Novel anti-corrosion and manufacturing method of steel-plastic conversion pipe fitting

Abstract

The invention discloses a novel anti-corrosion and manufacturing method of a steel-plastic conversion pipe fitting, which comprises the following steps: firstly, coating a steel pipe and a locking ring with an anti-corrosion layer by adopting an FBE anti-corrosion process to realize internal anti-corrosion, and after coating, assembling a PE plastic pipe, the steel pipe and the locking ring through a cold press molding or injection molding process to complete manufacturing of the FBE anti-corrosion steel-plastic conversion pipe fitting. Then the FEB anticorrosion steel-plastic conversion pipe fitting is spirally wound with a special anticorrosion adhesive tape, anticorrosion of the outer layer of the FEB anticorrosion steel-plastic conversion pipe fitting is achieved, through internal and external combined anticorrosion, on one hand, the steel-plastic conversion pipe fitting has a good anticorrosion effect, and on the other hand, even if local damage is caused to the outer anticorrosion layer in the process of transportation or construction installation and the like, the steel-plastic conversion pipe fitting cannot be damaged. Repair can be carried out at any time, and loss such as scrapping or secondary construction cannot be caused.

Description

Technical Field

[0001] The present invention relates to the field of gas pipeline systems, and in particular to a novel anti-corrosion and manufacturing method of a steel-plastic conversion pipe fitting. Background Art

[0002] Steel-plastic conversion fittings are typically used as inlet pipes for buried gas pipelines entering homes from courtyards. Outdoor buried gas pipelines are typically PE pipes, while metal pipes are required for the gas pipelines entering homes. Therefore, steel-plastic conversion fittings are used for the connection between the PE pipe and the metal pipe. Conventional steel-plastic conversion fittings primarily consist of three parts: a plastic end, a locking ring / inner support ring, and a metal component. The plastic component is located between the locking ring / inner support ring and the metal component and is cold-pressed in place by the metal structures on both the inner and outer sides. An anti-corrosion layer is applied to the outer surface of the steel-plastic conversion fitting to prevent corrosion during underground use, which could lead to gas leaks.

[0003] There are generally two mainstream corrosion protection methods. One is FBE (Fused Beta Carburization) corrosion protection, in which fused-beta carburization (FBE) powder is sprayed onto the steel pipe surface using a spray gun under high-voltage electrostatic pressure. Under high-temperature conditions, the powder coating leveled and cured on the steel pipe surface, forming a fused-beta carburization (FBE) powder coating. After FBE corrosion protection, the plastic end, locking ring / inner support ring, and metal parts are assembled through cold pressing or injection molding to form the steel-plastic conversion fitting. FBE-treated steel-plastic conversion fittings offer excellent resistance to acid, alkali, and electrochemical corrosion, but they also have some drawbacks, such as relatively poor resistance to bumps and scratches. Transportation and construction often damage the FBE layer, leading to severe corrosion within one or two years of use. To address this issue, some manufacturers use enhanced FBE corrosion protection, increasing the thickness of the anti-corrosion layer to improve bump resistance. Alternatively, double or multiple layers of FBE corrosion protection are used, with the inner layer prioritizing corrosion resistance and the outer layer emphasizing scratch and bump resistance. However, the anti-corrosion coating material used in these methods is still fusion-bonded epoxy powder coating. While this improves the anti-corrosion layer's resistance to knocks and bruises to a certain extent, it still cannot fundamentally address the inherent resistance of fusion-bonded epoxy powder coating. Furthermore, the thicker the FBE layer, the less ductile and brittle the anti-corrosion layer becomes, making it more susceptible to cracking during construction and use.

[0004] The other method is 3PE anti-corrosion, which uses a heat shrink sleeve (with an inner layer of polyolefin hot-melt adhesive and an outer layer of polyethylene) on top of the FBE anti-corrosion layer for secondary corrosion protection. The process involves preheating the surface of the assembled FBE anti-corrosion steel-plastic conversion pipe to above 60°C (some manufacturers require above 80°C), then applying epoxy primer. The pipe is then inserted into a cut-to-length heat shrink sleeve. The sleeve shrinks at 150-180°C, allowing the inner layer of hot-melt adhesive to firmly bond the polyethylene layer to the FBE anti-corrosion layer on the steel pipe. The heat shrink sleeve offers excellent resistance to bumps and scratches, and also provides excellent corrosion protection. However, the production process is relatively complicated, involving processes such as preheating of steel pipes, application of epoxy primer, and heat shrink sleeve covering. The production process also has high technical requirements. For example, the preheating temperature cannot be too low, and there are requirements for the uniformity of mixing the two components AB of the epoxy primer, the uniformity of application, and the use time of the primer. At the same time, the shrinkage temperature of the heat shrink sleeve is generally required to be at least around 150-180°C, while the softening point of the plastic end is only around 120°C. Therefore, it is easy to cause burns or scorching problems. At the same time, high temperature can easily have an adverse effect on the connection sealing of steel-plastic conversion fittings.

[0005] Other corrosion protection methods for steel-plastic conversion fittings are currently less commonly used. For example, galvanizing is far less effective than FBE and 3PE, and is therefore gradually being replaced. Polyurea and FBE combined with polyethylene coatings are limited by material and equipment costs, as well as high technical and process requirements, making them difficult to mass-produce for steel-plastic conversion fittings. Furthermore, damage to the surface corrosion protection layer during transportation, installation, or backfilling is difficult to repair on-site, resulting in the scrapping of steel-plastic conversion fittings, construction losses, and the loss of the long-term corrosion protection of the pipeline system.

[0006] To this end, the present invention proposes a new anti-corrosion and manufacturing method for steel-plastic conversion pipe fittings, which are resistant to knocks and scratches, easy to construct and more convenient to repair. Summary of the Invention

[0007] In view of the problems existing in the prior art, the purpose of the present invention is to provide a new anti-corrosion and manufacturing method for steel-plastic conversion pipe fittings, which solves the impact of high temperature conditions in the anti-corrosion process on the plastic end and the sealing structure of the pipe fittings, and is more convenient to construct. Even if the external anti-corrosion layer is locally damaged under special conditions during transportation or construction and installation, it can be repaired at any time without causing losses such as scrapping or secondary construction.

[0008] To achieve the above object, the technical solution of the present invention is as follows: A novel anti-corrosion and manufacturing method for a steel-plastic conversion pipe fitting, the steel-plastic conversion pipe fitting comprising a PE plastic pipe, a steel pipe and a locking ring, comprising the following steps: 1) First, the steel pipe and locking ring are coated with an anti-corrosion layer using the FBE anti-corrosion process. After coating, the PE plastic pipe, steel pipe and locking ring are assembled through cold pressing or injection molding to complete the production of the FBE anti-corrosion steel-plastic conversion pipe fittings; 2) After the production of the FBE anti-corrosion steel-plastic conversion pipe fittings in step 1 is completed, the FEB anti-corrosion steel-plastic conversion pipe fittings are spirally wrapped with anti-corrosion tape to achieve corrosion protection of the outer layer.

[0009] Furthermore, the specific process of step 2) is as follows: 2.1) First, check that the FBE steel-plastic conversion pipe fittings have no problems with epoxy layer damage, steel pipe surface dents, plastic parts scratches, and bends; 2.2) Then the anti-corrosion tape should be spirally wrapped starting from the plastic end, covering layer by layer, and the coverage area should reach 50%-70%, ending at the end of the steel pipe; 2.3) After the final wrapping is completed, the sealing position of the anti-corrosion tape should be set at a position where there is no obvious step on the product and it should be completely close to the surface of the pipe body to complete the wrapping.

[0010] Furthermore, in step 2.2), transition rings should be installed at locations where the outer diameter of the steel-plastic conversion pipe changes significantly to avoid local gaps caused by tape wrapping.

[0011] Furthermore, if a roll of anti-corrosion tape is used up during the winding process in step 2.2), the overlap length between the new tape and the end of the wound tape should be greater than 50 mm, but not more than the length of two wraps of the wound tape. The tape should be smoothed by hand while being wound to ensure that there are no bubbles on the product surface.

[0012] Furthermore, the length of the plastic end winding in step 2.2) is preferably 40-50 mm.

[0013] Furthermore, the anti-corrosion tape includes a room temperature adhesive layer and a vinyl chloride resin base material layer, wherein the vinyl chloride resin base material layer is arranged outside the room temperature adhesive layer, wherein the room temperature adhesive layer has a use temperature of -30°C to -80°C.

[0014] Furthermore, the anti-corrosion tape width*thickness is 25-50mm*0.5-3.0mm.

[0015] Furthermore, in step 1), the thickness of the FBE anti-corrosion layer is at least 300 μm.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: 1) The present invention first coats the steel pipe and the locking ring with an anti-corrosion layer using the FBE anti-corrosion process to achieve internal corrosion protection. After coating, the PE plastic pipe, the steel pipe and the locking ring are assembled through a cold pressing or injection molding process to complete the production of the FBE anti-corrosion steel-plastic conversion pipe fitting. Then, a special anti-corrosion tape is used to spirally wrap the FEB anti-corrosion steel-plastic conversion pipe fitting to achieve corrosion protection of its outer layer. Through the combined internal and external corrosion protection, on the one hand, the steel-plastic conversion pipe fitting has a good corrosion protection effect. On the other hand, even if the external anti-corrosion layer is partially damaged during transportation or construction and installation, it can be repaired at any time without causing losses such as scrapping or secondary construction. 2) The inner layer of the anti-corrosion tape of the present invention is a room-temperature adhesive layer that has good bonding properties at room temperature and does not require high-temperature heating. The outer layer is a vinyl chloride resin base material that has good UV resistance, weather resistance, chemical corrosion resistance, and electrical insulation properties; 3) The present invention has the characteristics of good anti-corrosion effect, excellent resistance to knock and scratch, simple anti-corrosion process, and no high temperature requirement. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a structural diagram of the steel-plastic conversion pipe fitting of the present invention; Figure 2 This is a schematic diagram of the structure of the steel-plastic conversion pipe fitting after corrosion protection.

[0018] In the figure: 1. PE plastic pipe; 2. Steel pipe; 3. Locking ring. DETAILED DESCRIPTION

[0019] The present invention will be further described below with reference to the accompanying drawings, but the scope of protection of the present invention is not limited to the described scope.

[0020] Please refer to Figure 1-2 A novel anti-corrosion and manufacturing method for a steel-plastic conversion pipe fitting, comprising a PE plastic pipe 1, a steel pipe 2 and a locking ring 3, comprising the following steps: 1) First, the steel pipe 2 and the locking ring 3 are coated with an anti-corrosion layer using the FBE anti-corrosion process. After coating, the PE plastic pipe 1, the steel pipe 2 and the locking ring 3 are assembled through a cold pressing or injection molding process to complete the production of the FBE anti-corrosion steel-plastic conversion pipe fitting; Furthermore, the thickness of the FBE anti-corrosion layer is at least 300um.

[0021] 2) Then, a special anti-corrosion tape is used to spirally wrap the FEB anti-corrosion steel-plastic conversion pipe fittings to achieve corrosion protection on their outer layer. The specific process is as follows: 2.1) First, check that the FBE steel-plastic conversion pipe fittings have no problems with epoxy layer damage, steel pipe surface dents, plastic parts scratches, and bends; 2.2) Then the anti-corrosion tape should be spirally wrapped starting from the plastic end, covering layer by layer, and the coverage area should reach 50%-70%, ending at the end of the steel pipe; Furthermore, in step 2.2), transition rings should be installed at locations where the outer diameter of the steel-plastic conversion pipe changes significantly to avoid local gaps caused by tape wrapping; Furthermore, if a roll of anti-corrosion tape is used up during the winding process in step 2.2), the overlap length between the new tape and the end of the wound tape should be greater than 50 mm, but not more than the length of two wraps of the wound tape. The tape should be smoothed by hand while being wound to ensure that there are no bubbles on the product surface.

[0022] Furthermore, the length of the plastic end winding in step 2.2) is preferably 40-50 mm.

[0023] 2.3) After the final wrapping is completed, the sealing position of the anti-corrosion tape should be set at a position where there is no obvious step on the product and it should be completely close to the surface of the pipe body to complete the wrapping.

[0024] The anti-corrosion tape of the present invention comprises a room-temperature adhesive layer and a vinyl chloride resin layer. The vinyl chloride resin base layer is disposed externally to the room-temperature adhesive layer. The room-temperature adhesive layer has an operating temperature range of -30°C to -80°C and exhibits excellent bonding properties at room temperature, without the need for high-temperature heating. The vinyl chloride resin layer exhibits excellent UV resistance, weather resistance, chemical resistance, and electrical insulation properties. The recommended dimensions of the anti-corrosion tape in this embodiment are 25-50 mm in width and 0.5-3.0 mm in thickness.

[0025] If the surface of the anti-corrosion tape is damaged by scratches, bumps, etc. during installation, construction, transportation, etc., the same tape can be used directly for on-site repair. The tape should cover the upper and lower parts of the damaged area by at least 50mm. The thickness of the anti-corrosion tape at the damaged part should not be less than the thickness of the main anti-corrosion layer of the steel-plastic conversion pipe fitting. Example 1

[0026] When the novel anti-corrosion and manufacturing method of the present invention is adopted, the FBE layer thickness of the steel pipe 2 and the locking ring 3 of the steel-plastic conversion pipe fitting is 300-400 μm, and the thickness of the anti-corrosion tape is 500 μm. The anti-corrosion effect of the steel-plastic conversion pipe fitting is shown in Table 1 below: Table 1: Anticorrosion Effect

[0027] As can be seen from Table 1, through the anti-corrosion and manufacturing method of the present invention, the steel-plastic conversion pipe fitting has good bending resistance, good impact strength, no leak points in the coating and good anti-corrosion effect.

Claims

1. A novel anti-corrosion and manufacturing method for a steel-plastic conversion pipe fitting, the steel-plastic conversion pipe fitting comprising a PE plastic pipe (1), a steel pipe (2) and a locking ring (3), characterized in that The steps include: 1) First, the steel pipe (2) and the locking ring (3) are coated with an anti-corrosion layer by using the FBE anti-corrosion process, and after the coating, the PE plastic pipe (1), the steel pipe (2) and the locking ring (3) are assembled by cold pressing or injection molding to complete the production of the FBE anti-corrosion steel-plastic conversion pipe fitting; 2) After the production of the FBE anti-corrosion steel-plastic conversion pipe fittings in step 1 is completed, the FEB anti-corrosion steel-plastic conversion pipe fittings are spirally wrapped with anti-corrosion tape to achieve corrosion protection of the outer layer.

2. A new type of anti-corrosion and manufacturing method for steel-plastic conversion pipe fittings according to claim 1, characterized in that The specific process of step 2) is as follows: 2.1) First check that the FBE steel-plastic conversion pipe fittings have no epoxy layer damage, steel pipe surface depressions, plastic parts scratches, and elbow wrinkles; 2.2) Then the anti-corrosion tape should be spirally wound starting from the plastic end, covering layer by layer, and the coverage area should reach 50%-70%, ending at the end of the steel pipe; 2.3) After the final winding is completed, the sealing position of the anti-corrosion tape should be set at a position where there is no obvious step on the product and it should be completely close to the surface of the pipe body to complete the winding.

3. A novel anti-corrosion manufacturing method for steel-plastic conversion pipe fittings according to claim 2, characterized in that In step 2.2), transition rings should be installed at locations where the outer diameter of the steel-plastic conversion pipe changes significantly to avoid local gaps caused by tape wrapping.

4. A novel anti-corrosion manufacturing method for steel-plastic conversion pipe fittings according to claim 2, characterized in that In step 2.2), if a roll of anti-corrosion tape is used up during the winding process, the overlap length between the new tape and the end of the wound tape should be greater than 50mm, but not more than two turns of the wound tape. The tape should be smoothed by hand while being wound to ensure that there are no bubbles on the product surface.

5. A novel anti-corrosion manufacturing method for steel-plastic conversion pipe fittings according to claim 2, characterized in that In step 2.2), the length of the plastic end wrapping should be 40-50mm.

6. The novel anti-corrosion manufacturing method of a steel-plastic conversion pipe fitting according to claim 1 is characterized in that The anticorrosive tape comprises a room temperature adhesive layer and a vinyl chloride resin substrate layer, wherein the vinyl chloride resin substrate layer is arranged outside the room temperature adhesive layer, wherein the room temperature adhesive layer has a use temperature of -30°C to -80°C.

7. The novel anti-corrosion manufacturing method of a steel-plastic conversion pipe fitting according to claim 1 is characterized in that The width and thickness of the anti-corrosion tape are 25-50mm*0.5-3.0mm.

8. The novel anti-corrosion manufacturing method of a steel-plastic conversion pipe fitting according to claim 1 is characterized in that In step 1), the thickness of the FBE anti-corrosion layer is at least 300um.

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