Socket and spigot type different-material multi-layer composite pipe and manufacturing method thereof

Abstract

The invention discloses a socket and spigot type different-material multi-layer composite pipe and a manufacturing method thereof, the composite pipe comprises an inner pipe, a middle layer and an outer pipe which are sequentially sleeved from inside to outside, the inner pipe and the outer pipe are bonded through the middle layer, the outer pipe comprises a socket, a pipe body and a spigot part which are sequentially connected, and the composite pipe is provided with a socket bushing ring and a spigot bushing ring. The manufacturing method comprises the steps that S1, the outer pipe is treated, the inner pipe and the middle layer are manufactured, and the bell mouth bushing ring and the spigot bushing ring are manufactured; s2, the middle layer and the inner pipe integrally penetrate into the outer pipe and are compounded through heating; and S3, a spigot bushing ring and a socket bushing ring are installed at the spigot part end and the socket end of the composite pipe correspondingly. The connection strength between the layers is high, the end face sealing performance is good, the negative pressure resistance is good, the situation that conveyed liquid is corroded and polluted by the pipe and the liquid permeates from the end face to cause layering is prevented, and the minimum thickness of the composite socket meeting the deformation requirement and the minimum thickness of the composite bell mouth meeting the strength requirement can be obtained through theoretical calculation.

Description

Technical Field

[0001] The invention belongs to the technical field of composite pipes, and in particular relates to a socket-and-spigot type heterogeneous material multi-layer composite pipe and a manufacturing method thereof. Background Art

[0002] Composite pipe is a kind of pipe widely used in liquid transportation network system. It is generally a socket-and-spigot structure, including an outer metal pipe and an inner plastic pipe, that is, the plastic pipe is used as an inner lining, one end of the metal pipe is a spigot, and the other end is a socket. During installation, multiple composite pipes are connected in sequence, and the spigot of a composite pipe is inserted into the socket of the adjacent composite pipe. Existing composite pipes have an overall anti-corrosion coating on the pipe body and both ends of the pipe body, but the inner wall of the socket and the outer wall of the spigot are generally directly painted with anti-corrosion paint, or sprayed / coated with plastic, and no overall anti-corrosion coating is formed with the pipe body. During use, long-term contact with the liquid in the pipeline causes anti-corrosion failure and corrosion of the pipe wall, which affects the service life of the pipeline and pollutes the liquid transported in the pipeline.

[0003] For water supply pipes in normal use, they will be subjected to a large internal water supply pressure, which is a positive pressure, so the pipes must meet the specified strength requirements. Some existing standards (group standards and national standards) specify the nominal wall thickness under different pressure levels and different nominal diameters. Pipes that meet the standards can meet the strength requirements within the corresponding pressure level range. Therefore, the pipes produced by existing pipe manufacturers generally meet the corresponding standard requirements.

[0004] However, when a pipe network fails, for example, a pipe bursts in the pipe network, water in the pipe network will spray out from the burst pipe, and the pressure in the pipe network will drop rapidly, even forming negative pressure. In addition, the pipe will also be subject to some external pressure, for example, the pipe buried in the soil will be subject to the gravity of the soil above it. Under the above external pressure and internal negative pressure, the pipe will deform radially. If the deformation of the socket is too large, the socket will separate from the socket connected to it, causing leakage at the connection between the socket and the socket, causing the inside of the water pipe to be contaminated. Therefore, it is necessary to ensure that the deformation of the socket of the pipe does not exceed a certain range under the above circumstances. To this end, for the socket, the minimum socket thickness that meets the deformation requirements must be obtained. If the socket thickness of the selected pipe is less than the minimum socket thickness that meets the deformation requirements, measures need to be taken to make it meet the deformation requirements. For example, when the pipe is secondary processed or installed, at least one layer of annular reinforcement ring is sleeved on the socket to form a composite socket to enhance the ability to resist deformation. However, the material of the reinforcement ring is often different from that of the base pipe (i.e., the outer pipe), because the reinforcement ring is in direct contact with the water in the pipe, and it needs to be made of corrosion-resistant materials such as stainless steel, while the base pipe generally uses relatively cheap materials such as ductile iron and Q235. Therefore, how to ensure that the above-mentioned composite socket meets the maximum deformation requirements while the thickness is minimum or close to minimum becomes a problem to be solved. The base pipe refers to the pipe in the factory setting, that is, the base pipe is not installed with a reinforcement ring and has not undergone secondary processing such as composite process. The base pipe includes a socket, a pipe body and a socket connected in sequence. The pipe body can be divided into two parts, namely the main body and the transition part. The transition part is used for the transition connection between the main body and the socket, that is, the socket, the transition part, the main body and the socket are connected in sequence. The inner wall surface of the pipe body is a cylindrical surface, that is, the inner diameter of the transition part is equal to the inner diameter of the main body. The main body is cylindrical, and the outer wall surface of the transition part is a conical surface. In other words, the thickness of the main body is uniform or substantially uniform at all places, and the thickness of the transition part gradually decreases along the direction from the socket to the socket. The outer diameter of the tube body refers to the outer diameter of the main body, the outer diameter of the base tube is the outer diameter of the tube body, and the thickness of the tube body refers to the thickness of the main body. Fig.17 In the figure, X is the length of the chamfer at the end of the socket along the axial direction, Y is the height of the chamfer at the end of the socket (i.e. the radial dimension), DE is the outer diameter of the socket, and T6 is the length of the socket.

[0005] For the socket, the existing standards do not give its wall thickness requirements, but generally it is necessary to ensure that its thickness is sufficient to meet the strength requirements. It is best to make the thickness of the socket at various locations minimum or close to the minimum while meeting the use strength. At present, the socket of a general base pipe is made of only one material, such as ductile iron or Q235 steel. This socket is a single-layer socket. However, in order to improve the performance of the pipe, the socket can be made into a composite socket, that is, a structure including at least two coaxial layers of different materials that are sequentially sleeved from the inside to the outside, such as an inner layer of stainless steel and an outer layer of Q235 steel, which can save costs while improving the corrosion resistance of the pipe. Similarly, if the composite socket can meet the strength requirements and the thickness is minimum or close to the minimum, the cost can also be greatly reduced. For the composite socket, the inner wall of the base pipe socket can be completely covered by the lining or not completely covered by the lining. When the inner wall of the base pipe socket is not completely covered by the liner, the composite socket includes a single-layer structure and a multi-layer structure. The single-layer structure is the part not covered by the liner and has only one layer, namely, the outermost base pipe. The multi-layer structure includes at least two layers, namely, the outermost base pipe and the liners sleeved in the base pipe. Summary of the invention

[0006] In view of the above-mentioned problems existing in the prior art, the purpose of the present invention is to provide a socket-and-spigot type heterogeneous material multi-layer composite pipe and a manufacturing method thereof, which has high connection strength between the layers of the pipe, good end face sealing, good resistance to negative pressure, and can prevent the inner wall of the pipe socket and the outer wall of the plug from rusting and contaminating the transported liquid, and prevent the liquid from penetrating from the end face of the pipe and causing separation between the layers. The minimum or near-minimum thickness of the composite plug that meets the deformation requirements and the minimum or near-minimum thickness of the composite socket that meets the strength requirements of socket-and-spigot pipes of different diameters can be obtained through theoretical analysis and calculation.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is: A socket-and-spigot type heterogeneous material multi-layer composite pipe comprises an inner pipe, an intermediate layer and an outer pipe which are sequentially sleeved from the inside to the outside, the inner pipe and the outer pipe are bonded via the intermediate layer, the outer pipe comprises a socket, a pipe body and a spigot which are sequentially connected, the inner wall of the socket is provided with steps and / or grooves, one end of the socket of the composite pipe is provided with a socket lining ring, the socket lining ring covers part of the inner wall of the socket and one end of the inner wall of the inner pipe, one end of the spigot of the composite pipe is provided with a spigot lining ring, the spigot lining ring covers the spigot.

[0008] As a further improvement of the above technical solution: Preferably, the outer tube is made of metal.

[0009] Preferably, the material of the middle layer is hot melt adhesive.

[0010] Preferably, the material of the inner tube is non-metal.

[0011] Preferably, the socket lining ring and the spigot lining ring are made of corrosion-resistant materials.

[0012] Preferably, sealing gaskets are provided at both ends of the composite pipe, the sealing gasket at the socket end covers the inner wall and end face of one end of the inner pipe and the end face of the middle layer, and the sealing gasket at the plug end covers the inner wall of the other end of the inner pipe and the end face of the plug end of the composite pipe.

[0013] Preferably, when the rust removal grade of the inner wall surface of the outer tube reaches Sa2.5 and the surface roughness is Ra12.5~Ra25, the thickness of the middle layer is not less than 0.1 mm.

[0014] Preferably, when the rust removal grade of the inner wall surface of the outer tube reaches Sa2.5 and the surface roughness is Ra25-Ra50, the thickness of the middle layer is not less than 0.15 mm.

[0015] More preferably, the total thickness of the inner tube and the intermediate layer is not less than 1.0 mm.

[0016] Preferably, when the rust removal grade of the inner wall surface of the outer tube reaches Sa2.5 and the surface roughness is greater than Ra50, the thickness of the intermediate layer is not less than 0.2 mm.

[0017] More preferably, the total thickness of the inner tube and the intermediate layer is not less than 1.2 mm.

[0018] Preferably, when two adjacent composite pipes are connected, one end of the spigot of one composite pipe is inserted into one end of the socket of the adjacent composite pipe and sealed by a sealing ring, the outer ring of the sealing ring contacts and presses the inner wall of the socket liner ring of one composite pipe, and the inner ring of the sealing ring contacts the outer wall of the spigot liner ring of the adjacent composite pipe.

[0019] More preferably, a stabilizing layer is provided between the inner wall of the socket and the socket lining ring, and a stabilizing layer is provided between the outer wall of the plug and the plug lining ring.

[0020] Preferably, the stabilizing layer is hot melt adhesive or rubber.

[0021] The spigot and the spigot lining ring form a composite spigot, the socket and the socket lining ring form a composite socket, and the design method of the composite spigot thickness includes the following steps: Step a1: Obtain the differential equation of radial deformation of the ring and the general solution of the differential equation according to the differential equation of the deflection curve of the ring and the moment balance equation; Step a2: Calculate and obtain a calculation formula for the maximum radial deformation of the ring according to the general solution of the differential equation obtained in step a1; Step a3: Calculating the minimum thickness of the socket of the base pipe that meets the deformation requirements according to the calculation formula of the maximum radial deformation obtained in step a2; Step a4: for a base pipe whose socket thickness is less than the minimum thickness obtained in step a3, at least one layer of annular reinforcement ring is sleeved in the socket of the base pipe to form a composite socket. If the material of the reinforcement ring is the same as that of the socket of the base pipe, the thickness of the composite socket is not less than the minimum thickness obtained in step a3. If the material of the reinforcement ring is different from that of the socket of the base pipe, go to step a5. Step a5: Determine the minimum thickness of the reinforcement ring. If the thickness of the reinforcement ring is not less than the minimum thickness, the thickness of the composite socket is the minimum thickness that meets the deformation requirement.

[0022] Assuming that the outermost layer of the composite socket is the base layer and the other layers are non-base layers, for the multi-layer structure in the composite socket, the design method includes the following steps: Step c1: Based on the same strain of each layer of the composite socket, the calculation formula of the hoop stress of any non-base layer is obtained according to the non-single-layer material equilibrium equation; Step c2: determining the relationship between the thickness of any non-base layer and the thickness of the base layer, the determination principle being that the ratio of the stress of the non-base layer to the yield strength of the material of the non-base layer is not greater than the ratio of the stress of the inner wall of the pipe body to the yield strength of the material of the pipe body; Step c3: Calculate the thickness of the non-base layer and / or base layer according to the relationship determined in step c2.

[0023] As a further improvement of the above technical solution: Step a2 includes the following steps: Step a21: Assuming that the annular ring is subjected to at least two radial concentrated forces that are symmetrical relative to the center of the circle, based on the assumption, calculating the constant term in the general solution of the differential equation to obtain the first form of the differential equation; Step a22: Based on the first form of the differential equation obtained in step a21, assuming that the annulus is subjected to only two radial concentrated forces that are symmetrical relative to the center of the circle, the first form of the differential equation is transformed into a second form of the differential equation; Step a23: introducing the internal negative pressure of the ring into the second form of the differential equation by introducing a coefficient, so as to obtain the third form of the differential equation; Step a24: Obtain a calculation formula for the maximum change in the diameter of the circular ring with coefficients according to the third form of the differential equation obtained in step a23.

[0024] Step a3 includes the following steps: Step a31: Calculate the parameters of a reference pipe according to an existing shear load formula, wherein the material and outer diameter of the reference pipe are respectively the same as the material and outer diameter of the base pipe; Step a32: obtaining the maximum deformation of the reference pipe socket through simulation according to the parameters calculated in step a31; Step a33: Substitute the maximum deformation of the socket obtained in step a32 into the calculation formula of step a2 to obtain the coefficient value in the calculation formula, thereby obtaining a calculation formula for the maximum radial deformation of the ring with a known coefficient; Step a34: Calculate the minimum thickness of the base pipe socket that meets the deformation requirements based on the allowable deformation regulations and the formula obtained in step a33.

[0025] In step a1, the radial deformation obtained is u The differential equation is: ; The general solution is: , in, R is the average value of the outer circle radius and the inner circle radius of the ring; E is the elastic modulus of the pipe, Pa; I is the moment of inertia of the tube cross section, m 4 ; M is the bending moment borne by a certain section of the ring in the local area, in units of N*m; establish a two-dimensional coordinate system, The deformation is u The line connecting the point at and the origin of the coordinate system is the same as the line connecting the point at and the origin of the coordinate system in the two-dimensional coordinate system. x The angle between the positive directions of the axes, ; A1, A2, A3, B2, B3 are constants.

[0026] In step a2, it is assumed that the ring is subjected to at least two radial concentrated forces P symmetrically relative to the center of the circle, and the angle between two adjacent radial concentrated forces P is , the ring satisfies the following three boundary conditions: First, in Because of symmetry, The rotation angle of the section at is 0, which satisfies the following formula: ; Second, due to symmetry, the total tangential displacement of the arc in each equally divided segment is 0; that is, ; Third, cut near point A, remove point A and the force P, and from the symmetry and equilibrium conditions, we know that the shear force on the section at the circular cut is , that is: ; Combining the above three formulas with the general solution of the differential equation, we get the first form of the differential equation: ; Assuming that the annulus is subjected to only two radial concentrated forces P which are symmetrical relative to the center of the circle, then: , we get the second form of the differential equation: ; Introducing the coefficient m, we get the third form of the differential equation: ; Point of application of force P The point is the point of maximum deformation, and the change in the diameter of the ring is: , where I = S 3 / 12, S is the wall thickness of the tube.

[0027] In step a5, the minimum thickness of the reinforcement ring is obtained and determined by experiment, simulation or theoretical calculation. When the minimum thickness of the reinforcement ring is obtained and determined by theoretical calculation, the minimum thickness of the reinforcement ring is obtained based on the socket thickness of the base pipe and the bending strength calculation formula of the longitudinal composite beam.

[0028] For the same base pipe, along the direction from the socket to the spigot, the inner wall of the socket includes a first step, a second step, a third step, a fourth step, and a fifth step arranged in sequence, one end of the inner wall of the pipe body is a sixth step, the chamfer at the connection between the fourth step and the fifth step is a first chamfer, the chamfer at the connection between the fifth step and the sixth step is a second chamfer, the chamfer at the connection between the second step and the third step is a third chamfer, the chamfer at the connection between the first step and the second step is a fourth chamfer, and the chamfer at the connection between the third step and the fourth step is a fifth chamfer.

[0029] In step c1, the multilayer structure is regarded as a structure including at least one pressure vessel with a conical inner wall and at least one annular reinforcement ring installed on the inner wall of the pressure vessel. In step c1, the first cone is a pressure vessel with a conical inner wall, and the first chamfer and the second chamfer are located on the inner wall of the first cone.

[0030] In step c1, assuming that there are m layers of non-base layer and one base layer, the equilibrium equation of the multilayer structure is: ; in, p is the internal pressure of the conical container, D is the diameter of the conical container to be calculated, is the cone height, S1, S2, …, S m are the thickness of each non-base layer, S b is the thickness of the base layer, , , …, are the hoop stresses of each non-base layer, is the hoop stress of the base layer, α is the half cone angle of the conical container; In step c1, the strain of the base layer The strain is the same as that of each non-base layer, satisfying: ,Right now , where E1, E2, …, E m are the elastic modulus of each non-base layer, E b is the elastic modulus of the base layer. Combined with the equilibrium equation, the calculation formula for the hoop stress of the nth non-base layer is: ,in, is the hoop stress of the nth non-base layer, n is 1~m, E n is the elastic modulus of the nth non-base layer.

[0031] In step c2, in order to make the composite socket meet the strength requirements, the internal stress of the nth non-base layer and the inner wall stress of the pipe body meet the following conditions: , , where Q0, Q n are the yield strengths of the pipe body and the nth non-base layer material respectively; is the hoop stress of the pipe body, S is the thickness of the pipe body, D0 is the outer diameter of the pipe body, and p is the pressure given by the fluid in the pipe. The calculation formula for the hoop stress of the nth non-base layer is combined to obtain the relationship between the thickness of the nth non-base layer and the thickness of the base layer: .

[0032] When the thickness of the base layer corresponding to the maximum stress point is known, the minimum thickness of the layer with the minimum yield stress is calculated based on the relationship between the thickness of the nth non-base layer and the thickness of the base layer. This layer is set as the minimum stress layer, and the thickness of other non-base layers is set to be not less than the minimum thickness of the minimum stress layer. When the thickness of the non-base layer is known, first, at least one point where the stress of the base layer is easily concentrated is selected. The selection principle is: after the strength of each selected point meets the requirements, the strength of other places of the base layer designed according to the outer wall design requirements also meets the requirements; then the thickness of each selected point is calculated based on the relationship between the thickness of the nth non-base layer and the thickness of the base layer.

[0033] A method for manufacturing a socket-and-spigot type heterogeneous material multilayer composite pipe, used for manufacturing the composite pipe, comprises the following steps: Step S1: processing the outer tube, making the inner tube and the middle layer, making the socket lining ring, and making the spigot lining ring; Step S2: inserting the entire plastic tube including the middle layer and the inner tube into the outer tube and compounding them by heating; Step S3: installing a spigot lining ring and a bell lining ring on the spigot end and the bell end of the composite pipe respectively.

[0034] When making the socket lining ring, it is divided into two parts, one part is the inner tube part, and the other part is the outer tube part. One end of the inner tube part is attached to the inner wall of the inner tube, and one end of the outer tube part is attached to the outer wall of the socket. The other end of the inner tube part and / or the other end of the outer tube part are bent and attached to the end face of one end of the socket of the composite pipe, and the inner tube part and the outer tube part are welded together, and the welding point is located on the end face of one end of the socket of the composite pipe.

[0035] More preferably, the outer tube portion of the socket lining ring and the outer wall of the socket are welded together, or hot melt adhesive is sprayed or coated on the outer wall of the socket before installing the outer tube portion.

[0036] The beneficial effects of the present invention are: (1) Good sealing between the various layers of the pipe: The socket end and the spigot end of the composite pipe are covered by a stainless steel liner ring. The socket liner ring presses and covers one end of the inner pipe and one end of the middle layer between the middle of the socket liner ring and the outer pipe, and the spigot liner ring covers the other end of the inner pipe and the other end of the middle layer in the spigot liner ring. Combined with the setting of the sealing gasket and the sealing ring, it effectively prevents liquid from penetrating into the layers through the pipe end, causing the joint surface between the hot melt adhesive and the inner wall of the metal pipe and the stainless steel ring to peel off due to the tension of water, thereby preventing the rust of the metal outer pipe socket and spigot to cause water pollution.

[0037] (2) Good corrosion resistance: The inner tube is made of polyethylene, which is suitable for the transportation of corrosive liquids. In addition, the sealing between the layers of the pipe is good, which prevents the liquid from penetrating into the layers through the pipe end, further improving the corrosion resistance of the composite pipe. The plastic inner tube improves the smoothness of the inner surface of the composite pipe, and the inner tube is thin, which can improve the pipeline transportation efficiency and reduce the operating energy consumption.

[0038] (3) The socket lining ring can cover the inner wall of the socket, and the spigot lining ring can cover the end face and outer wall of the spigot. In this way, when two adjacent composite pipes are connected by socket and spigot, the socket lining ring of one composite pipe and the spigot lining ring of the adjacent composite pipe can be respectively compressed by the outer ring and inner ring of the same set of sealing rings, thereby improving the strength and stability of the spigot lining ring and the socket lining ring after installation. At the same time, since there is a gap between the inner wall of the socket of one composite pipe and the outer wall of the spigot of the adjacent composite pipe after installation, liquid may enter. The spigot lining ring and the socket lining ring made of stainless steel prevent the inner wall of the socket and the outer wall of the spigot from directly contacting the liquid to cause corrosion and contamination of the transported liquid.

[0039] (4) Good resistance to negative pressure: The pre-fabricated intermediate layer is inserted into the outer tube and then connected to the inner tube and the outer tube by melting and solidifying. This effectively improves the uniformity of the thickness of the intermediate layer, avoids bubbles in the intermediate layer and points on the inner or outer tube that are not connected to the hot melt adhesive of the intermediate layer, improves the connection strength between the inner and outer tubes, and combines the good sealing performance of the pipe end to prevent the delamination of the inner lining caused by the negative pressure in the pipeline and prevent the inner tube from falling off and being washed away by the liquid.

[0040] (5) According to different pull-off strength requirements and production conditions, intermediate layers and inner tubes of different thicknesses are manufactured and used to meet user requirements, ensure the use effect and minimize production and use costs.

[0041] (6) The arrangement of hot melt adhesive and rubber sealing gasket prevents the contact between the metal outer tube and the stainless steel liner ring, which may cause electrochemical corrosion of the stainless steel liner ring.

[0042] (7) The minimum or near minimum thickness of the composite spigot that meets the deformation requirements and the minimum or near minimum thickness of the composite socket that meets the strength requirements of socket-and-spigot pipes of different diameters can be obtained through theoretical analysis and calculation, which saves materials and reduces the production, manufacturing and transportation costs of pipes. The method for designing the minimum wall thickness is theoretical calculation, which is low in cost and high in efficiency. It provides strong support for experiments and pipe design and provides a reference for secondary processing and installation. The pipe network system is more reliable in use, greatly reducing the leakage and water supply pollution caused by the separation of the spigot and the socket of the adjacent pipe due to excessive deformation of the spigot when the pipe bursts, as well as the cracking of the socket, thereby improving the corrosion resistance of the pipe. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a schematic diagram of the structure of the composite tube according to the first embodiment of the present invention.

[0044] Figure 2 It is a schematic diagram of the connection of two adjacent composite pipes according to the first embodiment of the present invention.

[0045] Figure 3 It is a schematic diagram of the structure of the composite tube according to the second embodiment of the present invention.

[0046] Figure 4 It is a schematic diagram of the connection of two adjacent composite pipes according to the second embodiment of the present invention.

[0047] Figure 5 It is a schematic diagram of the structure of the composite tube according to the third embodiment of the present invention.

[0048] Figure 6 It is a schematic diagram of the connection of two adjacent composite pipes according to the third embodiment of the present invention.

[0049] Figure 7It is a schematic diagram of the structure of the composite pipe without a stabilizing layer according to the fourth embodiment of the present invention.

[0050] Figure 8 It is a schematic diagram of the structure of the composite tube whose stabilizing layer is hot melt adhesive according to the fourth embodiment of the present invention.

[0051] Fig. 9 It is a schematic structural diagram of the composite tube whose stabilizing layer is rubber according to the fourth embodiment of the present invention.

[0052] Fig.10 It is a schematic diagram of the connection of two adjacent composite pipes according to the fourth embodiment of the present invention.

[0053] Fig.11 Schematic diagram of the cross-section before and after deformation when the socket is subjected to a pair of radially symmetrical concentrated forces.

[0054] Fig.12 for Fig.11 Schematic diagram of local analysis.

[0055] Fig.13 Schematic diagram of a circular ring subjected to multiple uniformly arranged radial concentrated forces.

[0056] Fig.14 This is the stress analysis diagram of socket-type pipe.

[0057] Fig.15 It is a schematic cross-sectional view of a composite socket per unit length of the present invention.

[0058] Fig.16 This is a schematic diagram of the composite socket structure of Example 1 of the present invention.

[0059] Fig.17 It is a schematic diagram of the spigot and socket connection of the socket type pipe of the present invention.

[0060] Fig.18 This is a schematic diagram showing that the inner wall of the socket is completely covered by the socket liner ring according to the first embodiment of the present invention. DETAILED DESCRIPTION

[0061] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0062] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0063] Embodiment 1

[0064] A socket-and-spigot type heterogeneous material multilayer composite pipe comprises an inner pipe 2, an intermediate layer 3 and an outer pipe 1 which are sleeved from the inside to the outside in sequence. The intermediate layer 3 is made of hot melt adhesive, and the inner pipe 2 as the lining is made of non-metal, preferably polyethylene. The outer pipe 1 is made of metal, preferably ductile iron or carbon steel. The inner pipe 2 and the outer pipe 1 are bonded together through the intermediate layer 3.

[0065] The outer pipe 1 comprises a socket 11, a pipe body 12 and a spigot 13 which are sequentially connected along the axial direction thereof, and the three are integrally cast, or the pipe body 12 and the spigot 13 are integrally formed, or the pipe body 12 and the socket 13 are welded. The inner surface of the socket 11 is stepped. When two composite pipes are connected, the spigot 13 of one composite pipe is inserted into the socket 11 of the adjacent composite pipe.

[0066] Preferably, in this embodiment, the length of the inner tube 2 and the length of the intermediate layer 3 are equal, and are equal to the sum of the lengths of the tube body 12 and the socket 13. At the socket 11 end of the composite tube, the end of the inner tube 2, the end of the intermediate layer 3 and the end of the tube body 12 are flush; at the socket 13 end of the composite tube, the end of the inner tube 2, the end of the intermediate layer 3 and the end of the socket 13 are flush.

[0067] A spigot lining ring 5 is provided at one end of the spigot 13 of the composite pipe, one end of the spigot lining ring 5 is pressed against the inner wall of the inner pipe 2, and the other end extends out to press against the end surface of the spigot 13 of the composite pipe, then turns over and continues to extend and press against the outer wall of the spigot 13, so as to cover the end of the end of the inner pipe 2 and the end of the middle layer 3, and prevent the ends of each layer from being separated from each other. That is, the spigot lining ring 5 presses and covers the inner wall and end surface of the inner pipe 2 at one end of the spigot 13 of the composite pipe and the outer wall of the spigot 13.

[0068] Similarly, a socket liner ring 6 is provided at one end of the socket 11 of the composite pipe. The socket liner ring 6 and the spigot liner ring 5 are made of corrosion-resistant materials, including but not limited to stainless steel, titanium, and composite materials, preferably stainless steel. The socket liner ring 6 is pressed against the inner wall of the inner pipe 2 and the inner wall of the socket 11 at one end of the socket 11 of the composite pipe, that is, the coverage range of the socket liner ring 6 is from the inner wall of the inner pipe 2 close to the socket 11 to the middle of the inner wall of the socket 11 or the entire inner wall of the socket 11.

[0069] Furthermore, both ends of the inner tube 2 are provided with sealing gaskets 4. The sealing gasket 4 at one end of the socket 11 is located between the inner tube 2 and the socket liner ring 6 and covers the inner wall and end surface of the inner tube 2 close to one end of the socket 11 and the end surface of the intermediate layer 3 close to one end of the socket 11. The sealing gasket 4 at one end of the plug 13 is located between the inner tube 2 and the plug liner ring 5 and covers the inner wall and end surface of one end of the inner tube 2, the end surface of the intermediate layer 3 and the end surface of the plug 13. The sealing gasket 4 is a rubber sealing gasket.

[0070] like Figure 1 As shown, the sealing gasket 4 includes a pressing edge 41 and a flange 42, which are connected as one piece. The pressing edge 41 can be regarded as a thin cylindrical shape, and the flange 42 is an annular shape. The inner diameter of the flange 42 is equal to the inner diameter of the pressing edge 41, and the outer diameter of the flange 42 is greater than the outer diameter of the pressing edge 41. The pressing edge 41 and the flange 42 share a common center line.

[0071] For the sealing gasket 4 at one end of the socket 11 of the composite pipe, the outer surface of the edge pressing 41 is in contact with the inner surface of the inner pipe 2, and the inner surface of the edge pressing 41 is in contact with the outer surface of the socket lining ring 6. One side of the flange 42 is in contact with the end face of the inner pipe 2, the end face of the intermediate layer 3 and the end face of the pipe body 12, and the other side of the flange 42 is in contact with the socket lining ring 6.

[0072] For the sealing gasket 4 at one end of the spigot 13 of the composite pipe, the outer surface of the edge pressing 41 fits the inner surface of the inner pipe 2, and the inner surface of the edge pressing 41 fits the outer surface of the spigot liner 5. One side of the flange 42 fits the end surface of the inner pipe 2, the end surface of the intermediate layer 3 and the end surface of the spigot 13, and the other side of the flange 42 fits the spigot liner 5.

[0073] In this embodiment, the socket lining ring 6 directly fits the sealing gasket 4 and the stepped inner wall of the socket 11 .

[0074] like Figure 1As shown, the socket 11 is sequentially provided with a first step 111, a second step 112, a third step 113, a fourth step 114 and a fifth step 115 from the end away from the pipe body 12 to the end close to the pipe body 12. The inner diameter of the first step 111 is smaller than the inner diameter of the second step 112, the inner diameter of the third step 113 is larger than the inner diameter of the first step 111 and smaller than the inner diameter of the second step 112, and the inner diameter of the fourth step 114 is smaller than or equal to the inner diameter of the second step 112 and larger than the inner diameter of the third step 113. The inner wall of the fourth step 114 is a cylindrical wall. The inner wall of the fifth step 115 is the outer side surface of a cylinder or a truncated cone. When it is the outer side surface of a truncated cone, it means that the inner diameter of the fifth step 115 gradually increases from the fourth step 114 toward the pipe body 12, which is equivalent to a bell mouth. Preferably, the maximum inner diameter of the fifth step 115 is smaller than the inner diameter of the fourth step 114. The minimum inner diameter of the fifth step 115 is greater than the inner diameter of the tube body 12. A sixth step 116 is formed at one end of the tube body 12 close to the fifth step 115.

[0075] The inner wall bell mouth of the fifth step 115 is provided to provide a deflection angle for the adjacent composite pipe connected thereto, i.e., to allow the center line of a composite pipe and the center line of the adjacent composite pipe connected thereto to be in an intersecting state rather than an overlapping state. This is to allow a certain installation angle deviation to facilitate actual operation, and to allow adjacent pipes to have a relative displacement of a certain angle when the soil moves naturally.

[0076] Preferably, the socket lining ring 6 covers the inner wall of the fourth step 114 and the inner wall of the fifth step 115 .

[0077] Based on the above structure, when two adjacent composite pipes are connected, Figure 2 As shown, the spigot 13 of a composite pipe is inserted into the socket 11 of an adjacent composite pipe and sealed by a sealing ring 7, the outer ring of the sealing ring 7 contacts and presses the inner wall of the socket liner 6 of a composite pipe, and the inner ring of the sealing ring 7 contacts the outer wall of the spigot liner 5 of the adjacent composite pipe. Preferably, the end face of one end of the sealing ring 7 contacts the end face of the first step 111, a part of the sealing ring 7 is accommodated on the second step 112, the third step 113 is inserted into the middle of the sealing ring 7, and the other part of the sealing ring 7 is located on the socket liner 6 on the fourth step 114. At the same time, there is a gap between the end face of one end of the spigot 13 of a composite pipe and the end face of the pipe body 12 of the adjacent composite pipe, and the existence of this gap is also to allow the existence of a deflection angle when two adjacent composite pipes are installed.

[0078] Preferably, the total thickness of the inner tube 2 and the middle layer 3 is greater than 1 mm.

[0079] The thickness of the intermediate layer 3 and the inner tube 2 are defined as follows: When the rust removal grade of the inner wall surface of the metal outer tube 1 reaches Sa2.5 and the surface roughness is Ra12.5~Ra25, the thickness of the intermediate layer 3 is not less than 0.1mm, and the total thickness of the inner tube 2 and the intermediate layer 3 is not less than 1.0mm.

[0080] The rust removal grade of the inner wall surface of the metal outer tube 1 reaches Sa2.5, the surface roughness is Ra25~Ra50, the thickness of the intermediate layer 3 is not less than 0.15mm, and the total thickness of the inner tube 2 and the intermediate layer 3 is not less than 1.0mm.

[0081] The rust removal grade of the inner wall surface of the metal outer tube 1 reaches Sa2.5, the surface roughness is greater than Ra50, the thickness of the intermediate layer 3 is not less than 0.2mm, and the total thickness of the inner tube 2 and the intermediate layer 3 is not less than 1.2mm.

[0082] The lining peel strength test found that when the rust removal grade of the inner wall surface of the metal outer tube 1 reaches Sa2.5 and the surface roughness is Ra12.5~Ra25, the thickness of the intermediate layer 3 is not less than 0.1mm, and the lining peel strength can stably reach more than 70N / cm; when the rust removal grade of the inner wall surface of the metal outer tube 1 reaches Sa2.5 and the surface roughness is Ra25~Ra50, the thickness of the intermediate layer 3 is not less than 0.15mm, and the lining peel strength can stably reach more than 120N / cm; when the rust removal grade of the inner wall surface of the metal outer tube 1 reaches Sa2.5 and the surface roughness is greater than Ra50, the thickness of the intermediate layer 3 is not less than 0.2mm, and the lining peel strength can stably reach more than 150N / cm.

[0083] The low-temperature freezing test found that under the test conditions of 0°C and 1000h, when the peel strength of the lining of the composite pipe is greater than 70N / cm, the lining will not be delaminated, that is, the lining will not separate from the outer pipe 1; under the test conditions of -45°C and 1000h, when the peel strength of the lining of the composite pipe is greater than 120N / cm, the lining will not be delaminated.

[0084] The hole opening test found that when the peeling strength of the composite pipe lining reaches 120N / cm, the lining plastic will not be peeled off from the inner wall of the metal outer pipe 1 by the hole opening tool after the hole is opened.

[0085] Through the composite process, it was found that when the surface roughness of the inner wall of the metal tube is Ra12.5~Ra50, and the thickness of the inner tube 2 and the intermediate layer 3 is more than 1.0 mm in total, the inner tube 2 will not melt through, and an inner surface with better flatness can be obtained; when the surface roughness of the inner wall of the metal tube is greater than Ra50, and the thickness of the inner tube 2 and the intermediate layer 3 is more than 1.2 mm in total, the inner tube 2 will not melt through, and an inner surface with better flatness can be obtained.

[0086] When the peel strength between the hot melt adhesive and the lining of this solution reaches 70N / cm, the corresponding bonding strength is 7MPa, that is, the liquid lateral scouring force that the pipe of this solution can withstand is 7Mpa, which is much greater than the maximum liquid lateral scouring force in the existing pipe network system.

[0087] A method for manufacturing a socket-and-spigot type heterogeneous material multilayer composite pipe, for manufacturing the composite pipe, comprises the following steps: Step S1: Process the inner wall and outer wall of the outer tube 1, manufacture the inner tube 2 and the intermediate layer 3, manufacture the socket lining ring 6 and the spigot lining ring 5.

[0088] In this step, the method for processing the inner and outer walls of the outer tube 1 is to first grind the inner wall of the outer tube 1, and then sandblast or shot blast the inner and outer walls. Use an internal grinder to grind the inner wall of the outer tube 1 made of metal, grind the inner wall of the tube flat, and remove surface oxide scale, scum and rust. Alternatively, after the inner wall of the outer tube 1 is polished flat, use a laser cleaning machine to clean the inner wall of the tube to deeply remove the oxide scale and rust on the inner wall of the tube. When sandblasting or shot blasting, remove dust, oxide scale, and rust on the inner and outer walls, and sandblast the inner and outer walls of the tube into a frosted surface.

[0089] The inner tube 2 and the middle layer 3 are manufactured by co-extrusion, and a double-layer molded plastic tube is manufactured by co-extrusion, vacuum sizing, pulling, and cutting. Extruders, vacuum boxes, pulling machines, and cutting machines in the prior art can be used for co-extrusion, vacuum sizing, pulling, and cutting.

[0090] The inner tube 2 and the middle layer 3 can also be made into round tubes independently.

[0091] The production of the socket lining ring 6 comprises the following steps: S161: Process the long stainless steel sheet into a ring or a thin cylinder to complete the rolling. In this step, the stainless steel sheet is processed into a ring or a thin cylinder by a rolling machine (the rolling machine technical solution in Patent 2020114372537 can be used).

[0092] S162: Cut the rolled stainless steel sheet and weld the ends thereof. In this step, a argon arc welder or a laser welder is used for welding.

[0093] S163: Expand the product obtained in step S162 into a desired shape. In this step, the product is expanded and formed by using an expansion device, and a multi-stage diameter expansion is performed to form a shape with multiple steps along its axial direction, so that it matches the multi-step step shape formed by the connection between the inner wall of the socket 11 and the inner tube 2.

[0094] It should be noted that the expansion forming of the last step S163 can be implemented when installing the socket liner ring 6, as described below for details.

[0095] When making the socket liner 5, it is divided into two parts, one part is the inner part of the tube; the other part is the outer part of the tube. The inner part and the outer part of the tube are both made by a rolling machine. The difference is that when making the inner part of the tube, the long strip of stainless steel sheet is processed into a shape with a flange (the same shape as the sealing gasket 4). When making the outer part of the tube, the long strip of stainless steel sheet is processed into a very thin cylindrical shape, and then the rolled part is cut and welded end to end using an argon arc welder or a laser welder. Among them, the outer diameter of the inner part of the tube inserted into the socket 13 is slightly smaller than the inner diameter of the inner tube 2 after the outer tube 1 and the inner tube 2 are combined. The outer diameter of the outer part of the tube is slightly larger than the outer diameter of the outer tube 1, and the length of the outer part of the tube is slightly larger than the length required for installation or the length of the socket 13.

[0096] Step S2: inserting the entire plastic tube including the middle layer 3 and the inner tube 2 into the outer tube 1 and compounding them by heating.

[0097] In this step, the pipe threading operation can be performed manually or by a pipe threading machine (the pipe threading machine technical solution in patent 202210750173X can be adopted).

[0098] During compounding, the pipe is heated by a medium frequency inductor or a heating furnace to melt the hot melt adhesive of the middle layer 3. The hot melt adhesive is cooled and solidified again, thereby bonding the outer pipe 1 and the inner pipe 2 together.

[0099] After the composite is completed, the excess plastic tubes at both ends of the composite pipe are cut off and trimmed. The trimming can be done by a trimming machine or manually, so that the end of the inner tube 2, the end of the middle layer 3 and the end of the pipe body 12 at one end of the socket 11 are aligned, and the end of the inner tube 2, the end of the middle layer 3 and the end of the socket 13 are aligned.

[0100] Step S3: installing the spigot lining ring 5 and the bell lining ring 6 at one end of the spigot 13 and one end of the bell 11 of the composite pipe respectively.

[0101] For the bell liner 6, if it is the bell liner 6 after expansion forming, that is, the bell liner 6 of the above steps S161 to S163 is completed, the installation steps are as follows: S361: The expanded socket stainless steel ring, i.e., the socket liner ring 6, is cut along the weld to form an incision.

[0102] S362: Put a rubber sealing gasket 4 with a flanged edge on the outer surface of the stepped portion with the smallest outer diameter of the socket lining ring 6, with the pressing edge 41 of the sealing gasket 4 close to the stepped portion with the smallest outer diameter of the socket lining ring 6, and the flanged edge 42 close to the surface perpendicular to the stepped portion with the smallest outer diameter.

[0103] S363: The cut edge of the socket liner ring 6 is curled to the wrong side. After curling, the inner diameter becomes smaller and can be inserted into the socket 11. The socket liner ring 6 is rolled back to the wrong side to restore its original shape. At this time, the pressing edge 41 fits the inner wall of the inner tube 2, and the flange 42 fits the end face of the inner tube 2, the end face of the middle layer 3 and the end face of the tube body 12.

[0104] S364: Weld the cut of the socket liner ring 6.

[0105] S365: Expand the small end of the bell liner 6, the small end refers to the step with the smallest inner diameter of the bell liner 6, that is, the step that fits the gasket 4. Use a diameter expander to expand the small end so that the small end fits the gasket 4 tightly against the inner wall of the inner tube 2 and the end face of the inner tube 2 and the end face of the intermediate layer 3.

[0106] Based on the above method, the socket liner ring 6 presses and covers the end of the inner pipe 2 and the end of the intermediate layer 3 between the middle of the socket liner ring 6 and the outer pipe 1 to prevent them from being eroded or seeped by liquid, and covers the inner wall of the socket 11.

[0107] If the bell liner ring 6 has not been expanded, that is, only the above steps S161 and S162 have been completed and step S163 has not been performed, the installation steps are as follows: S361': Put the rubber sealing pad 4 with flange on the outer surface of one end of the socket stainless steel ring, fix the position, and fix it with glue.

[0108] S362′: insert the socket stainless steel ring with the rubber sealing gasket 4 installed into the socket 11, so that the pressing edge 41 of the sealing gasket 4 fits the inner wall of the inner tube 2, and the flange 42 fits the end face of the inner tube 2, the end face of the middle layer 3 and part of the end face of the tube body 12.

[0109] S363': Expand the diameter of the small end of the socket lining ring 6.

[0110] S364': Use a supporting device to support and fix the small head position of the socket liner ring 6, and use a spinning machine to spin the portion of the socket liner ring 6 that connects to the socket 11 to expand the diameter as a whole or in sections until the socket liner ring 6 is close to the inner wall of the socket 11.

[0111] For the socket bushing 5, first, install the inner tube part and the outer tube part of the socket 13 respectively. When installing the inner tube part, first put the rubber sealing gasket 4 with flange on the outer wall of the inner tube part, and then insert it into the socket 13 together. When installing the outer tube part, put the outer tube part on the outer wall of the socket 13 and fix the position. Then, use the expansion machine to expand the inner tube part of the socket bushing 5 of the socket 13, so that the inner tube part of the socket bushing 5 presses the sealing gasket 4 on the inner wall of the inner tube 2 and the end face of the inner tube 2, the end face of the middle layer 3 and the end face of the socket 13. Then, use the edge pressing device to press the socket bushing 5 part (i.e., the outer tube part) on the outer wall of the socket 13 from the chamfered part of the socket to the end face of the tube until the outer tube part contacts the inner tube part on the end face, and the part exceeding the inner tube part is trimmed. Finally, the connection between the inner tube part and the outer tube part (located at the end surface of the socket 13) is welded.

[0112] In addition, the outer tube portion of the spigot bushing 5 and the outer tube 1 may be welded together.

[0113] After completing the above steps, the outer wall of the pipe is sprayed with paint or plastic coated or other methods are used for external anti-corrosion treatment.

[0114] In this embodiment, the length of the portion of the socket lining ring 5 extending into the pipe is not less than the length of the socket 13, and the length of the socket lining ring 5 covering the outer wall of the socket 13 is not less than the length of the socket 13, which is equivalent to the entire inner wall and the entire outer wall of the socket 13 being covered by the socket lining ring 5.

[0115] In this embodiment, the socket 11 of the outer tube and the socket lining ring 6 can both improve the strength of the socket of the composite tube, and the socket formed by the two is a composite socket. The socket 13 of the outer tube and the socket lining ring 5 form the socket of the pipe as a composite socket, because the socket lining ring 5 covers the entire inner and outer walls of the socket 13, which can improve the strength and deformation resistance of the entire socket 13. Therefore, the socket 13 and the lining ring pressure edge 51 form a three-layer composite socket. In addition, the middle layer 3 is made of hot melt adhesive, and the sealing gasket 4 is made of rubber, both of which are non-metallic flexible materials, which have little effect on the strength and deformation resistance of the socket 13, and therefore do not belong to the category of composite sockets that can resist deformation.

[0116] Next, the thickness of the spigot end and the socket end of the composite pipe is optimized and designed.

[0117] The design method of the thickness of the composite socket includes the following steps: Step a1: Obtain the radial deformation of the ring based on the differential equation of the deflection curve and the moment equilibrium equation of the ring Because the cross-sections of the tube body 12 and the socket 13 are circular rings, the deformation of the socket 13 is analyzed by analyzing the radial deformation of the circular ring. In addition, a cylinder of unit length can be regarded as a circular ring.

[0118] Step a2: Calculate and obtain a calculation formula for the maximum radial deformation of the ring based on the general solution of the differential equation obtained in step a1.

[0119] Step a3: The minimum thickness of the socket of the base pipe that meets the deformation requirements is obtained according to the calculation formula of the maximum radial deformation obtained in step a2.

[0120] Step a4: For a base pipe whose socket thickness is less than the minimum thickness obtained in step a3, at least one layer of annular reinforcement ring is sleeved in the socket of the base pipe to form a composite socket. If the material of the reinforcement ring is the same as that of the socket of the base pipe, the thickness of the composite socket is not less than the minimum thickness obtained in step a3. If the material of the reinforcement ring is different from that of the socket of the base pipe, go to step a5.

[0121] Step a5: When the material of the reinforcement ring and the material of the socket of the base pipe are different, the minimum thickness of the reinforcement ring is obtained based on the thickness of the socket of the base pipe and the calculation formula of the bending strength of the longitudinal composite beam. If the thickness of the reinforcement ring is not less than the minimum thickness, the thickness of the composite socket is the minimum thickness that meets the deformation requirements. In other words, the thickness of the composite socket of the pipe formed after the reinforcement ring is installed on the base pipe meets the deformation requirements and strength requirements.

[0122] The following is a detailed introduction to each step.

[0123] In step a1, the radial deformation obtained The differential equation is: (1) in ，R is half of the sum of the outer radius and the inner radius of the ring. In other words, R One quarter of the sum of the outer and inner diameters of the ring 。E is the elastic modulus of the pipe, Pa. I is the moment of inertia of the tube cross section, m 4 . M It is the bending moment borne by a certain section of the ring in the local area, in N*m. Establish a two-dimensional coordinate system, The deformation is u The line connecting the point at and the origin of the coordinate system is the same as the line connecting the point at and the origin of the coordinate system in the two-dimensional coordinate system. x The angle between the positive directions of the axes, In this embodiment, establish xy Coordinate system, point O is the coordinate origin and the center of the ring, such as Fig.11 Pointm 1 The radial deformation at u， but om 1 and x The angle between the positive directions of the axes is 。

[0124] The above differential equation (1) is obtained as follows: like Fig.11 and 12 As shown in the figure, the dotted line is the ring that has not been deformed by external force, and the solid line is the shape of the ring after being deformed by two symmetrical radial external forces P. The center point of the ring before and after deformation is O The position remains unchanged. Fig.11 midpoint O Too xy Vertex of the coordinate system ， point m and n are two points on the ring before deformation; m 1 and n 1 are two points on the deformed shape of the ring, and the points m 1 and n 1 Located on the line segment om and on superior, φ The deformation is u The line connecting the point at and point O is x The angle between the positive directions of the axes, om and on The angle between φ, set up u Centripetal movement is positive. Fig.12 Middle, straight line m 1 t Passing point m 1 and perpendicular to the line segment om ,straight line m 1 t 1 For passing point m 1 A tangent line to n 1 t’ Passing point n 1 and perpendicular to on ,straight line n 1 t1 ’ For passing point n 1 tangent.

[0125] Arc before deformation mn The arc length is ds , whose curvature is k 1 , arc after deformation m 1 n 1 The curvature is k 2 , du Yes m and Point n The difference in radial deformation is The arc before deformation mn exist m Tangent line of point and n The angle between the tangent lines of a point, The deformation amount is u The radius corresponding to the point at after deformation is, Is an arc mn Deform to Arc m 1 n 1 back ds The increment of The arc after deformation m 1 n 1 exist m 1 Tangent line of point and n 1 The angle between the tangent lines of the point is m 1 t 1 and The angle between , then: (2) (3) (4) (5) m 1 t 1 and m 1 t The angle between , n 1 t 1 ’ and n 1t’ The angle between .

[0126] m 1 section to n 1 The variable of the cross-section rotation is : (6) in, m The cross section is through om and perpendicular to the cross section of the ring, in other words, m The cross section is through the center axis and point of the corresponding pipe of the ring m The cross section of n The cross section is through on and perpendicular to the cross section of the ring, in other words, n The cross section is through the center axis and point of the corresponding pipe of the ring n cross section. m 1 t 1 and m 1 t The angle between m 1 The cross-sectional angle, n 1 t 1 ’ and n 1 t’ The angle between n 1 The corner of the cross section.

[0127] Substituting formula (5) and (6) into formula (4) yields: (7) By series expansion we have:

[0128] Ignoring the higher-order terms, substituting the series expansion into (7) yields: (8) Substituting (2) into (8), we obtain: (9) Omitting the higher-order terms, we get: (10) For a thin ring (i.e. a ring with a small difference between the outer and inner diameters relative to the diameter), we have: , by definition: ,therefore, , substituting into (10) we get, , combining formula (2) to obtain radial deformation The differential equation formula (1).

[0129] The general solution of the above differential equation (1) is: (11) Among them, A1, A2, A3, B2, and B3 are constants. If the external force is symmetrical, the odd function terms in the solution can be deleted, and the deflection curve equation is obtained as follows: (12) Step a2: Calculating and obtaining a calculation formula for the maximum radial deformation of the ring according to the general solution of the differential equation obtained in step a1, comprising the following steps: Step a21: Assume that the circular ring is subjected to at least two radial concentrated forces P that are symmetrical relative to the center of the circle. Based on this assumption, calculate the constant term in the general solution of the differential equation to obtain the first form of the differential equation.

[0130] Step a22: Based on the first form of the differential equation obtained in step a21, assuming that the annulus is subjected to only two radial concentrated forces P that are symmetrical relative to the center of the circle, the first form of the differential equation is transformed into the second form of the differential equation.

[0131] Step a23: Introduce the internal negative pressure on the annulus into the second form of the differential equation by introducing coefficients to obtain the third form of the differential equation.

[0132] Step a24: Obtain a calculation formula for the maximum change in the diameter of the circular ring with coefficients according to the third form of the differential equation obtained in step a23.

[0133] In step a21, it is assumed that the ring is subjected to at least two radial concentrated forces P symmetrically relative to the center of the ring. The radial concentrated force P means that the direction of the force P is radial to the ring and points to the center of the ring, and the angle between two adjacent radial concentrated forces P is ,like Fig.13 shown. Fig.11 The circular ring shown in FIG. 1 is subjected to two radial concentrated forces P which are symmetrical relative to the center of the circle, and the two radial concentrated forces P are located on the y-axis.

[0134] The ring satisfies the following three boundary conditions: (1) Due to symmetry, the rotation angle of the section at this location is 0, which satisfies the following formula: (13) (2) Due to symmetry, the total tangential displacement of the arc in each equally divided segment is 0; that is, (14) (3) Cutting near point A, removing point A and the acting force P, it can be seen from the symmetry and equilibrium conditions that the shear force on the cross section of the circular cut is , that is: (15) in, dM represents the differential with respect to M. It should be noted that point (3) is not a real cut of the ring, but an assumption.

[0135] Simultaneously formula (13), (14), (15), the solution is: (16) (17) (18) Substituting formulas (16), (17), and (18) into formula (12), we obtain: (19) Formula (19) is the first form of the differential equation obtained in step a21. is the radial deformation of the ring.

[0136] In step a22, if only one pair of radial forces P is applied to the ring, then , the deflection curve equation (19) becomes: (20) Formula (20) is the second form of the differential equation obtained in step a22.

[0137] In step a23, considering that the pipe generally needs to withstand an internal negative pressure of 0.1 MPa during testing, a coefficient m is introduced, that is, (twenty one) For water supply pipes, if a fault occurs during actual use, such as a burst pipe, a certain negative pressure will be formed inside the pipe. Therefore, when testing the pipe, a negative pressure will be created inside the pipe to ensure that the pipe performance meets the standards.

[0138] Formula (21) is the third form of the differential equation obtained in step a23.

[0139] In step a24, the maximum deformation is At the point where the force P acts, the change in the diameter of the ring is the maximum change in the diameter of the ring. u max : (twenty two) Formula (22) is the third form of the differential equation obtained in step a24.

[0140] Step a3: Calculate the minimum thickness of the base pipe that meets the deformation requirements based on the calculation formula of the maximum radial deformation obtained in step a2. It includes the following steps: Step a31: Calculate the parameters of a reference pipe according to the existing shear load formula. The material and outer diameter of the reference pipe are respectively the same as the material and outer diameter of the base pipe.

[0141] Step a32: Obtain the maximum deformation of the reference pipe socket through simulation based on the parameters calculated in step a31.

[0142] Step a33: Substitute the maximum deformation of the socket obtained in step a32 into the calculation formula of step a2 to obtain the coefficient value in the calculation formula, thereby obtaining the calculation formula for the maximum radial deformation of the ring with a known coefficient.

[0143] Step a34: Calculate the minimum thickness of the base pipe socket that meets the deformation requirements based on the national standard allowable deformation regulations and the formula obtained in step a33.

[0144] In step a31, the shear load formula used is derived from the group standard "Corrosion-resistant steel pipe with socket-type flexible joint for water supply and drainage" (T / CISA 108-2021), which is: (twenty three)

[0145] like Fig.14 As shown, W is the shear load, in Newton (N); F is the shear force acting on the interface, in Newton (N); M P is the weight of the test assembly steel tube and the weight of the object in the steel tube, in kilograms (kg); a The distance between the shear load application point and the end face of the socket inserted into the socket, in millimeters (mm); b The distance between the center of gravity of the steel pipe at the spigot end and the end face of the spigot inserted into the socket, in millimeters (mm); c It is the distance between the support point of the pad and the end face of the socket that has been inserted into the socket, in millimeters (mm).

[0146] In this embodiment, the nominal diameter of the base pipe is DN=600mm, and the material is Q235 steel. The nominal diameter of the reference pipe is DN=600mm, and the material is Q235. Its wall thickness is selected according to the provisions of the group standard, and the wall thickness when the nominal pressure is 3.0MPa, that is, the nominal wall thickness S=7mm. At this time, the outer diameter of the base pipe D0=630mm, R =312mm. In addition, the shear force FIt should be no less than 30 times of the nominal diameter DN. In this embodiment, 30 times is taken, that is, F = DN × 30 = 600 × 30 = 18000 N. Take the pipe length as 1m, c = 800mm.

[0147] In this embodiment, the parameters in formula (23) are M P and W The calculation process is as follows:

[0148]

[0149] in, is the density of water, is the density of steel. M P The diameter used in the calculation is the outer diameter D0 of the base pipe, and the calculation error is within the allowable range. In addition, in this embodiment, the material of the base pipe socket is Q235 steel, the elastic modulus of the steel pipe material is E=200GPa, I=S 3 / 12. It should be noted that the calculation formula for the moment of inertia I of the circular tube section also needs to be multiplied by the length, but this solution considers a cylinder of unit length (i.e., the circular ring), so the length is 1.

[0150] Step a31 is thus completed.

[0151] In step a32, based on the parameters obtained by the above calculation, simulation software is used. In this embodiment, the maximum deformation of the socket of the reference pipe is simulated by finite element simulation. u max =12.19 mm. During simulation, the material parameter Poisson's ratio = 0.3. The simulation method is well known to those skilled in the art and will not be described in detail here.

[0152] In step a33, u max =12.19 Substituting into formula (22) we get m =1.18 (Note: When calculating, the length units are meters, and the unit of elastic modulus E is Pa), thus: (twenty four) From formula (24), we can see that u max The value is related to the pipe diameter and pipe thickness.

[0153] In this embodiment, in step a34, for a pipe with DN=600mm, the national standard stipulates that the allowable deformation must not be greater than 3.6% of the outer diameter of the socket DE=635mm, that is, umax =22.86 mm, and substituting it into formula (24), we can calculate that for a pipe with DN=600 mm, the minimum wall thickness of the socket is S=5.7 mm.

[0154] Table 1 Nominal wall thickness and absolute deformation of DN=600mm pipes at various nominal pressures

[0155] In Table 1, each wall thickness is the nominal wall thickness under the corresponding nominal pressure specified in the industry standard, and the absolute deformation is calculated according to formula (24).

[0156] It can be seen from Table 1 that if the base tube purchased by the secondary processing enterprise or user is processed in accordance with the provisions of the industry standard, the base tubes with serial numbers 1, 2, and 3 in Table 1 have a socket thickness greater than 5.7 mm and an absolute deformation less than 22.86 mm, which meet the deformation requirements, while the base tubes with serial numbers 4, 5, and 6 have a socket thickness less than 5.7 mm and an absolute deformation greater than 22.86 mm, which do not meet the deformation requirements.

[0157] If the use requirement of the pipe in a certain occasion is to meet the nominal pressure within 2MPa, the general user will choose the pipe with serial number 4 in Table 1, and will not choose the pipe with serial number 1, 2 or 3 to meet the deformation requirement, because if one of these three is selected, although it will meet both the strength requirement and the deformation requirement, their thickness is larger and the cost will be much greater than the pipe with serial number 4. If the pipe with serial number 4 is selected, its strength meets the use requirement. For the deformation requirement, some measures can be taken, such as sleeve-fitting an annular reinforcement ring in the socket to increase the thickness of the socket and improve its ability to resist deformation, and this measure is low in cost.

[0158] Step a4: For a base pipe whose socket thickness is less than the minimum thickness obtained in step a3, at least one layer of annular reinforcement ring is sleeved in the socket of the base pipe to form a composite socket. If the material of the reinforcement ring is the same as that of the socket of the base pipe, the thickness of the composite socket is not less than the minimum thickness obtained in step a3. If the material of the reinforcement ring is different from that of the socket of the base pipe, go to step a5.

[0159] For example, in some occasions, the use requirement of the pipe is to meet the nominal pressure within 1.6MPa, and the selected base pipe is the pipe No. 5 in Table 1, with a wall thickness of 4mm. If the selected reinforcement ring and the base pipe are made of the same material, the thickness of the reinforcement ring is not less than 1.7mm to meet the deformation requirement, and the thickness of the composite socket is not less than 5.7mm.

[0160] Step a5: The material of the reinforcement ring is different from that of the socket of the base pipe. The minimum thickness of the reinforcement ring is obtained based on the socket thickness of the base pipe and the bending strength calculation formula of the longitudinal composite beam. The thickness of the reinforcement ring is not less than the minimum thickness. Then, the thickness of the composite socket is the minimum thickness that meets the deformation requirements.

[0161] In this embodiment, the calculation formula for the bending strength of the longitudinal composite beam is as follows: (25)

[0162] in, C i The area is A i The distance from the centroid of the cross section to the bending center, I oi is the moment of inertia of the ith section about its own centroidal axis, E i is the elastic modulus of the corresponding part material. E is the elastic modulus of the base tube material, and I is the moment of inertia of the cross section corresponding to the minimum thickness obtained in step a3.

[0163] In this embodiment, the socket lining ring 5 is equivalent to a reinforcement ring, and the socket lining ring 5 is turned outward to the outer wall of the socket 13, which is equivalent to the composite socket being provided with two layers of reinforcement rings.

[0164] The following is an example to illustrate this.

[0165] For the composite spigot of this embodiment, the use requirement of the pipe in some occasions is to meet the nominal pressure within 1.6MPa. The selected base pipe is the pipe No. 5 in Table 1, and its wall thickness is 4mm. The composite spigot includes a base pipe spigot and an annular reinforcement ring. In this embodiment, since the two layers of reinforcement rings are made of the same material, the two layers of reinforcement rings are regarded as a whole, and the thickness of the whole reinforcement ring is set to x ,like Fig.15 The figure shows the cross section per unit length of the composite socket or composite beam, where the plane of the cross section passes through the central axis of the base pipe. The base pipe is made of Q235, and the reinforcing ring is made of 304 stainless steel. Fig.15 The distance from the center point of the cross section shown (the center of the composite beam) to the outer or inner surface of the composite socket is (4+ x ) / 2, for the base tube socket (original socket): A i =4, E i =200, C i = x / 2; for the reinforcement ring: A i = x , Ei =193, C i =2, substituting into (25) we get:

[0166] Find: x =1.73mm.

[0167] Therefore, the total thickness of the reinforcement ring is not less than 1.73 mm, and the thickness of the socket liner ring 5 is not less than half of 1.73 mm, that is, 0.865 mm.

[0168] Based on the above, the design calculation of the minimum thickness of the composite socket is completed.

[0169] The design method of the thickness of the composite socket is as follows: The inner wall shape of the pipe socket 11 is in accordance with the inner wall shape specified in the group standard "Corrosion-resistant steel pipe with socket and spigot flexible joint for water supply and drainage" (T / CISA108-2021) and GB / T 13295-2008, such as Fig.17As shown. The inner wall of the socket 11 is stepped. For the same base pipe, along the direction from the socket 11 to the spigot 13, the inner wall of the socket 11 includes a first step 111, a second step 112, a third step 113, a fourth step 114, and a fifth step 115 arranged in sequence. One end of the inner wall of the pipe body 12 is a sixth step 116, and the corresponding inner diameters are: D2, D1, (D3-2F0), D3, D4, (D0-2S), wherein the inner diameters of the sixth step 116, the first step 111, the fifth step 115, the third step 113, the fourth step 114, and the second step 112 increase in sequence, that is, (D0-2S) < D2 < D4 < (D3-2F0) < D3 < D1. The lengths of the first step 111, the second step 112, the third step 113, the fourth step 114, and the fifth step 115 are respectively: T3, T4, T5, (T2-T4-T5), (T1-T2-T3), that is, T1 is the sum of the lengths of the first step 111, the second step 112, the third step 113, the fourth step 114, and the fifth step 115, and T2 is the sum of the lengths of the second step 112, the third step 113, and the fourth step 114, and the lengths refer to the dimensions of the corresponding parts in the axial direction of the base pipe. S is the wall thickness of the pipe body, and F0 is the height of the third step 113 protruding from the fourth step 114, and F0 ≥ 0. The connection of each step is processed with chamfers, wherein the chamfer at the connection of the fourth step 114 and the fifth step 115 is the first chamfer R1, the chamfer at the connection of the fifth step 115 and the sixth step 116 is the second chamfer R2, the chamfer at the connection of the second step 112 and the third step 113 is the third chamfer R3, the chamfer at the connection of the first step 111 and the second step 112 is the fourth chamfer R4, and the chamfer at the connection of the third step 113 and the fourth step 114 is the fifth chamfer R5. Wherein, D0 is the outer diameter of the base pipe of the pipe.

[0170] The above inner wall shape and size are generally for single-layer socket. The size and shape of the inner wall of the composite socket can also be designed according to the above single-layer socket. In this solution, the size and shape of the inner wall of the composite socket are also designed according to the above single-layer socket.

[0171] Assume that the outermost layer of the composite socket is the base layer F1, and the other layers are the non-base layer F2. The thickness of the base layer F1 is uneven, and the thickness of the non-base layer F2 is uniform. In other words, the thickness of the base layer F1 is different or not completely the same at different places, and the thickness of the non-base layer F2 is the same at different places.

[0172] For composite sockets, since the dimensions of the inner wall are fully given by the relevant standards, it is necessary to design some key dimensions of the outer wall and the thickness of each non-base layer F2 on this basis, in order to save material costs and meet strength requirements. In other words, for composite sockets, the purpose of this solution is to design the thickness of the composite socket so that it is the minimum or close to the minimum thickness while meeting the use strength, so as to reduce the production, manufacturing and transportation costs of pipes.

[0173] According to material mechanics knowledge and experience, the most likely places for stress concentration on the inner wall of the above-mentioned single-layer socket or composite socket are the first chamfer R1, the second chamfer R2 and the third chamfer R3. The analysis is as follows: For the inner wall of the stepped socket 11, according to mechanical knowledge, the stress concentration point is located at the connection between adjacent steps, that is, at each chamfer. Since the socket 11 is in a trumpet-like shape, the outer diameter of the socket 11 tends to decrease from the socket 11 to the spigot 13 of the same base pipe.

[0174] Based on the above conditions, since the inner diameter at the fourth chamfer R4 is equal to the inner diameter at the third chamfer R3, both are equal to D1, the wall thickness at the fourth chamfer R4 must be greater than the wall thickness at the third chamfer R3 to meet the requirement that the socket 11 is quasi-trumpet-shaped. Therefore, as long as the wall thickness at the third chamfer R3 meets the stress strength requirement, the wall thickness at the fourth chamfer R4 must meet the strength requirement. Similarly, the inner diameter at the fifth chamfer R5 is equal to the inner diameter at the first chamfer R1, both are D3, so the wall thickness at the fifth chamfer R5 must be greater than the wall thickness at the first chamfer R1 to meet the requirement that the socket 11 is quasi-trumpet-shaped. Therefore, as long as the wall thickness at the first chamfer R1 meets the stress strength requirement, the wall thickness at the fifth chamfer R5 must meet the strength requirement. Therefore, the places where stress is most likely to concentrate are the first chamfer R1, the second chamfer R2, and the third chamfer R3. Similarly, for the socket of a single-layer structure, as long as the thickness of the first chamfer R1, the second chamfer R2, and the third chamfer R3 meet the strength requirements, the base pipe socket manufactured according to the above requirements must also meet the strength requirements.

[0175] In the case where the inner wall of the base pipe socket is not completely covered by the lining, since the third step 113 is the installation location of the sealing ring 7, the coverage range of the non-base layer F2 is generally from the fourth step 114 to the sixth step 116. Figures 1 to 6 At this time, along the axial direction of the socket, one part is a single-layer structure, that is, there is no non-base layer F2 but only the base layer F1. In this solution, the first step 111, the second step 112, and the third step 113 are located in the single-layer structure part; the other part is a multi-layer structure, that is, there is a non-base layer F2 and a base layer F1. In this solution, the fourth step 114 and the fifth step 115 are located in the multi-layer structure part. Fig.16 shown.

[0176] For the composite socket, if both the single-layer structure part and the multi-layer structure part meet the strength requirements, then the entire composite socket meets the strength requirements.

[0177] For a single-layer structure, it is only necessary to ensure that the strength requirement is met at the point where the stress is maximum, and then the entire single-layer structure will meet the strength requirement.

[0178] For a single-layer structure of a composite socket, the design method includes the following steps: Step b1: Select at least one location where stress is likely to be concentrated in the single-layer structure. The selection principle is: if the wall thickness at each location meets the stress strength requirement, then the wall thickness at each location of the single-layer structure meets the strength requirement.

[0179] Step b2: Determine the minimum wall thickness of each selected location in step b1, and the determination principle is: when the material of the single-layer structure and the material of the pipe body are the same, the stress at each selected location is not greater than the stress of the inner wall of the pipe body; when the material of the single-layer structure and the material of the pipe body are different, the ratio of the stress at each selected location to the yield strength of the single-layer structure material is not greater than the ratio of the stress of the inner wall of the pipe body to the yield strength of the pipe body material.

[0180] In step b1, it can be seen from the above that the stress of the single-layer structure is most concentrated at the third chamfer R3, and the socket 11 is a trumpet-shaped structure. As long as the thickness of the third chamfer R3 meets the strength requirement, the entire single-layer structure meets the strength requirement.

[0181] For a thin-walled cylindrical pressure vessel, when the wall thickness is S, the internal pressure is p, and the diameter is D (the diameter D can be half of the sum of the outer diameter and the inner diameter of the cylinder, or the inner diameter of the cylinder, or the outer diameter of the cylinder), the hoop stress of the container wall is for: (26) For a thin-walled conical pressure vessel, when the wall thickness is S, the internal pressure is p, and the diameter is D (the diameter D is half of the sum of the outer diameter and the inner diameter of the corresponding part of the cone, or the inner diameter of the corresponding part, or the outer diameter of the corresponding part), the hoop stress of the container wall is for: (27) in, αis the semi-cone angle of the conical shell, that is, half of the opening angle. In other words, in the section passing through the central axis of the cone, the angle between the cone wall and the central axis is the semi-cone angle. In step b1, the base layer F1 is regarded as consisting of at least one pressure vessel with a conical inner wall plus several internal reinforcement rings j, and the reinforcement rings are connected to the inner wall of the pressure vessel. In other words, the base layer F1 is regarded as consisting of at least one conical pressure vessel plus several internal reinforcement rings j. At this time, as long as the corresponding conical pressure vessel meets the strength requirements, the base layer F1 will definitely meet the strength requirements. Therefore, it is sufficient to ensure that the conical pressure vessel meets the strength requirements.

[0182] In step b1, take the second cone and the reinforcement ring on the inner wall of the second cone, such as Fig.17 The dotted line between the first chamfer R1 and the third chamfer R3 is the inner wall section of the second cone. The first chamfer R1 and the third chamfer R3 are located on the inner wall of the second cone. For the area between the first chamfer R1 and the third chamfer R3, the portion between the inner wall of the second cone and the outer wall of the socket 11 is the entire side wall of the second cone, and the portion between the inner wall of the second cone and the inner wall of the socket 11 is the annular reinforcement ring on the inner wall of the second cone.

[0183] exist Fig.17 In the cross section shown, the angle between the straight line passing through the first chamfer R1 and the third chamfer R3 and the axis of the tube is the half cone angle of the second cone, which is set to α2.

[0184] but: (28) In step b2, if the material of the base layer F1 is consistent with the material of the pipe body, the pipe body meets the strength requirements. To make the single-layer structure meet the strength requirements, the hoop stress at the third chamfer R3 Not greater than the hoop stress of the pipe body , that is: (29) Then we have: (30) Among them, S b3 is the wall thickness of the base F1 at the third chamfer R3, S is the wall thickness of the tube body, and we get: (31) Since there is a sealing ring 7 at the third chamfer R3, in order to achieve sealing, the pressure of the sealing ring 7 on the socket 11 must be greater than the pressure p of the fluid in the pipe. According to existing research, the average pressure of the sealing ring 7 on the inner wall of the socket 11 is generally 1.4 times the fluid pressure. It can be obtained from formula (27) that the stress is proportional to the pressure and inversely proportional to the wall thickness. When the pressure increases to 1.4 times, in order to keep the stress unchanged, the wall thickness should be increased to 1.4 times at the same time. Then formula (31) is corrected to: (32) That is, the minimum wall thickness at the third chamfer R3 is: .

[0185] If the material of the base F1 is different from that of the pipe body, let the yield strength of the pipe body material be Q0, and the yield strength of the material used for the base F1 be Q1. Similarly, in order for the single-layer structure to meet the strength requirements, the stress at the third chamfer R3 and the stress on the inner wall of the pipe body should satisfy: (33) Then we have: (34) Considering the pressure of the sealing ring, the wall thickness at the third chamfer R3 is: (35) After the wall thickness at the third chamfer R3 is determined as above, the single-layer structure manufactured according to the above requirements meets the strength requirements.

[0186] For a multi-layer structure of a composite socket, the design method comprises the following steps: Step c1: Based on the same strain of each layer of the composite socket and the non-single-layer material equilibrium equation, the calculation formula for the hoop stress of any non-base layer F2 is obtained.

[0187] Step c2: Determine the relationship between the thickness of any non-base layer F2 and the thickness of the base layer F1. The determination principle is that the ratio of the stress of the non-base layer F2 to the yield strength of the material of the layer is not greater than the ratio of the stress of the inner wall of the pipe body to the yield strength of the pipe body material.

[0188] Step c3: Calculate the thickness of the non-base layer and / or base layer according to the relationship determined in step c2.

[0189] In step c1, for the multilayer structure, the multilayer structure is regarded as being composed of at least one pressure vessel with a conical inner wall and several internal reinforcement rings j, and the reinforcement rings are connected to the inner wall of the pressure vessel. In other words, the multilayer structure is regarded as being composed of at least one conical pressure vessel and several internal reinforcement rings j. At this time, as long as the corresponding conical pressure vessel meets the strength requirement, the multilayer structure will definitely meet the strength requirement. Therefore, it is sufficient to ensure that the conical pressure vessel meets the strength requirement.

[0190] In this solution, for the multilayer structure, the two places where the stress is most concentrated are the first chamfer R1 and the second chamfer R2. Fig.16 As shown. Therefore, the selected analysis area includes a conical pressure vessel plus an internal reinforcement ring, the conical pressure vessel is the first cone, the second cone and the first cone are two coaxially connected conical pressure vessels, and they share the same central axis with the socket 11. Fig.16 and 17 The dotted line between the first chamfer R1 and the second chamfer R2 is the inner wall section of the first cone. The first chamfer R1 and the second chamfer R2 are located on the inner wall of the first cone, the portion between the inner wall of the first cone and the outer wall of the socket 11 is the entire side wall of the first cone, and the portion between the inner wall of the first cone and the inner wall of the socket 11 (the innermost non-base layer F2) is an annular reinforcement ring j.

[0191] For the socket 11, the maximum load it bears is the tensile stress in the circumferential direction. The circumferential equilibrium equation for the thin-walled internal pressure conical shell is as follows: (36) in, p is the internal pressure of the conical shell, D is the diameter of the conical shell to be calculated, is the cone height, S is the side wall thickness of the conical shell to be calculated, is the hoop stress of the conical shell, α is the semi-cone angle of the conical shell.

[0192] For a composite socket, assuming there are m layers of non-base layer F2 and one layer of base layer F1, then: (37) Among them, S1, S2, …, S m are the thickness of each non-base layer F2, S b is the thickness of the base layer F1, , , …, are the hoop stresses of each non-base layer, is the hoop stress of the base layer F1.

[0193] Since it is a thin-walled container, the hoop tensile stress of the composite socket can be regarded as the tensile stress of the composite beam, that is, the strain of the base F1 and the strain of each non-base layer F2 The same means that: (38) Right now: (39) Among them, E1, E2, …, E m are the elastic modulus of each non-base layer F2, E b is the elastic modulus of the base layer F1.

[0194] The stresses in formula (37) are all To express, is the hoop stress of the nth non-base layer F2, where n is 1~m, then E n is the elastic modulus of the nth non-base layer F2, S n is the thickness of the nth non-base layer F2. Based on formula (39), formula (37) is rearranged to obtain: (40) Formula (40) can be rearranged to obtain the hoop stress of the nth non-base layer F2: (41) Step c1 is thus completed.

[0195] In step c2, in order to make the composite socket meet the strength requirements, the internal stress of the nth non-base layer F2 and the inner wall stress of the pipe body satisfy: (42) (43) Among them, Q0, Q n are the yield strengths of the pipe body and the nth non-base layer F2, respectively. The yield strength of the base layer F1 is Q b ;in is the hoop stress of the pipe body, S is the thickness of the pipe body, D0 is the outer diameter of the pipe body, and p is the pressure given by the fluid in the pipe.

[0196] Combining formulas (41), (42), and (43), we get: (44) Formula (44) is the relationship between the thickness of any non-base layer F2 and the thickness of the base layer F1.

[0197] The application of formula (44) can be carried out from two aspects: first, there is no limit on the thickness of the non-base layer F2; second, the thickness of the non-base layer F2 is limited.

[0198] When there is no limit on the thickness of the non-base layer F2, for a multi-layer structure, it is only necessary to ensure that the layer with the smallest yield stress meets the strength requirement. This layer is assumed to be the minimum stress layer, and the thickness of other layers is not less than that of the minimum stress layer. Then the entire multi-layer structure meets the strength requirement.

[0199] The yield stress of the base layer F1 is generally greater than the yield stress of the non-base layer F2, so the layer with the weakest yield stress is the non-base layer. Assuming that the yield stress of the nth layer of non-base layer F2 is the weakest, if yielding occurs, the nth layer should yield first. Based on this, if the thickness of the nth layer of non-base layer F2 meets the strength requirements, the minimum thickness of the base layer F1 and the thickness of other non-base layers F2 are not less than the thickness of the nth layer of non-base layer F2, then the strength of the base layer F1 and other non-base layers F2 will also meet the requirements. In addition, the thickness of the base layer F1 is generally greater than the thickness of the non-base layer. Therefore, it is necessary to calculate the thickness of the nth layer of non-base layer F2. Formula (42) is rewritten as: (45) in, is the maximum stress inside the nth non-base layer F2, that is From formula (41), we can see that in the analysis area, i.e., the first cone, Take the maximum value, then D takes the maximum value, and the thickness of other non-base layers F2 takes the minimum value, that is, The maximum point is located at the first chamfer R1, the maximum value of D in the first cone is D3, the thickness of other non-base layers F2 is not less than the thickness of the nth non-base layer F2, that is, the thickness of the non-base layer F2 is Sn, and the half cone angle is α 1. In Fig.16 and 17 In the cross section shown, the angle between the straight line passing through the first chamfer R1 and the second chamfer R2 and the axis of the pipe is the semi-cone angle of the first conical pressure vessel, that is: (46) Substituting formula (43) and (46) into formula (45), we can obtain: (47) From formula (47), we get: (48) In this embodiment, S b Take the thickness of the base layer F1 at the first chamfer R1.

[0200] From the above, the number of layers m of the non-base layer F2 and the material of each layer are known, the material, thickness, diameter and other dimensions of the pipe body are also known, so the yield strength and elastic modulus of each layer are also known, and the internal shape and size of the socket 11 are in accordance with relevant standards. Therefore, the semi-cone angle α 1 is also known. In other words, in formula (48), only S n and S b Two unknowns. The thickness S of the base layer F1 at the first chamfer R1 is given based on experience or other requirements. b After that, we can findS n The minimum value of .

[0201] Therefore, according to formula (48), the minimum thickness of the non-base layer F2 with the smallest yield stress can be obtained, and the thickness of other non-base layers F2 should not be less than this value.

[0202] For the base layer F1, the thickness S of the base layer F1 at the first chamfer R1 is b1 It is given that the thickness S of the base layer F1 at the third chamfer R3 b3 It has also been calculated by formula (35), so we only need to give or calculate the thickness S of the base layer F1 at the second chamfer R2: b2 The thickness of the base layer F1 at each location can be determined to ensure that the multi-layer structure of the composite socket meets the strength requirements.

[0203] For the thickness S of the base layer F1 at the second chamfer R2 b2 , can be given directly, or can be set to the thickness S of the base layer F1 at the first chamfer R1 b1 Equal, can also be obtained by using formula (44), specifically, formula (44) is rewritten as: (49) but: (50) The thickness S of the nth non-base layer F2 has been calculated by formula (48): n , and the thickness of other non-base layers is not less than S n , then formula (50) becomes: (51) The thickness S of the base layer F1 at the second chamfer R2 is obtained by formula (51): b2 .

[0204] From the above, the thickness of each non-base layer and the thickness of the first chamfer R1, the second chamfer R2 and the third chamfer R3 of the base layer F1 are obtained. According to the requirement of the trumpet shape of the outer wall of the socket 11, the outer walls corresponding to each chamfer are connected in sequence, and the thickness of each part of the base layer F1 and the thickness of each part of the composite socket are obtained. The outer diameter at the end face of the socket can be greater than the outer diameter at the third chamfer R3, and the specific value can be flexibly selected.

[0205] When the non-base layer F2 has only one layer, that is, the conical shell is a double-layer material, then formula (37) is in the following form: (52) Formulas (38) and (39) can be organized into the following forms: (53) For double-layer sockets, the material of the non-base layer F2 (i.e., inner lining layer) is generally stainless steel, and the material of the base layer F1 (i.e., outer layer) is generally Q235 steel or ductile iron. The yield stress of the non-base layer F2 is generally smaller than that of the base layer F1, that is, if yielding occurs, the non-base layer F2 should yield first. Based on this, the stress in formula (52) should be To express, based on formula (53), rearranging formula (52) we can get: (54) Formula (54) can be rearranged to obtain the hoop stress of the non-base layer F2: (55) In step c2, in this embodiment, formula (47) is in the following form: (56) The thickness of the non-base layer F2 is: (57) That is, the minimum thickness of the non-base layer F2 is: .

[0206] At this time, formula (50) is: (58) A specific example is shown below.

[0207] Assume the nominal diameter of the purchased base pipe is DN600 mm, E b =200GPa, E n =193GPa, the base F1 material and the pipe body material are both Q235 steel, and the yield strength of Q235 steel is 235MPa, that is, Q1=Q0=235MPa. The non-base F2 material is 304 stainless steel, with a yield strength of Qn=205MPa, S=7mm, D0=630 mm, D1=673.4 mm, D3=668 mm, D4=642.6 mm, =8.21 o , =5.82 o Assume that the thickness of the first chamfer R1 of the base layer F1 is Sb=6 mm.

[0208] The thickness of the non-base layer F2 is calculated by formula (57) to be Sn≥2.38 mm, and the thickness of other non-base layers is not less than 2.38 mm.

[0209] For the thickness S of the base layer F1 at the second chamfer R2 b2 It can be set equal to the thickness Sb=6 mm at the first chamfer R1, or calculated according to formula (57). When formula (57) is used, Sn=2.38 mm is taken, and each parameter is substituted into formula (57) to obtain Sb2 ≥5.68 mm.

[0210] For the thickness S of the base layer F1 at the third chamfer R3 b3 , obtained by formula (32), substituting each parameter into formula (32), and obtaining S b3 ≥10.53 mm.

[0211] When the inner wall of the entire base pipe socket is completely covered by the lining, it is equivalent to the entire composite socket being a multi-layer structure. In this case, the design method of the thickness of the base layer F1 and each non-base layer F2 is the same as the design method when the inner wall of the base pipe socket is not completely covered by the lining. The difference is that the base layer thickness S corresponding to the third chamfer R3 is b3 At this time, the base thickness S corresponding to the third chamfer R3 b3 The method for calculating the thickness of the base layer F1 at the second chamfer R2 is the same as that for calculating the thickness of the base layer F1 at the second chamfer R2. It can be given directly, or it can be set equal to the thickness of the base layer F1 at the first chamfer R1. It can also be calculated using formula (44). Specifically, formula (49) gives: (59) In the case where the inner wall of the entire base pipe socket is completely covered by the lining, there is generally no third step 113, or in other words, the inner diameter of the third step 113 is equal to the inner diameter of the fourth step 114, and the two are combined into a large step, such as Fig.18 shown.

[0212] In the second case, when the thickness of the non-base layer F2 is limited, for example, in this embodiment, a socket liner 6 made of corrosion-resistant material is sleeved in the socket 11, and the thickness of the liner is generally about 1 mm, which is equivalent to the thickness of the non-base layer F2 being known. In order to make the composite socket formed after the sleeve liner meet the strength requirements, it is necessary to calculate and design the thickness of the base layer F1 under this premise.

[0213] Based on this, formula (44) is rewritten as: (60) From the above analysis, it can be seen that in the multi-layer structure of the composite socket, the first chamfer R1 and the second chamfer R2 are the places where stress is most likely to concentrate, and the thickness of each non-base layer is uniform, that is, the thickness of each non-base layer is consistent. Therefore, it is only necessary to ensure that the thickness of the base layer F1 at the first chamfer R1 and the second chamfer R2 meets the strength requirements. The base layer F1 manufactured according to the above requirements and other parts of the multi-layer structure must also meet the strength requirements.

[0214] The thickness of the base layer F1 at the first chamfer R1 is S b1 , in formula (60), D is D3, and the half cone angle α for α1, then formula (60) is: (61) The thickness of the base layer F1 at the second chamfer R2 is S b2 , in formula (60), D is D4, and the half cone angle α for α 1, then formula (60) is: (62) From the above, after knowing the thickness and material of the non-base layer F2, the minimum thickness of the base layer F1 at the first chamfer R1 and the second chamfer R2 can be calculated. If the outer wall of the composite socket is designed according to the above-mentioned trumpet-shaped requirement, the composite socket meets the strength requirement.

[0215] A specific example is shown below.

[0216] Assume a base pipe with a nominal diameter of DN600 mm, E b =200 GPa, the material of the tube body and the base tube F1 is the same, both are Q235 steel, yield strength Q1=Q0=235 MPa, S=7 mm, D0=630 mm, D1=673.4 mm, D3=668 mm, D4=642.6 mm, =8.21 o , =5.82 o A socket liner 6 is sleeved inside, that is, a non-base layer F2 is provided, and the parameters of the liner are as follows: E n =193GPa, 304 stainless steel yield strength Q n =205 MPa, Q1=Q0=235 MPa, Sn=1 mm. Then, we can calculate from equations (61), (62), and (35) respectively: S b1 ≥7.33 mm, S b2 ≥7.01 mm, S b3 ≥10.53 mm.

[0217] When the inner wall of the entire base pipe socket is completely covered by the lining, it is equivalent to the entire composite socket being a multi-layer structure. In this case, the design method of the thickness of the base layer F1 and each non-base layer F2 is the same as the design method when the inner wall of the base pipe socket is not completely covered by the lining. The difference is that the base layer thickness S corresponding to the third chamfer R3 is b3 At this time, the thickness of the base layer F1 at the third chamfer R3 is S b3 , in formula (60), D is D1, and the half cone angle α for α 2, then formula (60) is: (63)

[0218] Embodiment 2

[0219] like Figure 3 As shown, the structure of the composite pipe of this embodiment is different from that of the first embodiment in that, in this embodiment, the inner wall of the socket 11 and the socket lining ring 6 are not directly attached, and a stabilizing layer 8 is provided between the inner wall of the socket 11 and the socket lining ring 6. A stabilizing layer 8 is also provided between the outer wall of the spigot 13 and the spigot lining ring 5, and the stabilizing layer 8 is hot melt adhesive or glue.

[0220] In this embodiment, the stainless steel rings (socket lining ring 6 and plug lining ring 5) are bonded together with the metal outer tube 1 by hot melt adhesive or glue, which can prevent the stainless steel rings from loosening during the loading and unloading and installation of the pipe.

[0221] The manufacturing method of the composite pipe of this embodiment is different from that of the first embodiment in that, before installing the spigot liner 5, the surface of the spigot liner 5 installed on the outer wall of the spigot 13 is first heated, and then the hot melt adhesive powder is sprayed or rotomolded, and finally the outer pipe portion of the spigot liner 5 is sleeved on the outer wall of the spigot 13. Similarly, before installing the socket liner 6, the wall surface of the inner wall of the socket 11 on which the socket liner 6 is installed is first heated, and then the hot melt adhesive powder is sprayed or rotomolded, and finally the socket liner 6 is sleeved into the socket 11, and then the socket 11 and the spigot 13 are heated, and the spigot liner 6 and the socket 11 are composited, and the spigot liner 5 and the spigot 13 are composited.

[0222] Preferably, the hot melt adhesive on the inner wall of the socket 11 and the hot melt adhesive on the middle layer 3 are connected as a whole, and the hot melt adhesive on the outer wall of the plug 13, the hot melt adhesive on the end face of the plug 13 and the hot melt adhesive on the middle layer 3 are connected as a whole.

[0223] In this embodiment, the hot melt adhesive between the socket liner ring 6 and the socket 11 can hardly improve the strength of the composite socket. Therefore, the composite socket in this embodiment is equivalent to the same as that in the first embodiment, and is a composite socket composed of the socket 11 and the socket liner ring 6. Similarly, the composite socket in this embodiment is the same as the composite socket in the first embodiment. Therefore, the thickness of the composite socket in this embodiment and the calculation method of the composite socket thickness are the same as those in the first embodiment.

[0224] Embodiment 3 like Figure 5 As shown, the structure of the composite pipe of this embodiment is different from that of the first embodiment in that, in this embodiment, the inner wall of the socket 11 and the socket liner ring 6 are not directly fitted, and a sealing gasket 4 is provided between the inner wall of the socket 11 and the socket liner ring 6. Preferably, the sealing gasket 4 is integrally connected with the sealing gasket 4 between the inner tube 2 and the socket liner ring 6.

[0225] Sealing gaskets 4 are provided between the outer wall of the socket 13 and the socket lining ring 5 and on the end surface of one end of the socket 13 of the composite pipe. The two sealing gaskets 4 are integrally connected with the sealing gasket 4 between the inner pipe 2 and the socket lining ring 5.

[0226] Rubber sealing pads 4 are provided between the socket lining ring 6 and the socket 11, and between the plug lining ring 5 and the plug 13, which prevent the metal outer tube 1 from directly contacting the stainless steel ring and causing electrochemical corrosion of the stainless steel ring, and further improve the sealing effect at both ends of the pipe.

[0227] The manufacturing method of the composite pipe of this embodiment is different from that of the first embodiment in that, before installing the spigot liner ring 5, the sealing gasket 4 is installed first, and the sealing gasket 4 is closely attached to the inner wall, end face and outer wall of the spigot end of the composite pipe, that is, the sealing gasket 4 is closely attached to the inner wall of the inner pipe 2, the end face of the inner pipe 2, the end face of the intermediate layer 3, the end face of the spigot 13 and the outer wall of the spigot 13 at one end of the spigot 13. Then the spigot liner ring 5 is installed.

[0228] Similarly, before installing the socket liner ring 6, the sealing gasket 4 is also installed first, and the sealing gasket 4 is closely attached to the inner wall of one end of the composite pipe, that is, the sealing gasket 4 is closely attached to the inner wall of the socket 11, the end face of the pipe body 12, the end face of the intermediate layer 3, the end face of the inner pipe 2 and the inner wall of one end of the inner pipe 2. Then the socket liner ring 6 is installed. In addition, the sealing gasket 4 can also be sleeved on the outer surface of the socket liner ring 6 first, and then inserted into one end of the socket 11 of the composite pipe together.

[0229] Similar to the second embodiment, the sealing gasket between the socket liner 6 and the socket 11 of this embodiment can hardly improve the strength of the composite socket, so the composite socket in this embodiment is equivalent to the same as the first embodiment. Similarly, the composite socket in this embodiment is the same as the composite socket in the first embodiment.

[0230] Embodiment 4 The present embodiment is different from the first, second and third embodiments in the structure of the socket 11 and the number of the sealing rings 7. The number of the sealing rings 7 can be two or more, and the structure of the corresponding socket 11 is also different.

[0231] like Figures 7-9 As shown, from the direction away from the pipe body 12 toward the direction close to the pipe body 12, the socket 11 includes a sealing ring installation part 119 and a transition part 117 which are connected in an integral manner and arranged in sequence on the same center line. The sealing ring installation part 119 is a cylindrical structure, and the inner wall of the sealing ring installation part 119 is provided with at least two annular grooves arranged at intervals, the annular grooves and the composite pipe have the same center line, and the grooves are sealing ring installation grooves 118. The transition part 117 includes a cylindrical part and a truncated cone part, and the sealing ring installation part 119, the cylindrical part, the truncated cone part and the pipe body 12 are connected in sequence. The inner diameter of the cylindrical part is larger than the inner diameter of the pipe body 12.

[0232] In this embodiment, two sealing ring installation grooves 118 are provided on the inner wall of the socket 11. The socket liner 6 covers the inner wall of the cylindrical part of the socket 11, the inner wall of the truncated cone part, and the inner wall of a sealing ring installation groove 118 close to the cylindrical part, and the socket liner 6 does not cover the inner wall of a sealing ring installation groove 118 away from the cylindrical part.

[0233] Based on the above structure, Fig.10 As shown, when two adjacent composite pipes are connected, the spigot 13 of one composite pipe is inserted into the socket 11 of the adjacent composite pipe and sealed by at least two sealing rings 7, each of which is installed in each sealing ring installation groove 118. Similarly, the inner ring of at least one sealing ring 7 contacts the outer wall of the spigot lining ring 5 on the outer wall of the spigot 13 of one composite pipe, and the outer ring of at least one sealing ring 7 contacts the inner wall of the socket lining ring 6 at one end of the socket 11 of the adjacent composite pipe.

[0234] In this embodiment, the sealing ring installation groove 118 is provided to facilitate the rapid installation and accurate positioning of the sealing ring 7. The provision of two or more sealing rings 7 further improves the sealing effect.

[0235] It should be noted that although the shape of the socket 11 of this embodiment is different from the shape of the socket 11 of the first embodiment, the minimum thicknesses at the first chamfer R1, the second chamfer R2 and the second chamfer R3 of the base layer F1 of the composite socket of the first embodiment can be calculated according to the method of the first embodiment, and the minimum thickness of the base layer F1 of the present embodiment can be set to be not less than the minimum thickness of the base layer F1 of the composite socket of the first embodiment.

[0236] Finally, it is necessary to explain here that the above embodiments are only used to further illustrate the technical solution of the present invention in detail and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by technicians in this field based on the above content of the present invention all fall within the scope of protection of the present invention.

Claims

1. A socket-and-spigot type heterogeneous material multilayer composite pipe, characterized in that: The composite pipe comprises an inner pipe (2), an intermediate layer (3) and an outer pipe (1) which are sleeved in sequence from the inside to the outside. The inner pipe (2) and the outer pipe (1) are bonded together via the intermediate layer (3). The outer pipe (1) comprises a socket (11), a pipe body (12) and a spigot (13) which are connected in sequence. The inner wall of the socket (11) is provided with a step and / or a groove. One end of the socket (11) of the composite pipe is provided with a socket lining ring (6). The socket lining ring (6) covers a portion of the inner wall of the socket (11) and one end of the inner wall of the inner pipe (2). One end of the spigot (13) of the composite pipe is provided with a spigot lining ring (5). The spigot lining ring (5) covers the spigot (13).

2. The composite pipe according to claim 1, characterized in that: The material of the outer tube (1) is metal, the material of the middle layer (3) is hot melt adhesive, the material of the inner tube (2) is non-metal, and the socket lining ring (6) and the plug lining ring (5) are made of corrosion-resistant materials.

3. The composite pipe according to claim 2, characterized in that: Both ends of the composite pipe are provided with sealing gaskets (4); the sealing gasket (4) at one end of the socket (11) covers the inner wall and end surface of one end of the inner pipe (2) and the end surface of the middle layer (3); the sealing gasket (4) at one end of the spigot (13) covers the inner wall of the other end of the inner pipe (2) and the end surface of one end of the spigot (13) of the composite pipe.

4. The composite pipe according to claim 2, characterized in that: When the rust removal grade of the inner wall surface of the outer tube (1) reaches Sa2.5 and the surface roughness is Ra12.5-Ra25, the thickness of the intermediate layer (3) is not less than 0.1 mm, and the total thickness of the inner tube (2) and the intermediate layer (3) is not less than 1.0 mm; When the rust removal grade of the inner wall surface of the outer tube (1) reaches Sa2.5 and the surface roughness is Ra25-Ra50, the thickness of the intermediate layer (3) is not less than 0.15 mm, and the total thickness of the inner tube (2) and the intermediate layer (3) is not less than 1.0 mm; When the rust removal grade of the inner wall surface of the outer tube (1) reaches Sa2.5 and the surface roughness is greater than Ra50, the thickness of the intermediate layer (3) is not less than 0.2 mm, and the total thickness of the inner tube (2) and the intermediate layer (3) is not less than 1.2 mm.

5. The composite pipe according to claim 2, characterized in that: When two adjacent composite pipes are connected, one end of the spigot (13) of one composite pipe is inserted into one end of the socket (11) of the adjacent composite pipe and sealed by a sealing ring (7); the outer ring of the sealing ring (7) contacts and presses the inner wall of the socket liner (6) of one composite pipe, and the inner ring of the sealing ring (7) contacts the outer wall of the spigot liner (5) of the adjacent composite pipe; a stabilizing layer (8) is provided between the inner wall of the socket (11) and the socket liner (6); a stabilizing layer (8) is provided between the outer wall of the spigot (13) and the spigot liner (5); and the stabilizing layer (8) is hot melt adhesive or rubber.

6. The composite pipe according to any one of claims 1 to 5, characterized in that: The socket (13) and the socket lining ring (5) form a composite socket, and the socket (11) and the socket lining ring (6) form a composite socket. The design method of the thickness of the composite socket comprises the following steps: Step a1: Obtain the differential equation of radial deformation of the ring and the general solution of the differential equation according to the differential equation of the deflection curve of the ring and the moment balance equation; Step a2: Calculate and obtain a calculation formula for the maximum radial deformation of the ring according to the general solution of the differential equation obtained in step a1; Step a3: Calculating the minimum thickness of the socket of the base pipe that meets the deformation requirements according to the calculation formula of the maximum radial deformation obtained in step a2; Step a4: for a base pipe whose socket thickness is less than the minimum thickness obtained in step a3, at least one layer of annular reinforcement ring is sleeved in the socket of the base pipe to form a composite socket. If the material of the reinforcement ring is the same as that of the socket of the base pipe, the thickness of the composite socket is not less than the minimum thickness obtained in step a3. If the material of the reinforcement ring is different from that of the socket of the base pipe, go to step a5. Step a5: determining the minimum thickness of the reinforcement ring. If the thickness of the reinforcement ring is not less than the minimum thickness, the thickness of the composite socket is the minimum thickness that meets the deformation requirement. Assuming that the outermost layer of the composite socket is the base layer (F1), and the other layers are non-base layers (F2), for the multi-layer structure in the composite socket, the design method includes the following steps: Step c1: Based on the same strain of each layer of the composite socket, the calculation formula of the hoop stress of any non-base layer (F2) is obtained according to the non-single-layer material equilibrium equation; Step c2: Determine the relationship between the thickness of any non-base layer (F2) and the thickness of the base layer (F1), and the determination principle is: the ratio of the stress of the non-base layer (F2) to the yield strength of the material of the non-base layer is not greater than the ratio of the stress of the inner wall of the pipe body to the yield strength of the material of the pipe body; Step c3: Calculate the thickness of the non-base layer and / or base layer according to the relationship determined in step c2.

7. The composite pipe according to claim 6, characterized in that: Step a2 includes the following steps: Step a21: Assuming that the annular ring is subjected to at least two radial concentrated forces that are symmetrical relative to the center of the circle, based on the assumption, calculating the constant term in the general solution of the differential equation to obtain the first form of the differential equation; Step a22: Based on the first form of the differential equation obtained in step a21, assuming that the annulus is subjected to only two radial concentrated forces that are symmetrical relative to the center of the circle, the first form of the differential equation is transformed into a second form of the differential equation; Step a23: introducing the internal negative pressure of the ring into the second form of the differential equation by introducing a coefficient, so as to obtain the third form of the differential equation; Step a24: Obtain a calculation formula for the maximum change in the diameter of the circular ring with coefficients according to the third form of the differential equation obtained in step a23.

8. The composite pipe according to claim 6, characterized in that: Step a3 includes the following steps: Step a31: Calculate the parameters of a reference pipe according to an existing shear load formula, wherein the material and outer diameter of the reference pipe are respectively the same as the material and outer diameter of the base pipe; Step a32: obtaining the maximum deformation of the reference pipe socket through simulation according to the parameters calculated in step a31; Step a33: Substitute the maximum deformation of the socket obtained in step a32 into the calculation formula of step a2 to obtain the coefficient value in the calculation formula, thereby obtaining a calculation formula for the maximum radial deformation of the ring with a known coefficient; Step a34: Calculate the minimum thickness of the base pipe socket that meets the deformation requirements based on the allowable deformation regulations and the formula obtained in step a33.

9. The composite pipe according to claim 6, characterized in that: In step a1, the radial deformation obtained is u The differential equation is: ; The general solution is: , in, R is the average value of the outer circle radius and the inner circle radius of the ring; E is the elastic modulus of the pipe, Pa; I is the moment of inertia of the tube cross section, m 4 ; M is the bending moment borne by a certain section of the ring in the local area, in units of N*m; establish a two-dimensional coordinate system, The deformation is u The line connecting the point at and the origin of the coordinate system is the same as the line connecting the point at and the origin of the coordinate system in the two-dimensional coordinate system. x The angle between the positive directions of the axes, ; A1, A2, A3, B2, B3 are constants.

10. The composite pipe according to claim 9, characterized in that: In step a2, it is assumed that the ring is subjected to at least two radial concentrated forces P symmetrically relative to the center of the circle, and the angle between two adjacent radial concentrated forces P is , the ring satisfies the following three boundary conditions: First, in Because of symmetry, The rotation angle of the section at is 0, which satisfies the following formula: ; Second, due to symmetry, the total tangential displacement of the arc in each equally divided segment is 0; That is: ; Third, cut near point A, remove point A and the force P, and from the symmetry and equilibrium conditions, we know that the shear force on the section at the circular cut is , that is: ; Combining the above three formulas with the general solution of the differential equation, we get the first form of the differential equation: ； Assuming that the annulus is subjected to only two radial concentrated forces P which are symmetrical relative to the center of the circle, then: , we get the second form of the differential equation: ； Introducing the coefficient m, we get the third form of the differential equation: ； Point of application of force P The point is the point of maximum deformation, and the change in the diameter of the ring is: , where I = S 3 / 12, S is the wall thickness of the tube body.

11. The composite pipe according to claim 6, characterized in that: In step a5, the minimum thickness of the reinforcement ring is obtained and determined by experiment, simulation or theoretical calculation. When the minimum thickness of the reinforcement ring is obtained and determined by theoretical calculation, the minimum thickness of the reinforcement ring is obtained based on the socket thickness of the base pipe and the bending strength calculation formula of the longitudinal composite beam.

12. The composite pipe according to claim 6, characterized in that: For the same base pipe, along the direction from the socket to the spigot, the inner wall of the socket includes a first step (111), a second step (112), a third step (113), a fourth step (114), and a fifth step (115) arranged in sequence, one end of the inner wall of the pipe body is a sixth step (116), the chamfer at the connection between the fourth step (114) and the fifth step (115) is a first chamfer (R1), the chamfer at the connection between the fifth step (115) and the sixth step (116) is a second chamfer (R2), the chamfer at the connection between the second step (112) and the third step (113) is a third chamfer (R3), the chamfer at the connection between the first step (111) and the second step (112) is a fourth chamfer (R4), and the chamfer at the connection between the third step (113) and the fourth step (114) is a fifth chamfer (R5).

13. The composite pipe according to claim 12, characterized in that: In step c1, the multilayer structure is regarded as a structure including at least one pressure vessel with a conical inner wall and at least one annular reinforcement ring installed on the inner wall of the pressure vessel. In step c1, the first cone is a pressure vessel with a conical inner wall, and the first chamfer (R1) and the second chamfer (R2) are located on the inner wall of the first cone.

14. The composite pipe according to claim 13, characterized in that: In step c1, assuming that there are m layers of non-base layer (F2) and one base layer (F1), the equilibrium equation of the multi-layer structure is: ； in, p is the internal pressure of the conical container, D is the diameter of the conical container to be calculated, is the cone height, S1, S2, …, S m are the thickness of each non-base layer (F2), S b is the thickness of the base layer (F1), , , …, are the hoop stresses of each non-base layer, is the hoop stress of the base layer (F1), α is the half cone angle of the conical container; In step c1, the strain of the base layer (F1) The strain is the same as that of each non-base layer (F2), satisfying: ,Right now , where E1, E2, …, E m are the elastic modulus of each non-base layer (F2), E b is the elastic modulus of the base layer (F1), and the calculation formula for the hoop stress of the nth non-base layer (F2) is obtained by combining the equilibrium equation: ,in, is the hoop stress of the nth non-base layer, n is 1~m, E n is the elastic modulus of the nth non-base layer.

15. The composite pipe according to claim 14, characterized in that: In step c2, in order to make the composite socket meet the strength requirements, the internal stress of the nth non-base layer (F2) and the stress of the inner wall of the pipe body meet the following conditions: , , where Q0, Q n are the yield strengths of the pipe body and the nth non-base layer (F2) respectively; is the hoop stress of the pipe body, S is the thickness of the pipe body, D0 is the outer diameter of the pipe body, and p is the pressure given by the fluid in the pipe. The hoop stress calculation formula of the nth non-base layer (F2) is combined to obtain the relationship between the thickness of the nth non-base layer (F2) and the thickness of the base layer (F1): .

16. The composite pipe according to claim 15, characterized in that: When the thickness of the base layer (F1) corresponding to the maximum stress point is known, the minimum thickness of the layer with the minimum yield stress is calculated based on the relationship between the thickness of the n-th non-base layer (F2) and the thickness of the base layer (F1), and this layer is set as the minimum stress layer. The thickness of other non-base layers (F2) is set to be not less than the minimum thickness of the minimum stress layer; when the thickness of the non-base layer (F2) is known, first, at least one point where the stress of the base layer (F1) is easily concentrated is selected, and the selection principle is: after the strength of each selected point meets the requirements, the strength of other places of the base layer (F1) designed according to the outer wall design requirements also meets the requirements; then the thickness of each selected point is calculated based on the relationship between the thickness of the n-th non-base layer (F2) and the thickness of the base layer (F1).

17. A method for manufacturing a socket-and-spigot type heterogeneous material multilayer composite pipe, used for manufacturing the composite pipe according to any one of claims 1 to 5, characterized in that: The steps include: Step S1: processing the outer tube (1), manufacturing the inner tube (2) and the intermediate layer (3), manufacturing the socket lining ring (6), and manufacturing the spigot lining ring (5); Step S2: inserting the entire plastic tube including the middle layer (3) and the inner tube (2) into the outer tube (1) and compounding them by heating; Step S3: installing the spigot lining ring (5) and the bell lining ring (6) on one end of the spigot (13) and one end of the bell (11) of the composite pipe respectively.

18. The manufacturing method according to claim 17, characterized in that: When manufacturing the socket liner (5), it is divided into two parts, one part is the inner tube part, and the other part is the outer tube part. One end of the inner tube part is attached to the inner wall of the inner tube (2), and one end of the outer tube part is attached to the outer wall of the socket (13). The other end of the inner tube part and / or the other end of the outer tube part are bent and attached to the end surface of one end of the socket (13) of the composite pipe, and the inner tube part and the outer tube part are welded together. The welding point is located on the end surface of one end of the socket (13) of the composite pipe. The outer tube part of the socket liner (5) and the outer wall of the socket (13) are welded together, or hot melt adhesive is sprayed or coated on the outer wall of the socket (13) before installing the outer tube part.

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