Pipe end structure of plastic-lined composite steel pipe
By setting up a concave annular groove on the inner wall of the outer steel pipe and covering the welding layer, the damage problem of plastic liner pipe during welding of the inner lined plastic composite steel pipe is solved, the connection strength and sealing are improved, the corrosion resistance is maintained, and the application range is expanded.
Patent Information
- Application Number
- CN202422661451.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-01
- Publication Date
- 2025-08-01
- Estimated Expiration
- 2034-11-01
AI Technical Summary
The welding connection method of existing plastic composite steel pipes is easy to damage the plastic liner pipes, resulting in a reduced corrosion resistance, and the traditional connection method is insufficient in strength and sealing, making it easy to leak.
A concave annular groove is provided on the inner wall of the pipe end of the outer steel pipe, and the weld layer is covered with the surfacing layer. The material of the surfacing layer is corrosion-resistant stainless steel or nickel alloy. A spacing and anti-corrosion sealing layer are provided between the plastic liner and the surfacing layer. When welding, contact the surfacing layer rather than the end face of the plastic liner.
It improves the strength and sealing of welding connections, reduces damage to plastic liners, maintains overall corrosion resistance, and expands the scope of use.
Smart Images
Figure CN223178481U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of the structure of plastic-lined composite steel pipes, in particular to a pipe end structure of a plastic-lined composite steel pipe. Background Art
[0002] The plastic-lined composite steel pipe is a composite structure composed of an outer steel pipe and an inner plastic lining pipe. It has both the mechanical properties of the steel pipe and the corrosion resistance of the plastic pipe, with the characteristics of slow scale formation and not easy to grow microorganisms. It is an ideal pipeline for transporting media such as acids, alkalis, salts, and corrosive gases. The plastic-lined composite steel pipe can effectively solve the problem of corrosion of the inner wall of the steel pipe and can withstand temperatures above 90°C. In recent years, it has been widely used.
[0003] For the existing plastic-lined composite steel pipes, the length of the outer steel pipe is equal to the length of the inner plastic lining pipe, and the ends of the outer steel pipe and the inner plastic lining pipe are flush. If the welding method is used to weld two plastic-lined composite steel pipes, in order to ensure the welding quality, the part of the plastic-lined composite steel pipe to be welded will be processed before welding to form a bevel surface. If the pipe orifice end face of the plastic-lined composite steel pipe is directly cut to form an inclined surface (bevel surface), the pipe orifice end face of the inner plastic lining pipe is part of the bevel surface. During welding, the high-temperature solder directly contacts the pipe orifice end face of the inner plastic lining pipe, which will cause damage or partial defect of the inner plastic lining pipe inside the plastic-lined composite steel pipe after welding.
[0004] Since the inner plastic lining pipe plays an anti-corrosion effect, after welding, the damage to the inner plastic lining pipe will reduce the overall corrosion resistance of the plastic-lined composite steel pipe (for example: under the action of high temperature, part of the pipe wall of the inner plastic lining pipe is melted, resulting in the exposure of the inner wall of the outer steel pipe; during subsequent use, the corrosive gas or liquid directly contacts the exposed inner wall of the outer steel pipe, causing corrosion of the exposed inner wall of the steel pipe in this part).
[0005] Therefore, generally, the welding method is not directly used to weld two plastic-lined composite steel pipes. At present, the connection between two plastic-lined composite steel pipes basically adopts the threaded connection and the snap connection methods, but the connection strength between the two plastic-lined composite steel pipes is low and the sealing effect is poor under these two methods. During the subsequent pipeline operation, leakage is likely to occur at the connection end of the two steel pipes. Summary of the Utility Model
[0006] The purpose of the utility model is to provide a pipe end structure of a plastic-lined composite steel pipe to solve the technical problem that if the welding method is directly used to weld two plastic-lined composite steel pipes under the existing pipe end structure of the plastic-lined composite steel pipe, it is easy to reduce the corrosion resistance of the plastic-lined composite steel pipe after welding. The structure of the utility model is simple.
[0007] In order to achieve the above purpose, the utility model adopts the following technical solutions:
[0008] A pipe end structure of a plastic-lined composite steel pipe, the outer layer of the plastic-lined composite steel pipe is an outer steel pipe, and the inner layer is a plastic lining pipe; the inner wall of the pipe end of the outer steel pipe is radially provided with an inwardly concave annular groove, and the inwardly concave annular groove extends inward along the edge of the pipe orifice of the outer steel pipe; the inner wall of the inwardly concave annular groove is covered with a surfacing layer; the surfacing layer is tubular;
[0009] There is a spacing between the outer pipe end of the surfacing layer and the pipe end of the plastic lining pipe;
[0010] The outer pipe end of the surfacing layer is provided with a welding groove surface;
[0011] The material of the surfacing layer is corrosion-resistant stainless steel or nickel alloy.
[0012] Furthermore, there is a covering section between the outer wall of the end of the plastic lining pipe and the inner wall of the surfacing layer;[[ID=1,5]]
[0013] Furthermore, an anti-corrosion sealing layer is provided between the pipe end of the plastic lining pipe and the inner wall of the surfacing layer.
[0014] Furthermore, the length of the covering section is 10-15 mm; the length of the surfacing layer is more than 60 mm;
[0015] The spacing length between the outer pipe end of the surfacing layer and the pipe end of the plastic lining pipe is more than 45 mm.
[0016] Furthermore, the thickness of the surfacing layer is 2-3 mm.
[0017] Furthermore, the inner diameter of the surfacing layer is equal to the inner diameter of the outer steel pipe.
[0018] Furthermore, the welding groove surface is an inclined surface, and the groove surface angle is between 30-35 degrees.
[0019] Furthermore, the outer pipe end of the surfacing layer is also provided with a root face.
[0020] Furthermore, the inwardly concave annular groove is composed of two parts, a circular side wall and a root side wall, which are distributed from outside to inside in sequence; the included angle between the root side wall and the perpendicular line of the pipe wall of the outer steel pipe is between 35-45 degrees.
[0021] Compared with the prior art, the present utility model provides a pipe end structure of a plastic-lined composite steel pipe, which has the following beneficial effects:
[0022] 1. In the present utility model, the pipe end structure of the outer plastic-lined composite steel pipe is improved, and a surfacing layer is added at the pipe end of the plastic-lined composite steel pipe.
[0023] The surfacing layer is arranged in the concave annular groove on the inner wall of the pipe end in the radial direction. The concave annular groove extends inward along the pipe orifice edge of the outer steel pipe, that is, the concave annular groove has a certain length, and the outer edge of the inner wall of the concave annular groove is the pipe orifice edge of the outer steel pipe; the surfacing layer is tubular and completely covers the inner wall of the concave annular groove.
[0024] Moreover, there is a gap between the outer pipe end of the surfacing layer and the pipe end of the plastic liner, that is, the pipe end of the plastic liner is located in the pipe cavity of the plastic-lined composite steel pipe and is far from the outer end (i.e., the outer pipe end) of the surfacing layer. And the outer pipe end of the surfacing layer is provided with a welding groove surface, that is, the welding groove surface is the outer pipe end of the surfacing layer rather than the pipe orifice end face of the plastic liner.
[0025] In subsequent welding operations, the welding contact surface is the welding groove surface arranged at the outer pipe end of the surfacing layer. Since there is a certain gap between the pipe end of the plastic liner and the outer pipe end of the surfacing layer, during welding, the welding temperature is first conducted to the surfacing layer, and the welding material does not directly contact the pipe end of the plastic liner either. In this way, the damage to the plastic liner caused by the high welding temperature during the welding process can be reduced.
[0026] 2. At the same time, because there is a covering section between the outer wall of the pipe end of the plastic liner and the inner wall of the surfacing layer, a better connection and transition can be formed between the plastic liner and the surfacing layer, and the exposed inner wall of the outer steel pipe in the pipe cavity of the plastic-lined composite steel pipe can be avoided.
[0027] Also, since the material of the surfacing layer is corrosion-resistant stainless steel or nickel alloy, in this way, the inner wall of the entire plastic-lined composite steel pipe formed by the inner wall of the surfacing layer and the inner wall of the plastic liner has corrosion resistance.
[0028] 3. At the same time, an anti-corrosion sealing layer is provided between the pipe end of the plastic liner and the inner wall of the surfacing layer, which further enhances the sealing performance between the plastic liner and the surfacing layer, can reduce the possibility of corrosive gas seeping into the inner wall of the outer steel pipe from the connection between the plastic liner and the surfacing layer during use, and reduce the corrosion risk to the outer steel pipe. Description of the Drawings
[0029] Figure 1 It is a schematic structural diagram of a plastic-lined composite steel pipe containing the pipe end structure described in the present invention.
[0030] Figure 2 is Figure 2 the side view of
[0031] Figure 3 is the sectional view taken along the line A-A.
[0032] Figure 4 is the sectional structural schematic diagram of the outer steel pipe after the inner wall of the end is processed by turning and expanding the diameter.
[0033] Figure 5It is a schematic diagram of the cross-sectional structure of two plastic-lined composite steel pipes after being butted together in the utility model.
[0034] In the picture:
[0035] 1-outer steel pipe, 12-annular expansion groove, 121-annular side wall, 123-root side wall, 2-surfacing layer, 21-welding groove surface, 22-blunt edge, 3-plastic liner, 4-plastic-lined composite steel pipe lumen, 5-welding groove. DETAILED DESCRIPTION
[0036] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.
[0037] like Figures 2 to 4 As shown, the present invention provides a pipe end structure of a plastic-lined composite steel pipe, wherein the outer layer of the plastic-lined composite steel pipe is an outer steel pipe 1, and the inner layer is a plastic liner 3. The outer steel pipe 1 is a carbon steel pipe, and the material can be 16Mn, L245, L415, etc., which comply with pipeline materials such as GB / T3091, GB / T3092, and GB / T9711. The material of the plastic liner 3 can be hard polyethylene (PVC-U), chlorinated polyvinyl chloride (CPVC), polyethylene (PE), polypropylene (PP), cross-linked polyethylene (PEX), etc., which comply with the CJ / T136 standard. There is an adhesive between the outer steel pipe 1 and the plastic liner 3 to enhance the connection strength between the outer pipe and the inner pipe.
[0038] like Figure 3 As shown, the inner wall of the outer steel pipe 1 is provided with a concave annular groove in the radial direction. The concave annular groove extends inward along the edge of the pipe mouth of the outer steel pipe 1. The inner wall of the concave annular groove is covered with a tubular cladding layer 2. In this embodiment, the concave annular groove is an inner groove provided in the radial direction of the inner wall of the outer steel pipe 1. The cladding layer 2 is used to accommodate the cladding layer 2. The cladding layer 2 located in the concave annular groove covers the inner wall of the concave annular groove and fills the concave annular groove. Figure 2 、 3 shown.
[0039] like Figure 3 As shown, the inner diameter of the cladding layer 2 is equal to the inner diameter of the outer steel pipe 1, that is, the inner wall of the cladding layer 2 is flush with the inner wall of the outer steel pipe 1. The material of the cladding layer 2 can be corrosion-resistant stainless steel or nickel alloy materials such as 304, 316, 316L, 2209, and 625.
[0040] In this embodiment, a welding groove surface 21 is provided at the outer pipe end of the surfacing layer 2, as shown in Figure 3 . After the two plastic-lined composite steel pipes are butted, the welding groove between the two welding groove surfaces 21 is the welding groove. During welding, the welding groove surface 21 is the part to be welded and is in direct contact with the solder.
[0041] In this embodiment, the length of the surfacing layer 2 is L1, and L1 is also the length of the inner wall of the surfacing layer 2; there is a covering section between the outer wall of the end of the plastic liner 3 and the inner wall of the surfacing layer 2 (specifically as shown in Figure 3 ), and the length of this covering section is L3; there is a spacing between the outer pipe end of the surfacing layer 2 and the pipe end of the plastic liner 3, and this spacing is L2. As shown in Figure 3 , L2 = L1 - L3.
[0042] Preferably, the thickness of the surfacing layer 2 can be set to 2 - 3 mm, and L3 can be set to 10 - 15 mm; at the same time, when L1 is set to more than 60 mm, then L2 is at least more than 45 mm. In this way, it is ensured that the surfacing layer 2 has a certain thickness, and the pipe end of the plastic liner 3 is at a certain distance from the welding groove surface 21, and during the subsequent welding process, the risk of damage to the pipe end of the plastic liner 3 caused by the welding high temperature is smaller.
[0043] As shown in Figure 3 , due to the existence of the covering section, a good transitional connection is formed between the surfacing layer 2 and the plastic liner 3, and there is no exposed inner wall of the outer steel pipe 1 between the surfacing layer 2 and the plastic liner 3.
[0044] At the same time, an anti-corrosion sealing layer is provided between the pipe end of the plastic liner 3 and the inner wall of the surfacing layer 2, which can be used to further enhance the sealing performance between the plastic liner 3 and the surfacing layer 2, and can reduce the risk of corrosive gas infiltrating from the connection between the plastic liner 3 and the surfacing layer 2 into the inner wall of the outer steel pipe 1 during use, and reduce the corrosion risk to the outer steel pipe 1.
[0045] However, when two plastic-lined composite steel pipes including the pipe end structure described in the present invention are welded and connected, since the end face of the plastic liner 3 is not the welding contact surface and is far from the welding groove surface 21 at the outer pipe end of the surfacing layer 2, during welding, the plastic liner 3 is not in direct contact with the solder and is less affected by high temperature. Therefore, after welding, the loss of the plastic liner 3 is smaller. At the same time, since the surfacing layer 2 is formed by surfacing with a corrosion-resistant stainless steel or nickel alloy material, it has a certain corrosion resistance. After welding, the inner wall of the connected plastic-lined composite steel pipe is jointly formed by the inner wall of the surfacing layer 2 and the inner wall of the plastic liner 3. Therefore, the inner wall of the entire plastic-lined composite steel pipe has corrosion resistance.
[0046] By using the pipe end structure of the present invention, two plastic-lined composite steel pipes can be connected by welding, thereby improving the connection strength of the connection part, reducing the shortcomings of the original threaded structure and snap-on structure due to their lack of resistance to high pressure and easy leakage, and at the same time expanding the scope of product use.
[0047] The manufacturing process of the plastic-lined composite steel pipe including the pipe end structure described in the utility model is briefly as follows:
[0048] First, the inner wall of the port of the outer steel pipe 1 is expanded and turned to form an annular expansion groove 12, as shown in FIG. Figure 4 As shown. The inner wall of the annular expansion groove 12 is composed of an annular side wall 121 and a root side wall 123; Figure 4 As shown, the annular side wall 121 is close to the pipe opening of the outer steel pipe 1 and is located on the outside. The root side wall 123 is an inclined surface and is located on the inside. The inclined surface is perpendicular to the pipe wall of the outer steel pipe 1 (as shown in FIG. Figure 4 The angle between the vertical dotted line in Figure 4 The angle a) can be between 35-45 degrees.
[0049] Next, corrosion-resistant stainless steel or nickel alloy is welded inside the annular expansion groove using automated tungsten inert gas arc welding. This creates an annular weld overlay of a predetermined thickness along the inner wall of the annular expansion groove, tightly covering the inner wall. The inner wall of the weld overlay is then lathed until it is flush with the unmachined inner wall of the outer steel pipe 1, resulting in an inner diameter that is identical to the inner diameter of the outer steel pipe 1. This eliminates any steps during the subsequent expansion of the plastic liner, preventing it from being assembled and expanding.
[0050] Then, a plastic liner with an outer wall coated with adhesive is placed in the inner cavity of the outer steel pipe 1 to expand the diameter, so that the carbon steel pipe and the inner liner are compounded into a plastic-lined composite pipe.
[0051] Next, part of the plastic liner on the surfacing filling layer is cut off, leaving 10-15 mm covering the surfacing filling layer, and an anti-corrosion sealant (such as epoxy resin) is used to seal between the inner wall of the surfacing filling layer and the end of the plastic liner to form a sealing layer.
[0052] Finally, the end of the plastic-lined composite steel pipe is cut and grooved. After the groove is grooved, the angle between the welding groove surface 21 and the vertical line of the outer steel pipe 1 (i.e. Figure 5 Angle b) can be between 30 and 35 degrees. Angle b also represents the groove angle of weld groove surface 21. In this embodiment, a blunt edge 22 is left at the end of weld overlay layer 2. This blunt edge 22 can be between 0.8 and 2.4 mm. A blunt edge is the ungrooved end surface along the thickness of the weldment during weld beveling.
[0053] As Figure 3 shown, in this embodiment, the structures of the left and right pipe ends of the plastic-lined composite steel pipe are the same.
[0054] As Figure 5 shown, the outer pipe end of the surfacing layer 2 and the pipe end face of the outer steel pipe 1 together form a bevel face. After two plastic-lined composite steel pipes are butted, a V-shaped welding groove 5 is formed between the two bevel faces, as Figure 5 shown.
[0055] After welding the two plastic-lined composite steel pipes as Figure 3 shown, the inner walls of the formed plastic-lined composite steel pipes are both composed of the surfacing layer 2 and the plastic lining pipe 3, that is, the inner walls of the outer steel pipe 1 are covered by the surfacing layer 2 with corrosion resistance and the plastic lining pipe 3, and a sealant is also used between the surfacing layer 2 and the plastic lining pipe 3, so that the inner wall of the plastic-lined composite steel pipe after welding still has good corrosion resistance.
Claims
1. A pipe end structure of a plastic-lined composite steel pipe. The outer layer of the plastic-lined composite steel pipe is an outer steel pipe (1), and the inner layer is a plastic lining pipe (3); characterized in that: The inner wall of the pipe end of the outer steel pipe (1) is radially provided with an inwardly concave annular groove, which extends inward along the edge of the pipe orifice of the outer steel pipe (1); the inner wall of the inwardly concave annular groove is covered with a surfacing layer (2); the surfacing layer (2) is tubular; There is a spacing between the outer pipe end of the surfacing layer (2) and the pipe end of the plastic liner pipe (3); The outer pipe end of the surfacing layer (2) is provided with a welding groove surface (21); The material of the surfacing layer (2) is corrosion-resistant stainless steel or nickel alloy.
2. The pipe end structure of a plastic-lined composite steel pipe according to claim 1, characterized in that: There is a covering section between the outer wall of the end of the plastic liner pipe (3) and the inner wall of the surfacing layer (2).
3. The pipe end structure of the plastic-lined composite steel pipe according to claim 2, characterized in that: An anti-corrosion sealing layer is provided between the pipe end of the plastic liner pipe (3) and the inner wall of the surfacing layer (2).
4. The pipe end structure of a plastic-lined composite steel pipe according to claim 3, characterized in that: The length of the covering section is 10 - 15 mm; the length of the surfacing layer (2) is more than 60 mm; The length of the spacing between the outer pipe end of the surfacing layer (2) and the pipe end of the plastic liner pipe (3) is more than 45 mm.
5. The pipe end structure of a plastic-lined composite steel pipe according to claim 4, characterized in that: The thickness of the surfacing layer (2) is 2 - 3 mm.
6. A pipe end structure of a plastic-lined composite steel pipe according to any one of claims 1-5, characterized in that: The inner diameter of the surfacing layer (2) is equal to the inner diameter of the outer steel pipe (1).
7. The pipe end structure of a plastic-lined composite steel pipe according to claim 6, characterized in that: The welding groove surface (21) is an inclined surface, and the groove surface angle is between 30 - 35 degrees.
8. The end structure of the plastic-lined composite steel pipe according to claim 7, characterized in that: The outer pipe end of the surfacing layer (2) is also provided with a root face (22).
9. The pipe end structure of a plastic-lined composite steel pipe according to claim 8, characterized in that: The inwardly concave annular groove is composed of two parts: an annular side wall (121) and a root side wall (123) which are distributed from outside to inside in sequence; the included angle between the root side wall (123) and the perpendicular line of the pipe wall of the outer steel pipe (1) is between 35 - 45 degrees.