A socket-and-spigot type heterogeneous material multilayer composite pipe and a manufacturing method thereof

Abstract

The present invention discloses a socket-and-spigot type heterogeneous material multilayer composite pipe and a manufacturing method thereof. The composite pipe comprises an inner pipe, an intermediate layer and an outer pipe which are sleeved in sequence from the inside to the outside. The inner pipe and the outer pipe are bonded through the intermediate layer. The outer pipe comprises a socket, a pipe body and a spigot part which are connected in sequence. The composite pipe is provided with a socket lining ring and a spigot lining ring. The manufacturing method comprises: S1: processing the outer pipe, making the inner pipe and the intermediate layer, making the socket lining ring and the spigot lining ring; S2: inserting the intermediate layer and the inner pipe as a whole into the outer pipe and compounding them by heating; S3: installing the spigot lining ring and the socket lining ring at one end of the spigot part and one end of the socket of the composite pipe respectively. The present invention has high connection strength between the layers, good end face sealing, good negative pressure resistance, prevents the pipe from being corroded and contaminated by the transported liquid and the liquid from penetrating from the end face to cause delamination, and can obtain the minimum thickness of the composite spigot that meets the deformation requirements and the minimum thickness of the composite socket that meets the strength requirements through theoretical calculation.

Description

Technical Field

[0001] The present 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 type of pipe widely used in liquid transportation pipe network systems. It is generally a socket-and-spigot structure, including an outer metal pipe and an inner plastic pipe, that is, the plastic pipe serves as an inner lining, and 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 one 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 do not form an overall anti-corrosion coating with the pipe body. During use, long-term contact with the liquid in the pipeline causes the 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] Normal water supply pipes are subject to significant internal water pressure, which is positive pressure. Therefore, the pipe material must meet specified strength requirements. Existing standards (both group and national) specify nominal wall thicknesses for different pressure levels and nominal diameters. Pipes that meet these standards meet the strength requirements within the corresponding pressure level range. Therefore, existing pipe manufacturers generally produce pipes that meet these standards.

[0004] However, when a pipe network malfunctions, such as a pipe burst, water in the network will spray out from the burst, causing the pressure in the network to drop rapidly, even forming negative pressure. Furthermore, the pipes are subject to external pressure, such as the gravity of the soil above them when buried in the soil. Under these external pressures and internal negative pressures, the pipes can deform radially. If the socket deformation is excessive, the socket can separate from the socket it connects to, causing leakage at the socket-to-spike connection and contamination of the water pipe interior. Therefore, it is necessary to ensure that the deformation of the pipe socket in these situations does not exceed a certain range. To this end, the socket must have a minimum thickness that meets deformation requirements. If the selected pipe socket thickness is less than this minimum thickness, measures must be taken to ensure that it meets deformation requirements. For example, during secondary processing or installation of the pipe, at least one annular reinforcement ring can be added to the socket to form a composite socket to enhance its resistance to 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 directly contacts the water inside the pipe, it requires a corrosion-resistant material such as stainless steel. However, the base pipe is generally made of relatively inexpensive materials such as ductile iron and Q235. Therefore, ensuring that the composite socket meets maximum deformation requirements while maintaining minimum or near-minimum thickness becomes a challenge. The base pipe refers to the pipe in its factory-installed state, meaning it has not been fitted with a reinforcement ring or undergone secondary processing such as composite processes. The base pipe comprises a socket, a pipe body, and a socket, which are connected in sequence. The pipe body can be divided into two parts: a main body and a transition section. The transition section serves as the transitional connection between the main body and the socket, i.e., the socket, transition section, main body, and socket are connected in sequence. The inner wall of the pipe body is cylindrical, meaning the inner diameter of the transition section is equal to that of the main body. The main body is cylindrical, while the outer wall of the transition section is conical. In other words, the thickness of the main body is uniform or substantially uniform throughout, while the thickness of the transition section gradually decreases 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. Figure 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 all locations the 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 type of 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 while having the minimum or close to the minimum thickness, it can also greatly reduce costs. 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 lining, the composite socket includes a single-layer structure and a multi-layer structure. The single-layer structure is the part not covered by the lining 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 inside the base pipe. Summary of the Invention

[0006] In response to 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 prevents the inner wall of the pipe socket and the outer wall of the plug from rusting and contaminating the transported liquid, and prevents 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:

[0008] 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 being bonded together through the intermediate layer, the outer pipe comprising a socket, a pipe body and a spigot which are sequentially connected, the inner wall of the socket being provided with steps and / or grooves, a socket lining ring being provided at one end of the socket of the composite pipe, the socket lining ring covering part of the inner wall of the socket and one end of the inner wall of the inner pipe, a spigot lining ring being provided at one end of the spigot of the composite pipe, the spigot lining ring covering the spigot.

[0009] As a further improvement of the above technical solution:

[0010] Preferably, the outer tube is made of metal.

[0011] Preferably, the material of the middle layer is hot melt adhesive.

[0012] Preferably, the material of the inner tube is non-metal.

[0013] Preferably, the socket lining ring and the spigot lining ring are made of corrosion-resistant materials.

[0014] 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.

[0015] 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 intermediate layer is not less than 0.1 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 Ra25~Ra50, the thickness of the intermediate layer is not less than 0.15 mm.

[0017] More preferably, the total thickness of the inner tube and the intermediate layer is not less than 1.0 mm.

[0018] 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.

[0019] More preferably, the total thickness of the inner tube and the intermediate layer is not less than 1.2 mm.

[0020] 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 lining ring of one composite pipe, and the inner ring of the sealing ring contacts the outer wall of the spigot lining ring of the adjacent composite pipe.

[0021] 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.

[0022] Preferably, the stabilizing layer is hot melt adhesive or rubber.

[0023] The socket and the socket lining ring form a composite socket, and the socket and the socket lining ring form a composite socket. The design method of the composite socket thickness includes the following steps:

[0024] Step a1: Obtain the differential equation of the radial deformation of the ring and the general solution of the differential equation based on the deflection curve differential equation and the moment balance equation of the ring;

[0025] Step a2: Calculating and obtaining a calculation formula for the maximum radial deformation of the ring based on the general solution of the differential equation obtained in step a1;

[0026] Step a3: Calculating the minimum thickness of the base pipe socket that meets the deformation requirements based on the calculation formula for the maximum radial deformation obtained in step a2;

[0027] Step a4: For a base pipe whose socket thickness is less than the minimum thickness obtained in step a3, at least one annular reinforcement ring is sleeved into 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 needs to be no 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, proceed to step a5.

[0028] 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.

[0029] 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:

[0030] Step c1: Based on the same strain in 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 is obtained;

[0031] Step c2: Determine the relationship between the thickness of any non-base layer and the thickness of the base layer, where the determination principle is: 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 pipe body material;

[0032] Step c3: Calculate the thickness of the non-base layer and / or base layer according to the relationship determined in step c2.

[0033] As a further improvement of the above technical solution:

[0034] Step a2 includes the following steps:

[0035] Step a21: Assuming that the annular ring is subjected to at least two radial concentrated forces that are symmetrical with respect to the center of the annular ring, 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;

[0036] 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;

[0037] Step a23: introducing the internal negative pressure on the ring into the second form of the differential equation by introducing a coefficient to obtain the third form of the differential equation;

[0038] Step a24: Obtain a calculation formula for the maximum change in the diameter of the ring with a coefficient according to the third form of the differential equation obtained in step a23.

[0039] Step a3 includes the following steps:

[0040] Step a31: Calculating parameters of a reference pipe according to an existing shear load formula, wherein the material and outer diameter of the reference pipe are the same as those of the base pipe;

[0041] Step a32: obtaining the maximum deformation of the reference pipe socket through simulation based on the parameters calculated in step a31;

[0042] Step a33: Substituting 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;

[0043] 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.

[0044] In step a1, the radial deformation obtained u The differential equation is: ;

[0045] The general solution is: ,

[0046] in, R is the average value of the outer radius and the inner radius of the ring; E is the elastic modulus of the pipe, Pa; I is the moment of inertia of the tube 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 in the two-dimensional coordinate system x The angle between the positive directions of the axes, ; A1, A2, A3, B2, B3 are constants.

[0047] In step a2, it is assumed that the ring is subjected to at least two radial concentrated forces P that are symmetrical relative to the center of the circle, and the angle between the two adjacent radial concentrated forces P is , the ring satisfies the following three boundary conditions:

[0048] First, in Due to symmetry, The rotation angle of the section at is 0, which satisfies the following formula: ;

[0049] Second, due to symmetry, the total tangential displacement of the arc in each equally divided segment is 0; that is, ;

[0050] Third, when the cut is made near point A, point A and the acting force P are removed. According to the symmetry and equilibrium conditions, the shear force on the section of the circular cut is , that is: ;

[0051] Combining the above three formulas and the general solution of the differential equation, we get the first form of the differential equation:

[0052] ;

[0053] Assuming that the ring is subjected to only two radial concentrated forces P that are symmetrical relative to the center, then: , we get the second form of the differential equation:

[0054] ;

[0055] Introducing the coefficient m, we get the third form of the differential equation:

[0056] ;

[0057] Point of application of force P The point is the point of maximum deformation, and the change in the ring diameter is:

[0058] , where I=S 3 / 12, S is the wall thickness of the tube.

[0059] In step a5, the minimum thickness of the reinforcement ring is obtained and determined through experiments, simulations, or theoretical calculations. When the minimum thickness of the reinforcement ring is obtained and determined through theoretical calculations, 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.

[0060] For the same base pipe, along the direction from the socket to the spigot, the inner wall of the socket includes the first step, the second step, the third step, the fourth step, and the fifth step arranged in sequence, one end of the inner wall of the pipe body is the sixth step, the chamfer at the connection between the fourth step and the fifth step is the first chamfer, the chamfer at the connection between the fifth step and the sixth step is the second chamfer, the chamfer at the connection between the second step and the third step is the third chamfer, the chamfer at the connection between the first step and the second step is the fourth chamfer, and the chamfer at the connection between the third step and the fourth step is the fifth chamfer.

[0061] 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.

[0062] 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:

[0063] ;

[0064] 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;

[0065] 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.

[0066] 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 stress of the inner wall of the pipe body must meet the following conditions: , , where Q0, Q n are the yield strengths of the pipe body and the nth non-base layer 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 is combined to obtain the relationship between the thickness of the nth non-base layer and the thickness of the base layer: .

[0067] 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 no 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.

[0068] A method for manufacturing a socket-and-spigot type heterogeneous material multilayer composite pipe, for manufacturing the composite pipe, comprises the following steps:

[0069] 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;

[0070] Step S2: inserting the entire plastic tube including the middle layer and the inner tube into the outer tube and compounding them by heating;

[0071] 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.

[0072] When making a 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.

[0073] 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.

[0074] The beneficial effects of the present invention are:

[0075] (1) Good sealing between the various layers of the pipe: The socket end and the spigot end of the composite pipe are both 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.

[0076] (2) Good corrosion resistance: The inner tube is made of polyethylene, which is suitable for transporting corrosive liquids. In addition, the layers of the pipe are well sealed, preventing liquid from penetrating through the pipe ends and entering between the layers, further improving the corrosion resistance of the composite pipe. The plastic inner tube improves the smoothness of the inner surface of the composite pipe. The thin inner tube can improve pipeline transportation efficiency and reduce operating energy consumption.

[0077] (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 in a socket-and-spigot manner, the socket lining ring of one composite pipe and the spigot lining ring of the adjacent composite pipe can be respectively pressed 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 will enter. The stainless steel spigot lining ring and the socket lining ring 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.

[0078] (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 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 ends to prevent the lining from being delaminated due to negative pressure in the pipeline, and prevents the inner tube from falling off and being washed away by the liquid.

[0079] (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 costs and use costs.

[0080] (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.

[0081] (7) The minimum or near minimum thickness of the composite spigot of the socket-and-spigot pipes of different diameters that meets the deformation requirements and the minimum or near minimum thickness of the composite socket that meets the strength requirements can be obtained through theoretical analysis and calculation, which saves materials and reduces the production, manufacturing and transportation costs of the pipes. The method for designing the minimum wall thickness is theoretical calculation, which is low in cost and high in efficiency, 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, and improving the corrosion resistance of the pipe. BRIEF DESCRIPTION OF THE DRAWINGS

[0082] Figure 1Schematic diagram of the structure of the composite tube according to the first embodiment of the present invention.

[0083] Figure 2 Schematic diagram of the connection of two adjacent composite tubes according to the first embodiment of the present invention.

[0084] Figure 3 Schematic diagram of the structure of the composite tube according to the second embodiment of the present invention.

[0085] Figure 4 Schematic diagram of the connection of two adjacent composite tubes according to the second embodiment of the present invention.

[0086] Figure 5 Schematic diagram of the structure of the composite tube according to the third embodiment of the present invention.

[0087] Figure 6 Schematic diagram of the connection of two adjacent composite tubes according to the third embodiment of the present invention.

[0088] Figure 7 Schematic diagram of the structure of the composite pipe without a stabilizing layer according to the fourth embodiment of the present invention.

[0089] Figure 8 3 is a schematic structural diagram of the composite tube in which the stabilizing layer is hot melt adhesive according to the fourth embodiment of the present invention.

[0090] Figure 9 3 is a schematic structural diagram of the composite tube in which the stabilizing layer is made of rubber according to the fourth embodiment of the present invention.

[0091] Figure 10 Schematic diagram of the connection of two adjacent composite pipes according to the fourth embodiment of the present invention.

[0092] Figure 11 Schematic diagram of the cross-section before and after deformation when the socket is subjected to a pair of radially symmetrical concentrated forces.

[0093] Figure 12 for Figure 11 Schematic diagram of local analysis.

[0094] Figure 13 Schematic diagram of a circular ring subjected to multiple uniformly arranged radial concentrated forces.

[0095] Figure 14 This is the stress analysis diagram of socket-and-spigot pipe.

[0096] Figure 15 It is a schematic cross-sectional view of a composite socket per unit length of the present invention.

[0097] Figure 16 This is a schematic diagram of the composite socket structure of Example 1 of the present invention.

[0098] Figure 17It is a schematic diagram of the spigot and socket connection of the socket type pipe of the present invention.

[0099] Figure 18 This is a schematic diagram showing that the inner wall of the bell mouth is completely covered by the bell mouth lining ring according to the first embodiment of the present invention. DETAILED DESCRIPTION

[0100] The following describes the specific embodiments of the present invention in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0101] For ease of description, spatially relative terms such as "above," "above," "on the upper surface of," and "upper" may be used herein to describe the spatial positional relationship of a device or feature to other devices or features as shown in the figures. It should be understood that spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if a device in a drawing is inverted, a device described as "above" or "on top of" another device or structure would then be positioned as "below" or "below" the other device or structure. Thus, the exemplary term "above" can include both the "above" and "below" orientations. The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used herein should be interpreted accordingly.

[0102] Example 1

[0103] A socket-and-spigot type, multi-layer composite pipe with different materials comprises an inner pipe 2, an intermediate layer 3, and an outer pipe 1, which are sequentially sleeved from the inside out. The intermediate layer 3 is made of hot-melt adhesive, and the inner pipe 2, which serves as the lining, is made of a non-metallic material, preferably polyethylene. The outer pipe 1 is made of metal, preferably ductile iron or carbon steel. The inner and outer pipes 2 and 1 are bonded together via the intermediate layer 3.

[0104] The outer tube 1 comprises a socket 11, a tube body 12, and a spigot 13, connected in sequence along its axis. These three components are integrally cast, or the tube body 12 and spigot 13 are integrally formed or welded together. The inner surface of the spigot 11 is stepped. When two composite tubes are connected, the spigot 13 of one composite tube is inserted into the socket 11 of the adjacent composite tube.

[0105] 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 ends of the inner tube 2, the intermediate layer 3, and the tube body 12 are flush; at the socket 13 end of the composite tube, the ends of the inner tube 2, the intermediate layer 3, and the socket 13 are flush.

[0106] A spigot liner 5 is provided at one end of the spigot 13 of the composite pipe. One end of the spigot liner 5 is pressed against the inner wall of the inner pipe 2, while the other end extends outward 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, thereby covering the end of the inner pipe 2 and the end of the intermediate layer 3, thereby preventing the ends of the layers from separating from each other. In other words, the spigot liner 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, as well as the outer wall of the spigot 13.

[0107] Similarly, a bell liner ring 6 is provided at one end of the bell 11 of the composite pipe. The bell 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 bell liner ring 6 is pressed against the inner wall of the inner tube 2 and the inner wall of the bell 11 at one end of the bell 11 of the composite pipe. In other words, the bell liner ring 6 covers the inner wall of the inner tube 2, which is close to the bell 11, to the middle of the inner wall of the bell 11 or the entire inner wall of the bell 11.

[0108] Furthermore, both ends of the inner tube 2 are provided with sealing gaskets 4. The sealing gasket 4 at the end of the bell mouth 11 is located between the inner tube 2 and the bell mouth liner 6 and covers the inner wall and end surface of the inner tube 2 near the bell mouth 11, as well as the end surface of the intermediate layer 3 near the bell mouth 11. The sealing gasket 4 at the end of the spigot 13 is located between the inner tube 2 and the spigot liner 5 and covers the inner wall and end surface of the inner tube 2, the end surface of the intermediate layer 3, and the end surface of the spigot 13. The sealing gasket 4 is a rubber sealing gasket.

[0109] like Figure 1 As shown, the sealing gasket 4 includes a pressing edge 41 and a flange 42, which are integrally connected. The pressing edge 41 can be considered a thin cylindrical shape, while the flange 42 is annular. The inner diameter of the flange 42 is equal to that of the pressing edge 41, and the outer diameter of the flange 42 is larger than that of the pressing edge 41. The pressing edge 41 and the flange 42 share a common centerline.

[0110] Regarding the sealing gasket 4 at one end of the composite pipe's socket 11, the outer surface of the pressing edge 41 abuts the inner surface of the inner pipe 2, and the inner surface of the pressing edge 41 abuts the outer surface of the socket liner 6. One side of the flange 42 abuts 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 abuts the socket liner 6.

[0111] Regarding the sealing gasket 4 at one end of the composite pipe's spigot 13, the outer surface of the pressing edge 41 abuts the inner surface of the inner pipe 2, while the inner surface of the pressing edge 41 abuts the outer surface of the spigot liner 5. One side of the flange 42 abuts the end face of the inner pipe 2, the end face of the intermediate layer 3, and the end face of the spigot 13, while the other side of the flange 42 abuts the spigot liner 5.

[0112] In this embodiment, the socket lining ring 6 directly contacts the sealing gasket 4 and the stepped inner wall of the socket 11 .

[0113] like Figure 1 As shown, the socket 11 comprises, in order, a first step 111, a second step 112, a third step 113, a fourth step 114, and a fifth step 115, extending from the end away from the pipe body 12 toward the end closer to the pipe body 12. The inner diameter of the first step 111 is smaller than that of the second step 112. The inner diameter of the third step 113 is larger than that of the first step 111 but smaller than that of the second step 112. The inner diameter of the fourth step 114 is smaller than or equal to that of the second step 112 but larger than that 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 surface of a cylinder or a frustum. When it is the outer surface of a frustum, the inner diameter of the fifth step 115 gradually increases from the fourth step 114 toward the pipe body 12, 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 adjacent to the fifth step 115.

[0114] The inner wall bell mouth of the fifth step 115 is provided to provide a deflection angle for the adjacent composite pipe connected thereto, that is, to allow the center line of one composite pipe and the center line of the adjacent composite pipe connected thereto to intersect, rather than overlap, in order to allow a certain installation angle deviation to facilitate actual operation, and to allow adjacent pipes to have a relative offset of a certain angle when the soil moves naturally.

[0115] Preferably, the socket lining ring 6 covers the inner wall of the fourth step 114 and the inner wall of the fifth step 115 .

[0116] Based on the above structure, when two adjacent composite pipes are connected, Figure 2 As shown, the spigot 13 of one 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 compresses the inner wall of the socket liner 6 of one composite pipe, while the inner ring of the sealing ring 7 contacts the outer wall of the spigot liner 5 of the adjacent composite pipe. Preferably, one end face of the sealing ring 7 contacts the end face of the first step 111, a portion of the sealing ring 7 is accommodated on the second step 112, the third step 113 is engaged in the middle of the sealing ring 7, and the other portion of the sealing ring 7 is located on the socket liner 6 on the fourth step 114. Furthermore, a gap exists between the end face of one composite pipe spigot 13 and the end face of the adjacent composite pipe body 12. This gap is present to allow for a deflection angle between the two adjacent composite pipes during installation.

[0117] Preferably, the total thickness of the inner tube 2 and the intermediate layer 3 is greater than 1 mm.

[0118] The thickness of the intermediate layer 3 and the inner tube 2 are defined as follows:

[0119] 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.

[0120] 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.

[0121] 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 0.2 mm, and the total thickness of the inner tube 2 and the intermediate layer 3 is not less than 1.2 mm.

[0122] 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.

[0123] The low-temperature freezing test found that under the test conditions of 0°C and 1000h, the lining will not be delaminated when the peel strength of the lining of the composite pipe is greater than 70N / cm, that is, the lining will not separate from the outer pipe 1; under the test conditions of -45°C and 1000h, the lining will not be delaminated when the peel strength of the lining of the composite pipe is greater than 120N / cm.

[0124] The hole opening test found that when the peeling strength of the composite pipe lining reached 120 N / cm, the lining plastic would not be peeled off from the inner wall of the metal outer pipe 1 by the hole opening tool after the hole was opened.

[0125] 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 total thickness of the inner tube 2 and the intermediate layer 3 is more than 1.0 mm, 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 total thickness of the inner tube 2 and the intermediate layer 3 is more than 1.2 mm, the inner tube 2 will not melt through and an inner surface with better flatness can be obtained.

[0126] 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 pipe of this solution can withstand a liquid lateral scouring force of 7Mpa, which is much greater than the maximum liquid lateral scouring force in the existing pipe network system.

[0127] A method for manufacturing a socket-and-spigot type heterogeneous material multilayer composite pipe, comprising the following steps:

[0128] Step S1: Process the inner and outer walls of the outer tube 1, manufacture the inner tube 2 and the intermediate layer 3, and manufacture the socket lining ring 6 and the spigot lining ring 5.

[0129] In this step, the inner and outer walls of outer tube 1 are treated by first grinding the inner wall, then sandblasting or shot blasting the inner and outer walls. An internal grinder is used to grind the inner wall of the metal outer tube 1 until it is smooth and removes surface scale, scum, and rust. Alternatively, after the inner wall of outer tube 1 is polished, a laser cleaner is used to clean the inner wall of the tube to thoroughly remove scale and rust. During sandblasting or shot blasting, dust, scale, and rust are removed from the inner and outer walls, and the inner and outer walls of the tube are sandblasted to a frosted finish.

[0130] The inner tube 2 and the middle layer 3 are manufactured by co-extrusion, and the double-layered plastic tube is manufactured by co-extrusion, vacuum sizing, pulling, and cutting. The co-extrusion, vacuum sizing, pulling, and cutting can be performed by an extruder, a vacuum box, a pulling machine, and a cutting machine in the prior art.

[0131] The inner tube 2 and the middle layer 3 can also be independently made into round tubes.

[0132] The production of the socket lining ring 6 includes the following steps:

[0133] S161: Processing the long stainless steel sheet into a ring or a very thin cylindrical shape to complete the rolling. In this step, the stainless steel sheet is processed into a ring or a very thin cylindrical shape using a rolling machine (the rolling machine technology solution described in Patent 2020114372537 can be used).

[0134] S162: Cut the rolled stainless steel sheet and weld the ends together. In this step, an argon arc welder or a laser welder is used for welding.

[0135] S163: The product obtained in step S162 is expanded into the desired shape. In this step, the product is expanded and formed using an expanding 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 shape formed by the connection between the inner wall of the socket 11 and the inner tube 2.

[0136] It should be noted that the expansion forming of the last step S163 can be implemented when installing the socket lining ring 6, as described below.

[0137] When making the socket liner 5, it is divided into two parts: one part is the inner tube part; the other part is the outer tube part. The inner tube part and the outer tube part are both made by a rolling machine. The difference is that when making the inner tube part, the long stainless steel sheet is processed into a shape with a flange (the same shape as the sealing gasket 4). When making the outer tube part, the long 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 tube part 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 tube part is slightly larger than the outer diameter of the outer tube 1, and the length of the outer tube part is slightly larger than the length required for installation, or the length of the socket 13.

[0138] Step S2: inserting the entire plastic tube including the intermediate layer 3 and the inner tube 2 into the outer tube 1 and compounding them by heating.

[0139] 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 used).

[0140] 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, bonding the outer pipe 1 and the inner pipe 2 together.

[0141] After the composite is completed, the excess plastic tubes at both ends of the composite pipe are cut off and trimmed. Trimming can be performed 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.

[0142] 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.

[0143] For the bell liner 6, if it is the bell liner 6 after expansion molding, that is, the bell liner 6 of the above steps S161 to S163 is completed, the installation steps are as follows:

[0144] S361: The expanded socket stainless steel ring, i.e., the socket lining ring 6, is cut along the weld to form an incision.

[0145] S362: Put a rubber sealing gasket 4 with a flange 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 flange 42 close to the surface perpendicular to the stepped portion with the smallest outer diameter.

[0146] S363: Curl the cut edge of the socket lining ring 6 to the wrong side. After curling, the inner diameter becomes smaller and can be inserted into the socket 11. Curl it back to the wrong side to restore the socket lining ring 6 to its original shape. At this time, the pressing edge 41 fits the inner wall of the inner tube 2, and the flanging edge 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.

[0147] S364: Weld the cut of the socket lining ring 6.

[0148] 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, the end face of the inner tube 2, and the end face of the intermediate layer 3.

[0149] Based on the above method, the socket lining 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 lining 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.

[0150] 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:

[0151] S361': Put the rubber sealing gasket 4 with a flange on the outer surface of one end of the socket stainless steel ring, fix the position, and fix it with glue.

[0152] 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 .

[0153] S363': Expand the diameter of the small end of the socket lining ring 6.

[0154] S364': Use a supporting device to support and fix the small head position of the socket liner 6, and use a spinning machine to spin the portion of the socket liner 6 that connects to the socket 11 to expand the diameter as a whole or in sections until the socket liner 6 is close to the inner wall of the socket 11.

[0155] For the spigot liner 5, first install the inner and outer portions of the spigot 13 separately. When installing the inner portion, first place a rubber sealing gasket 4 with a flanged edge over the outer wall of the inner portion and then insert both into the spigot 13. When installing the outer portion, place it over the outer wall of the spigot 13 and secure it in place. Next, use a diameter expander to expand the inner portion of the spigot liner 5 so that the inner portion of the spigot liner 5 presses the sealing gasket 4 against the inner wall of the inner tube 2, the end face of the inner tube 2, the end face of the intermediate layer 3, and the end face of the spigot 13. Then, use a crimping device to crimp the portion of the spigot liner 5 on the outer wall of the spigot 13 (i.e., the outer portion) from the chamfered portion of the spigot toward the end face of the pipe until the outer portion contacts the inner portion on the end face. The portion that extends beyond the inner portion is trimmed. Finally, the connection between the inner portion of the tube and the outer portion of the tube (located at the end surface of the socket 13) is welded.

[0156] In addition, the outer pipe portion of the spigot bushing 5 and the outer pipe 1 can be welded together.

[0157] 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.

[0158] 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.

[0159] In this embodiment, the outer tube's socket 11 and the socket lining 6 both enhance the strength of the composite pipe's socket, and the resulting socket formed by the two is a composite socket. The outer tube's spigot 13 and the spigot lining 5 form a composite spigot. Because the spigot lining 5 covers the entire inner and outer walls of the spigot 13, it enhances the spigot's strength and resistance to deformation. Therefore, the spigot 13 and the lining lining 51 form a three-layer composite spigot. Furthermore, the middle layer 3 is made of hot-melt adhesive, and the sealing gasket 4 is made of rubber. Both are non-metallic, flexible materials that have little impact on the spigot's strength and resistance to deformation, and therefore do not fall within the category of deformation-resistant composite spigots.

[0160] Next, the thickness of the spigot end and the bell end of the composite pipe are optimized and designed.

[0161] The design method of the thickness of the composite socket includes the following steps:

[0162] Step a1: Obtain the radial deformation of the ring based on the differential equation of the ring's deflection curve and the moment balance equation 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.

[0163] 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.

[0164] Step a3: Calculate the minimum thickness of the base pipe socket that meets the deformation requirements based on the calculation formula for the maximum radial deformation obtained in step a2.

[0165] Step a4: For a base pipe whose socket thickness is less than the minimum thickness obtained in step a3, at least one annular reinforcement ring is sleeved into 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 only needs to be no 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, proceed to step a5.

[0166] Step a5: If the material of the reinforcement ring is different from that of the base pipe socket, the minimum thickness of the reinforcement ring is obtained based on the thickness of the base pipe socket and the calculation formula for the bending strength of the longitudinal composite beam. If the thickness of the reinforcement ring is not less than this 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 formed by the base pipe after the reinforcement ring is installed meets the deformation requirements and the strength requirements.

[0167] The following is a detailed introduction to each step.

[0168] In step a1, the radial deformation obtained The differential equation is:

[0169] (1)

[0170] in ，R is half the sum of the outer and inner radii 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 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 in the two-dimensional coordinate system x The angle between the positive directions of the axes, In this embodiment, the xy Coordinate system, point Ois the coordinate origin and the center of the ring, such as Figure 11 As shown. m 1 The radial deformation at u， but om 1 and x The angle between the positive directions of the axes is 。

[0171] The above differential equation (1) is obtained as follows:

[0172] like Figure 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. Figure 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 point m 1 and n 1 Located on the line segments 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 d φ, set up u Centripetal movement is positive. Figure 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 Tangent line. n 1 t’ passing point n 1 and perpendicular to on,straight line n 1 t 1 ’ For passing point n 1 tangent.

[0173] 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, The arc before deformation mn exist m Tangent and n The angle between the tangent lines of a point, The deformation amount is u The radius corresponding to the point after deformation is, It is an arc mn Deform to arc m 1 n 1 back ds The increment of Is the arc after deformation m 1 n 1 exist m 1 Tangent and n 1 The angle between the tangent lines of the point is m 1 t 1 and The angle between , then:

[0174] (2)

[0175] (3)

[0176] (4)

[0177] (5)

[0178] m 1 t 1 and m 1 t The angle between , n 1 t 1 ’ and n 1 t’ The angle between .

[0179] m 1 section to n 1 The variable of the cross-section angle is :

[0180] (6)

[0181] 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.

[0182] Substituting formulas (5) and (6) into formula (4) yields:

[0183] (7)

[0184] By series expansion we have:

[0185] Omit the higher-order terms and substitute the series expansion into (7) to obtain: (8)

[0186] Substituting (2) into (8) we get:

[0187] (9)

[0188] Omitting higher-order terms, we can get: (10)

[0189] For a thin ring (i.e. a ring with a small difference between the outer and inner diameters relative to the ring diameter), we have: , by definition: ,therefore, , substituting into (10) we get, , combining formula (2) to obtain radial deformation The differential equation formula (1).

[0190] The general solution of the above differential equation (1) is:

[0191] (11)

[0192] 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

[0193] (12)

[0194] Step a2: Calculating and obtaining a formula for the maximum radial deformation of the ring based on the general solution of the differential equation obtained in step a1, including the following steps:

[0195] Step a21: Assume that the annulus 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.

[0196] Step a22: Based on the first form of the differential equation obtained in step a21, assuming that the ring is only subjected to 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.

[0197] Step a23: Introduce the internal negative pressure on the ring into the second form of the differential equation by introducing coefficients to obtain the third form of the differential equation.

[0198] Step a24: Obtain a calculation formula for the maximum change in the diameter of the ring with a coefficient according to the third form of the differential equation obtained in step a23.

[0199] 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 Figure 13 shown. Figure 11The circular ring shown in FIG is subjected to two radial concentrated forces P that are symmetrical relative to the center of the circle, and the two radial concentrated forces P are located on the y-axis.

[0200] The ring satisfies the following three boundary conditions:

[0201] (1) In Due to symmetry, the rotation angle of the section at this location is 0, which satisfies the following formula:

[0202] (13)

[0203] (2) Due to symmetry, the total tangential displacement of the arc in each equally divided segment is 0; that is,

[0204] (14)

[0205] (3) When the cut is made near point A, point A and the acting force P are removed. According to the symmetry and equilibrium conditions, the shear force on the section at the circular cut is , that is:

[0206] (15)

[0207] in, dM represents the differential with respect to M. It should be noted that point (3) is not a true cut of the ring, but an assumption.

[0208] Simultaneously formula (13), (14), (15), the solution is:

[0209] (16)

[0210] (17)

[0211] (18)

[0212] Substituting formulas (16), (17), and (18) into formula (12), we obtain:

[0213] (19)

[0214] Formula (19) is the first form of the differential equation obtained in step a21. is the radial deformation of the ring.

[0215] In step a22, if only one pair of radial forces P is applied to the ring, then , the deflection curve equation (19) becomes:

[0216] (20)

[0217] Formula (20) is the second form of the differential equation obtained in step a22.

[0218] In step a23, considering that the pipe generally needs to withstand an internal negative pressure of 0.1 MPa during testing, the coefficient m is introduced, that is,

[0219] (twenty one)

[0220] 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.

[0221] Formula (21) is the third form of the differential equation obtained in step a23.

[0222] In step a24, the maximum deformation is At the point where the force P is applied, the change in the diameter of the ring is the maximum change in the diameter of the ring. u max :

[0223] (twenty two)

[0224] Formula (22) is the third form of the differential equation obtained in step a24.

[0225] Step a3: Calculate the minimum thickness of the base pipe socket that meets the deformation requirements based on the calculation formula for the maximum radial deformation obtained in step a2. This includes the following steps:

[0226] 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 the same as those of the base pipe.

[0227] Step a32: obtaining the maximum deformation of the reference pipe socket through simulation based on the parameters calculated in step a31.

[0228] 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.

[0229] 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.

[0230] In step a31, the shear load formula used is derived from the group standard "Corrosion-resistant steel pipes with flexible socket joints for water supply and drainage" (T / CISA 108-2021), which is:

[0231] (twenty three)

[0232] like Figure 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 socket end steel pipe and the end face of the socket 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).

[0233] 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 is selected 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, shear force F It should be no less than 30 times 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.

[0234] In this embodiment, the parameters in formula (23) are M P and W The calculation process is as follows:

[0235]

[0236]

[0237] in, is the density of water, is the density of steel, the above M P The diameter used in the calculation is the outer diameter of the base pipe D0, 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 a circular tube section also requires multiplication by the length, but this solution considers a cylinder of unit length (i.e., the aforementioned ring), so the length is 1.

[0238] Step a31 is thus completed.

[0239] In step a32, based on the parameters obtained by the above calculation, the maximum deformation of the socket of the reference pipe is simulated by finite element simulation using simulation software. u max =12.19 mm. During the simulation, the material parameter Poisson's ratio was 0.3. The simulation method is well known to those skilled in the art and will not be described in detail here.

[0240] In step a33, u max =12.19 Substituting into formula (22) we get m =1.18 (Note: In the calculation, the unit of each length is meter, and the unit of elastic modulus E is Pa), thus we get:

[0241] (twenty four)

[0242] From formula (24), we can see that u max The value is related to the pipe diameter and pipe thickness.

[0243] 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, u max =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.

[0244] Table 1 Nominal wall thickness and absolute deformation of DN=600mm pipe at various nominal pressures

[0245]

[0246] 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).

[0247] As shown in Table 1, if the base tubes purchased by secondary processing companies or users are processed in accordance with the industry standards, the base tubes numbered 1, 2, and 3 in Table 1 have a spigot thickness greater than 5.7 mm and an absolute deformation less than 22.86 mm, which meet the deformation requirements. However, the base tubes numbered 4, 5, and 6 have a spigot thickness less than 5.7 mm and an absolute deformation greater than 22.86 mm, which do not meet the deformation requirements.

[0248] If the pipe requirement for a particular application is to maintain a nominal pressure of less than 2 MPa, users will generally choose pipe numbered 4 in Table 1 rather than pipe numbers 1, 2, or 3 to meet deformation requirements. While these three options would meet both strength and deformation requirements, they are thicker and cost significantly more than pipe numbered 4. While pipe numbered 4 provides sufficient strength, its strength meets the requirements. To address deformation requirements, some measures can be taken, such as inserting an annular reinforcement ring inside the socket to increase its thickness and improve its ability to resist deformation, and this is a relatively low-cost measure.

[0249] Step a4: For a base pipe whose socket thickness is less than the minimum thickness obtained in step a3, at least one annular reinforcement ring is sleeved into 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 only needs to be no 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, proceed to step a5.

[0250] For example, in certain applications, the pipe material requirement is to meet a nominal pressure of less than 1.6 MPa. The selected base pipe is material No. 5 in Table 1, with a wall thickness of 4 mm. If the reinforcement ring is made of the same material as the base pipe, the thickness of the reinforcement ring must be at least 1.7 mm to meet the deformation requirement. In this case, the thickness of the composite splice must be at least 5.7 mm.

[0251] 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 thickness of the socket of the base pipe and the calculation formula of the bending strength 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.

[0252] In this embodiment, the calculation formula for the bending strength of the longitudinal composite beam is as follows:

[0253] (25)

[0254] 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 i-th section around its own centroid axis, E i is the elastic modulus of the corresponding material. E is the elastic modulus of the base tube material. I is the moment of inertia of the cross section corresponding to the minimum thickness obtained in step a3.

[0255] 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.

[0256] The following is an example to illustrate this.

[0257] For the composite spigot of this embodiment, the use requirement of the pipe in certain occasions is to meet the nominal pressure within 1.6MPa. The base pipe selected is the pipe No. 5 in Table 1, which has a wall thickness of 4mm. The composite spigot includes the base pipe spigot and the 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. The thickness of the whole reinforcement ring is set to x ,like Figure 15 The figure shows the cross section of the composite socket or composite beam per unit length, 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 reinforcement ring is made of 304 stainless steel. Figure 15 The distance from the center point of the cross section shown (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 , E i =193, C i =2, substituting into (25) we get:

[0258]

[0259] Obtain: x =1.73mm.

[0260] Therefore, the total thickness of the reinforcement ring is not less than 1.73 mm, and the thickness of the socket backing ring 5 is not less than half of 1.73 mm, that is, 0.865 mm.

[0261] Based on the above, the design calculation of the minimum thickness of the composite socket is completed.

[0262] The design method of the thickness of the composite socket is as follows:

[0263] 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 Figure 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. The corresponding inner diameters are: D2, D1, (D3-2F0), D3, D4, (D0-2S), among which 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, second step 112, third step 113, fourth step 114, and fifth step 115 are T3, T4, T5, (T2-T4-T5), and (T1-T2-T3), respectively. T1 is the sum of the lengths of the first step 111, second step 112, third step 113, fourth step 114, and fifth step 115, and T2 is the sum of the lengths of the second step 112, third step 113, and fourth step 114. These lengths refer to the axial dimensions of the corresponding portions of the base pipe. S is the wall thickness of the pipe, and F0 is the height of the third step 113 protruding from the fourth step 114, with F0 ≥ 0. The connection points of each step are chamfered. The chamfer at the connection between the fourth step 114 and the fifth step 115 is the first chamfer R1, the chamfer at the connection between the fifth step 115 and the sixth step 116 is the second chamfer R2, the chamfer at the connection between the second step 112 and the third step 113 is the third chamfer R3, the chamfer at the connection between the first step 111 and the second step 112 is the fourth chamfer R4, and the chamfer at the connection between the third step 113 and the fourth step 114 is the fifth chamfer R5. D0 is the outer diameter of the base pipe.

[0264] The above inner wall shape and size are generally specified for single-layer sockets. The size and shape of the inner wall of a composite socket can also be designed in accordance with the above-mentioned single-layer socket regulations. In this solution, the size and shape of the inner wall of a composite socket are also designed in accordance with the above-mentioned single-layer socket regulations.

[0265] Assume that the outermost layer of the composite socket is the base layer F1, and the remaining layers are the non-base layer F2. The thickness of the base layer F1 is uneven, while the thickness of the non-base layer F2 is uniform. In other words, the thickness of the base layer F1 varies or is not exactly the same at all locations, while the thickness of the non-base layer F2 is uniform at all locations.

[0266] For composite sockets, since the dimensions of the inner wall are fully specified in relevant standards, it is necessary to design certain key dimensions of the outer wall and the thickness of each non-base layer F2 based on this, aiming to achieve both material savings and strength requirements while also meeting them. In other words, the goal of this solution is to design the thickness of the composite socket to achieve the minimum or near-minimum thickness while still meeting operational strength requirements, thereby reducing pipe production, manufacturing, and transportation costs.

[0267] Based on material mechanics knowledge and experience, the points where stress is most likely to concentrate 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:

[0268] Mechanical knowledge indicates that stress concentration on the inner wall of the stepped bell 11 occurs at the junctions of adjacent steps, i.e., at the chamfers. Because the bell 11 is shaped like a trumpet, the outer diameter of the bell 11 decreases from the bell 11 to the spigot 13 of the same base pipe.

[0269] 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 shaped like a trumpet. 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 will definitely 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 shaped like a trumpet. 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 will definitely 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 thicknesses 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.

[0270] 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 As shown in Figure 16. At this time, along the axis of the socket, one part is a single-layer structure, that is, there is no non-base layer F2 and 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 the base layer F1. In this solution, the fourth step 114 and the fifth step 115 are located in the multi-layer structure part. Figure 16 shown.

[0271] 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.

[0272] For a single-layer structure, it is only necessary to ensure that the strength requirements are met at the point where the stress is maximum, and then the entire single-layer structure will meet the strength requirements.

[0273] For a single-layer structure of a composite socket, the design method includes the following steps:

[0274] Step b1: Select at least one location of the single-layer structure where stress is likely to concentrate. The selection principle is: if the wall thickness of each location meets the stress strength requirement, then the wall thickness of each location of the single-layer structure meets the strength requirement.

[0275] Step b2: Determine the minimum wall thickness of each selected location in step b1. 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.

[0276] 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. It is only necessary to ensure that the thickness of the third chamfer R3 meets the strength requirements, and the entire single-layer structure meets the strength requirements.

[0277] 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:

[0278] (26)

[0279] 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:

[0280] (27)

[0281] in, αThe semi-cone angle of the conical shell, or half of the opening angle, is defined as the angle between the conical wall and the central axis in a cross-section passing through the cone's central axis. In step b1, base layer F1 is considered to consist of at least one pressure vessel with a conical inner wall and several internal reinforcement rings j, which are attached to the inner wall of the pressure vessel. In other words, base layer F1 is considered to consist of at least one conical pressure vessel with several internal reinforcement rings j. As long as the corresponding conical pressure vessel meets the strength requirements, base layer F1 will also meet the strength requirements. Therefore, ensuring that the conical pressure vessel meets the strength requirements is sufficient.

[0282] In step b1, take the second cone and the reinforcement ring on the inner wall of the second cone, such as Figure 17 The dashed line between the first chamfer R1 and the third chamfer R3 represents the inner wall section of the second cone. The first and third chamfers R1 and R3 are located on the inner wall of the second cone. The area between the first and third chamfers R1 and R3, the portion between the inner wall of the second cone and the outer wall of the socket 11, represents the entire sidewall of the second cone. The portion between the inner wall of the second cone and the inner wall of the socket 11 represents the annular reinforcement ring on the inner wall of the second cone.

[0283] exist Figure 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 pipe is the semi-cone angle of the second cone, which is set to α2.

[0284] but:

[0285] (28)

[0286] 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:

[0287] (29)

[0288] Then we have:

[0289] (30)

[0290] Among them, S b3 is the wall thickness of the base layer F1 at the third chamfer R3, S is the wall thickness of the tube body, and we get:

[0291] (31)

[0292] 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. According to formula (27), stress is proportional to pressure and inversely proportional to 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:

[0293] (32)

[0294] That is, the minimum wall thickness at the third chamfer R3 is: .

[0295] If the material of the base layer 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 of the base layer 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:

[0296] (33)

[0297] Then we have:

[0298] (34)

[0299] Considering the pressure of the sealing ring, the wall thickness at the third chamfer R3 is:

[0300] (35)

[0301] 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.

[0302] For a multi-layer structure of a composite socket, the design method includes the following steps:

[0303] Step c1: Based on the same strain in 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.

[0304] 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: 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.

[0305] Step c3: Calculate the thickness of the non-base layer and / or base layer according to the relationship determined in step c2.

[0306] In step c1, the multi-layer structure is considered to consist of at least one pressure vessel with a conical inner wall and several internal reinforcement rings j, which are connected to the inner wall of the pressure vessel. In other words, the multi-layer structure is considered to consist of at least one conical pressure vessel and several internal reinforcement rings j. In this case, as long as the corresponding conical pressure vessel meets the strength requirements, the multi-layer structure will also meet the strength requirements. Therefore, it is sufficient to ensure that the conical pressure vessel meets the strength requirements.

[0307] In this solution, for the multi-layer structure, the two places where the stress is most concentrated are the first chamfer R1 and the second chamfer R2. Figure 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, and the second cone and the first cone are two coaxially connected conical pressure vessels. They share the same central axis with the socket 11. Figure 16 and 17 The dashed line between the first chamfer R1 and the second chamfer R2 represents the inner wall section of the first cone. The first and second chamfers R1 and R2 are located on the inner wall of the first cone. The section between the inner wall of the first cone and the outer wall of the socket 11 constitutes the entire sidewall of the first cone. The section between the inner wall of the first cone and the inner wall of the socket 11 (the innermost non-base layer F2) constitutes an annular reinforcement ring j.

[0308] 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:

[0309] (36)

[0310] 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.

[0311] For a composite socket, assuming there are m layers of non-base layer F2 and one layer of base layer F1, then:

[0312] (37)

[0313] 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.

[0314] 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, that is, satisfying:

[0315] (38)

[0316] Right now:

[0317] (39)

[0318] 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.

[0319] The stresses in formula (37) are all expressed as 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:

[0320] (40)

[0321] Formula (40) can be rearranged to obtain the hoop stress of the nth non-base layer F2:

[0322] (41)

[0323] Step c1 is thus completed.

[0324] 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 must meet the following conditions:

[0325] (42)

[0326] (43)

[0327] Among them, Q0, Q n The yield strength of the material of the pipe body and the nth non-base layer F2 is Q, and the yield strength of the material 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.

[0328] Combining formulas (41), (42), and (43), we get:

[0329] (44)

[0330] Formula (44) is the relationship between the thickness of any non-base layer F2 and the thickness of the base layer F1.

[0331] 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.

[0332] 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 set as 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.

[0333] 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 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 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 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 non-base layer F2. Formula (42) is rewritten as:

[0334] (45)

[0335] 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, that is, the first cone, Taking the maximum value, 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 layer of non-base layer F2. That is, the thickness of non-base layer F2 is Sn. The half cone angle is α 1. In Figure 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:

[0336] (46)

[0337] Substituting formulas (43) and (46) into formula (45), we can obtain:

[0338] (47)

[0339] From formula (47), we get:

[0340] (48)

[0341] In this embodiment, S b Take the thickness of the base layer F1 at the first chamfer R1.

[0342] 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 find S n The minimum value of .

[0343] Therefore, according to formula (48), the minimum thickness of the non-base layer F2 with the minimum yield stress can be obtained, and the thickness of other non-base layers F2 must not be less than this value.

[0344] For the base layer F1, the thickness S of the base layer F1 at the first chamfer R1 is b1 It has been 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.

[0345] For the thickness S of the base layer F1 at the second chamfer R2 b2 , can be given directly or set to the thickness S of the base layer F1 at the first chamfer R1 b1 Equal, can also be obtained using formula (44), specifically, formula (44) is rewritten as:

[0346] (49)

[0347] but:

[0348] (50)

[0349] The thickness S of the nth non-base layer F2 has been calculated from formula (48): n , and the thickness of other non-base layers is not less than S n , then formula (50) becomes:

[0350] (51)

[0351] The thickness S of the base layer F1 at the second chamfer R2 is obtained from formula (51): b2 .

[0352] Based on the above, the thickness of each non-base layer and the thickness of the base layer F1 at the first chamfer R1, second chamfer R2, and third chamfer R3 are calculated. Based on the aforementioned requirement for the trumpet-shaped outer wall of the socket 11, the outer walls corresponding to each chamfer are sequentially connected to obtain the thickness of each location of the base layer F1 and the thickness of each location of the composite socket. The outer diameter of the end face of the socket can be larger than the outer diameter at the third chamfer R3, and the specific value can be flexibly selected.

[0353] When the non-base layer F2 has only one layer, that is, the conical shell is a double-layer material, then formula (37) is as follows:

[0354] (52)

[0355] Formulas (38) and (39) are organized as follows:

[0356] (53)

[0357] 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), we can rearrange formula (52) to get:

[0358] (54)

[0359] Formula (54) can be rearranged to obtain the hoop stress of the non-base layer F2:

[0360] (55)

[0361] In step c2, in this embodiment, formula (47) is as follows:

[0362] (56)

[0363] The thickness of the non-base layer F2 is:

[0364] (57)

[0365] That is, the minimum thickness of the non-base layer F2 is: .

[0366] At this time, formula (50) is: (58)

[0367] A specific case is shown below.

[0368] 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 Sb of the first chamfer R1 of the base layer F1 is 6 mm.

[0369] According to formula (57), the thickness of the non-base layer F2 is calculated to be Sn≥2.38 mm, and the thickness of other non-base layers is not less than 2.38 mm.

[0370] The thickness S of the base layer F1 at the second chamfer R2 is 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, take Sn=2.38 mm, substitute the parameters into formula (57), and calculate S b2 ≥5.68 mm.

[0371] The thickness S of the base layer F1 at the third chamfer R3 is b3 , obtained by formula (32), substituting each parameter into formula (32), and obtaining S b3 ≥10.53 mm.

[0372] 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 b3The 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:

[0373] (59)

[0374] 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 Figure 18 shown.

[0375] In the second case, when the thickness of the non-base layer F2 is limited, as in this embodiment, a bell collar 6 made of a corrosion-resistant material is sleeved within the bell 11. The sleeve thickness is generally around 1 mm, which corresponds to the known thickness of the non-base layer F2. To ensure that the composite bell formed after the sleeve collar meets the strength requirements, the thickness of the base layer F1 must be calculated and designed under this premise.

[0376] Based on this, formula (44) is rewritten as:

[0377] (60)

[0378] 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 layer of 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.

[0379] The thickness of the base layer F1 at the first chamfer R1 is S b1 , D in formula (60) is D3, and the half cone angle α for α 1, then formula (60) is:

[0380] (61)

[0381] The thickness of the base layer F1 at the second chamfer R2 is S b2 , D in formula (60) is D4, and the half cone angle α for α 1, then formula (60) is:

[0382] (62)

[0383] 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 requirements, the composite socket meets the strength requirements.

[0384] A specific case is shown below.

[0385] 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, with 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 lining ring 6 is sleeved inside, that is, a non-base layer F2 is provided. The parameters of the lining ring 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:

[0386] S b1 ≥7.33 mm, S b2 ≥7.01 mm, S b3 ≥10.53 mm.

[0387] 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 , D in formula (60) is D1, and the half cone angle α for α 2, then formula (60) is:

[0388] (63)

[0389] Example 2

[0390] like Figure 3As shown, the structure of the composite pipe of this embodiment differs from that of the first embodiment in that, in this embodiment, the inner wall of the bell mouth 11 and the bell mouth lining ring 6 are not directly attached to each other. Instead, a stabilizing layer 8 is provided between the inner wall of the bell mouth 11 and the bell mouth lining ring 6. A stabilizing layer 8 is also provided between the outer wall of the spigot 13 and the spigot lining ring 5. The stabilizing layer 8 is made of hot melt adhesive or glue.

[0391] In this embodiment, the stainless steel rings (socket lining ring 6 and spigot lining ring 5) are bonded to the metal outer tube 1 by hot melt adhesive or glue, which can prevent the stainless steel rings from loosening during the pipe loading and unloading and installation process.

[0392] The manufacturing method of the composite pipe of this embodiment differs from that of the first embodiment in that, before installing the spigot liner 5, the surface of the outer wall of the spigot 13 where the spigot liner 5 is to be installed is first heated, then hot melt adhesive powder is sprayed or rotationally molded, and finally, the outer portion of the spigot liner 5 is sleeved onto the outer wall of the spigot 13. Similarly, before installing the bell liner 6, the surface of the inner wall of the bell 11 where the bell liner 6 is to be installed is first heated, then hot melt adhesive powder is sprayed or rotationally molded, and finally, the bell liner 6 is sleeved into the bell 11. The bell 11 and spigot 13 are then heated to composite the spigot liner 6 with the bell 11, and the spigot liner 5 with the spigot 13.

[0393] 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 one, and the hot melt adhesive on the outer wall of the socket 13, the hot melt adhesive on the end face of the socket 13 and the hot melt adhesive on the middle layer 3 are connected as one.

[0394] In this embodiment, the hot melt adhesive between the socket liner 6 and the socket 11 barely increases the strength of the composite socket. Therefore, the composite socket in this embodiment is equivalent to that in the first embodiment, consisting of the socket 11 and the socket liner 6. Similarly, the composite socket in this embodiment is identical to that in the first embodiment. Therefore, the thickness of the composite socket in this embodiment and the method for calculating the composite socket thickness are the same as those in the first embodiment.

[0395] Example 3

[0396] like Figure 5 As shown, the structure of the composite pipe of this embodiment is different from that of embodiment 1 in that, in this embodiment, the inner wall of the socket 11 and the socket lining ring 6 are not directly fitted together, and a sealing gasket 4 is provided between the inner wall of the socket 11 and the socket lining ring 6. Preferably, the sealing gasket 4 is integrally connected with the sealing gasket 4 between the inner tube 2 and the socket lining ring 6.

[0397] 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. These two sealing gaskets 4 are integrally connected to the sealing gasket 4 between the inner pipe 2 and the socket lining ring 5.

[0398] Rubber sealing gaskets 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.

[0399] The manufacturing method of the composite pipe of this embodiment differs from that of the first embodiment in that, before installing the spigot liner 5, the sealing gasket 4 is first installed. 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 tube 2, the end face of the inner tube 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 5 is installed.

[0400] Similarly, before installing the bell collar 6, the gasket 4 is also installed. The gasket 4 is tightly attached to the inner wall of one end of the composite pipe, that is, the gasket 4 is tightly attached to the inner wall of the bell 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. The bell collar 6 is then installed. Alternatively, the gasket 4 can be first placed on the outer surface of the bell collar 6, and then inserted into the bell 11 end of the composite pipe.

[0401] Similar to the second embodiment, the sealing gasket between the socket lining ring 6 and the socket 11 of this embodiment can hardly improve the strength of the composite socket. Therefore, the composite socket in this embodiment is equivalent to that in the first embodiment. Similarly, the composite socket in this embodiment is the same as that in the first embodiment.

[0402] Example 4

[0403] The difference between this embodiment and the first, second and third embodiments is the structure of the socket 11 and the number of sealing rings 7. The number of sealing rings 7 can be two or more, and the structure of the corresponding socket 11 is also different.

[0404] 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 mounting portion 119 and a transition portion 117, which are integrally connected and arranged in sequence along the same centerline. The sealing ring mounting portion 119 is a cylindrical structure, and the inner wall of the sealing ring mounting portion 119 is provided with at least two spaced-apart annular grooves, which are co-centerline with the composite pipe. The grooves are sealing ring mounting grooves 118. The transition portion 117 includes a cylindrical portion and a frustum portion, and the sealing ring mounting portion 119, the cylindrical portion, the frustum portion, and the pipe body 12 are sequentially connected. The inner diameter of the cylindrical portion is larger than the inner diameter of the pipe body 12.

[0405] In this embodiment, two sealing ring installation grooves 118 are provided on the inner wall of the bell mouth 11. The bell mouth lining ring 6 covers the inner wall of the cylindrical portion of the bell mouth 11, the inner wall of the frustum portion, and the inner wall of the sealing ring installation groove 118 close to the cylindrical portion. The bell mouth lining ring 6 does not cover the inner wall of the sealing ring installation groove 118 away from the cylindrical portion.

[0406] Based on the above structure, Figure 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 a sealing ring installation groove 118. Similarly, the inner ring of at least one sealing ring 7 contacts 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 liner 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 liner 6 at one end of the socket 11 of the adjacent composite pipe.

[0407] 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.

[0408] 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 Example 1, the minimum thicknesses of the base layer F1 of the composite socket of Example 1 at the first chamfer R1, the second chamfer R2 and the second chamfer R3 can be calculated according to the method of Example 1, and the minimum thickness of the base layer F1 of this embodiment can be set to not less than the minimum thickness of the base layer F1 of the composite socket of Example 1.

[0409] 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) being bonded together via the intermediate layer (3), the outer pipe (1) comprising a socket (11), a pipe body (12) and a spigot (13) which are connected in sequence, the inner wall of the socket (11) being provided with a step and / or a groove, a socket lining ring (6) being provided at one end of the socket (11) of the composite pipe, the socket lining ring (6) covering a portion of the inner wall of the socket (11) and one end of the inner wall of the inner pipe (2), a spigot lining ring (5) being provided at one end of the spigot (13) of the composite pipe, the spigot lining ring (5) covering the spigot (13); 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 composite socket 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: 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.

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 claim 1, 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 symmetrical with respect to the center of the circle, the first form of the differential equation is transformed into the 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.

7. The composite pipe according to claim 1, 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.

8. The composite pipe according to claim 1, 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, φ 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.

9. The composite pipe according to claim 8, 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: .

10. The composite pipe according to claim 1, 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.

11. The composite pipe according to claim 1, 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).

12. The composite pipe according to claim 11, 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.

13. The composite pipe according to claim 12, 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, l 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.

14. The composite pipe according to claim 13, 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 layer of non-base layer (F2) is combined to obtain the relationship between the thickness of the nth layer of non-base layer (F2) and the thickness of the base layer (F1): .

15. The composite pipe according to claim 14, 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).

16. 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.

17. The manufacturing method according to claim 16, characterized in that: When manufacturing the spigot bushing (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 spigot (13). The other end of the inner tube part and / or the other end of the outer tube part is bent and attached to the end surface of one end of the spigot (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 spigot (13) of the composite pipe. The outer tube part of the spigot bushing (5) and the outer wall of the spigot (13) are welded together, or hot melt adhesive is sprayed or coated on the outer wall of the spigot (13) before installing the outer tube part.

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