A sealing method for composite pipe

Abstract

The present invention relates to a method for sealing a composite pipe, and belongs to the technical field of pipe sealing processing. In order to solve the existing problems of poor operational stability and poor connection strength, a method for sealing a composite pipe is provided, which includes machining a selected plastic connecting pipe, forming an annular clearance groove penetrating the end face on the outer sides of both ends of the plastic connecting pipe, and having a first groove wall facing the axial direction of the plastic connecting pipe; heating and hot-melting the two groove walls of the annular clearance groove, and heating and hot-melting the surface of the outer layer of the plastic connecting pipe used for welding the pipe head; heating and hot-melting the inner side wall of the pipe head and the end face of the annular baffle; extruding and sleeve welding, and after cooling and solidification, obtaining the corresponding sealed composite pipe. It can effectively maintain the bonding strength performance of the middle fiber reinforced layer, so that it has better shear strength performance.

Description

Technical Field

[0001] The invention relates to a sealing method for a composite pipeline, belonging to the technical field of pipeline sealing processing. Background Art

[0002] CFRTP composite pipe is a fluid conveying pipe that is a composite of corrosion-resistant plastic and non-corrosion-resistant high-strength material. It usually adopts a three-layer structure. The inner layer is a corrosion-resistant and wear-resistant thermoplastic material layer, the middle layer is provided with a reinforcement material layer, and the outer layer is a protective outer plastic layer. In actual use, for long conveying pipelines, multiple pipes such as CFRTP composite pipes are required to be connected end to end. Common pipe body connection methods include hot melt connection and electric fusion connection, which are melted to form an integrated connection.

[0003] However, when used as a water supply pipeline, the overall design life of the pipeline is required to be more than 50 years. When the water supply is turned off and on, the strong water flow impact will generate strong axial and radial loads. Its instantaneous explosive force is 2-3 times that under normal use conditions. This is an important reason for the damage of the pipeline connection in the first place. The damage causes the reinforcing material of the middle layer to penetrate the fluid and be corroded by the water source, which may cause the drinking water in the pipeline to be contaminated by the reinforcing material. In order to improve the overall connection strength of the pipeline and avoid the contamination of the water source by the reinforcing material in the middle due to the easy damage of the pipeline, there is a method of heat-melting the pipeline sealing ring on the end face of the pipeline to achieve the purpose of improving the connection strength after heat melting, such as the existing patent document (authorization announcement number: CN 215721591 U) discloses a pipe connection structure, which connects sealing rings at both ends of the connecting pipe, wherein the outer sealing ring is connected to the outer side wall of the connecting pipe by heat melting. Since the pipe and the sealing ring are directly heat-melted and then squeezed together to solidify, the resistance encountered during the extrusion process is large, which is not conducive to operation; at the same time, the end face of the connecting pipe is directly pressed against the sealing ring for heat melting connection. Since the radial end faces are heat-melted synchronously from the inside to the outside, the intermediate reinforcement layer on the rear end face of the heat melting rear end will be uncertain during the heat melting process, and the processing stability cannot be guaranteed. Moreover, when the pipe head is sleeved, due to Due to the blocking effect of the sealing ring, during the extrusion process, when the pipe end face and the sealing ring are docked, the molten material tends to squeeze toward the inside of the pipe. This will cause the end of the middle fiber reinforced layer to be more likely to turn inward under the action of this trend, and the distance between it and the inner layer will be less than the thickness of the inner layer. In this way, when a high-load water source is supplied in the pipeline, the drinking water in the pipe will penetrate and erode the middle reinforcement layer, thereby causing the bonding strength between them to decrease, reducing the shear strength performance between the layers, and causing the pollution of the drinking water in the pipe due to the penetration caused by the reduction in the distance between the fiber reinforced layers. Summary of the Invention

[0004] In view of the above defects in the prior art, the present invention provides a sealing method for a composite pipe, which solves the problem of how to effectively improve operational stability, avoid inward turning of the reinforcing material in the pipe and improve the overall strength performance of the pipe.

[0005] The objective of the present invention is achieved through the following technical solution: a method for sealing a composite pipe, the composite pipe comprising a plastic connecting pipe and a cylindrical pipe head, the plastic connecting pipe comprising, from the inside to the outside, an inner layer, a fiber reinforced layer, and an outer layer, the pipe head having an inwardly protruding annular retaining edge at an inner edge of one end, characterized in that the method comprises the following steps:

[0006] A. Machining a selected plastic connecting pipe to form an annular clearance groove penetrating the end surface on the outer sides of both ends of the plastic connecting pipe, so that the annular clearance groove has a first groove wall facing the axial direction of the plastic connecting pipe, and the end surface of the fiber reinforcement layer penetrates and is located at the first groove wall;

[0007] B. Heat and hot-seal the two groove walls of the annular relief groove at both ends of the plastic connecting pipe, and heat and hot-seal the surface of the outer layer of the plastic connecting pipe for welding to the pipe head; heat and hot-seal the inner side wall and the end surface of the annular retaining edge for abutting against the end face of the plastic connecting pipe;

[0008] C. After heating is completed, the pipe head is extruded from the corresponding end of the plastic connecting pipe for sleeve bonding and compounding until the annular retaining edge abuts against the end face of the plastic connecting pipe and is welded. During the extrusion process, part of the hot-melt material of the pipe head fills the annular recess and is welded together. After cooling and solidification, the corresponding sealed composite pipe is obtained.

[0009] The present invention first machines the plastic connecting pipe to form a corresponding annular relief groove. During the machining process, the formed first groove wall is extended to the outer surface of the inner layer, which effectively ensures that the fiber reinforcement layer material in the middle is removed at the same time, so that its end is formed at the first groove wall and penetrates the structure. In this way, the distance between the end of the fiber reinforcement layer on the end face and the end face of the plastic connecting pipe is effectively avoided, which is equivalent to forming a distance from the annular relief groove to the groove wall in the radial direction of the plastic connecting pipe, forming a dislocation, and more effectively avoiding the possibility of infiltration from the end face connection of the pipe; at the same time, due to the structure of the annular relief groove The structural design ensures that when the two groove walls of the annular yield groove are heated and melted, the welding surfaces are ensured to be heated and melted, while the inner layer material on the inner side of the end portion of the machined fiber reinforced layer is not easy to be completely heated and melted, in order to avoid hot melting on the same end surface and ensure the supporting strength of the inner layer. Compared with the position that is completely heated and melted, it has a higher hardness requirement. In this way, when the extrusion sleeve is performed, the partially melted material of the pipe head will slowly be squeezed into the annular yield groove to form an integrated filling and will be squeezed toward the first groove wall side under the action of an annular retaining edge. Due to the radial direction of the entire first groove wall side, the The surfaces will be heated and melted, while the inner layer material on the radially inner side of the end of the corresponding fiber reinforced layer maintains its support, thereby effectively ensuring that the end of the fiber reinforced layer can be folded outward in the direction of the molten state during the extrusion process, and can also completely fill the space of the corresponding annular clearance groove, thereby effectively improving the operational stability of the extrusion sleeve process, avoiding the defect of the distance between the fiber material and the inner side of the pipe caused by the inward turning of the end surface of the middle fiber reinforced layer, and effectively avoiding the problem of erosion of the fiber reinforced layer of the middle layer due to the high pressure infiltration of the water source in the pipe or damage to the relatively thinned position during use due to the reduction of the distance between the pipe and the inner side. The method can effectively avoid the erosion of the middle fiber reinforced layer, so that the overall strength performance of the pipeline, especially the axial shear strength performance, can be effectively achieved by adopting the method of the present invention, and the contamination of the water source in the pipe by the fiber reinforced layer material can be effectively avoided; at the same time, since the overall outward turning characteristic of the end of the fiber reinforced layer is effectively ensured, the welding bonding strength between it and the outer layer material can be better achieved, thereby achieving a double performance improvement, so that the pipeline has better welding strength performance and better ensures the advantage that the pipeline is not easily damaged during use.

[0010] In the above-mentioned composite pipe sealing method, preferably, during the machining in step A, the first groove wall of the annular relief groove extends radially inwardly of the plastic connecting pipe to the outer surface of the inner layer, and the end surface of the fiber-reinforced layer is flush with the surface of the first groove wall. This is equivalent to machining to remove the entire outer layer and the fiber-reinforced layer, completely retaining the material of the inner layer, and forming a gap between the fiber-reinforced layer and the outer surface of the inner layer. This design facilitates the molten material to be squeezed out from the boundary between them during extrusion after hot melting, thereby more effectively ensuring that the end of the fiber-reinforced layer located on the first groove wall is squeezed outward, more effectively preventing the end of the fiber-reinforced layer from turning inward, thereby improving the operational stability of the extrusion process, and effectively preventing the problem of water infiltration and erosion of the middle fiber-reinforced layer during use due to inversion. It better maintains the bonding and shear strength between the layers, and effectively ensures the overall strength of the pipe.

[0011] In the above-mentioned composite pipe sealing method, preferably, the end surface of the plastic connecting pipe is not heated during the heating and hot melting in step B. The outer end surface of the plastic connecting end is not heated. This is to maintain the softening of the inner layer material corresponding to the annular recess due to the heating and melting of the end surface, thereby maintaining the inner layer's good hardness. This is also more conducive to ensuring that the end surface of the fiber reinforcement layer on the first groove wall is turned outward during welding.

[0012] In the above-mentioned composite pipe sealing method, preferably, during the extrusion process in step C, the ends of the fiber-reinforced layer are folded outwardly in the radial direction of the plastic connecting pipe to form a stopper. With the assistance of the annular retaining edge of the pipe end cap and through the extrusion operation, the ends of the fiber-reinforced layer can be effectively turned outward. Thus, when heated and molten, the corresponding ends can be partially embedded in the outer plastic material, forming a composite state, which can provide a better stopper, a better bonding effect, and more effectively improve the shear strength performance.

[0013] In the above-mentioned composite pipe sealing method, preferably, the stopper is folded outwardly at an angle in the circumferential direction, forming an angle between the stopper and the outer surface of the inner layer. This angled, outward folding allows the molten material to fill this area during the extrusion process for welding, thereby encapsulating the ends of the fiber-reinforced layer and increasing the weld surface with the inner layer to enhance bonding strength, more effectively achieving improved overall shear strength. Furthermore, preferably, in step C, the material molten during the extrusion process of the pipe seal also fills the angle between the stopper and the outer surface of the inner layer, forming a protrusion.

[0014] In the above-mentioned composite pipe sealing method, preferably, the pipe head in step B is also pre-processed to form an annular cavity on the inner side wall of the pipe head along the circumference of the pipe head. When the plastic connecting pipe is sleeved and fused to the pipe head, the annular cavity is located radially outside the radial groove surface. When heated and melted, the plastic connecting pipe and the pipe head are fused together, and the annular cavity is squeezed to the radial outside of the first groove wall. This can provide more deformation space in the radial direction, which is more conducive to squeezing the end of the fiber reinforcement layer outward to form an inclination during the extrusion process, thereby ultimately better ensuring the overall performance of the pipe. As a further preference, the distance from the annular cavity to the annular retaining edge is slightly smaller than the distance from the first groove wall to the corresponding end face of the plastic connecting pipe. This is equivalent to taking into account the extrusion deformation space reserved for the annular retaining edge during heating and melting, and more effectively ensuring that it is basically located radially outside the first groove wall after the composite is completed.

[0015] In the above-mentioned composite pipe sealing method, preferably, the machining in step A is performed by cutting to form the annular clearance grooves at both ends of the plastic connecting pipe. Cutting can facilitate flushing of the end surface of the fiber-reinforced layer on the first groove surface after machining, and improves overall flatness, which is more conducive to subsequent welding operations.

[0016] In summary, the present invention has the following advantages compared with the prior art:

[0017] 1. By adopting the method of the present invention, the annular yield groove is processed and the end of the fiber reinforced layer is located at the first groove wall, which effectively achieves the operational stability of the extrusion process, ensures that the end of the fiber reinforced layer is extruded outward during the extrusion process, and can better achieve the fusion bonding strength between it and the outer layer material, thereby achieving a double performance improvement, so that the pipeline has better fusion strength performance, better ensures the advantage that the pipeline is not easily damaged during use, and can also effectively maintain the bonding strength performance of the middle fiber reinforced layer, so that it has better shear strength performance, avoiding the problem of erosion affecting strength caused by the inversion of the fiber material.

[0018] 2. By extending the first groove wall of the annular relief groove inwardly along the radial direction of the plastic connecting pipe to the outer surface of the inner layer and being flush with it, the probability of the end of the fiber reinforced layer turning inward is more effectively avoided, the operational stability of the extrusion process is improved, and the bonding force and shear strength between the layers are better maintained.

[0019] 3. The structural design of the annular cavity provides more deformation space in the radial direction, which is more conducive to causing the end of the fiber-reinforced layer to be squeezed outward to form an inclination during the extrusion process, thereby ultimately better ensuring the overall performance of the pipeline. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram showing the cross-sectional structure of the plastic connecting pipe and the pipe head before welding of the composite pipe.

[0021] Figure 2 It is a schematic diagram of the cross-sectional structure of the composite pipeline.

[0022] Figure 3 yes Figure 2 Schematic diagram of the enlarged structure at point A in the middle.

[0023] Figure 4 yes Figure 3 Schematic diagram of the partial cross-section structure of the middle pipe head.

[0024] Figure 5 It is in Figure 3 Schematic diagram of the partial cross-sectional structure of the plastic connecting pipe.

[0025] Figure 6 It is a schematic diagram of the process of hot melting the plastic connecting pipe and the pipe head of the composite pipe.

[0026] Figure 7 This is another schematic diagram of the cross-sectional structure of a plastic connecting pipe and a pipe head before welding of a composite pipe.

[0027] Figure 8 It corresponds to Figure 7 Schematic diagram of the hot-melting process of the plastic connecting pipe and pipe head.

[0028] In the figure, 1. plastic connecting pipe; 11. annular relief groove; 111. first groove wall; 12. inner layer; 13. fiber reinforced layer; 131. limiting part; 14. outer layer; 2. pipe head; 21. annular retaining edge; 22. annular welding part; 221. protrusion; 3. hot melt heating equipment. DETAILED DESCRIPTION

[0029] The technical solution of the present invention will be further specifically described below through specific embodiments and drawings, but the present invention is not limited to these embodiments.

[0030] Example 1

[0031] Combine Figure 1-6As shown, the composite pipe includes a plastic connecting pipe 1 and a cylindrical pipe head 2. The plastic connecting pipe 1 includes an inner layer 12, a fiber reinforced layer 13 and an outer layer 14 from the inside to the outside. The inner edge of one end of the pipe head 2 has an inwardly protruding annular retaining edge 21. If the above-mentioned plastic connecting pipe 1 adopts a CFRTP pipe, the pipe head 2 can adopt a PE pipe. They are hot-melt connected and fixedly connected through the above-mentioned structure to form a composite pipe of the above-mentioned structure. The outer diameter of the plastic connecting pipe 1 is slightly larger than the inner diameter of the pipe head 2 to form an extrusion weld. This can be adjusted according to the processing size requirements. More importantly, the sealing method of the composite pipe of the present invention is completed by the following method. The specific method is as follows:

[0032] According to the sealing requirements of the composite pipe, the corresponding plastic connecting pipe 1 and the pipe head 2 are selected, and then the selected plastic connecting pipe 1 is machined to form an annular clearance groove 11 penetrating the end surface on the outer side of both ends of the plastic connecting pipe 1, so that the annular clearance groove 11 has a first groove wall 111 facing the axial direction of the plastic connecting pipe 1. After machining, the end surface of the fiber reinforced layer 13 penetrates and is located at the first groove wall 111; after such machining, the end surface of the fiber reinforced layer 13 and the end surface of the plastic connecting pipe 1 form an axial distance space of the annular clearance groove 11. The machining here can be performed by mechanical processing to remove part of the material to form the annular clearance groove 11, and the machining is completed at both ends of the plastic connecting pipe 1;

[0033] Then, the heating and melting process is entered. The hot melting heating device 3 is used to heat and melt the two groove walls of the annular recess 11 at both ends of the plastic connecting pipe 1, and the surface of the outer layer 14 of the plastic connecting pipe 1 used for welding the pipe head 2 is also heated and melted until it reaches a molten state and can be welded. The heating length of the outer layer 14 can be controlled and required according to the length and size of the pipe head 2.

[0034] The inner side wall of the pipe end cap 2 and the annular retaining edge 21 are heated and melted for contact with the end face of the plastic connecting pipe 1; Figure 6 As shown, when heating and melting, a general hot melt heating device 3 can be used for heating. The heating temperature can be controlled according to the general temperature to ensure that the molten bonding is achieved. The temperature control can be controlled by the general temperature control of the pipe head welding. The heating of the plastic connecting pipe 1 and the pipe head 2 can be heated separately or simultaneously.

[0035] After the heating is completed, the composite process is started, and the pipe head 2 is extruded from the corresponding end of the plastic connecting pipe 1 for sleeve composite, until the annular retaining edge 21 abuts against the end face of the plastic connecting pipe 1 and is welded. During the extrusion process, part of the hot-melt material of the pipe head 2 fills the annular give way groove 11 and is welded together. After cooling and solidification, the corresponding sealed composite pipe is obtained.

[0036] In a further embodiment, during the machining process described above, the first groove wall 111 of the annular clearance groove 11 extends radially inwardly of the plastic connecting tube 1 to the outer surface of the inner layer 12, and the end surface of the fiber-reinforced layer 13 is flush with the surface of the first groove surface 111. This can be achieved by controlling the radial depth of the cut, such as when using a cutter, so that the cut reaches the outer surface of the corresponding inner layer 12, effectively cutting through the outer layer 14 and the corresponding intermediate fiber-reinforced layer 13, leaving the inner layer 12. It is also preferable that the first groove surface 111 is formed radially, that is, facing the axial direction of the plastic connecting tube 1 and perpendicular to the axial direction. The machining process described above involves cutting to form the annular clearance groove 11 at both ends of the plastic connecting tube 1.

[0037] When the plastic connecting tube 1 is heated and melted, the end surface of the plastic connecting tube 1 is not heated. That is, the first groove wall of the annular relief groove 11 and the other groove wall facing the plastic connecting tube 1 in the radial direction are heated, while the end surface of the outermost end of the plastic connecting tube 1 abutting against the annular retaining edge 21 is not heated. This prevents the end surface from being completely melted in the radial direction, thereby maintaining the supporting capacity of the inner layer 12. Moreover, the end surface is not heated, which can better maintain the original shape of the end surface.

[0038] After the above heating is complete, further operation is performed by folding the end of the fiber-reinforced layer 13 radially outward along the plastic connecting pipe 1 during the extrusion process to form a stopper 131. The stopper 131 is further folded outward at an angle in the circumferential direction, so that an angle is formed between the stopper 131 and the outer surface of the inner layer 12. This process is gradually formed during the extrusion welding. This is equivalent to the hot-melt material of the pipe head 2 being filled into the angle between the stopper 131 and the outer surface of the inner layer 12 during the extrusion process to form a protrusion 221. Taking advantage of the certain fluidity of the molten material, the molten material can be squeezed to the corresponding angle position through the extrusion process, and the end of the fiber-reinforced layer 12 at this position is also folded outward.

[0039] The control of the heating and melting temperature of the plastic connecting pipe 1 and the pipe sealing head 2 can be adjusted according to the selected materials of the corresponding pipes.

[0040] The performance of the product obtained by sealing using the above-mentioned method of the present invention was tested. The results showed that after processing, the ends of the fiber-reinforced layer 13 of the composite pipe can achieve the characteristic of turning outward, thereby ensuring the quality of the product. At the same time, it also has excellent overall strength performance and high shear strength.

[0041] Example 2

[0042] Combine Figure 2 、 Figure 7 and Figure 8 The sealing method of the composite pipe of this embodiment is basically the same as that of the first embodiment, except that the following processing is different: before heating and melting the pipe head, the pipe head 2 is pre-processed, combined with Figure 7 and Figure 8 The above-mentioned specific pre-processing is to form an annular cavity 23 on the inner side wall of the pipe head 2 along the circumference of the pipe head 2 by machining such as cutting. The position of the annular cavity 23 is selected in combination with Figure 8 The welding composite method, after the composite, when the plastic connecting pipe 1 and the pipe head 2 are sleeved and welded, the annular cavity 23 is located radially outside the first groove wall 111. After the welding, since the welding is carried out in a heated and molten state, the annular cavity 23 is preferably filled with molten material during molding, and finally forms the following Figure 2 This structural design provides greater room for deformation when the fiber-reinforced layer ends are turned outward, further ensuring the advantages of outward turning. It is best to ensure that the distance from the annular cavity 23 to the annular retaining edge 21 is slightly smaller than the distance from the first groove wall 11 to the corresponding end face of the plastic connecting pipe 1. The remaining operations are essentially the same as those in Example 1 and will not be described in detail here. The specific processing procedures in Example 1 will suffice.

[0043] The specific embodiments described herein are merely illustrative of the spirit of the present invention. Persons skilled in the art may make various modifications, additions, or substitutions to the described embodiments without departing from the spirit of the present invention or exceeding the scope of the appended claims.

[0044] Although the present invention has been described in detail and certain specific embodiments have been cited, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.

Claims

1. A method for sealing a composite pipe, the composite pipe comprising a plastic connecting pipe (1) and a cylindrical pipe sealing head (2), wherein the plastic connecting pipe (1) comprises an inner layer (12), a fiber reinforced layer (13) and an outer layer (14) from the inside to the outside, and an inner edge of one end of the pipe sealing head (2) is provided with an inwardly protruding annular retaining edge (21), characterized in that: The method comprises the following steps: A. Machining the selected plastic connecting tube (1), forming an annular relief groove (11) penetrating the end surface on the outer circumference of both ends of the plastic connecting tube (1), so that the annular relief groove (11) has a first groove wall (111) facing the axial direction of the plastic connecting tube (1), and the end surface of the fiber reinforced layer (13) penetrates and is located at the first groove wall (111); during machining, the first groove wall (111) of the annular relief groove (11) extends inwardly along the radial direction of the plastic connecting tube (1) to the outer surface of the inner layer (12), and the end surface of the fiber reinforced layer (13) is flush with the surface of the first groove wall (111); B. Heat and melt the two groove walls of the annular relief groove (11) at both ends of the plastic connecting pipe (1), and heat and melt the surface of the outer layer of the plastic connecting pipe (1) for welding the pipe head (2); heat and melt the inner side wall of the pipe head (2) and the end face of the annular retaining edge (21) for contacting the end face of the plastic connecting pipe (1); C. After the heating is completed, the pipe seal (2) is extruded from the corresponding end of the plastic connecting pipe (1) for sleeve bonding and compounding until the annular retaining edge (21) abuts against the end face of the plastic connecting pipe (1) and is welded. During the extrusion process, part of the hot-melt material of the pipe seal (2) is filled into the annular relief groove (11) and welded together. During the extrusion process, the end of the fiber reinforced layer (13) is folded outwardly along the radial direction of the plastic connecting pipe (1) to form a limiting portion (131). The limiting portion (131) is folded outwardly in a circumferential direction, so that an angle is formed between the limiting portion (131) and the outer surface of the inner layer (12). After cooling and solidification, the corresponding sealed composite pipe is obtained.

2. The method for sealing a composite pipe according to claim 1, characterized in that: During the heating and hot melting in step B, the end surface of the plastic connecting pipe (1) is not heated.

3. The method for sealing a composite pipe according to claim 1 or 2, characterized in that: During the extrusion process in step C, the hot-melt material of the pipe sealing head (2) is also filled into the angle between the limiting portion (131) and the outer surface of the inner layer (12) to form a protrusion (221).

4. The method for sealing a composite pipe according to claim 1 or 2, characterized in that: In step B, the pipe seal head (2) is further pre-processed so that an annular cavity (23) is formed on the inner side wall of the pipe seal head (2) along the circumference of the pipe seal head (2). When the plastic connecting pipe (1) and the pipe seal head (2) are sleeved and welded, the annular cavity (23) is located radially outside the first groove wall (111).

5. The method for sealing a composite pipe according to claim 4, characterized in that: The distance between the annular cavity (23) and the annular retaining edge (21) is slightly smaller than the distance between the first groove wall (11) and the corresponding end face of the plastic connecting pipe (1).

6. The method for sealing a composite pipe according to claim 1 or 2, characterized in that: The machining in step A is to form the annular relief grooves (11) at both ends of the plastic connecting pipe (1) by cutting.

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