Method for repairing falling blocks of runner of small and medium-sized water turbine in high-water-head and high-sediment river

Abstract

The invention relates to a high-water-head high-sediment river small and medium-sized water turbine runner falling block repairing method, and belongs to the technical field of hydroelectric generation. The method comprises the steps of working platform building, surface cleaning, drying, damage recording, blade repair material preparation and installation, alignment placement, welding and the like. The three repairing modes of manual electric welding, argon tungsten-arc welding and high-speed flame spraying are combined, online repairing in a narrow and limited space without disassembling the rotating wheel is achieved, the problem that flow passage components of a field mixed-flow type unit of a medium-high water head hydropower station are abraded and damaged is solved, the cavitation resistance of the surface of the rotating wheel of the water turbine is improved, faults of the water turbine are reduced, and the service life of the water turbine is prolonged. The maintenance period is shortened, the maintenance cost is reduced, and the repair efficiency is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of hydropower generation, and in particular relates to a method for repairing runner block drop of small and medium-sized water turbines in high-head and high-sediment rivers. Background Art

[0002] The hydropower reserves are based on the special regional conditions of great terrain height difference, large river drop and high sediment content in the river. When high-speed water flow hits the runner blades, various forms of cavitation and erosion wear will inevitably occur on the surface of the turbine flow parts. Especially for the runner, the core component of the turbine, if the unit continues to operate after cracks appear in the turbine runner blades, the crack defects will continue to develop, which will easily cause increased friction between the rotating and fixed parts of the unit, increased turbine swing, blade cracks, splitting and dislocation, and even blade pieces falling off, resulting in reduced power generation efficiency, shortening the life of the turbine runner, extending the maintenance period, and increasing costs; in severe cases, it will cause unplanned shutdown of the unit, endangering the safe operation of the unit. It seriously restricts the economic benefits of the hydropower plant and affects the sustainable development of the economy.

[0003] At present, the repair of small and medium-sized turbine runner blocks is almost always done by disassembling and hoisting them underground. The entire repair period is long and the amount of work is large, generally requiring more than 100 days. The reason is that the small and medium-sized runners are located in a small and humid space, 10-30 meters below the ground. Therefore, how to overcome the shortcomings of the existing technology and realize online repair is an urgent problem to be solved in the field of hydropower generation technology. Summary of the invention

[0004] The purpose of the present invention is to solve the deficiencies of the prior art and to provide a simple and efficient method for repairing runner block fall of small and medium-sized water turbines in high-head and high-sediment rivers.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] A method for repairing a runner block fall of a small or medium-sized water turbine in a high-head and high-sediment river comprises the following steps:

[0007] S1: Work platform construction: Set up a work platform in the tailwater pipe to ensure that the turbine runner is located directly above the tailwater work platform;

[0008] S2: Surface cleaning and drying: Use a cleaning agent to remove oil and dirt from the surface of the wheel, and then dry it; at the same time, control the humidity of the environment where the wheel is located not higher than 60% and the temperature not lower than 18°C;

[0009] S3: Damage record: Perform 100% PT flaw detection on the rotor surface, record and mark the distribution, size and type of rotor chipping and cracks;

[0010] S4: Preparation and installation of blade filler material: The blade filler material is made of the same stainless steel material as the runner blade; in the stainless steel material, the mass fraction of Cr is ≥13% and the mass fraction of Ni is ≥4%; the size of the blade filler material is determined according to the maximum abrasion area of ​​the blade;

[0011] The surface and periphery of the blade patch material are polished until smooth; at the same time, the blade to be repaired is trimmed according to the size of the blade patch material, and the trimmed part is polished until the metallic luster is exposed, and then a V-shaped groove is opened at the joint where the blade to be repaired and the blade patch material are to be welded; after trimming, the joint should first be checked by PT for cracks; if cracks exist, the trimming and grinding need to be performed again; if there are no cracks, go to S5;

[0012] S5: Alignment: Before welding, align the blade material with the blade to be repaired, and fix them with spot welding after alignment;

[0013] S6: Welding: Weld the blade patch material placed in position with the blade to be repaired; during welding, the arc starting points of each layer should be staggered by at least 50mm, and the interlayer temperature should be controlled below 170℃;

[0014] S7: Stress relief annealing: Stress relief is required during welding. After the groove is fully welded, an annealing layer needs to be welded and insulation measures should be taken to allow it to cool slowly.

[0015] S8: Surface polishing: Polish the repaired surface of the blade to be repaired until the repaired surface has a smooth transition with the original blade profile, and polish until the surface roughness is Ra1.6;

[0016] S9: Quality inspection: Use PT and UT nondestructive testing to inspect. If the inspection is qualified, go to S10; if the PT or UT nondestructive testing fails, go to S6;

[0017] S10: Metal surface activation: Evenly sandblast the repaired blades. Use 20# white corundum or brown corundum as the sandblasting material. The surface roughness after sandblasting should reach Ra6μm-Ra12μm.

[0018] S11: Spraying of carbonized bustard coating: Spraying of carbonized bustard coating. When spraying, the repaired blade is sprayed in different areas. The allowable range of carbonized bustard coating thickness is 0.30mm-0.35mm. The edge thickness of the repaired part and the original blade part must have a smooth transition. The transition width range is 30mm-50mm.

[0019] Furthermore, preferably, in S2, the drying temperature is controlled at 100°C to 180°C, and the drying time is not less than 1 hour.

[0020] Further, preferably, in S4, the specific method of trimming is: making a cardboard template according to the size of the blade repair material, using the cardboard template to draw a trimming line on the blade to be repaired, and then trimming.

[0021] Furthermore, preferably, in S6, during welding, the welding joint and the area within at least 100 mm on both sides need to be preheated, the preheating temperature is not less than 120°C, and this preheating temperature is maintained during the welding process; the preheating method can be flame heating method.

[0022] Furthermore, preferably, in S6, the base layer and the cover layer are welded by argon arc welding, and the middle layer is welded by manual arc welding; a narrow weld is used during the repair welding operation, with a maximum width of 15-20 mm; and a thin weld layer is used, with a maximum thickness of 4-6 mm for each layer; after the cover layer is welded, another layer is welded on the cover layer to achieve the purpose of tempering the cover layer weld, and the tempered layer cannot contact the parent materials on both sides; the arc starting and arc ending points should be polished with a grinder or cleaned and polished with a carbon arc air planer.

[0023] Further, preferably, in S6, the welding method adopts metal inert gas shielded welding; the welding material is: 13-5 stainless steel welding wire; welding current: 110A ~ 160A; welding voltage: 20V ~ 24V; welding speed: 200mm ~ 400mm.

[0024] Furthermore, preferably, in S6, during welding, the welding is performed in different areas to disperse the heat as much as possible, and the size of each area is 28-32mm×28-32mm; and each layer except the bottom layer and the surface layer is hammered until the weld surface yields.

[0025] Further, preferably, in S7, the repaired surface of the runner is heated and insulated, and the heating and cooling rates do not exceed 150°C / h; when the weld thickness is less than 50mm, the insulation time is calculated as one hour per 25mm, and the minimum insulation time is 30min; when the weld thickness is more than 50mm, the insulation time is calculated according to the following formula: Where σ is the weld thickness in mm.

[0026] Further, preferably, in S10, the interval time between sandblasting and spraying of the carbide coating should not exceed 2 hours, otherwise the sandblasting process needs to be repeated.

[0027] Further, preferably, in S11, when spraying the narrow flow channel, a 90° angle gun is used for spraying, and the spraying range should be from the water outlet edge of the long blade to the root of the water outlet edge of the short blade via spraying along the flow channel.

[0028] After the S1 working platform of the present invention is built, the argon arc welding machine, the manual electric welding machine, the argon gas cylinder, the oxygen cylinder, and the acetylene cylinder are placed outside the tail water inlet, and the heater is placed at the inlet and outlet of the rotor chamber.

[0029] In S2 of the present invention, there is no special restriction on the cleaning agent, and a conventional cleaning agent can be used as long as it can remove oil and dirt from the surface of the rotating wheel. When drying, a belt-type local heating device is preferably used, and the temperature is controlled at 100°C to 180°C, and the insulation time at the same position is not less than 1 hour. In S7, when heating, a belt-type local heating device is also preferably used.

[0030] In S2 of the present invention, a heating fan or the like can be used to control the environment in which the rotor is located.

[0031] In S4 of the present invention, the size of the blade filler is determined according to the maximum abrasion area of ​​the blade and is determined according to conventional methods, and the present invention does not impose any special restrictions on this. Preferably, the trimming is performed by air planing;

[0032] In S5 of the present invention, a cardboard template can be made using the shape of the patch material to check whether the placement position is correct.

[0033] In the present invention S6, small specifications and short arc operation are used as much as possible during welding. During welding, the arc starting points of each layer should be staggered by at least 50 mm, and good fusion should be ensured. Before welding the next weld, all slag on the weld surface should be removed, and visible defects such as cracks, lack of fusion, weld bumps, poor weld formation and other defects that will have an adverse effect on welding quality should be polished and removed, and attention should be paid to filling the arc pit during operation. Multiple repair welding areas can be completed by alternating welding, and the interlayer temperature is controlled below 170°C.

[0034] In S7 of the present invention, during the welding process, a method such as hammering is used to eliminate stress.

[0035] In S8 of the present invention, grinding and polishing tools are used to grind the repaired surface to make a smooth transition with the original runner profile, and a blade shaping card (a special tool for line comparison used for repairing the runner blade by welding) is used for comparison to make the profile meet the requirements of the design drawing, and the blade surface roughness is Ra1.6;

[0036] In S10 of the present invention, the surface roughening sandblasting material should be 20# white corundum or brown corundum, and all surfaces that need to be sandblasted should be uniformly roughened, and the surface roughness after sandblasting should reach Ra6-12μm. After the sandblasting is completed, it is necessary to check whether there are pores, cracks, and falling blocks. If defects are found, they should be handled in time and recorded.

[0037] In S11 of the present invention, the metal carbide coating is sprayed by high-speed flame spraying. When a 90° angle gun is used for spraying, the speed after the angle gun loss should not be lower than the HVOF spraying speed.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] (1) The present invention combines three repair methods, namely manual electric welding, tungsten inert gas welding and high velocity flame (HVOF) spraying, to achieve online repair of the runner in a narrow and limited space (inlet and outlet diameter ≤ 600 mm) without disassembling the runner, solving the problem of abrasion damage of flow-through components on site of medium and high head hydropower stations. The wear resistance and cavitation resistance of the repaired runner can be improved by 200%, and the bonding performance of the surface layer is about 90% or more of that of the substrate;

[0040] (2) The repair method provided by the present invention configures the blade repair material of the same material steel plate according to the blade 3D model, shortens the repair period to 20% of the original, and reduces the repair cost and engineering workload to 10% of the original;

[0041] (3) The present invention adopts on-site online repair to shorten the repair cycle, reduce costs, and ensure the safe and stable operation of the unit. It also has great practical significance for improving the economic benefits of power plants and even improving energy utilization efficiency.

[0042] (4) The method of the present invention has the advantages of simple operation, low cost, good repair effect, etc. The turbine runner block repaired by this method can restore the original structure and performance, extend the service life of the turbine, and improve the operating efficiency of the turbine. It can be widely used in hydropower plants with small and medium-sized turbines in high-head and high-sediment rivers. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 Schematic diagram of the runner repair work site;

[0044] Figure 2 Schematic diagram of replacing blades of the same material at the water outlet of the blades;

[0045] Figure 3 Schematic diagram of the wheel spraying position. DETAILED DESCRIPTION

[0046] The present invention is further described in detail below in conjunction with embodiments.

[0047] Those skilled in the art will appreciate that the following examples are only used to illustrate the present invention and should not be considered to limit the scope of the present invention. If no specific techniques or conditions are specified in the examples, the techniques or conditions described in the literature in the art or the product specifications are used. If the manufacturer of the materials or equipment used is not specified, they are all conventional products that can be purchased.

[0048] Example 1

[0049] A method for repairing a runner block fall of a small or medium-sized water turbine in a high-head and high-sediment river comprises the following steps:

[0050] S1: Work platform construction: Set up a work platform in the tailwater pipe to ensure that the turbine runner is located directly above the tailwater work platform;

[0051] S2: Surface cleaning and drying: Use a cleaning agent to remove oil and dirt from the surface of the wheel, and then dry it; at the same time, control the humidity of the environment where the wheel is located not higher than 60% and the temperature not lower than 18°C;

[0052] S3: Damage record: Perform 100% PT flaw detection on the rotor surface, record and mark the distribution, size and type of rotor chipping and cracks;

[0053] S4: Preparation and installation of blade filler material: The blade filler material is made of the same stainless steel material as the runner blade; in the stainless steel material, the mass fraction of Cr is ≥13% and the mass fraction of Ni is ≥4%; the size of the blade filler material is determined according to the maximum abrasion area of ​​the blade;

[0054] The surface and periphery of the blade patch material are polished until smooth; at the same time, the blade to be repaired is trimmed according to the size of the blade patch material, and the trimmed part is polished until the metallic luster is exposed, and then a V-shaped groove is opened at the joint where the blade to be repaired and the blade patch material are to be welded; after trimming, the joint should first be checked by PT for cracks; if cracks exist, the trimming and grinding need to be performed again; if there are no cracks, go to S5;

[0055] S5: Alignment: Before welding, align the blade material with the blade to be repaired, and fix them with spot welding after alignment;

[0056] S6: Welding: Weld the blade patch material placed in position with the blade to be repaired; during welding, the arc starting points of each layer should be staggered by at least 50mm, and the interlayer temperature should be controlled below 170℃;

[0057] S7: Stress relief annealing: Stress relief is required during welding. After the groove is fully welded, an annealing layer needs to be welded and insulation measures should be taken to allow it to cool slowly.

[0058] S8: Surface polishing: Polish the repaired surface of the blade to be repaired until the repaired surface has a smooth transition with the original blade profile, and polish until the surface roughness is Ra1.6;

[0059] S9: Quality inspection: Use PT and UT nondestructive testing to inspect. If the inspection is qualified, go to S10; if the PT or UT nondestructive testing fails, go to S6;

[0060] S10: Metal surface activation: Evenly sandblast the repaired blades. Use 20# white corundum or brown corundum as the sandblasting material. The surface roughness after sandblasting should reach Ra6μm-Ra12μm.

[0061] S11: Spraying of carbonized bustard coating: Spraying of carbonized bustard coating. When spraying, the repaired blade is sprayed in different areas. The allowable range of carbonized bustard coating thickness is 0.30mm-0.35mm. The edge thickness of the repaired part and the original blade part must have a smooth transition. The transition width range is 30mm-50mm.

[0062] Example 2

[0063] A method for repairing a runner block fall of a small or medium-sized water turbine in a high-head and high-sediment river comprises the following steps:

[0064] S1: Work platform construction: Set up a work platform in the tailwater pipe to ensure that the turbine runner is located directly above the tailwater work platform;

[0065] S2: Surface cleaning and drying: Use a cleaning agent to remove oil and dirt from the surface of the wheel, and then dry it; at the same time, control the humidity of the environment where the wheel is located not higher than 60% and the temperature not lower than 18°C;

[0066] S3: Damage record: Perform 100% PT flaw detection on the rotor surface, record and mark the distribution, size and type of rotor chipping and cracks;

[0067] S4: Preparation and installation of blade filler material: The blade filler material is made of the same stainless steel material as the runner blade; in the stainless steel material, the mass fraction of Cr is ≥13% and the mass fraction of Ni is ≥4%; the size of the blade filler material is determined according to the maximum abrasion area of ​​the blade;

[0068] The surface and periphery of the blade patch material are polished until smooth; at the same time, the blade to be repaired is trimmed according to the size of the blade patch material, and the trimmed part is polished until the metallic luster is exposed, and then a V-shaped groove is opened at the joint where the blade to be repaired and the blade patch material are to be welded; after trimming, the joint should first be checked by PT for cracks; if cracks exist, the trimming and grinding need to be performed again; if there are no cracks, go to S5;

[0069] S5: Alignment: Before welding, align the blade material with the blade to be repaired, and fix them with spot welding after alignment;

[0070] S6: Welding: Weld the blade patch material placed in position with the blade to be repaired; during welding, the arc starting points of each layer should be staggered by at least 50mm, and the interlayer temperature should be controlled below 170℃;

[0071] S7: Stress relief annealing: Stress relief is required during welding. After the groove is fully welded, an annealing layer needs to be welded and insulation measures should be taken to allow it to cool slowly.

[0072] S8: Surface polishing: Polish the repaired surface of the blade to be repaired until the repaired surface has a smooth transition with the original blade profile, and polish until the surface roughness is Ra1.6;

[0073] S9: Quality inspection: Use PT and UT nondestructive testing to inspect. If the inspection is qualified, go to S10; if the PT or UT nondestructive testing fails, go to S6;

[0074] S10: Metal surface activation: Evenly sandblast the repaired blades. Use 20# white corundum or brown corundum as the sandblasting material. The surface roughness after sandblasting should reach Ra6μm-Ra12μm.

[0075] S11: Spraying of carbonized bustard coating: Spraying of carbonized bustard coating. When spraying, the repaired blade is sprayed in different areas. The allowable range of carbonized bustard coating thickness is 0.30mm-0.35mm. The edge thickness of the repaired part and the original blade part must have a smooth transition. The transition width range is 30mm-50mm.

[0076] In S2, the drying temperature is controlled at 100°C to 180°C, and the drying time is not less than 1 hour.

[0077] In S4, the specific method of trimming is: making a cardboard template according to the size of the blade repair material, using the cardboard template to draw a trimming line on the blade to be repaired, and then trimming.

[0078] In S6, during welding, the welding joint and the area within at least 100mm on both sides shall be preheated to a temperature not lower than 120°C and this preheating temperature shall be maintained during the welding process; the preheating method may be flame heating.

[0079] In S6, the base layer and the cover layer are welded by argon arc welding, and the middle layer is welded by manual arc welding; a narrow weld is used for the repair welding operation, with a maximum width of 15-20mm; and a thin weld layer is used, with a maximum thickness of 4-6mm for each layer; after the cover layer is welded, another layer is welded on the cover layer to achieve the purpose of tempering the cover layer weld, and the tempered layer cannot contact the parent material on both sides; the arc starting and arc ending points should be polished with a grinder or cleaned and polished with a carbon arc air planer.

[0080] In S6, the welding method adopts metal inert gas shielded welding; welding materials: 13-5 stainless steel welding wire; welding current: 110A ~ 160A; welding voltage: 20V ~ 24V; welding speed: 200mm ~ 400mm.

[0081] In S6, during welding, the welding is performed in different areas to disperse the heat as much as possible. The size of each area is 28-32mm×28-32mm. Except for the bottom layer and the surface layer, each layer is hammered until the weld surface yields.

[0082] In S7, the repaired surface of the runner is heated, and the heating and cooling speed does not exceed 150℃ / h; when the weld thickness is less than 50mm, the insulation time is calculated as one hour per 25mm, and the minimum insulation time is 30min; when the weld thickness is more than 50mm, the insulation time is calculated according to the following formula: Where, σ is the weld thickness, in mm.

[0083] In S10, the interval between sandblasting and carbide coating spraying should not exceed 2 hours, otherwise it needs to be sandblasted again.

[0084] In S11, when spraying the narrow flow channel, a 90° angle gun is used for spraying, and the spraying range should be from the water outlet edge of the long blade to the root of the water outlet edge of the short blade by spraying along the flow channel.

[0085] Application Example 1

[0086] In a hydropower plant with high head and high sediment flow, during the C-level maintenance of Unit 3, it was found that the 8# long blade of the runner had a large area of ​​broken pieces, with the pieces falling 260mm*180mm. The overall erosion of the runner was quite serious, and the broken pieces of the turbine runner needed to be repaired. The method described in Example 2 was used, which specifically included the following steps:

[0087] S1: Equipment installation: Set up a tailwater working platform in the tailwater pipe to ensure that the turbine runner is located directly above the tailwater working platform. Argon arc welding machine, manual electric welding machine, argon gas cylinder, oxygen cylinder, and acetylene cylinder are placed outside the tailwater inlet door, and the heater is placed at the inlet and outlet of the runner room;

[0088] S2: Surface cleaning and drying: Use a cleaning agent to remove oil and dirt from the surface of the runner, use a heating belt type local heating device to heat the surface of the runner blades, control the temperature at 100℃~180℃, and keep the temperature at the same position for no less than 1h. At the same time, use a heating fan to ensure that the humidity of the environment where the runner is located is no higher than 60% and the temperature is no lower than 18℃;

[0089] S3: Damage record: Perform 100% PT flaw detection on the rotor surface, record and mark the distribution, size and type of rotor chipping and cracks;

[0090] S4: Preparation and installation of filler material:

[0091] (1) Make a cardboard template according to the actual shape of the filler material to be processed, use the template to draw the cutting edge line on the blade, and trim it using an air planer or other method. Grind the trimmed area to reveal the metallic luster, which can be matched with the filler material.

[0092] (2) The joint has a V-shaped groove, and PT can be used to check whether there are cracks, etc.

[0093] (3) Place a 3-5 mm stainless steel plate on the back of the V-shaped groove, fix it with spot welding, use welding rod to fill the V-shaped groove, gradually fill the groove, and hammer between layers to eliminate stress; do not hammer the first and last layers.

[0094] (4) Polishing.

[0095] S5: Positioning:

[0096] Before welding, place the steel plate and blade in position, check whether the placement is correct with a sample, and fix them by spot welding after positioning.

[0097] S6: Welding: Welding process

[0098] (1) Before welding, clean the area to be welded and thoroughly remove impurities such as water, oil, and rust that are harmful to welding.

[0099] (2) Before welding, use steam cutting to preheat the area to be welded, and the preheating temperature should not be lower than 80℃.

[0100] (3) Welding process parameters are shown in Table 1.

[0101] Table 1

[0102]

[0103]

[0104] (4) Grinding: After welding, the blades are trimmed and polished according to the template. The front and back sides are trimmed and polished according to the half-section template of the runner wooden mold drawing to make the profile meet the requirements of the design drawing and the blade surface roughness is Ra1.6.

[0105] S7: stress relief annealing: heating the repaired surface of the runner using a heating belt type local heating device;

[0106] S8: Surface polishing: Use grinding and polishing tools to make the repaired surface smoothly transition with the original runner profile, and use the blade shaping card for comparison; make the profile conform to the requirements of the design drawings, and the blade surface roughness is Ra1.6;

[0107] S9: Quality inspection: Use PT and UT nondestructive testing to inspect, if unqualified, return for repair;

[0108] S10: Metal surface activation: Surface roughening sandblasting materials should use 20# white corundum or brown corundum. All surfaces to be sprayed should be evenly roughened. The surface roughness after sandblasting should reach Ra6-12μm.

[0109] S11: Carbide bustard coating spraying: The blades are sprayed in different areas, and the coating thickness is allowed to range from 0.30mm to 0.35mm. The coating thickness transitions smoothly at the edge of the designated area, and the transition width is determined according to the location, and the width range is 30mm to 50mm. After the blade surface is sprayed with high-speed flame metal carbide bustard, the penetration protection material is brushed on the coating surface.

[0110] S12: Completion acceptance

[0111] Application Example 2

[0112] In a hydropower plant with high head and high sediment flow, a 250mm long through-crack was found in the 8# long blade of the runner during the C-level overhaul of Unit 2, and the blade crack was forked and misaligned. The crack of the 8# long blade of the runner was cut out and repaired using the method for repairing the falling pieces of the turbine runner, using the method described in Example 2, which specifically includes the following steps:

[0113] S1: Equipment installation: Set up a tailwater working platform in the tailwater pipe to ensure that the turbine runner is located directly above the tailwater working platform. Argon arc welding machine, manual electric welding machine, argon gas cylinder, oxygen cylinder, and acetylene cylinder are placed outside the tailwater inlet door, and the heater is placed at the inlet and outlet of the runner room;

[0114] S2: Surface cleaning and drying: Use a cleaning agent to remove oil and dirt from the surface of the runner, use a heating belt type local heating device to heat the surface of the runner blades, control the temperature at 100℃~180℃, and keep the temperature at the same position for no less than 1h. At the same time, use a heating fan to ensure that the humidity of the environment where the runner is located is no higher than 60% and the temperature is no lower than 18℃;

[0115] S3: Damage record: Perform 100% PT inspection on the wheel surface, record and mark the distribution, size and type of wheel chipping and cracks; grind the trimmed parts into a V-shaped slope to reveal the metallic luster, and use PT to check whether it is clean.

[0116] S4: Preparation and installation of filler material:

[0117] (1) Start cutting the 8# long blade of the runner from 100mm behind the crack and remove all the cracks. Make a cardboard template according to the actual shape of the patch material to be processed. Use the template to draw the cutting line on the blade, and trim it by air planing, etc. The trimmed part is polished to reveal the metallic luster, which can be matched with the patch material.

[0118] (2) The joint has a V-shaped groove, and PT can be used to check whether there are cracks, etc.

[0119] (3) Place a 3-5 mm stainless steel plate on the back of the V-shaped groove, fix it with spot welding, use welding rod to fill the V-shaped groove, gradually fill the groove, and hammer between layers to eliminate stress; do not hammer the first and last layers.

[0120] (4) Polishing

[0121] S5: Positioning:

[0122] Before welding, place the steel plate and blade in position, check whether the placement is correct with a sample, and fix them by spot welding after positioning.

[0123] S6: Welding: Welding process

[0124] (1) Before welding, clean the area to be welded and thoroughly remove impurities such as water, oil, and rust that are harmful to welding.

[0125] (2) Before welding, use steam cutting to preheat the area to be welded, and the preheating temperature should not be lower than 80℃.

[0126] (3) Welding process parameters are shown in Table 2.

[0127] Table 2

[0128]

[0129]

[0130] (4) Grinding: After welding, the blades are trimmed and polished according to the template. The front and back sides are trimmed and polished according to the half-section template of the runner wooden mold drawing to make the profile meet the requirements of the design drawing and the blade surface roughness is Ra1.6.

[0131] S7: stress relief annealing: heating the repaired surface of the runner using a heating belt type local heating device;

[0132] S8: Surface polishing: Use grinding and polishing tools to make the repaired surface smoothly transition with the original runner profile, and use the blade shaping card for comparison; make the profile conform to the requirements of the design drawings, and the blade surface roughness is Ra1.6;

[0133] S9: Quality inspection: Use PT and UT nondestructive testing to inspect, if unqualified, return for repair;

[0134] S10: Metal surface activation: Surface roughening sandblasting materials should use 20# white corundum or brown corundum. All surfaces to be sprayed should be evenly roughened. The surface roughness after sandblasting should reach Ra6-12μm.

[0135] S11: Carbonized bustard coating spraying: The blades are sprayed in different areas. The coating thickness is allowed to range from 0.30mm to 0.35mm. The coating thickness transitions smoothly at the edge of the designated area. The transition width is determined according to the location and the width range is 30mm-50mm.

[0136] S12: Completion acceptance

[0137] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for repairing runner block loss of small and medium-sized water turbines in high-head and high-sediment rivers, characterized in that: The steps include: S1: Work platform construction: Set up a work platform in the tailwater pipe to ensure that the turbine runner is located directly above the tailwater work platform; S2: Surface cleaning and drying: Use a cleaning agent to remove oil and dirt from the surface of the wheel, and then dry it; at the same time, control the humidity of the environment where the wheel is located not higher than 60% and the temperature not lower than 18°C; S3: Damage record: Perform 100% PT flaw detection on the rotor surface, record and mark the distribution, size and type of rotor chipping and cracks; S4: Preparation and installation of blade filler material: The blade filler material is made of the same stainless steel material as the runner blade; in the stainless steel material, the mass fraction of Cr is ≥13% and the mass fraction of Ni is ≥4%; the size of the blade filler material is determined according to the maximum abrasion area of ​​the blade; The surface and periphery of the blade patch material are polished until smooth; at the same time, the blade to be repaired is trimmed according to the size of the blade patch material, and the trimmed part is polished until the metallic luster is exposed, and then a V-shaped groove is opened at the joint where the blade to be repaired and the blade patch material are to be welded; after trimming, the joint should first be checked by PT for cracks; if cracks exist, the trimming and grinding need to be performed again; if there are no cracks, go to S5; S5: Alignment: Before welding, align the blade material with the blade to be repaired, and fix them with spot welding after alignment; S6: Welding: Weld the blade patch material placed in position with the blade to be repaired; during welding, the arc starting points of each layer should be staggered by at least 50mm, and the interlayer temperature should be controlled below 170℃; S7: Stress relief annealing: Stress relief is required during welding. After the groove is fully welded, an annealing layer needs to be welded and insulation measures should be taken to allow it to cool slowly. S8: Surface polishing: Polish the repaired surface of the blade to be repaired until the repaired surface has a smooth transition with the original blade profile, and polish until the surface roughness is Ra1.6; S9: Quality inspection: Use PT and UT nondestructive testing to inspect. If the inspection is qualified, go to S10; if the PT or UT nondestructive testing fails, go to S6; S10: Metal surface activation: Evenly sandblast the repaired blades. Use 20# white corundum or brown corundum as the sandblasting material. The surface roughness after sandblasting should reach Ra6μm-Ra12μm. S11: Spraying of carbonized bustard coating: Spraying of carbonized bustard coating. When spraying, the repaired blade is sprayed in different areas. The allowable range of carbonized bustard coating thickness is 0.30mm-0.35mm. The edge thickness of the repaired part and the original blade part must have a smooth transition. The transition width range is 30mm-50mm.

2. The method for repairing runner block loss of small and medium-sized turbines in high-head and high-sediment rivers according to claim 1 is characterized in that: In S2, the drying temperature is controlled at 100°C to 180°C, and the drying time is not less than 1 hour.

3. The method for repairing runner block loss of small and medium-sized turbines in high-head and high-sediment rivers according to claim 1 is characterized in that: In S4, the specific method of trimming is: making a cardboard template according to the size of the blade repair material, using the cardboard template to draw a trimming line on the blade to be repaired, and then trimming.

4. The method for repairing runner block loss of small and medium-sized turbines in high-head and high-sediment rivers according to claim 1 is characterized in that: In S6, during welding, the welding joint and the area within at least 100mm on both sides shall be preheated to a temperature not lower than 120°C and this preheating temperature shall be maintained during the welding process; the preheating method may be flame heating.

5. The method for repairing runner block loss of small and medium-sized turbines in high-head and high-sediment rivers according to claim 1 is characterized in that: In S6, the welding method adopts metal inert gas shielded welding; welding materials: 6mm, 13-5 stainless steel welding wire; welding current: 110A ~ 160A; welding voltage: 20V ~ 24V; welding speed: 200mm ~ 400mm.

6. The method for repairing runner block loss of small and medium-sized turbines in high-head and high-sediment rivers according to claim 1 is characterized in that: In S6, the base and cover layers are welded by argon arc welding, and the middle layer is welded by manual arc welding; narrow welds are used for repair welding, with a maximum width of 15-20mm; A thin welding layer is used, with a maximum thickness of 4-6mm for each layer. After the welding of the cover layer is completed, another layer is welded on the cover layer to achieve the purpose of tempering the cover layer weld. The tempered layer cannot contact the parent material on both sides. The arc starting and arc ending points should be polished with a grinder or cleaned and polished with a carbon arc air planer.

7. The method for repairing runner block loss of small and medium-sized turbines in high-head and high-sediment rivers according to claim 1 is characterized in that: In S6, during welding, the welding is performed in different areas to disperse the heat as much as possible. The size of each area is 28-32mm×28-32mm. Except for the bottom layer and the surface layer, each layer is hammered until the weld surface yields.

8. The method for repairing runner block loss of small and medium-sized water turbines in high-head and high-sediment rivers according to claim 1 is characterized in that: In S7, the repaired surface of the runner is heated and insulated, and the heating and cooling speed does not exceed 150℃ / h; when the weld thickness is less than 50mm, the insulation time is calculated as one hour per 25mm, and the minimum insulation time is 30min; when the weld thickness is more than 50mm, the insulation time is calculated according to the following formula: Where σ is the weld thickness in mm.

9. The method for repairing runner block loss of small and medium-sized turbines in high-head and high-sediment rivers according to claim 1 is characterized in that: In S10, the interval between sandblasting and carbide coating spraying should not exceed 2 hours, otherwise it needs to be sandblasted again.

10. The method for repairing runner block loss of small and medium-sized water turbines in high-head and high-sediment rivers according to claim 1 is characterized in that: In S11, when spraying the narrow flow channel, a 90° angle gun is used for spraying, and the spraying range should be from the water outlet edge of the long blade to the root of the water outlet edge of the short blade by spraying along the flow channel.

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