A kind of multi-layered socket-and-spigot pipe with corrosion-resistant metal lining and its manufacturing method

Abstract

The present invention discloses a multi-layered socket-and-spigot pipe with a corrosion-resistant metal lining and a manufacturing method thereof. The 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 wall of the socket is provided with a step or a groove. The outer pipe comprises a socket, a pipe body and a socket which are connected in sequence. At least one layer of the inner pipe and the outer pipe is made of a metal material. The manufacturing method comprises the following: S1: treating the outer pipe, making the inner pipe and the intermediate layer; S2: arranging the inner pipe, the intermediate layer and the outer pipe from the inside to the outside; S3: pressing the inner pipe and the intermediate layer onto the outer pipe; S4: compounding; when the material of the intermediate layer is plastic or rubber, there is no step S4. The stainless steel lining of the present invention prevents the outer pipe from rusting and polluting the water quality. The intermediate layer separates the inner and outer pipes to prevent the inner pipe from electrochemically corroding. A lining ring and a sealing gasket are arranged at the end of the pipe to prevent the bonding surface ends between the layers of materials from contacting with water to pollute the water and the lining from being washed away. The minimum thickness of the composite socket and the minimum thickness of the single-layer socket can be obtained by theoretical calculation.

Description

Technical Field

[0001] The invention belongs to the technical field of pipes, and in particular relates to a socket-and-spigot type multi-layer pipe with a corrosion-resistant metal lining and a manufacturing method thereof. Background Art

[0002] Composite pipes are widely used pipes, often used in liquid transportation pipe network systems. They are generally of a socket-and-spigot structure, including an outer metal pipe and an inner plastic pipe, that is, the plastic pipe is used as an inner lining, one end of the metal pipe is a spigot, and the other end is a socket. During installation, multiple composite pipes are connected in sequence, and the spigot of a composite pipe is inserted into the socket of the adjacent composite pipe. However, the thermal expansion coefficient of the plastic pipe lining is quite different from that of the metal outer pipe. The inner and outer pipes will produce a certain amount of internal stress that separates them from each other due to temperature changes, which will cause the lining to delaminate. In addition, liquids can easily penetrate from the pipe ends, causing the outer pipe to rust and contaminate the transported liquid, and causing the end faces of each layer to peel off and delaminate. The inner layer may even be washed away under long-term scouring.

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

[0004] However, when a pipe network fails, for example, a pipe bursts in the pipe network, water in the pipe network will spray out from the burst pipe, and the pressure in the pipe network will drop rapidly, even forming negative pressure. In addition, the pipe will also be subject to some external pressure, for example, the pipe buried in the soil will be subject to the gravity of the soil above it. Under the above external pressure and internal negative pressure, the pipe will deform radially. If the deformation of the socket is too large, the socket will separate from the socket connected to it, causing leakage at the connection between the socket and the socket, causing the inside of the water pipe to be contaminated. Therefore, it is necessary to ensure that the deformation of the socket of the pipe does not exceed a certain range under the above circumstances. To this end, for the socket, the minimum socket thickness that meets the deformation requirements must be obtained. If the socket thickness of the selected pipe is less than the minimum socket thickness that meets the deformation requirements, measures need to be taken to make it meet the deformation requirements. For example, when the pipe is secondary processed or installed, at least one layer of annular reinforcement ring is sleeved on the socket to form a composite socket to enhance the ability to resist deformation. However, the material of the reinforcement ring is often different from that of the base pipe. Since the reinforcement ring is in direct contact with the water in the pipe, it needs to be made of corrosion-resistant materials such as stainless steel, while the base pipe generally uses relatively cheap materials such as ductile iron and Q235. Therefore, how to ensure that the above-mentioned composite socket meets the maximum deformation requirements while the thickness is minimum or close to the minimum becomes a problem to be solved. The existing standards do not give the wall thickness requirements for the socket that is plugged into the composite socket, 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 each part of the socket minimum or close to the minimum while meeting the use strength.

[0005] The base pipe refers to the pipe in the factory setting, that is, the base pipe has no reinforcement ring installed and no secondary processing such as composite process. The base pipe includes a socket, a pipe body and a spigot connected in sequence. The pipe body can be divided into two parts, namely the main body and the transition part. The transition part is used for the transition connection between the main body and the socket, that is, the socket, the transition part, the main body and the spigot are connected in sequence. The inner wall surface of the pipe body is a cylindrical surface, that is, the inner diameter of the transition part is equal to the inner diameter of the main body. The main body is cylindrical, and the outer wall surface of the transition part is a conical surface. In other words, the thickness of the main body is basically uniform everywhere, and the thickness of the transition part gradually decreases along the direction from the socket to the spigot. The outer diameter of the pipe body refers to the outer diameter of the main body, and the thickness of the pipe body refers to the thickness of the main body. The outer diameter of the base pipe is the outer diameter of the pipe body. Fig.10 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. Summary of the invention

[0006] In view of the above-mentioned problems existing in the prior art, the purpose of the present invention is to provide a socket-type multi-layer pipe with a corrosion-resistant metal lining and a manufacturing method thereof. The inner pipe of the corrosion-resistant metal material is used as the inner lining to prevent the outer pipe from rusting and polluting the water quality. The thickness of the inner lining is relatively small, which improves the water conveyance efficiency of the pipeline and reduces the operating energy consumption. The middle layer is made of hot melt adhesive, plastic or rubber of insulating material, which completely separates the inner pipe and the outer pipe to prevent the outer pipe and the inner pipe from contacting and causing electrochemical corrosion of the inner pipe, and at the same time eliminates the disadvantage of using ordinary liquid glue in the middle layer. When the middle layer is hot melt adhesive, the hot melt adhesive bonds the inner and outer layers together. When the middle layer is rubber, the elasticity of the rubber causes the metal outer pipe and the corrosion-resistant metal inner pipe to form mutual elastic force, which has good sealing performance for the inner wall of the metal pipe. Corrosion-resistant metal lining rings and rubber sealing pads are arranged at the ends of the pipe to prevent water pollution caused by contact between the ends of the bonding surfaces of the layers of materials and the inner lining from being washed away.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] A multi-layered socket-and-spigot pipe with a corrosion-resistant metal lining comprises an inner pipe, an intermediate layer and an outer pipe which are sleeved in sequence from the inside to the outside, the inner wall of the socket is provided with steps and / or grooves, the inner pipe, the intermediate layer and the outer pipe are bonded to form the pipe or compressed to form the pipe, the outer pipe comprises a socket, a pipe body and a spigot which are connected in sequence, and at least one layer of the inner pipe and the outer pipe is made of metal material.

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

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

[0011] Preferably, the middle layer is made of non-metallic material.

[0012] More preferably, the material of the middle layer is hot melt adhesive.

[0013] More preferably, the material of the middle layer is plastic.

[0014] More preferably, the material of the middle layer is rubber.

[0015] The inner tube is made of corrosion-resistant material.

[0016] The thickness of the middle layer is not less than 0.2mm, and the thickness of the inner tube is not less than 0.1mm.

[0017] At the socket end, the end face of the inner tube, the end face of the middle layer and the end face of the pipe body are all flush; at the spigot end, the end face of the inner tube, the end face of the middle layer and the end face of the spigot are all flush.

[0018] Each end of the pipe is provided with a sealing gasket and a lining ring. At the socket end, the sealing gasket covers the end face of the pipe body, the end face of the middle layer, the end face of the inner tube and the inner wall of one end of the inner tube. At the plug end, the sealing gasket covers the end face of the plug, the end face of the middle layer, the end face of the inner tube and the inner wall of the other end of the inner tube. The lining ring presses the sealing gasket. When in use, the lining ring and the sealing gasket at one end of the plug form a full seal with the end face of the plug, and the lining ring and the sealing gasket at one end of the socket form a full seal with the end face of the pipe body.

[0019] The sealing gasket includes a sealing gasket pressing edge and a sealing gasket flange. The sealing gasket pressing edge is cylindrical and the sealing gasket flange is annular. The lining ring includes a lining ring pressing edge and a lining ring flange. The lining ring pressing edge and the lining ring flange are an integral whole. The lining ring pressing edge is cylindrical and the lining ring flange is annular. The lining ring pressing edge presses the sealing gasket pressing edge tightly and the lining ring flange presses the sealing gasket flange tightly.

[0020] The length of the liner ring edge shall not be less than 20mm.

[0021] The socket is a single-layer socket, and the spigot and the inner tube covering the inner wall of the spigot form a composite spigot.

[0022] The design method of the composite socket thickness includes the following steps:

[0023] 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;

[0024] 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;

[0025] 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;

[0026] 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.

[0027] 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.

[0028] The design method of single-layer socket thickness includes the following steps:

[0029] Step b1: Select multiple locations on the inner wall of the single-layer socket where stress is likely to be concentrated. The selection principle is: if the wall thickness of these locations meets the stress strength requirements, then the wall thickness of each location of the single-layer socket designed according to the outer wall design requirements meets the strength requirements;

[0030] Step b2: Determine the minimum wall thickness of each selected location in step b1, and obtain the outer wall of each selected location. The determination principle is: when the material of the single-layer socket 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 socket 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 socket 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.

[0031] Step a2 includes the following steps:

[0032] 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;

[0033] 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;

[0034] 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;

[0035] 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.

[0036] Step a3 includes the following steps:

[0037] 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;

[0038] Step a32: obtaining the maximum deformation of the reference pipe socket through simulation according to the parameters calculated in step a31;

[0039] 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;

[0040] 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.

[0041] In step a1, the radial deformation obtained isu The differential equation is:

[0042] ,

[0043] The general solution is: ,

[0044] 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, ; A 1 , A 2 , A 3 , B 2 , B 3 is a constant.

[0045] 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:

[0046] First, in Because of symmetry, The rotation angle of the section at is 0, which satisfies the following formula: ;

[0047] Second, due to symmetry, the total tangential displacement of the arc in each equally divided segment is 0; that is, ;

[0048] 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: ;

[0049] Combining the above three formulas with the general solution of the differential equation, we get the first form of the differential equation:

[0050] ;

[0051] 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:

[0052] ;

[0053] Introducing the coefficient m, we get the third form of the differential equation:

[0054] ;

[0055] Point of application of force P The point is the point of maximum deformation, and the change in the diameter of the ring is:

[0056] Where I = S 3 / 12, S is the thickness of the tube body.

[0057] 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.

[0058] For the same base pipe, along the direction from the single-layer socket to the spigot, the inner wall of the single-layer socket includes a first step, a second step, a third step, a fourth step, and a fifth step arranged in sequence, one end of the inner wall of the pipe body is a sixth step, the chamfer at the connection between the fourth step and the fifth step is a first chamfer, the chamfer at the connection between the fifth step and the sixth step is a second chamfer, the chamfer at the connection between the second step and the third step is a third chamfer, the chamfer at the connection between the first step and the second step is a fourth chamfer, and the chamfer at the connection between the third step and the fourth step is a fifth chamfer.

[0059] In step b2, the minimum wall thickness of each selected point in step b1 is calculated by the stress calculation formula, and the single-layer socket is regarded as a pressure vessel including at least two coaxially connected pressure vessels with conical inner walls and at least one annular reinforcement ring installed on the inner wall of the pressure vessel. , ,in, is the hoop stress of the pipe body, is the hoop stress at the selected location, D 0 is the outer diameter of the base tube, D is the diameter of the selected location, p is the pressure of the fluid in the base tube, S is the thickness of the base tube, S 0 is the wall thickness at the selected location, and α is the semi-cone angle of the cone at the selected location.

[0060] When the material of the single-layer socket is the same as that of the pipe body, the stress calculation formula is: .

[0061] When the material of the single-layer socket is different from that of the pipe body, the stress calculation formula is: , where Q0 is the yield strength of the pipe material, Q 1 It is the yield strength of the material used for single-layer socket.

[0062] A method for manufacturing a multi-layered bell-and-spigot pipe with a corrosion-resistant metal lining, for manufacturing the pipe, comprises the following steps:

[0063] Step S1: processing the outer tube, making the inner tube and the middle layer;

[0064] Step S2: Arrange the inner tube, the middle layer and the outer tube in sequence from inside to outside;

[0065] Step S3: Pressing the inner tube and the middle layer onto the outer tube;

[0066] Step S4: compounding;

[0067] When the material of the middle layer is plastic or rubber, there is no step S4.

[0068] The manufacturing method further comprises step S5: inserting a sealing gasket and a liner ring into each end of the pipe.

[0069] When the middle layer is hot melt adhesive or plastic, in step S1, a tubular middle layer can be made separately, and in step S2, the middle layer is put on the outside of the inner tube and then put into the outer tube as a whole; or powdered hot melt adhesive or plastic is first rotationally molded or sprayed on the inner wall of the outer tube, and then in step S2, the inner tube is put into the outer tube; or powdered hot melt adhesive or plastic is first rotationally molded or sprayed on the outer wall of the inner tube, and then in step S2, the inner tube is put into the outer tube.

[0070] The beneficial effects of the present invention are:

[0071] (1) The inner tube made of corrosion-resistant metal material is used as the inner lining to completely isolate the outer tube from the liquid flowing in the tube, effectively preventing the outer tube from rusting, playing a good anti-corrosion role, increasing the service life of the tube, avoiding the rust of the outer tube from polluting the water quality, and improving the liquid transportation performance.

[0072] (2) Compared with plastic pipe linings, the inner pipe made of corrosion-resistant metal material as the inner lining eliminates the inner surface wrinkles and uneven defects caused by the melting of the inner lining plastic during compounding, improves the flatness of the inner surface of the pipe, and has a smaller lining thickness, which improves the water delivery efficiency of the pipeline and reduces operating energy consumption.

[0073] (3) The inner pipe made of corrosion-resistant metal material is used as the inner lining. Compared with the plastic pipe lining, the pipe can be used to transport high-temperature liquid media.

[0074] (4) The middle layer is made of insulating hot melt adhesive, plastic or rubber, which completely separates the inner tube from the outer tube to prevent the outer tube from contacting the inner tube and causing electrochemical corrosion to the inner tube. At the same time, it eliminates the uneven glue layer caused by the flow of ordinary liquid glue in the middle layer, and the electrochemical corrosion caused by the direct contact between the inner lining corrosion-resistant metal and the outer metal tube without bonding. It also overcomes the problems of easy aging and poor insulation of ordinary glue.

[0075] (5) When the middle layer is hot melt adhesive, the hot melt adhesive will bond the inner and outer layers together to prevent the inner lining from being delaminated due to negative pressure in the pipeline. When the middle layer is rubber, the elasticity of the rubber will cause the metal outer tube and the corrosion-resistant metal inner tube to form a mutual elastic force, which has good sealing performance for the inner wall of the metal tube and can prevent the liquid from contacting the inner wall of the metal outer tube and causing corrosion of the tube wall.

[0076] (6) Corrosion-resistant metal liner rings and rubber gaskets are installed at the ends of the pipes to prevent the ends of the bonding surfaces between the layers of materials from coming into contact with water and peeling off due to the tension of water, thereby preventing the inner wall of the metal outer pipe from rusting and peeling off, causing water pollution. The liner rings and gaskets fix the inner pipe. When the seal fails and the inner liner is completely delaminated, they can still protect the inner liner from being washed away by the scouring effect of the water flow. The installation of liner rings and gaskets enhances the ring stiffness of the pipe port, makes the socket less likely to deform, facilitates the installation of the pipe, improves the uniform sealing effect of the gasket and the sealing ring at the connection between the two pipes, and reduces pipeline leakage.

[0077] (7) The minimum or near minimum thickness of the composite spigot that meets the deformation requirements of socket-and-spigot pipes of different diameters and the minimum or near minimum thickness of the single-layer spigot 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 pipes. The method for designing the minimum wall thickness is theoretical calculation, which is low in cost and high in efficiency. It provides strong support for experiments and pipe design and provides a reference for secondary processing and installation. After the thickness of the base pipe spigot is known, the minimum thickness of the reinforcement ring of the composite spigot that meets the deformation requirements can be calculated. The pipes and pipe network systems installed in this way are more reliable to 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0078] Figure 1 It is a schematic structural diagram of the pipe without sealing pads and lining rings at both ends of the pipe of the present invention.

[0079] Figure 2 It is a structural schematic diagram of the present invention when there are sealing gaskets and lining rings at both ends of the pipe.

[0080] Figure 3 yes Figure 2 An enlarged schematic diagram of point B.

[0081] Figure 4 yes Figure 2 An enlarged schematic diagram of point A.

[0082] Figure 5 Schematic diagram of the cross-section deformation before and after the socket is subjected to a pair of radially symmetrical concentrated forces.

[0083] Figure 6 for Figure 5 Schematic diagram of local analysis.

[0084] Figure 7 Schematic diagram of a circular ring subjected to multiple uniformly arranged radial concentrated forces.

[0085] Figure 8 This is the stress analysis diagram of socket-type pipe.

[0086] Fig. 9 The figure is a schematic cross-sectional view of a composite socket per unit length according to an embodiment of the present invention.

[0087] Fig.10 It is a schematic diagram of the socket and spigot connection of the present invention. DETAILED DESCRIPTION

[0088] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0089] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0090] A multi-layered socket-and-spigot pipe with a corrosion-resistant metal lining, the pipe is mainly used for passing water and corrosive liquids. Figure 1 and 2 As shown, it includes an inner tube 2, a middle layer 3 and an outer tube 1 which are sequentially sleeved from the inside to the outside.

[0091] The outer tube 1 is made of metal, preferably ductile iron or carbon steel. The outer tube 1 includes a socket 11, a tube body 12 and a spigot 13 connected in sequence along its axial direction. The three are integrally cast, or the tube body 12 and the spigot 13 are integrally formed, and the tube body 12 and the socket 11 are welded together. The spigot 13 is cylindrical, and the spigot 13 is chamfered along the circumferential direction. The inner diameter, outer diameter and thickness of the tube body 12 are equal to or unequal to the inner diameter, outer diameter and thickness of the spigot 13.

[0092] The inner tube 2 is made of a metal material with corrosion resistance, including but not limited to stainless steel and titanium, preferably stainless steel, and the inner tube 2 is cylindrical.

[0093] The material of the middle layer 3 is non-metal, preferably hot melt adhesive, plastic or rubber. When the material of the middle layer 3 is hot melt adhesive, the hot melt adhesive has adhesive properties, and the inner tube 2 and the outer tube 1 are bonded together through the middle layer 3; when the material of the middle layer 3 is plastic or rubber, the plastic or rubber does not have adhesive properties, and the inner tube 2 presses the middle layer 3 against the inner wall of the outer tube 1.

[0094] The length of the inner tube 2 is equal to the length of the middle layer 3, which is equal to the sum of the lengths of the pipe body 12 and the socket 13. At the end of the socket 11, the ends of the inner tube 2, the middle layer 3 and the pipe body 12 are flush; at the end of the socket 13, the ends of the inner tube 2, the middle layer 3 and the socket 13 are flush.

[0095] The thickness of the intermediate layer 3 is not less than 0.2 mm, and the thickness of the inner tube 2 is not less than 0.1 mm.

[0096] The main function of the inner tube 2 is corrosion protection, so its thickness should not be too large. A large number of welding tests have shown that under the conditions of fiber laser welding, a stainless steel plate with a minimum wall thickness of 0.1 mm can obtain a weld with high welding strength and small deformation. Taking into account the complexity of the welding process equipment, the investment cost, and the fact that the middle layer 3 shrinks at low temperatures due to its large thermal expansion coefficient, and generates internal stress that separates it from the outer tube 1, it is necessary to give full play to the supporting role of the inner tube 2 on the middle layer 3 to offset the internal stress of the outer tube 1 and the middle layer 3. The preferred thickness of the inner tube 2 is 0.1 mm-2 mm.

[0097] When the material of the middle layer 3 is hot melt adhesive, it acts as an adhesive layer. When the inner wall of the outer tube 1 is rough during compounding, the middle layer is heated and melted to fill the pits on the inner wall of the outer tube 1. If the thickness of the middle layer 3 is too small, poor adhesion is likely to occur in areas with large local roughness. At the same time, the middle layer 3 also acts as an insulating layer, and a certain thickness is required to produce an insulating effect between the outer tube 1 and the inner tube 2. The electric spark test and the peel strength test show that when the thickness of the middle layer 3 reaches 0.2mm or more, good peel strength and insulation performance can be stably obtained. The preferred thickness is 0.2mm-2mm.

[0098] Compared with the thickness of the inner lining stainless steel required by the standard "Inner lining stainless steel composite steel pipe (CJ / T 192-2017)", when the middle layer 3 uses hot melt adhesive, the inner lining stainless steel thickness is thinner and the cost is lower. When the inner diameter of the outer pipe 1 is the same, the inner diameter of the pipe is larger and the transportation efficiency is higher.

[0099] The conclusions of the lining peel strength test (this test uses an outer tube with an inner diameter of 100-300mm and an inner lining stainless steel thickness of 0.1mm-0.3mm) are as follows:

[0100] When the rust removal grade of the inner wall surface of the metal outer tube 1 reaches Sa2.5, the surface roughness is Ra12.5~Ra25, and the thickness of the intermediate layer 3 is not less than 0.2mm, the peel strength between the hot melt adhesive and the outer tube can stably reach more than 70N / cm; the peel strength between the hot melt adhesive and the inner lining can stably reach more than 150N / cm;

[0101] When the rust removal grade of the inner wall surface of the metal outer tube 1 reaches Sa2.5, the surface roughness is Ra25~Ra50, and the thickness of the intermediate layer 3 is above 0.2mm, the peel strength between the hot melt adhesive and the outer tube can stably reach above 120N / cm; the peel strength between the hot melt adhesive and the inner lining can stably reach above 150N / cm;

[0102] When the rust removal level of the inner wall surface of the metal outer tube 1 reaches Sa2.5, the surface roughness is greater than Ra50, and the thickness of the intermediate layer 3 is above 0.2 mm, the peel strength between the hot melt adhesive and the outer tube can stably reach above 150 N / cm; the peel strength between the hot melt adhesive and the inner lining can stably reach above 150 N / cm.

[0103] The peel strength between the hot melt adhesive and the lining of this solution can reach 150N / cm, and the corresponding bonding strength is 15MPa, that is, the pipe of this solution can withstand a liquid lateral scouring force of 15MPa, which is much greater than the maximum liquid lateral scouring force in the existing pipe network system.

[0104] When the middle layer 3 is hot melt adhesive, the thickness of the middle layer 3 is preferably 0.2 mm to 0.5 mm. When the thickness of the middle layer 3 is greater than 0.5 mm, the peel strength remains substantially unchanged.

[0105] A lining ring 5 and a sealing gasket 4 are provided at one end of the socket 13 of the pipe, and a lining ring 5 and a sealing gasket 4 are also provided at one end of the socket 11. The lining ring 5 is made of corrosion-resistant metal, preferably stainless steel, and the sealing gasket 4 is made of rubber. The sealing gasket 4 at one end of the socket 13 is used to cover and compress the end face and inner wall of the socket 13 of the pipe, and the lining ring 5 is pressed on the sealing gasket 4. The sealing gasket 4 at one end of the socket 11 is used to cover and compress the end face and inner wall of the pipe body 12 of the pipe near the socket 11, and the lining ring 5 is pressed on the sealing gasket 4.

[0106] like Figure 3 and 4 As shown, the sealing gasket 4 includes a sealing gasket pressing edge 41 and a sealing gasket flange 42, which are connected as one piece, and the sealing gasket pressing edge 41 can be regarded as a thin cylindrical shape, and the sealing gasket flange 42 is annular. The inner diameter of the sealing gasket flange 42 is equal to the inner diameter of the sealing gasket pressing edge 41, and the outer diameter of the sealing gasket flange 42 is greater than the outer diameter of the sealing gasket pressing edge 41. The sealing gasket pressing edge 41 and the sealing gasket flange 42 share a common center line.

[0107] The structure of the liner ring 5 is similar to that of the gasket 4. The liner ring 5 includes an integrally connected liner ring pressure edge 51 and a liner ring flange 52. The liner ring pressure edge 51 can be regarded as a thin cylindrical shape, and the liner ring flange 52 is annular. The inner diameter of the liner ring flange 52 is equal to the inner diameter of the liner ring pressure edge 51, and the outer diameter of the liner ring flange 52 is larger than the outer diameter of the liner ring pressure edge 51. The liner ring pressure edge 51 and the liner ring flange 52 share a common center line.

[0108] In this embodiment, the length H of the backing ring pressing edge 51 is not less than 20 mm and is less than the length of the socket 13 .

[0109] Figure 4 In the illustrated view, the upper end surface of the sealing gasket flange 42 does not extend beyond the upper end surface of the backing ring flange 52 .

[0110] At one end of the socket 11, the outer surface of the sealing gasket pressing edge 41 of the sealing gasket 4 fits the inner surface of the inner tube 2, and the inner surface of the sealing gasket pressing edge 41 fits the outer surface of the liner ring 5. One side of the sealing gasket flange 42 fits the end face of the inner tube 2, the end face of the intermediate layer 3 and the end face of the pipe body 12, and the other side of the sealing gasket flange 42 fits the liner ring 5. The liner ring pressing edge 51 of the liner ring 5 fits and compresses the sealing gasket pressing edge 41, and the liner ring flange 52 fits and compresses the sealing gasket flange 42.

[0111] At one end of the socket 13, the outer surface of the sealing gasket pressing edge 41 of the sealing gasket 4 fits the inner surface of the inner tube 2, and the inner surface of the sealing gasket pressing edge 41 fits the outer surface of the liner ring 5. One side of the sealing gasket flange 42 fits the end surface of the inner tube 2, the end surface of the intermediate layer 3 and the end surface of the socket 13, and the other side of the sealing gasket flange 42 fits the liner ring 5. The liner ring pressing edge 51 of the liner ring 5 fits and compresses the sealing gasket pressing edge 41, and the liner ring flange 52 fits and compresses the sealing gasket flange 42.

[0112] A method for manufacturing a multi-layer bell-and-spigot pipe with a corrosion-resistant metal lining, for manufacturing the pipe, comprises the following steps:

[0113] Step S1: Process the inner wall and outer wall of the outer tube 1, make the inner tube 2, and make the liner ring 5.

[0114] In this step, the method for processing the inner and outer walls of the outer tube 1 is to first grind the inner wall of the outer tube 1, and then sandblast or shot blast the inner and outer walls. Use an internal grinder to grind the inner wall of the outer tube 1 made of metal, grind the inner wall of the tube flat, and remove surface oxide scale, scum and rust. Alternatively, after the inner wall of the outer tube 1 is polished flat, use a laser cleaning machine to clean the inner wall of the tube to deeply remove the oxide scale and rust on the inner wall of the tube. When sandblasting or shot blasting, remove dust, oxide scale, and rust on the inner and outer walls, and sandblast the inner and outer walls of the tube into a frosted surface.

[0115] Making the inner tube 2 comprises the following steps:

[0116] Step S11: Process the stainless steel sheet into a ring shape or a thin cylindrical shape to complete the rolling. In this step, the rolling is performed by a rolling machine.

[0117] Step S12: Cut the rolled stainless steel sheet and weld it into a cylindrical shape to obtain the tube blank of the inner tube 2. In this step, if a single roll is obtained in step S11, a straight seam welding is performed using a argon arc welder or a laser welder, and the weld extends from one end to the other end of the inner tube 2. If multiple spirally connected rolls are obtained in step S11, a spiral seam welding machine is used to weld the multiple spirally connected rolls in sequence to form a thin cylindrical shape.

[0118] Preferably, the length of the stainless steel round tube obtained in step S12 is greater than the length of the inner tube 2 of the pipe material that is finally processed. Specifically, the length of the stainless steel round tube obtained in step S12 is greater than the sum of the length of the tube body 12 and the length of the socket 13.

[0119] When making the liner ring 5, two sections can be cut from the stainless steel round tube obtained in step S12 as the tube blank of the liner ring 5. Alternatively, the liner ring 5 can be made separately. The method for making the liner ring 5 is as follows:

[0120] Step S11': using a flanging and rolling machine to process the stainless steel sheet into a rolled shape with a flanging, that is, a structure with a liner ring pressing edge 51 and a liner ring flanging edge 52. In this step, the rolling is performed by a rolling machine.

[0121] Step S12 ′: using an argon arc welder or a laser welder to weld the rolled incision obtained in step S11 ′ to form the shape of the liner ring 5 .

[0122] Step S13': put the sealing gasket 4 on the outer wall of the liner ring 5 obtained in step S12'.

[0123] Step S2: Arrange the inner tube 2, the middle layer 3 and the outer tube 1 in sequence from the inside to the outside.

[0124] In this step, when the material of the middle layer 3 is hot melt adhesive or plastic, step S2 can be completed in the following three ways:

[0125] The first way is as follows:

[0126] First, the hot melt adhesive or plastic is formed into a round tube by extrusion molding, vacuum sizing, pulling, and cutting. Extrusion molding, vacuum sizing, pulling, and cutting can be performed by an extruder, a vacuum box, a tractor, and a cutting machine in the prior art. The extrusion molding is a prior art and will not be described in detail here.

[0127] Then, the obtained shaped intermediate layer 3 is sleeved on the outer wall of the inner tube 2. In this step, the sleeve can be made manually or by a sleeve machine.

[0128] Finally, the intermediate layer 3 and the inner tube 2 are inserted into the outer tube 1 as a whole. Similarly, in this step, the tube insertion can be completed manually or by a tube insertion machine.

[0129] The second way is as follows:

[0130] First, after the inner wall of the outer tube 1 is heated, a roller coating machine or a plastic coating machine is used to roll or spray powdered hot melt adhesive or plastic on the inner wall of the tube body 12 and the inner wall of the socket 13 of the outer tube 1. The thickness of the roll or spray coating is greater than 0.2 mm.

[0131] Then, the inner tube 2 is inserted into the outer tube 1 with the middle layer 3 on the inner wall.

[0132] The third way is as follows:

[0133] First, after heating the outer wall of the inner tube 2, a powdered hot melt adhesive or plastic is roto-molded or spray-molded on the outer wall of the stainless steel inner tube 2 using a roller coating machine or a plastic coating machine. The thickness of the roto-molding or spray-molding is greater than 0.2 mm. Then, the inner tube 2 with the intermediate layer 3 on the outer wall is inserted into the outer tube 1.

[0134] When the material of the middle layer 3 is rubber, the rubber sheet is first rolled onto the outer wall of the inner tube 2, and then the rubber seams are bonded with adhesive, and then the inner tube 2 with the rubber sleeve is inserted into the outer tube 1. Alternatively, the rubber tube is sleeved onto the outer wall of the inner tube 2 and then the entire tube is sleeved into the outer tube 1. The length of the rubber should be sufficient to cover the inner wall of the tube body 12 and the inner wall of the socket 13.

[0135] Step S3: Press the inner tube 2 and the middle layer 3 onto the outer tube 1 .

[0136] This step can be completed by spin forming or hydraulic forming. In spin forming, the inner tube 2 is spin-formed by a tube spinning machine so that the inner tube 2, the middle layer 3, and the outer tube 1 are closely attached in sequence. In hydraulic forming, the two ends of the inner tube 2 made of stainless steel that penetrates the outer tube 1 are sealed, and water is injected into the tube to increase pressure so that the inner tube 2, the middle layer 3, and the outer tube 1 are closely attached in sequence.

[0137] Step S4: Compounding.

[0138] In this step, the pipe is heated by a medium frequency inductor or a heating furnace, the hot melt adhesive is melted, and after cooling, the outer pipe 1 and the inner pipe 2 are bonded together.

[0139] When the material of the middle layer 3 is plastic or rubber, there is no step S4.

[0140] Step S5: Backing ring.

[0141] In this step, first, two lining rings 5 ​​with sealing gaskets 4 are manually placed at both ends of the pipe. Then, the lining rings 5 ​​are expanded by a diameter expander so that the lining rings 5 ​​press the sealing gaskets 4 against the inner wall and end surface of the pipe.

[0142] If the liner ring 5 tube blank is two sections cut from the stainless steel round tube obtained in step S12, then in this step, after the liner ring 5 with the sealing gasket 4 is inserted into the tube end, it is also necessary to perform flanging to form a liner ring flanging 52.

[0143] After completing the above steps, remove excess burrs and apply paint, plastic coating or other methods to the outer wall of the pipe for external anti-corrosion treatment.

[0144] In this embodiment, the socket 11 of the outer tube is made of a single material and can be regarded as a single-layer socket. The entire inner wall of the socket 13 is covered by the inner tube 2. Therefore, the socket 13 of the outer tube and the portion of the inner tube 2 covering the inner wall of the socket 13 can both improve the strength and deformation resistance of one end of the socket, and the socket formed by the two is a composite socket. Because the middle layer 3 is made of non-metallic flexible materials such as hot melt adhesive, rubber, and plastic, it has basically no effect on the strength and deformation resistance of the socket 13, so it does not belong to the category of composite sockets that can resist deformation. Although the liner ring 5 at one end of the socket 13 is made of metal, it does not cover the entire inner wall of the socket 13. The most vulnerable part of the socket 13 is composed of the socket 13 and the portion of the inner tube 2 covering the socket 13.

[0145] Next, the thickness of the spigot end and the socket end of the composite pipe is optimized and designed.

[0146] The design method of the thickness of the composite socket includes the following steps:

[0147] Step a1: Obtain the radial deformation of the ring based on the differential equation of the deflection curve and the moment equilibrium equation of the ring The differential equation and the general solution of the differential equation; Because the cross-section of the pipe body and the socket is a circular ring, the deformation of the socket is analyzed by analyzing the radial deformation of the circular ring. In addition, the cylinder of unit length can be regarded as a circular ring.

[0148] 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.

[0149] Step a3: The minimum thickness of the socket of the base pipe that meets the deformation requirements is obtained according to the calculation formula of the maximum radial deformation obtained in step a2.

[0150] 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.

[0151] Step a5: The material of the reinforcement ring is different from that of the socket of the base pipe. The minimum thickness of the reinforcement ring is obtained based on the socket thickness of the base pipe and the 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. In other words, the thickness of the composite socket of the pipe formed after the reinforcement ring is installed on the base pipe meets the deformation requirements and strength requirements.

[0152] The following is a detailed introduction to each step.

[0153] In step a1, the radial deformation obtained The differential equation is:

[0154] (1)

[0155] in ，R is half of the sum of the outer radius and the inner radius of the ring. In other words, R One quarter of the sum of the outer and inner diameters of the ring 。E is the elastic modulus of the pipe, Pa. I is the moment of inertia of the tube cross section, m 4 . M It is the bending moment borne by a certain section of the ring in the local area, in N*m. Establish a two-dimensional coordinate system, 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, In this embodiment, establish xy Coordinate system, point O is the coordinate origin and the center of the ring, such as Figure 5 Point m 1 The radial deformation at u， but om 1 and x The angle between the positive directions of the axes is φ.

[0156] The above differential equation (1) is obtained as follows:

[0157] like Figure 5 and 6 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 5 midpoint O Too xy Vertex of the coordinate system ， point m and n are two points on the ring before deformation; m 1 and n 1 are two points on the deformed shape of the ring, and the points m 1 and n 1 Located on the line segment om and on superior, φ The deformation is u The line connecting the point at and point O is x The angle between the positive directions of the axes, om and on The angle between φ, set up u Centripetal movement is positive. Figure 6 Middle, straight line m 1 t Passing point m 1 and perpendicular to the line segment om ,straight line m 1 t 1 For passing point m 1 A tangent line to n 1 t’ Passing point n 1 and perpendicular to on ,straight line n 1 t 1 ’ For passing point n 1 tangent.

[0158] Arc before deformation mn The arc length is ds , whose curvature isk 1 , arc after deformation m 1 n 1 The curvature is k 2 , du Yes m and Point n The difference in radial deformation is The arc before deformation mn exist m Tangent line of point and n The angle between the tangent lines of a point, The deformation amount is u The radius corresponding to the point at after deformation is Is an arc mn Deform to Arc m 1 n 1 back ds The increment of The arc after deformation m 1 n 1 exist m 1 Tangent line of point and n 1 The angle between the tangent lines of the point is m 1 t 1 and The angle between , then:

[0159] (2)

[0160] (3)

[0161] (4)

[0162] (5)

[0163] m 1 t 1 and m 1 t The angle between , n 1 t 1 ’ and n 1t’ The angle between .

[0164] m 1 Section to n 1 The variable for the cross-sectional rotation is :

[0165] (6)

[0166] 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.

[0167] Substituting formula (5) and (6) into formula (4) yields:

[0168] (7)

[0169] By series expansion we have:

[0170] Ignoring the higher-order terms, substituting the series expansion into (7) yields: (8)

[0171] Substituting (2) into (8), we obtain: (9)

[0172] Omitting the higher-order terms, we get: (10)

[0173] For a thin ring (i.e. a ring with a small difference between the outer and inner diameters relative to the diameter), we have: , by definition: ,therefore, , substituting into (10) we get, , combining formula (2) to obtain radial deformation The differential equation formula (1).

[0174] The general solution of the above differential equation (1) is:

[0175] (11)

[0176] Among them, A 1 , A 2 , A 3 , B 2 , B 3 is a constant. If the external force is symmetrical, the odd function terms in the solution can be deleted, so the deflection curve equation is:

[0177] (12)

[0178] Step a2: Calculating and obtaining a calculation formula for the maximum radial deformation of the ring according to the general solution of the differential equation obtained in step a1, comprising the following steps:

[0179] Step a21: Assume that the circular ring is subjected to at least two radial concentrated forces P that are symmetrical relative to the center of the circle. Based on this assumption, calculate the constant term in the general solution of the differential equation to obtain the first form of the differential equation.

[0180] Step a22: Based on the first form of the differential equation obtained in step a21, assuming that the annulus is subjected to only two radial concentrated forces P that are symmetrical relative to the center of the circle, the first form of the differential equation is transformed into the second form of the differential equation.

[0181] Step a23: Introduce the internal negative pressure on the annulus into the second form of the differential equation by introducing coefficients to obtain the third form of the differential equation.

[0182] 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.

[0183] 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 7 shown. Figure 5The circular ring shown in FIG. 1 is subjected to two radial concentrated forces P which are symmetrical relative to the center of the circle, and the two radial concentrated forces P are located on the y-axis.

[0184] The ring satisfies the following three boundary conditions:

[0185] First, in Because of symmetry, The rotation angle of the section at is 0, which satisfies the following formula:

[0186] (13)

[0187] Second, due to symmetry, the total tangential displacement of the arc in each equally divided segment is 0; that is,

[0188] (14)

[0189] 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:

[0190] (15)

[0191] in, dM represents the differential of M. It should be noted that the third point is not a real cut of the ring, but an assumption.

[0192] By combining formulas (13), (14) and (15), we get:

[0193] (16)

[0194] (17)

[0195] (18)

[0196] Substituting formulas (16), (17), and (18) into formula (12), we obtain:

[0197] (19)

[0198] Formula (19) is the first form of the differential equation obtained in step a21. is the radial deformation of the ring.

[0199] In step a22, if only one pair of radial forces P is applied to the ring, then , the deflection curve equation (19) becomes:

[0200] (20)

[0201] Formula (20) is the second form of the differential equation obtained in step a22.

[0202] 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:

[0203] (twenty one)

[0204] 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.

[0205] Formula (21) is the third form of the differential equation obtained in step a23.

[0206] In step a24, the maximum deformation is At the point where the force P acts, the change in the diameter of the ring is the maximum change in the diameter of the ring. u max :

[0207] (twenty two)

[0208] Formula (22) is the third form of the differential equation obtained in step a24.

[0209] Step a3: Calculate the minimum thickness of the base pipe that meets the deformation requirements based on the calculation formula of the maximum radial deformation obtained in step a2. It includes the following steps:

[0210] Step a31: Calculate the parameters of a reference pipe according to the existing shear load formula. The material and outer diameter of the reference pipe are respectively the same as the material and outer diameter of the base pipe.

[0211] Step a32: Obtain the maximum deformation of the reference pipe socket through simulation based on the parameters calculated in step a31.

[0212] 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.

[0213] 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.

[0214] In step a31, the shear load formula used is derived from the group standard "Corrosion-resistant steel pipe with socket-type flexible joint for water supply and drainage" (T / CISA 108-2021), which is:

[0215] (twenty three)

[0216] like Figure 8 As shown, W is the shear load, in Newton (N); F is the shear force acting on the interface, in Newton (N); M P is the weight of the test assembly steel tube and the weight of the object in the steel tube, in kilograms (kg); a The distance between the shear load application point and the end face of the socket inserted into the socket, in millimeters (mm); b The distance between the center of gravity of the steel pipe at the spigot end and the end face of the spigot inserted into the socket, in millimeters (mm); c It is the distance between the support point of the pad and the end face of the socket that has been inserted into the socket, in millimeters (mm).

[0217] In this embodiment, the nominal diameter of the base pipe is DN=600mm, and the material is Q235 steel. The nominal diameter of the reference pipe is DN=600mm, and the material is Q235. Its wall thickness is selected according to the provisions of the group standard, and the wall thickness when the nominal pressure is 3.0MPa, that is, the nominal wall thickness S=7mm. At this time, the outer diameter D of the base pipe is 0 =630mm, R =312mm. In addition, the shear force F It should be no less than 30 times of the nominal diameter DN. In this embodiment, 30 times is taken, that is, F = DN × 30 = 600 × 30 = 18000 N. Take the pipe length as 1m, c = 800mm.

[0218] In this embodiment, the parameters in formula (23) are M P and W The calculation process is as follows:

[0219]

[0220]

[0221] in, is the density of water, is the density of steel. M P The diameter used in the calculation is the outer diameter of the base tube D 0 , the calculation error is within the allowable range. In addition, in this embodiment, the material of the pipe socket is Q235 steel, the elastic modulus of the steel pipe material is E=200GPa, I=S 3 / 12. It should be noted that the calculation formula for the moment of inertia I of the circular tube section also needs to be multiplied by the length, but this solution considers a cylinder of unit length (i.e., the circular ring), so the length is 1.

[0222] Step a31 is thus completed.

[0223] In step a32, based on the parameters obtained by the above calculation, simulation software is used. In this embodiment, the maximum deformation of the socket of the reference pipe is simulated by finite element simulation. u max =12.19 mm. During simulation, the material parameter Poisson's ratio = 0.3. The simulation method is well known to those skilled in the art and will not be described in detail here.

[0224] In step a33, u max =12.19 Substituting into formula (22) we get m =1.18 (Note: When calculating, the length units are meters, and the unit of elastic modulus E is Pa), thus:

[0225] (twenty four)

[0226] From formula (24), we can see that u max The value is related to the pipe diameter and pipe thickness.

[0227] 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.

[0228] Table 1 Nominal wall thickness and absolute deformation of DN=600mm pipes at various nominal pressures

[0229]

[0230] 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).

[0231] It can be seen from Table 1 that if the base tube purchased by the secondary processing enterprise or user is processed in accordance with the provisions of the industry standard, the base tubes with serial numbers 1, 2, and 3 in Table 1 have a socket thickness greater than 5.7 mm and an absolute deformation less than 22.86 mm, which meet the deformation requirements, while the base tubes with serial numbers 4, 5, and 6 have a socket thickness less than 5.7 mm and an absolute deformation greater than 22.86 mm, which do not meet the deformation requirements.

[0232] If the use requirement of the pipe in a certain occasion is to meet the nominal pressure within 2MPa, the general user will choose the pipe with serial number 4 in Table 1, and will not choose the pipe with serial number 1, 2 or 3 to meet the deformation requirement, because if one of these three is selected, although it will meet both the strength requirement and the deformation requirement, their thickness is larger and the cost will be much greater than the pipe with serial number 4. If the pipe with serial number 4 is selected, its strength meets the use requirement. For the deformation requirement, some measures can be taken, such as sleeve-fitting an annular reinforcement ring in the socket to increase the thickness of the socket and improve its ability to resist deformation, and this measure is low in cost.

[0233] 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.

[0234] For example, in some occasions, the use requirement of the pipe is to meet the nominal pressure within 1.6MPa, and the selected base pipe is the pipe No. 5 in Table 1, with a wall thickness of 4mm. If the selected reinforcement ring and the base pipe are made of the same material, the thickness of the reinforcement ring is not less than 1.7mm to meet the deformation requirement, and the thickness of the composite socket is not less than 5.7mm.

[0235] Step a5: The material of the reinforcement ring is different from that of the socket of the base pipe. The minimum thickness of the reinforcement ring is obtained based on the socket thickness of the base pipe and the bending strength calculation formula of the longitudinal composite beam. The thickness of the reinforcement ring is not less than the minimum thickness. Then, the thickness of the composite socket is the minimum thickness that meets the deformation requirements.

[0236] In this embodiment, the calculation formula for the bending strength of the longitudinal composite beam is as follows:

[0237] (25)

[0238] in, C i The area is A i The distance from the centroid of the cross section to the bending center, I oi is the moment of inertia of the ith section about its own centroidal axis, E i is the elastic modulus of the corresponding part material. E is the elastic modulus of the base tube material, and I is the moment of inertia of the cross section corresponding to the minimum thickness obtained in step a3.

[0239] For example, in some occasions, the use requirement of the pipe is to meet the nominal pressure within 1.6MPa. The selected base pipe is the pipe No. 5 in Table 1, with a wall thickness of 4mm. The composite spigot includes the base pipe spigot and a layer of annular reinforcement ring (i.e., the part of the inner pipe 2 covering the spigot 13). The thickness of the reinforcement ring is x ,like Fig. 9 The figure shows the cross section per unit length of the composite socket or composite beam, where the plane of the cross section passes through the central axis of the base pipe. The base pipe is made of Q235, and the reinforcing ring is made of 304 stainless steel. Fig. 9 The distance from the center point of the cross section shown (the center of the composite beam) to the outer or inner surface of the composite socket is (4+ x ) / 2, for the base tube socket (original socket): A i =4, E i =200, C i = x / 2; For the reinforcement ring: A i = x , E i =193, C i =2, substituting into (25) we get:

[0240]

[0241] Find: x =1.73mm.

[0242] Therefore, the thickness of the reinforcement ring should not be less than 1.73 mm.

[0243] For another example, if the thickness of the inner tube 2 is known due to process or other requirements, the required thickness of the original socket can be calculated using formula (25).

[0244] It should be noted that when the length of the liner ring edge 51 is not less than the length of the socket 13, that is, when the liner ring edge 51 covers the entire inner wall of the socket 13, the liner ring edge 51, the socket 13 and the portion of the inner tube 2 covering the inner wall of the socket 13 form a composite socket. Obviously, the composite socket is a three-layer structure. Generally, the liner ring edge 51 and the inner tube 2 are made of the same material, both stainless steel. At this time, the liner ring edge 51 and the portion of the inner tube 2 covering the inner wall of the socket 13 can be regarded as an integral reinforcement ring. The thickness of the overall reinforcement ring is calculated according to formula (25) and then divided by 2, which is the thickness of the liner ring edge 51 or the inner tube 2, or the thickness of the two can be allocated according to the thickness of the overall reinforcement ring. If the socket 13, the inner tube 2 and the liner ring edge 51 are made of different materials, then in this case, there are two unknowns, namely the thickness of the inner tube 2 and the liner ring edge 51, and there is only one equation, formula (25). Therefore, it is necessary to limit the thickness of one layer according to the actual situation in order to calculate the thickness of the other. For example, if the minimum thickness of the inner tube 2 has been determined through a peel strength test, the thickness of the liner ring edge 51 can be calculated based on the thickness of the socket end 13 and the inner tube 2 according to formula (25).

[0245] The above is the design method for the thickness of the composite socket.

[0246] The design method of the thickness of the single-layer socket is as follows:

[0247] The inner wall shape of the single-layer socket of the pipe material 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 / CISA 108-2021) and GB / T 13295-2008, such as Fig.10 The inner wall of the single-layer socket is stepped. For the same base pipe, along the direction from the single-layer socket to the spigot, the inner wall of the single-layer socket includes the first step 111, the second step 112, the third step 113, the fourth step 114, and the fifth step 115 arranged in sequence. One end of the inner wall of the pipe body is the sixth step 116. The corresponding inner diameters are: D 2 , D 1 , (D 3 -2F 0 )、D 3 , D 4 , (D 0 -2S), wherein the inner diameters of the sixth step 116, the first step 111, the fifth step 115, the third step 113, the fourth step 114, and the second step 112 increase in sequence, that is: (D 0 -2S)<D 2 <D 4 <(D 3 -2F 0 )<D 3 <D 1The lengths of the first step 111, the second step 112, the third step 113, the fourth step 114, and the fifth step 115 are respectively: T 3 , T 4 , T 5 , (T 2 -T 4 -T 5 )、(T 1 -T 2 -T 3 ), that is, T 1 is the sum of the lengths of the first step 111, the second step 112, the third step 113, the fourth step 114, and the fifth step 115, T 2 is the sum of the lengths of the second step 112, the third step 113, and the fourth step 114, and the length refers to the size of the corresponding part in the axial direction of the base pipe. S is the wall thickness of the pipe body, and F 0 is the height of the third step 113 protruding from the fourth step 114, F 0 ≥0. The connection of each step is chamfered, where the chamfer at the connection between the fourth step 114 and the fifth step 115 is the first chamfer R 1 The chamfer at the connection between the fifth step 115 and the sixth step 116 is the second chamfer R 2 The chamfer at the connection between the second step 112 and the third step 113 is the third chamfer R 3 The chamfer at the connection between the first step 111 and the second step 112 is the fourth chamfer R 4 , the chamfer at the connection between the third step 113 and the fourth step 114 is the fifth chamfer R 5 Among them, D 0 It is the base pipe outer diameter of the pipe.

[0248] Since the dimensions of the inner wall of the single-layer socket are fully given by the relevant standards, it is necessary to design some key dimensions of the outer wall on this basis, aiming to save material costs and meet strength requirements at the same time. In other words, the thickness of the single-layer socket is designed to be the minimum or close to the minimum while meeting the use strength requirements, so as to reduce the production, manufacturing and transportation costs of the pipe.

[0249] When the two pipes are connected, the socket 13 of one pipe is inserted into the socket 11 of the adjacent pipe and sealed by a sealing ring. In this embodiment, the inner wall of the fourth step 114 is a cylindrical wall. The inner wall of the fifth step 115 is the outer side of a truncated cone, that is, from the fourth step 114 toward the direction of the pipe body 12, the inner diameter of the fifth step 115 gradually increases, which is equivalent to a trumpet. 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 larger than the inner diameter of the pipe body 12. In this way, the sixth step 116 is formed at the end of the pipe body 12 close to the fifth step 115. The inner wall bell mouth of the fifth step 115 is provided to provide a deflection angle for the adjacent pipes connected thereto, i.e., to allow the center line of a pipe and the center line of the adjacent pipe connected thereto to be in an intersecting state rather than an overlapping state. This is to allow a certain installation angle deviation to facilitate actual operation, and to allow adjacent pipes to have a relative displacement of a certain angle when the soil moves naturally.

[0250] The design method of single-layer socket includes the following steps:

[0251] Step b1: Select multiple locations on the inner wall of the single-layer socket where stress is likely to concentrate. The selection principle is: if the wall thickness of these locations meets the stress strength requirements, then the wall thickness of each location of the single-layer socket meets the strength requirements.

[0252] Step b2: Determine the minimum wall thickness of each selected location in step b1, and obtain the outer wall of each selected location. The determination principle is: when the material of the single-layer socket 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 socket 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 socket 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.

[0253] Step b3: Connect the outer walls of the selected locations in sequence to obtain the outer wall shape and thickness of the single-layer socket.

[0254] In step b1, based on material mechanics knowledge and experience, several locations on the inner wall of the single-layer socket where stress is most likely to concentrate are selected as the first chamfer R 1 The second chamfer R 2 and the third chamfer R 3 The analysis is as follows:

[0255] For the inner wall of the stepped single-layer socket, according to mechanical knowledge, the stress concentration point is located at the connection between adjacent steps, that is, at each chamfer. Since the single-layer socket is in a trumpet shape, the outer diameter of the single-layer socket decreases from the single-layer socket of the same base pipe to the spigot.

[0256] Based on the above premise, due to the fourth chamfer R 4The inner diameter and the third chamfer R 3 The inner diameters at the four corners are equal, all equal to D1, so the fourth chamfer R 4 The wall thickness at the third chamfer R 3 The wall thickness at the fourth chamfer R 4 The wall thickness at the third chamfer R 3 At this time, only the third chamfer R 3 The wall thickness at meets the stress strength requirements, and the fourth chamfer R 4 The wall thickness at the fifth chamfer R 5 The inner diameter and the first chamfer R 1 The inner diameters at the same 3 , so the fifth chamfer R 5 The wall thickness at the first chamfer R 1 The wall thickness at the first chamfer R 1 The wall thickness at meets the stress strength requirements, and the fifth chamfer R 5 The wall thickness at the point must meet the strength requirements. Therefore, the stress concentration point finally selected is the first chamfer R 1 , Second chamfer R 2 、Third chamfer R 3 In other words, the analysis area of ​​the single-layer socket is the third chamfer R 3 From the second chamfer R 2 The area between.

[0257] In step b2, the minimum wall thickness of each location selected in step b1 is calculated by the stress calculation formula. The specific method is as follows: the analysis area of ​​the single-layer socket is regarded as consisting of at least two coaxial pressure vessels with conical inner walls connected end to end, plus several internal reinforcement rings, and the reinforcement rings are connected to the inner wall of the pressure vessel. In other words, the analysis area of ​​the single-layer socket is regarded as consisting of at least two conical pressure vessels plus several internal reinforcement rings. At this time, as long as the corresponding conical pressure vessel meets the strength requirements, the single-layer socket must meet the strength requirements. Fig.10 shown.

[0258] For a thin-walled cylindrical pressure vessel, its wall thickness is S and its diameter is D 0 , the internal pressure is p, and the axial stress σ of the pressure vessel wall can be obtained from material mechanics 轴 and hoop stress σ 环 They are as follows:

[0259] (26)

[0260] (27)

[0261] The hoop stress σ 环 That is the circumferential stress. Diameter D 0 Take 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.

[0262] Similarly, for a thin-walled conical pressure vessel, when the wall thickness is S, the internal pressure is p, and the diameter is D, the stress σ in the axial direction of the vessel wall is 轴 and hoop stress σ 环 They are:

[0263] (28)

[0264] (29)

[0265] in α It is the semi-cone angle of the conical pressure vessel, that is, half of the opening angle. In other words, in the section passing through the central axis of the cone, the angle between the cone wall and the central axis is the semi-cone angle. Wherein, 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.

[0266] From the above, in this embodiment, the analysis area of ​​the single-layer socket includes two coaxially connected conical pressure vessels plus several internal reinforcement rings. The two coaxially connected conical pressure vessels are the first cone and the second cone, which share the same central axis with the single-layer socket. Among them, the first chamfer R 1 and the second chamfer R 2 is located on the inner wall of the first cone, such as Fig.10 First chamfer R 1 and the second chamfer R 2 The dotted line between is the inner wall section of the first cone. 1 and the third chamfer R 3 is located on the inner wall of the second cone, such as Fig.10 First chamfer R 1 and the third chamfer R 3 The dotted line between is the inner wall section of the second cone. 1 and the second chamfer R 2 The area between the first chamfer R and the first chamfer R is the entire side wall of the first cone, and the area between the first chamfer R and the first chamfer R is the entire side wall of the first cone. 1 and the third chamfer R 3 The area between the second cone inner wall and the single-layer socket outer wall is the entire side wall of the second cone, and the area between the second cone inner wall and the single-layer socket inner wall is another annular reinforcement ring.

[0267] exist Fig.10 In the cross section shown, after the first chamfer R 1 and the second chamfer R 2 The angle between the straight line at and the axis of the tube is the semi-cone angle of the first cone, set as α 1 After the first chamfer R 1 and the third chamfer R 3 The angle between the straight line at and the axis of the tube is the semi-cone angle of the second cone, set as α 2 .

[0268] but:

[0269] (30)

[0270] (31)

[0271] When the pipe body meets the strength requirements and the material of the single-layer socket is consistent with that of the pipe body, in order to make the single-layer socket meet the strength requirements, the first chamfer R 1 Hoop stress at Not greater than the hoop stress of the pipe body , Second chamfer R 2 Hoop stress at Not greater than the hoop stress of the pipe body 、Third chamfer R 3 Hoop stress at Not greater than the hoop stress of the pipe body , that is:

[0272] (32)

[0273] (33)

[0274] (34)

[0275] Then we have:

[0276] (35)

[0277] (36)

[0278] (37)

[0279] Among them, S 1 , S 2 , S 3 The first chamfer R 1 , Second chamfer R 2 、Third chamfer R 3 The wall thickness at is:

[0280] (38)

[0281] (39)

[0282] (40)

[0283] Since the third chamfer R 3 There is a sealing ring z at the socket. In order to achieve sealing, the pressure of the sealing ring z on the single-layer socket must be greater than the pressure p of the fluid in the pipe. According to existing research, the average pressure of the sealing ring z on the inner wall of the single-layer socket is generally 1.4 times the fluid pressure. It can be obtained from formulas (28) and (29) that the stress is proportional to the pressure and inversely proportional to the wall thickness. When the pressure increases to 1.4 times, in order to keep the stress unchanged, the wall thickness should be increased to 1.4 times at the same time. Then formula (40) is corrected to:

[0284] (41)

[0285] So we have:

[0286] (42)

[0287] (43)

[0288] (44)

[0289] Among them, S 1m , S 2m , S 3m The first chamfer R 1 , Second chamfer R 2 、Third chamfer R 3 Minimum wall thickness at .

[0290] From above, Fig.10 As shown, the second chamfer R 2 Minimum outer diameter at d 1 , first chamfer R 1 Minimum outer diameter at d 2 、Third chamfer R 3 Minimum outer diameter at d 3 They are as follows:

[0291] (45)

[0292] (46)

[0293] (47)

[0294] The following example is used to calculate the wall thickness parameters of a single-layer socket.

[0295] In this embodiment, the material of the pipe body and the single-layer socket is Q235.

[0296] Table 2 is the socket size parameter table for the nominal pipe diameters of 600mm and 1200mm at a pressure of 3MPa as specified in the relevant standards:

[0297] Table 2 Dimensional parameters of sockets with nominal pipe diameters of 600 mm and 1200 mm as specified in relevant standards

[0298]

[0299] Based on this scheme, the wall thickness dimensions of the two single-layer sockets in Table 2 are calculated and shown in Table 3.

[0300] Table 3 Wall thickness, outer diameter and semi-cone angle of two single-layer sockets

[0301]

[0302] In step b3, the outer diameter of the end face of the socket is greater than the third chamfer R 3 The outer diameter of the location can be used, and the specific value can be selected flexibly.

[0303] When the pipe body meets the strength requirements and the material of the single-layer socket is inconsistent with the pipe body, in order to make the single-layer socket meet the strength requirements, the first chamfer R 1 , Second chamfer R 2 、Third chamfer R 3 The stress at the pipe and the stress on the inner wall of the pipe should satisfy:

[0304] (48)

[0305] (49)

[0306] (50)

[0307] Among them, Q 0 is the yield strength of the pipe material, Q 1 It is the yield strength of the material used for single-layer socket.

[0308] Then we have:

[0309] (51)

[0310] (52)

[0311] (53)

[0312] Similarly, for the third chamfer R 3 Considering the influence of the sealing ring, the wall thickness of each chamfer is:

[0313] (54)

[0314] (55)

[0315] (56)

[0316] Therefore, the first chamfer R 1 , Second chamfer R 2 、Third chamfer R 3 The minimum wall thickness at is as follows:

[0317] (57)

[0318] (58)

[0319] (59)

[0320] Based on the above, the design calculation of the minimum thickness of the single-layer socket is completed.

[0321] 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 multi-layer bell-and-spigot pipe with a corrosion-resistant metal lining, characterized in that: The pipe material 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 wall of the socket (11) is provided with steps and / or grooves; the inner pipe (2), the intermediate layer (3) and the outer pipe (1) are bonded together or pressed together to form the pipe material; the outer pipe (1) comprises a socket (11), a pipe body (12) and a spigot (13) which are connected in sequence; at least one layer of the inner pipe (2) and the outer pipe (1) is made of metal material; The socket (11) is a single-layer socket, and the spigot (13) and the portion of the inner tube (2) covering the inner wall of the spigot (13) form a composite spigot. 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 deflection curve differential equation and the moment balance equation of the ring; 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. The design method of single-layer socket thickness includes the following steps: Step b1: Select multiple locations on the inner wall of the single-layer socket where stress is likely to be concentrated. The selection principle is: if the wall thickness of these locations meets the stress strength requirements, then the wall thickness of each location of the single-layer socket meets the strength requirements; Step b2: Determine the minimum wall thickness of each selected location in step b1, and obtain the outer wall of each selected location. The determination principle is: when the material of the single-layer socket 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 socket 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 socket 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.

2. The pipe according to claim 1, characterized in that: The outer tube (1) is made of a metal material, and the inner tube (2) is made of a material having a corrosion-resistant function.

3. The pipe according to claim 2, characterized in that: The material of the middle layer (3) is hot melt adhesive, plastic or rubber, the thickness of the middle layer (3) is not less than 0.2 mm, and the thickness of the inner tube (2) is not less than 0.1 mm.

4. The pipe according to claim 1, characterized in that: At one end of the socket (11), 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) are flush, and at one end of the spigot (13), the end face of the inner tube (2), the end face of the middle layer (3) and the end face of the spigot (13) are flush.

5. The pipe according to claim 3, characterized in that: Each end of the pipe is provided with a sealing gasket (4) and a lining ring (5). At the end of the socket (11), the sealing gasket (4) covers 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). At the end of the plug (13), the sealing gasket (4) covers the end face of the plug (13), the end face of the intermediate layer (3), the end face of the inner pipe (2) and the inner wall of the other end of the inner pipe (2). The lining ring (5) presses the sealing gasket (4). When in use, the lining ring (5) and the sealing gasket (4) at one end of the plug (13) form a full seal with the end face of the plug (13), and the lining ring (5) and the sealing gasket (4) at one end of the socket (11) form a full seal with the end face of the pipe body (12). The sealing gasket (4) comprises a sealing gasket pressing edge (41) and a sealing gasket flange (42), the sealing gasket pressing edge (41) is cylindrical, and the sealing gasket flange (42) is annular; the lining ring (5) comprises a lining ring pressing edge (51) and a lining ring flange (52), the lining ring pressing edge (51) and the lining ring flange (52) are an integral part, the lining ring pressing edge (51) is cylindrical, and the lining ring flange (52) is annular; the lining ring pressing edge (51) presses the sealing gasket pressing edge (41), and the lining ring flange (52) presses the sealing gasket flange (42), and the length of the lining ring pressing edge (51) is not less than 20 mm.

6. The 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 that are symmetrical relative to the center of the circle, the first form of the differential equation is transformed into a second form of the differential equation; Step a23: introducing the internal negative pressure of the annulus into the second form of the differential equation by introducing coefficients 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 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 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 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 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 pipe according to claim 1, characterized in that: For the same base pipe, along the direction from the single-layer socket to the spigot, the inner wall of the single-layer 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 pipe according to claim 11, characterized in that: In step b2, the minimum wall thickness of each selected point in step b1 is calculated by the stress calculation formula, and the single-layer socket is regarded as a pressure vessel including at least two coaxially connected pressure vessels with conical inner walls and at least one annular reinforcement ring installed on the inner wall of the pressure vessel. , ,in, is the hoop stress of the pipe body, is the hoop stress at the selected location, D0 is the outer diameter of the base pipe, D is the diameter of the selected location, p is the pressure of the fluid in the base pipe, S is the thickness of the base pipe, S0 is the wall thickness of the selected location, and α is the semi-cone angle of the cone at the selected location.

13. The pipe according to claim 12, characterized in that: When the material of the single-layer socket is the same as that of the pipe body, the stress calculation formula is: .

14. The pipe according to claim 12, characterized in that: When the material of the single-layer socket is different from that of the pipe body, the stress calculation formula is: , where Q0 is the yield strength of the pipe body material and Q1 is the yield strength of the material used for the single-layer socket.

15. A method for manufacturing a multi-layer bell-and-spigot type pipe with a corrosion-resistant metal lining, used for manufacturing the pipe according to any one of claims 3 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); Step S2: arranging the inner tube (2), the middle layer (3) and the outer tube (1) in sequence from the inside to the outside; Step S3: pressing the inner tube (2) and the middle layer (3) onto the outer tube (1); Step S4: compounding; When the material of the middle layer (3) is plastic or rubber, there is no step S4.

16. The manufacturing method according to claim 15, characterized in that: The manufacturing method further comprises step S5: inserting a sealing gasket (4) and a lining ring (5) into each end of the pipe.

17. The manufacturing method according to claim 15, characterized in that: When the middle layer (3) is a hot melt adhesive or plastic, in step S1, a tubular middle layer (3) can be separately manufactured, and in step S2, the middle layer (3) is sheathed on the outside of the inner tube (2) and then sheathed as a whole into the outer tube (1); or firstly, powdered hot melt adhesive or plastic is rotationally molded or sprayed on the inner wall of the outer tube (1), and then in step S2, the inner tube (2) is sheathed into the outer tube (1); or firstly, powdered hot melt adhesive or plastic is rotationally molded or sprayed on the outer wall of the inner tube (2), and then in step S2, the inner tube (2) is sheathed into the outer tube (1).

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