary grinding wheel or the like, sandblasting, etc.

[0034] It is preferable that there is no step at the boundary between the specific roughness end and other regions in the outer circumferential surface of the composite pipe 10 (i.e., the specific roughness end is not narrower than other regions via a step). The absence of a step can further increase the strength of the composite pipe 10.

[0035] Examples of a method for manufacturing the composite pipe 10 include the method for manufacturing a composite pipe described in Japanese Patent Application Laid-Open No. 2001-205711, paragraphs

[0016] to

[0019] , the method for manufacturing a composite pipe described in Japanese Patent Application Laid-Open No. 2001-205712, paragraphs

[0020] to

[0028] , and the method for manufacturing a composite pipe described in Japanese Patent Application Laid-Open No. 10-193467, paragraphs

[0009] to

[0019] . That is, an endless steel belt is wound spirally around the peripheral surface of a cylindrical mold rotating about the tube axis, while the material for the inner layer 8, the material for the fifth FRP layer 7, the material for the fourth FRP layer, the third FRP layer 5, the core material 4, the first FRP layer 3, the second FRP layer 2, and the material for the outer layer 1 are supplied in this order onto the surface of the wound steel belt, and each resin composition is cured to continuously form a composite pipe 10. The steel belt advances as the cylindrical mold rotates, and passes from the end of the cylindrical mold through the inside of the mold and returns to the start of the mold. As a result, the compound pipe 10 is elongated in the axial direction of the cylindrical mold. The compound pipe 10 thus elongated is cut to a desired length to obtain a compound pipe 10 product. According to this manufacturing method, the inner diameter of the compound pipe 10 can be adjusted by changing the outer diameter of the mold.

[0036] (Piping structure) The piping structure of the present invention includes a composite pipe and a joint having a socket, and an end of the composite pipe is located inside the socket. That is, the piping structure is formed by inserting the plug of the composite pipe into the socket of the joint. Hereinafter, the piping structure of this embodiment will be described with reference to the drawings.

[0037] The piping structure 100 in FIG. 3 includes a first compound pipe 10 a , a second compound pipe 10 b , and a joint 20 . The joint 20 is cylindrical and has an opening 29a that opens to one side in the direction of the axis O and an opening 29b that opens to the other side. That is, the joint 20 has a socket that opens to one side in the direction of the axis O, and a socket that opens to the other side.

[0038] Within the joint 20, there is a first seal rubber 22 located near one end face, a second seal rubber 26 located near the other end face, and a stopper rubber 24 located between the first seal rubber 22 and the second seal rubber 26, closer to the first seal rubber 22.

[0039] In this embodiment, the first seal rubber 22 is the same as the second seal rubber 26. The seal rubber will be described with reference to FIGS. The second seal rubber 26 in Fig. 4 is an annular member with the axis O as its central axis. The outer circumferential surface of the second seal rubber 26 contacts the inner surface of the joint 20. The second seal rubber 26 receives the end portion 12 of the second compound pipe 10b therein (Fig. 3). In this state, the inner surface of the second seal rubber 26 and the outer circumferential surface of the end portion 12 of the second compound pipe 10b contact each other.

[0040] The second seal rubber 26 of the present embodiment has a lip portion 26a. The lip portion 26a protrudes toward the axis O (protrudes radially inward of the joint 20) and approaches the axis O from the opening 29b toward the opening 29a. By having the lip portion 26a with such a shape, the second compound pipe 10b received in the second seal rubber 26 is made difficult to come off. The second seal rubber 26 of the present embodiment has one lip portion 26a. However, the number of the lip portions 26a may be two or more, and is preferably one to three. When the seal rubber has two or more lip portions, the lip portions may be the same size or different sizes.

[0041] As described above, the first seal rubber 22 is similar to the second seal rubber 26. As shown in Figures 3 and 4, the outer circumferential surface of the first seal rubber 22 contacts the inner surface of the joint 20. The first seal rubber 22 receives the end portion 13 of the first compound pipe 10a therein. In this state, the inner surface of the first seal rubber 22 and the outer circumferential surface of the end portion 13 of the first compound pipe 10a contact each other.

[0042] The stopper rubber 24 is an annular member with the axis O as its central axis. The outer peripheral surface of the stopper rubber 24 contacts the inner surface of the joint 20. When the stopper rubber 24 is attached inside the joint 20, the stopper rubber 24 in this embodiment has a protruding portion 24a that protrudes toward the axis O (protrudes radially inward of the joint 20) at a position near the other end face. The stopper rubber 24 receives the end 13 of the first compound pipe 10a therein. The inner surface of the stopper rubber 24 contacts the outer circumferential surface of the end 13 of the first compound pipe 10a. The end face of the end 13 of the first compound pipe 10a contacts the protruding portion 24a. The end face of the end 12 of the second compound pipe 10b contacts the protruding portion 24a. When the end faces of the first composite pipe 10a and the second composite pipe 10b abut against the protruding portion 24a of the stopper rubber 24, the inner faces of the first composite pipe 10a, the second composite pipe 10b and the inner face of the protruding portion 24a are flush with each other.

[0043] Examples of the material of the second seal rubber 26 include synthetic rubbers such as styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), butadiene rubber (BR), chloroprene rubber (CR), and ethylene propylene rubber (EPDM), and natural rubber (NR). The tensile strength of the second seal rubber 26 is preferably 10 MPa or more, more preferably 14 MPa or more. The upper limit of the tensile strength of the second seal rubber 26 is not particularly limited, but is preferably, for example, 30 MPa or less. The tensile strength is determined in accordance with JIS K 6251 (2017) (however, a dumbbell-shaped No. 3 test piece is used as the test piece).

[0044] The tensile elongation of the second seal rubber 26 is preferably 200 to 600%, and more preferably 400 to 600%. The tensile elongation is determined in accordance with JIS K 6251 (2017) (however, a dumbbell-shaped No. 3 test piece is used as the test piece).

[0045] The compression set of the second seal rubber 26 is preferably 30% or less, and more preferably 20% or less. The compression set is determined in accordance with "5. Compression set test" of JIS K 6262 (2013) (however, the test conditions are 70°C x 22 hr, 25% compression).

[0046] The size of the second seal rubber 26 can be appropriately determined taking into consideration the outer diameter of the second compound pipe 10b, the inner diameter of the joint 20, and the like.

[0047] The material of the first seal rubber 22 is similar to the material of the second seal rubber 26. The material of the first seal rubber 22 and the material of the second seal rubber 26 may be the same or different. The physical properties (tensile strength, tensile elongation, compression set) of the first seal rubber 22 are similar to those of the second seal rubber 26. The physical properties of the first seal rubber 22 and the second seal rubber 26 may be the same or different. The size of the first seal rubber 22 is similar to the size of the second seal rubber 26. The size of the first seal rubber 22 and the size of the second seal rubber 26 may be the same or different.

[0048] The material of the stopper rubber 24 is the same as the material of the second seal rubber 26. The material of the stopper rubber 24 and the material of the second seal rubber 26 may be the same or different. The physical properties (tensile strength, tensile elongation, compression set) of the stopper rubber 24 are similar to those of the second seal rubber 26. The physical properties of the stopper rubber 24 and the second seal rubber 26 may be the same or different. The size of the stopper rubber 24 is similar to the size of the second seal rubber 26 .

[0049] <Manufacturing method of piping structure> The method for manufacturing a piping structure of the present invention includes a step of inserting an end of a composite pipe into a socket of a joint and fixing the composite pipe within the socket. An example of a method for manufacturing a piping structure will be described below with reference to FIG.

[0050] The first seal rubber 22, the stopper rubber 24, and the second seal rubber 26 are attached inside the joint 20. At this time, the first seal rubber 22, the stopper rubber 24, and the second seal rubber 26 are fitted into grooves on the inner surface of the joint 20. Alternatively, the first seal rubber 22, the stopper rubber 24, and the second seal rubber 26 are bonded to the inner surface of the joint 20.

[0051] Next, the end 13 of the first compound pipe 10a is inserted into the joint 20 from the opening 29a without cutting the outer circumferential surface of the end 13. At this time, if the end 13 of the first compound pipe 10a is a specific roughness end, it can be easily inserted into the first seal rubber 22 and the stopper rubber 24. When the end 13 is inserted into the first seal rubber 22, the end 13 presses the lip portion in a direction (outward) away from the axis O. As a result, the lip portion is urged in a direction that pushes back the end 13, and comes into contact with the first compound pipe 10a. When the lip portion is in contact with the first compound pipe 10a, the outer peripheral surface of the end 13 has a specific arithmetic surface roughness Ra, so that the contact area between the inner peripheral surfaces of the first seal rubber 22 (particularly the lip portion) and the stopper rubber 24 and the outer peripheral surface of the end 13 becomes large, making it more difficult for the first compound pipe 10a to come off.

[0052] Next, the end 12 of the second compound pipe 10b is inserted into the joint 20 from the opening 29b (in the direction of the arrow F) without cutting the outer circumferential surface of the end 12. At this time, if the end 12 of the second compound pipe 10b is a specific roughness end, it can be easily inserted into the second seal rubber 26. When end 12 is inserted into second seal rubber 26, end 13 presses lip portion 26a in a direction (outward) away from axis 0. As a result, lip portion 26a is urged in a direction that pushes back end 12, and comes into contact with second compound pipe 10b. With lip portion 26a in contact with second compound pipe 10b, the outer circumferential surface of end 12 has a specific mathematical surface roughness, so that the contact area between the inner circumferential surface of second seal rubber 26 and the outer circumferential surface of end 12 becomes large, making it more difficult for second compound pipe 10b to slip out.

[0053] In the piping structure 100 obtained by the above-mentioned manufacturing method, the end 13 of the first composite pipe 10a and the end 12 of the second composite pipe 10b have their outer surfaces not machined, so that the ends of the composite pipes 10 in the obtained piping structure have excellent strength.

[0054] In addition, according to the above manufacturing method, since the composite pipe is not cut, the amount of waste generated can be reduced, and the environmental load can be reduced.

[0055] (Other embodiments) In the above-described embodiment, the composite pipe has a core material, but in the present invention, it is sufficient for the composite pipe to have an FRP layer, and the composite pipe does not necessarily have to have a core material.

[0056] In the above-described embodiment, the outer FRP layer is two layers, but the present invention is not limited to this, and it may be one layer or three or more layers. Furthermore, in the above-described embodiment, the inner FRP layer is three layers, but the present invention is not limited to this, and the inner FRP layer may be two layers or less, or four layers or more. The number of FRP layers may be one or more and can be appropriately determined depending on the strength and application required of the composite pipe.

[0057] In the above embodiment, the composite pipe has an outer layer and an inner layer, but the present invention is not limited thereto, and one or both of the outer layer and the inner layer may be omitted. However, from the viewpoint of more reliably forming the specific roughness end portion in the composite pipe, it is preferable to have the outer layer. Also, from the viewpoint of further increasing the strength of the composite pipe, it is preferable to have the outer layer and the inner layer.

[0058] In the above-described embodiment, the joint has a cylindrical shape, but the present invention is not limited to this, and the joint may be bent or may have three or more sockets. EXAMPLES

[0059] The present invention will be described in more detail below using examples, but the present invention is not limited to these examples.

[0060] (Evaluation method) <Workability> A piping structure similar to that shown in FIG. 3 was manufactured, and the workability thereof was evaluated according to the following evaluation criteria.

[0061] Evaluation Criteria ○: The composite pipe could be inserted into the joint using a 1.0 ton lever hoist chain block. ×: A 1.6-ton lever hoist chain block was required to insert the composite pipe into the joint.

[0062] <Flatness test> An external pressure test was conducted as specified in "8.2 External Pressure Test" on JIS A 5350 (1991) Type 5 internal pressure pipe, C type φ500, and the standard deflection external pressure value was measured.

[0063] Example 1 A composite pipe (nominal diameter = 500 mm, thickness T = 11 mm) having a structure similar to that of the pipe wall 11 in FIG. 2 was produced. The specifications of the outer layer and inner layer of the composite pipe of this example were the same as those of the composite pipe 10 of Figures 1 and 2. That is, from the axis line radially outward, the pipe wall was made up of the inner layer, the fifth FRP layer, the fourth FRP layer, the third FRP layer, the core material, the first FRP layer, the second FRP layer, and the outer layer in this order. The thicknesses of the outer and inner layers were as shown in the table. The arithmetic surface roughness, workability and flatness tests were carried out on the outer surface of the obtained composite pipe, and the results are shown in the table.

[0064] (Examples 2 to 4) Except for the thicknesses of the outer layer and the inner layer being as shown in the table, the composite pipes of each example were obtained in the same manner as in Example 1. The outer peripheral surface of the obtained composite pipes was subjected to arithmetic surface roughness, workability, and flatness tests, and the results are shown in the table.

[0065] Comparative Example 1 A composite pipe similar to that of Example 2 was produced, except that the thickness T was set to 12 mm. The outer peripheral surface of the end of the produced composite pipe was cut to form an outer layer with the thickness shown in the table, and this was used as the composite pipe of this example. The arithmetic surface roughness, workability, and flatness tests were performed on the outer peripheral surface of the obtained composite pipe, and the results are shown in the table.

[0066] [Table 1]

[0067] As shown in Table 1, in all of Examples 1 to 4 in which the present invention was applied, the workability was rated "good" and the flattening test values ​​were 22.4 to 22.7 kN / m. In Comparative Example 1, in which the arithmetic surface roughness Ra of the end portion was 0.946 μm, the workability was rated as “×” and the flattening test value was 19.3 kN / m. From these results, it was confirmed that the application of the present invention can increase strength and provide excellent workability. [Explanation of symbols]

[0068] 1 outer layer 2, 3, 5, 6, 7 Fiber reinforced resin layer 8 Inner layer 10, 10a, 10b composite pipe 11 Pipe wall 12, 13 End 20 Joints 100 Piping structure

Claims

1. In a composite pipe having a fiber-reinforced resin layer, A composite pipe, wherein the arithmetic surface roughness Ra of the outer circumferential surface of at least one or both ends in the axial direction is 0.4 μm or less.

2. 2. The compound pipe according to claim 1, wherein an outer circumferential surface of the end portion is formed of a cured resin.

3. A pipe according to claim 1 or 2, and a joint having a socket, A piping structure, wherein an end of the composite pipe is located within the receiving port.

4. A method for manufacturing the piping structure according to claim 3, A method for manufacturing a piping structure, comprising the step of inserting an end of the composite pipe into the receiving port without cutting an outer peripheral surface of the end of the composite pipe.

Images