Under-pressure in-situ repair method for equipment pipeline of large hydropower station

Abstract

The invention discloses an under-pressure in-situ repair method for an equipment pipeline of a large hydropower station, and belongs to the technical field of additive repair, and the under-pressure in-situ repair method for the equipment pipeline of the large hydropower station is characterized by comprising the following steps: S1, carrying out surface treatment on a to-be-repaired matrix to remove oil stains; s2, the defect area is filled with casting glue; and S3, the metal-polymer composite powder is used as a raw material, and a cold spraying process is adopted to conduct spraying repair on the defect area. According to the cold spraying technology, a compact coating with excellent mechanical property can be formed, so that the risks of thermal stress, deformation and crack propagation are avoided, the repair reliability is remarkably improved, the potential safety hazard of fire operation in dangerous environments such as high pressure is avoided, efficient online repair can be realized, and the cold spraying technology is suitable for equipment repair in various complex environments; wide application prospects are realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of additive repair technology, in particular to a large hydropower station equipment pipeline in-situ repair method under pressure. BACKGROUND

[0002] As key pressure-bearing components of the fluid conveying system of a hydropower station, the structural integrity and sealing reliability of pipelines and valves are directly related to the safe and stable operation of the entire power station. These devices are in high-pressure and high-load working conditions for a long time and are continuously exposed to complex media such as air, water vapor, and oil, and bear alternating loads and medium erosion and corrosion, which can easily cause cracks, corrosion perforation, and other damage, thereby causing medium leakage and seriously threatening the safe and stable operation of the power station.

[0003] In the face of leakage problems, the most direct way for the current industry is to replace new components, but this requires the system to be shut down for a long time, which will result in huge power generation losses and economic costs.

[0004] In addition to replacing components, the main way to deal with leakage of key pressure-bearing components is on-site repair. The traditional on-site repair method mainly uses welding and sealing glue to plug leaks.

[0005] CN120907036A discloses a pressure pipeline repair device and method. The repair assembly of the invention uses an electromagnetic plate to generate an alternating magnetic field to non-contact heat the plugging plate and the low-melting welding fusion plate. The low-melting welding fusion plate can effectively bond the plugging plate and the damaged part of the pipeline after cooling, achieving online welding repair of the leakage point from the outside of the pipeline.

[0006] CN120799251A discloses a quick leak plugging and repair method for a hydropower station pressure pipeline. The invention accurately injects strong corrosion-resistant fast-setting sealant into the leakage site using a high-pressure glue gun to fill the sealing space and complete the repair. The invention can quickly and effectively plug and repair the leakage site of the pressure pipeline without stopping the operation of the hydropower station.

[0007] However, the above traditional repair methods have the following limitations: 1) The high-temperature heat input generated during the welding process will introduce a large amount of concentrated thermal stress, which can easily cause the original micro-cracks in the component to expand or induce new welding cracks and deformation, leading to "more cracks after repair" and exacerbating the risk of leakage.

[0008] 2) Welding in a high-pressure environment also poses a significant safety hazard. Improper operation can cause serious safety accidents.

[0009] 3) The sealing glue depends on the strength and adhesion of the adhesive itself, and in the harsh working conditions of continuous high pressure (such as more than 0.5MPa) and medium scouring, the sealing glue is easy to be washed out by high pressure medium, and the long-term sealing reliability and pressure bearing capacity are insufficient.

[0010] CN107794525A discloses a cold spraying sealing method for a vacuum system, which adopts cold spraying technology to seal the determined leakage point, and can realize sealing of the vacuum system. The leakage point position of the vacuum system includes weld cracks, pipeline and vacuum valve connection, pipeline and expansion joint connection, and flange connection.

[0011] Although such cold process technology does not have heat input influence and has certain application potential, it is mainly suitable for repairing micro cracks or surface damage at present, and is limited by technical characteristics. It is still difficult to effectively and quickly seal the leakage for macro corrosion perforation, notch and other larger defects (such as >3mm) commonly seen in the pressure pipeline / equipment of the hydropower station.

[0012] In summary, the existing technical system urgently needs a safe and efficient repair method that can simultaneously have reliable pressure bearing capacity and effectively repair various defects including macro holes under the premise of not stopping and not generating thermal stress when facing the in-situ repair demand of the pressure pipeline valve of the hydropower station.

[0013] In order to solve the above problems, a large-scale hydropower station equipment pipeline pressure in-situ repair method is provided on the basis of the existing technology. SUMMARY

[0014] The purpose of the present application is to prepare a dense coating with excellent mechanical properties, thereby avoiding the risk of thermal stress, deformation and crack propagation, significantly improving the repair reliability, avoiding safety hazards in high pressure and other dangerous environments, and realizing efficient online repair, suitable for equipment repair in various complex environments, and having wide application prospect.

[0015] The above technical purpose of the present application is realized by the following technical scheme: The present application provides a large-scale hydropower station equipment pipeline pressure in-situ repair method, the steps are as follows: S1, surface treatment is performed on the repaired substrate to remove oil stains; S2, the defect area is filled with foundry glue; S3, using metal-polymer composite powder as raw material, cold spraying process is used to spray and repair the defect area.

[0016] Further, steps S4 and S5 are further included: S4, the surface of the coating obtained by step S3 is polished to be smooth; S5. Clean the area to be repaired by spraying, removing excess spraying material and impurities.

[0017] Furthermore, in step S3, the metal-polymer composite powder includes resin, metal powder, and ceramic powder.

[0018] Furthermore, the preparation method of the metal-polymer composite powder is as follows: 1) Using resin and metal powder as raw materials, prepare a resin-coated metal powder; 2) Mix the coating powder and ceramic powder to form a metal-polymer composite powder.

[0019] Furthermore, the raw material components of the resin include bisphenol A type epoxy acrylate and acrylate compounds containing alicyclic epoxy functional groups.

[0020] Furthermore, the metal powder is aluminum powder, and the particle size of the aluminum powder is 15μm to 53μm.

[0021] Furthermore, the ceramic powder is alumina powder, and the particle size of the alumina powder is 5μm to 50μm.

[0022] Furthermore, the weight ratio of resin to metal powder is 5-10:90-95; the weight ratio of coating powder to ceramic powder is 90-96:4-10.

[0023] Furthermore, the time interval between steps S2 and S3 is 15 min to 35 min.

[0024] Furthermore, in step S3, the sprayed repair area completely covers the defect area in step S2, and the boundary of the sprayed repair area extends outward by 1cm to 2cm from the boundary of the defect area.

[0025] Furthermore, in step S3, the process parameters for cold spraying are: spraying temperature of 200-350℃, spraying pressure of 400Psi-500Psi, spraying angle of 60°-90°, and spraying distance of 25-40mm.

[0026] In summary, the present invention has the following beneficial effects.

[0027] 1. The cold spraying technology used in this invention is based on the principle of solid deposition. It has the characteristics of low process temperature, short spraying time, and almost no oxidation and phase change during coating preparation. It can form a dense coating with excellent mechanical properties, thereby avoiding the risks of thermal stress, deformation and crack propagation, and significantly improving the reliability of repair.

[0028] 2. The low heat and solid deposition characteristics of cold spraying process can effectively avoid welding / hot work safety hazards in dangerous environments such as high pressure.

[0029] 3. Due to its characteristics, cold spraying technology can achieve efficient online repair, significantly reduce or even eliminate system shutdown and depressurization processes, and greatly reduce power generation losses caused by shutdown. This method is highly economical, easy to operate, and highly efficient, and is suitable for equipment repair in various complex environments, with broad application prospects.

[0030] 4. The repaired part of the present invention has high bonding strength. Under the harsh working conditions of continuous high pressure and media erosion, it can effectively avoid the defect that the sealing colloid is easily washed out by the high pressure medium, and has high long-term sealing reliability and strong pressure resistance.

[0031] 5. The method of the present invention exceeds the application limitation of cold spraying technology in the repair of micro-cracks (<1mm) or surface damage. It can be applied to the repair of larger defects such as macro-corrosion perforation and gaps that are common in pressure pipelines / equipment, and can achieve effective and rapid leak sealing.

[0032] 6. The coating structure in this invention includes a casting adhesive layer to fill the defect and a sprayed repair layer covering the surface of the defect. After the casting adhesive is applied to the defect to repair it, a certain leak-stopping effect has been achieved. The use of cold spraying technology to prepare the sprayed repair layer will further improve the sealing effect. Moreover, due to its dense and high adhesion properties, the cold spray repair layer can effectively isolate the corrosion of the adhesive by external air and moisture, ensuring the long-term and stable leak-stopping effect.

[0033] In the sprayed repair layer, the surface of the metal powder is coated with a layer of resin, which provides a basic bonding and cross-linking skeleton, ensuring the mechanical properties of the sprayed repair layer and improving the bonding effect between the sprayed repair coating and the casting adhesive layer. The mixing of metal powder and ceramic powder can effectively improve the powder flowability and the heat resistance of epoxy resin, making it more suitable for the process requirements of cold spraying. At the same time, due to its process characteristics, cold spraying technology will not cause the resin in the powder to oxidize or decompose, which helps to ensure that the resin cross-linking skeleton in the sprayed repair layer plays an effective role.

[0034] Among them, the interface between the casting adhesive layer and the sprayed repair layer can form a strong chemical bond and mechanical interlock, thereby effectively improving the bonding strength between the cold sprayed repair coating and the substrate material and the coated adhesive. Detailed Implementation

[0035] The present invention will now be described in further detail with reference to the embodiments.

[0036] Example 1: A method for in-situ repair of pressurized pipelines in large hydropower stations, the steps of which are as follows: S1. Perform surface treatment on the substrate to be repaired, grind and clean all areas that need to be repaired, remove oil stains, expose the substrate, and meet the requirements of cold spray repair construction. S2, the defect area (plugging point and pit need to be repaired) is filled with foundry glue, and the original substrate surface to be repaired is leveled off, and the next process can be performed after 15-35 minutes; S3, using metal-polymer composite powder (resin, metal powder and ceramic powder) as raw material, portable low pressure cold spraying equipment can be used, and the gun is moved at a uniform speed to spray and repair the defect area and the surrounding area of the foundry glue in step S2. The sprayed and repaired area completely covers the defect area in step S2, and the boundary of the sprayed and repaired area expands outward 1-2 cm based on the boundary of the defect area, forming a dense protective layer.

[0037] The preparation method of the metal-polymer composite powder is as follows: 1) Using resin and metal powder as raw materials, coated powder (coating structure can use common solution mixing method, melting mixing method) of resin wrapped metal powder is prepared; the resin is selected from 80 parts of bisphenol A type epoxy acrylate (CAS number: 71281-65-7, providing basic bonding and crosslinking skeleton to ensure mechanical properties) and 20 parts of acrylate compound containing alicyclic epoxy functional group (such as 3, 4-epoxy cyclohexyl methacrylate ECHMMA, adjusting the viscosity of the system and improving the flowability), the resin can be cured by UV curing, preferably the dual curing mode of UV curing and thermal curing can be used, the thermal curing temperature can be selected from 80-180℃, and the UV curing energy can be selected from 100-1000 mj / cm 2 . The particle size of the aluminum powder is 15-53 μm. The weight ratio of the resin to the metal powder is 10:90.

[0038] 2) Mix the coated powder and ceramic powder to form a metal-polymer composite powder, and the ceramic powder is selected from alumina powder with a particle size of 5-50 μm. The weight ratio of the coated powder to the ceramic powder is 90:10.

[0039] In step S3, the process parameters of cold spraying are as follows: the spraying temperature is 200-350℃, the spraying pressure is 400-500 Psi, the spraying angle is 60-90°, and the spraying distance is 25-40 mm.

[0040] S4, the coating surface obtained by spraying and repairing in step S3 is polished to be smooth to ensure the appearance quality, and the bonding condition of the coating and the substrate is checked to ensure that there are no defects such as bubbles and cracks; S5, the sprayed and repaired area is cleaned to remove excess sprayed material and impurities, and the surface of the equipment is restored to be clean and beautiful.

[0041] Example 2: The difference from example 1 is that the metal powder is selected from nickel powder, and the ceramic powder is selected from aluminum nitride.

[0042] Example 3: The difference from Example 1 is that the weight ratio of resin to aluminum powder is 5:95.

[0043] Example 4: The difference from Example 1 is that the weight ratio of the coating powder to the alumina powder is 96:4.

[0044] Comparative Example 1: A method for in-situ repair of pressurized pipelines in a large hydropower station, the steps of which are as follows: S1. Perform surface treatment on the substrate to be repaired, grind and clean all areas that need to be repaired, remove oil stains, expose the substrate, and meet the requirements of cold spray repair construction. S2. Using metallic aluminum powder and ceramic alumina powder as raw materials, a portable low-pressure cold spraying equipment can be used to move the spray gun at a uniform speed to spray and repair the defective area and its surrounding area. The boundary of the sprayed repair area covers the defective area, and extends outward by 1cm to 2cm from the boundary of the defective area to form a cold spray coating.

[0045] Comparative Example 2: A method for in-situ repair of pressurized pipelines in a large hydropower station, the steps of which are as follows: S1. Perform surface treatment on the substrate to be repaired, grind and clean all areas that need to be repaired, remove oil stains, expose the substrate, and meet the requirements of cold spray repair construction. S2. Fill the defective areas (leakage points and pits that need to be repaired) with casting adhesive until it is flush with the original substrate surface to be repaired. Wait 15 to 35 minutes before proceeding to the next step. S3. Using metallic aluminum powder and ceramic alumina powder as raw materials, a portable low-pressure cold spraying device can be used to move the spray gun at a uniform speed to spray and repair the defective area of ​​the casting adhesive in step S2 and its surrounding area. The sprayed repair area completely covers the defective area in step S2, and the boundary of the sprayed repair area extends outward by 1cm to 2cm from the boundary of the defective area to form a cold spray coating.

[0046] Comparative Example 3: The difference from Example 1 is that in step S3, the resin raw materials in the metal-polymer composite powder are selected as 80 parts of phenolic epoxy acrylate resin and 20 parts of 3,4-epoxycyclohexyl methacrylate.

[0047] The performance tests performed on the samples prepared in the examples and comparisons are as follows: Considering the unique characteristics of in-situ pressurized repair of pipelines in large hydropower stations and the practicalities of cold spraying technology, and given the special nature of the sprayed objects, which preclude destructive testing, in order to verify the effectiveness of the spraying process and the quality of the coating, we prepared accompanying test pieces using the same equipment, the same batch of raw material powder, the same process, and continuous time intervals after the sprayed product, and conducted relevant tests.

[0048] 1) Bond strength performance test The test was performed according to the standard of ASTM C633.

[0049] 2) Hardness test The test was performed according to the standard of GB / T 4340.1.

[0050] 3) Porosity test The test was performed according to the standard of ASTM E2109, and the porosity of the coating was tested by image method, 5 metallographic photos at 200 times were selected, the porosity was detected respectively and the average value was calculated.

[0051] The test results are shown in Table 1.

[0052] Table 1 Test results of the structure performance of the repair coating prepared in the examples Example Bond strength / MPa Hardness HV0.1 Porosity % Example 1 44 65 0.45 Example 2 38 245 0.67 Example 3 36 60 0.56 Example 4 32 61 0.51 Comparative Example 1 19 46 2.3 Comparative Example 2 25 60 0.48 Comparative Example 3 34 61 0.86

[0053] The test results show that after the casting adhesive is coated on the defect part in the scheme, a certain plugging effect can be achieved, and the use of the cold spraying technology to prepare the sprayed repair layer can further improve the plugging effect. In the sprayed repair layer, the metal powder is coated with a layer of resin, which can ensure the mechanical properties of the sprayed repair layer and improve the bonding effect between the sprayed repair coating and the casting adhesive layer.

[0054] The specific embodiments are only an explanation of the present application, and are not a limitation of the present application. Those skilled in the art can make modifications to the embodiments without creative contribution after reading the specification, but as long as the modifications are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A method for in-situ repair coating of a pipeline of a large hydroelectric power plant equipment under pressure, characterized by the steps of As follows: S1, surface treatment is performed on the substrate to be repaired to remove oil stains; S2, the defect area is filled with foundry glue; S3, the defect area is sprayed and repaired by using a cold spraying process with metal-polymer composite powder as raw material.

2. The method according to claim 1, characterized in that, Steps S4 and S5 are also included: S4, the surface of the coating obtained by step S3 is polished to be smooth; S5, the sprayed and repaired area is cleaned to remove excess sprayed material and impurities.

3. The method according to claim 1, characterized in that: In step S3, the metal-polymer composite powder includes resin, metal powder and ceramic powder.

4. The method according to claim 3, characterized in that, The preparation method of the metal-polymer composite powder is as follows: 1) using resin and metal powder as raw material, coated powder of resin wrapped metal powder is prepared; 2) mixing the coated powder and ceramic powder to form metal-polymer composite powder.

5. The method according to claim 4, characterized in that: The raw material components of the resin include bisphenol A type epoxy acrylate and acrylate compound containing alicyclic epoxy functional group.

6. The method according to claim 4, characterized in that: The metal powder is aluminum powder, and the particle size of the aluminum powder is 15μm-53μm.

7. The method according to claim 4, characterized in that, The ceramic powder is alumina powder, and the particle size of the alumina powder is 5μm-50μm.

8. The method according to claim 4, characterized in that: The weight ratio of resin to metal powder is 5-10:90-95; the weight ratio of coated powder to ceramic powder is 90-96:4-10.

9. The method according to any one of claims 1 to 8, characterized in that: The operation time interval of step S2 and step S3 is 15min-35min.

10. The method according to any one of claims 1 to 8, characterized in that: The sprayed and repaired area in step S3 completely covers the defect area in step S2, and the boundary of the sprayed and repaired area extends outward 1cm-2cm based on the boundary of the defect area.

11. The method according to claim 1, characterized in that, In step S3, the process parameters of cold spraying are as follows: spraying temperature is 200-350℃, spraying pressure is 400Psi-500Psi, spraying angle is 60°-90°, and spraying distance is 25-40mm.