A high-pressure water jet cleaning robot for nuclear power main bolts and a working method thereof

Abstract

The application discloses a high-pressure water jet cleaning robot for nuclear power main bolts and a working method thereof, which comprises a box assembly, a box cover assembly, a high-pressure water unit and a control console. The box assembly comprises a water tank assembly, a nut dismounting assembly, a roller assembly, a nut cleaning assembly, a bolt cleaning assembly and a steam-water separation assembly. The nut dismounting assembly automatically dismounts and mounts the main nut; the roller assembly drives the main bolt to rotate; the nut cleaning assembly and the bolt cleaning assembly adopt high-pressure water jet for non-contact cleaning and air drying, the working pressure is 5-30 MPa and is steplessly adjustable, and the phosphating layer is not damaged; and the steam-water separation assembly maintains the negative pressure of-50 to-100 Pa in the box to prevent radioactive leakage. The application realizes full-automatic dismounting, cleaning, air drying and quality inspection of the main bolt and the main nut, has high cleaning efficiency, no damage and no secondary pollution, and significantly reduces the radiation dose of personnel.

Description

Technical Field

[0001] This invention relates to a high-pressure water jet cleaning robot, specifically to a high-pressure water jet cleaning robot and its working method for cleaning the main bolts of a nuclear power plant reactor pressure vessel. Background Technology

[0002] Nuclear power is gaining increasing importance due to its environmentally friendly advantages. During refueling and overhauls at nuclear power plants, cleaning the main bolts and nuts of the reactor pressure vessel is a crucial step in ensuring the vessel's sealing and safe operation. As the core load-bearing components connecting the pressure vessel's top cover and flanges, the main bolts are subjected to high temperature, high pressure, and high radiation environments for extended periods. Their surfaces and thread gaps are prone to accumulating radioactive corrosion products, boron crystal residues, and oxide layers. In most domestic units, a large amount of loosening agent is injected during the installation of the main bolts, resulting in a significant amount of dirt adhering to the threaded surfaces after removal. To ensure the sealing effect of the reactor pressure vessel in subsequent uses, the surfaces of the main bolts and nuts must be cleaned. Traditional cleaning methods mainly rely on manual hand tools (such as wire brushes) to remove dirt. This method is not only inefficient and inconsistent in its cleaning effect, but also exposes operators to high levels of radiation.

[0003] Existing nuclear power plant main bolt cleaning devices suffer from the following technical defects: First, they generally employ a contact brushing method, where the brush bristles directly rub against the main bolt threads. The relatively long brushes have limited brushing force, resulting in inconsistent cleaning effectiveness against anti-seize agents adhering to the bottom of the thread grooves and the existence of cleaning dead zones. Furthermore, the brush bristles continuously wear down and become contaminated during use, making maintenance inconvenient. Additionally, the bristles are prone to shedding during repeated use, and the shed bristle debris forms solid waste that can adhere to the main bolt thread surface, affecting cleaning quality, and can also mix into the circulating water, causing secondary pollution. Second, existing abrasives... The mixed jet method has inherent drawbacks such as damaging the phosphating layer and increasing the difficulty of radioactive solid waste disposal; third, most existing devices do not have integrated functions for fully automatic disassembly, transfer and cleaning of the main nut, and the disassembly and assembly of the main nut still rely on manual participation, which increases the risk of radiation exposure to personnel; fourth, due to the large amount of water vapor and water stains remaining at the root of the thread generated during the cleaning process, the drying process relies on a single compressed air blowing, which is time-consuming and ineffective; fifth, the cleaning process is prone to generating radioactive dust, and the existing box sealing method is complex and difficult to reliably achieve the complete seal required to maintain a negative pressure environment.

[0004] Regarding cleaning media, while high-pressure water jet technology without abrasives has been applied in industries such as petrochemicals and shipbuilding, its application in cleaning the main bolts of nuclear power plant reactor pressure vessels faces significant technical obstacles: the main bolts can be M170 or larger, with deep thread gaps and large dimensions, requiring specialized design and verification of parameters such as the pressure of the high-pressure water jet, nozzle movement speed, and nozzle angle; at the same time, it must meet the equipment reliability requirements under nuclear radiation environments and verify the non-destructive nature of the high-pressure water jet on the phosphate layer of the workpiece surface across the entire pressure range, making the technical difficulty significantly higher than conventional industrial applications; existing cases mostly utilize high-pressure water jet technology to remove the phosphate layer, while comparative literature all choose contact brushing, confirming a widespread technical bias in the field regarding this technical approach.

[0005] Therefore, it is necessary to propose a high-pressure water jet cleaning robot for main bolts in nuclear power plants and its working method, which specifically addresses the following issues: How to achieve automatic disassembly and installation of the main nut; How to achieve automatic cleaning of the main bolts and main nuts; How to thoroughly clean a workpiece without damaging the phosphate layer on its surface; How to improve overall work efficiency; How to avoid secondary pollution during the cleaning process. Summary of the Invention

[0006] This invention provides a high-pressure water jet cleaning robot for main bolts in nuclear power plants and its operating method, aiming to solve the following technical problems: automatically cleaning main bolts and nuts, automatically disassembling and assembling main nuts, ensuring that the cleaning process does not damage the workpiece surface, and avoiding secondary pollution during the cleaning process. The equipment mainly includes a housing assembly, a cover assembly, a high-pressure water unit, and a control console.

[0007] The enclosure assembly mainly includes a water tank assembly, a nut removal assembly, a roller assembly, a nut cleaning assembly, a bolt cleaning assembly, and a vapor-water separation assembly. The water tank assembly provides a working space for cleaning the main bolts and nuts. The nut removal assembly enables automatic disassembly and installation of the main nuts. The roller assembly radially supports the main bolts and drives their rotation. The nut cleaning assembly automatically cleans and dries the internal threads of the main nuts. The bolt cleaning assembly automatically cleans and dries the threaded sections of the main bolts. The vapor-water separation assembly is responsible for separating water vapor within the enclosure assembly, maintaining a negative pressure state (design value -50 to -100 Pa, referring to nuclear power plant ventilation system standards such as GB50457), and preventing the leakage of radioactive aerosols and other radioactive waste from the enclosure. The water tank assembly mainly includes a water tank, a water tank frame, and anchor bolts. The water tank frame consists of upper and lower layers. The water tank is installed on the upper layer of the water tank frame, which provides support and fixation for the water tank. The water tank frame is placed on the ground using anchor bolts.

[0008] The water tank assembly has a three-layer strip sealing structure around the tank opening. The sealing structure is made of EPDM material, which meets the requirements for radiation resistance and is easy to compress and seal.

[0009] The nut removal assembly mainly includes a guide rod, a chuck frame, clamping cylinders, a double-acting cylinder, a sprocket mechanism, and a sprocket motor. Multiple clamping cylinders are evenly distributed circumferentially along the chuck frame, automatically clamping the main nut. The chuck frame is mounted on the guide rod and can slide axially along the guide rod, thereby moving the main nut along the guide rod. The cylinder barrel of the double-acting cylinder is connected to the chuck frame, and its piston rod is connected to the clamping end of the main nut, applying axial tension during the main nut removal process. The sprocket motor drives the chuck frame to move through the sprocket mechanism, realizing the transfer of the main nut, and completing the cleaning and drying of the internal threads of the main nut at the cleaning station.

[0010] The roller assembly includes rollers, brackets, a drive shaft, a transmission mechanism, a drive shaft, and a motor. Multiple brackets are arranged side-by-side inside the water tank, and the rollers are mounted on the brackets. The rollers are linked together via the drive shafts. One end of the drive shaft is mounted on the bracket, and the other end is connected to the motor. The motor transmits power to the rollers through the drive shaft, transmission mechanism, and drive shaft, driving the rollers to rotate, which in turn drives the main bolts on the rollers to rotate.

[0011] The nut cleaning assembly mainly includes a motor and a nozzle. The nozzle is mounted on the motor, which provides power for the nozzle's rotation. The nozzle has dual fluid channels, allowing for the introduction of high-pressure water and compressed air respectively. Switching between the two fluid channels supports both automatic switching (controlled by the control console program) and manual switching modes, enabling automatic cleaning and drying of the main nut's internal threads. The high-pressure water working pressure is infinitely adjustable within the range of 5–30 MPa, and can be flexibly set according to the degree of contamination of the main nut's internal threads.

[0012] The bolt cleaning assembly mainly includes a guide rod, a wind blade, a connecting rod, a spray bar, a camera assembly, a support, a drive motor, a slider, and a lead screw pair. The drive motor is connected to the lead screw pair, one end of the slider is connected to the lead screw pair, and the other end is connected to the guide rod. The guide rod is fixed to the support, providing axial guidance for the slider. The wind blade and spray bar are mounted on the slider, and the two sets of sliders are synchronously linked through the connecting rod, allowing them to move linearly along the guide rod under the action of the drive motor. The camera assembly is mounted on the slider and captures images of the threaded area segment by segment as the slider moves axially. These images are then stitched together to form a complete image of the thread, facilitating the identification of residual contaminants and defects on the thread surface. The spray bar sprays a continuously adjustable high-pressure water stream within the range of 5–30 MPa to clean the main bolt threads, while the wind blade blows compressed air to dry the main bolt threads.

[0013] Both the nut cleaning assembly and the bolt cleaning assembly use high-pressure water as the cleaning medium. While effectively removing contaminants, the high-pressure water jet has been tested and verified to not damage the phosphate layer on the workpiece surface within a pressure range of 5 to 30 MPa. Operators can flexibly adjust the water pressure within this range according to the degree of thread contamination to achieve non-destructive cleaning of the phosphate layer on the workpiece surface, balancing cleaning efficiency and workpiece surface protection.

[0014] The gas-water separation assembly mainly includes a gas-water separator and a blower. The gas-water separator, blower, and water tank are connected by ductwork to form a closed gas circulation loop in which air circulates. The blower provides power for the gas circulation, and the heat generated during its operation can assist in heating the air, accelerating the drying of the main bolts. The blower drives the gas containing water vapor to circulate through the gas-water separator. The separated liquid water, after leaving the gas phase, flows back to the sedimentation tank, continuously reducing the total amount of gas inside the tank, thereby maintaining a relatively negative pressure environment inside the tank and effectively inhibiting the escape of radioactive waste such as radioactive aerosols. The gas-water separator is used to separate the circulating air, and the separated wastewater flows back to the sedimentation tank, eliminating the need for an additional drainage device and achieving closed-loop control of the water circuit.

[0015] The lid assembly mainly consists of a frame, a nitrogen spring, and a hinge seat. It is installed above the container assembly. When closed, the lid assembly uses its own weight to press against the sealing structure, achieving a complete seal of the container. This provides a reliable basis for the formation and maintenance of a negative pressure environment inside the container, preventing the leakage of radioactive waste such as radioactive aerosols. The nitrogen spring provides support when the lid is open, and the lid assembly is connected to the container via the hinge seat, ensuring smooth opening and closing.

[0016] The high-pressure water unit mainly consists of a sedimentation tank, centrifugal pump, filter, plunger pump, accumulator, and valve assembly. Its primary function is to provide high-pressure water for the entire cleaning robot and to achieve closed-loop water circulation control. The water in the sedimentation tank is pressurized by the centrifugal pump, then filtered through a multi-stage filter, and subsequently pressurized again by the plunger pump to form a high-pressure water flow. This high-pressure water is then distributed to each execution terminal via the valve assembly. An accumulator is connected in series in the loop, storing energy when the system pressure increases and releasing it when the pressure decreases, effectively suppressing pressure fluctuations and maintaining system pressure stability.

[0017] The control console sends control commands to each actuator and receives execution results and system status feedback signals in real time, forming a closed-loop control. It integrates dedicated digital twin software, whose main functions include real-time status monitoring, fault warning, visual inspection, operation simulation exercises, and cleaning parameter recording, enabling comprehensive operation control and dynamic operation status display of the reactor pressure vessel main bolt and nut cleaning robot.

[0018] To better achieve the above objectives, this invention also provides a method for operating a high-pressure water jet cleaning robot for nuclear power plant main bolts. This invention uses the main bolts of a typical third-generation pressurized water reactor pressure vessel as the operating object for illustration. The method includes the following steps: Step 1: Hoist the main bolt to the equipment operating area and place it horizontally on the roller assembly; Step 2: The bolt cleaning assembly starts from the initial position and cleans the right section of the main bolt thread; Step 3: The chuck frame and the main nut are aligned and engaged, the clamping cylinder clamps the main nut, the roller assembly drives the main bolt to rotate, and the double-acting cylinder applies axial tension to complete the disassembly of the main nut; Simultaneously, the bolt cleaning assembly advances to clean the left section of the main bolt thread. Step 4: After the main nut is disassembled, the nut cleaning component cleans the internal threads of the main nut, and the bolt cleaning component cleans the middle section of the main bolt's threads; Step 5: The bolt cleaning component dries the main bolt as a whole, and the nut cleaning component dries the inner threads of the main nut; Step 6: The control panel starts the image acquisition program, and the camera component moves along the thread segment with the slider, acquiring images segment by segment and stitching them into a complete thread image, facilitating confirmation of cleaning quality and identification of thread defects; Step 7: The main nut is installed onto the main bolt using the nut disassembly component; Step 8: The bolt cleaning component dries the outer surface of the main nut, completing the fully automated disassembly, assembly, and cleaning operation of the main bolt and main nut.

[0019] The beneficial effects of this invention are as follows: With a high degree of automation, this invention significantly reduces radiation dose to personnel. Through the coordinated operation of the housing assembly, nut removal assembly, bolt cleaning assembly, nut cleaning assembly, and control console, the invention can automatically complete the entire cleaning process of main bolts and nuts, including disassembly, cleaning, drying, and dirt collection. No personnel need to directly contact the workpieces during the cleaning process.

[0020] The cleaning is thorough and causes no damage to the workpiece surface. This invention uses high-pressure water jet as the cleaning medium to perform deep cleaning of the threads of main bolts and nuts in a non-contact manner. It can thoroughly remove contaminants such as anti-seize agents, radioactive corrosion products, boron crystal residues, and oxide layers adhering to the thread gaps. Compared with traditional brush cleaning methods, this invention avoids problems such as brush bristle wear, brush bristle contamination, and cleaning dead corners. Furthermore, it has been verified through testing that the high-pressure water jet will not damage the phosphate layer on the workpiece surface within the full pressure range of 5–30 MPa. Operators can flexibly adjust the water pressure according to the degree of thread contamination, balancing cleaning efficiency and workpiece surface protection.

[0021] The cleaning efficiency is high, significantly shortening the operation cycle. This invention performs multiple processes such as nut disassembly and assembly, bolt cleaning, nut cleaning, and air drying in parallel, effectively reducing the overall operation time. The air drying process adopts a composite drying method that combines compressed air blowing with negative pressure hot air circulation inside the chamber. While quickly removing residual moisture from the surface of the workpiece, the heat generated during the operation of the fan is used to assist in heating the circulating air, further improving the air drying efficiency. The cleaning cycle of a single main bolt can be shortened from 20-25 minutes using traditional manual methods to 12-20 minutes.

[0022] This invention integrates cleaning effectiveness inspection and thread defect detection functions to ensure process quality. It features cleaning effectiveness inspection and thread surface defect inspection functions, which can help identify residual contaminants and thread defect locations on the surface of main bolts and nuts. This provides a basis for workpiece quality judgment and subsequent handling, preventing the reactor pressure vessel's sealing performance from being affected by incomplete cleaning or undetected thread damage.

[0023] Real-time digital twin mapping enhances operational visualization. The control console of this invention integrates dedicated digital twin software, whose monitoring interface can map the equipment's operating status in real time. Operators can monitor the cleaning process dynamics of the main bolts and nuts, the equipment's execution status, and key process parameters at any time. This enables functions such as real-time status monitoring, fault warning, visual inspection, operation simulation exercises, and cleaning parameter recording, thereby improving the overall operability and traceability of the machine.

[0024] This invention is environmentally friendly and effectively prevents secondary pollution. It employs wet high-pressure water jet cleaning, generating no dust and preventing aerosol spillage during operation. The combination of the cover assembly and the body assembly forms a sealed working chamber. The air-water separation component uses a fan to create a negative pressure environment of -50 to -100 Pa inside the chamber, effectively suppressing the escape of radioactive aerosols or radioactive waste and preventing the splashing and diffusion of dirt into the work space. The high-pressure water unit uses a closed-loop circuit consisting of a sedimentation tank, filter, plunger pump, and accumulator to achieve the recycling of cleaning water, resulting in a small amount of overall waste liquid generation, which is friendly to the working environment and surrounding personnel.

[0025] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the present invention. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the device structure according to an embodiment of the present invention; Figure 2 This is a schematic diagram of a housing assembly according to an embodiment of the present invention; Figure 3 This is a schematic diagram of a water tank assembly according to an embodiment of the present invention; Figure 4 This is a schematic diagram of a nut removal assembly according to an embodiment of the present invention; Figure 5 This is a schematic diagram of a roller assembly according to an embodiment of the present invention; Figure 6 This is a schematic diagram of a nut cleaning assembly according to an embodiment of the present invention; Figure 7 This is a schematic diagram of a bolt cleaning assembly according to an embodiment of the present invention; Figure 8 This is a flowchart of a steam-water separation process according to an embodiment of the present invention; Figure 9 This is a schematic diagram of a high-pressure water circulation according to an embodiment of the present invention.

[0027] Among them, the attached figures are labeled 1. Housing assembly 11 Water Tank Components 111 water tank 112 Water Tank Frame 113 anchor bolts 12-nut assembly 121 guide rod 122 chuck holder 123 Clamping Cylinder 124 double-acting cylinder 125 sprocket mechanism 126 sprocket motor 13 roller assembly 131 rollers 132 stents 133 drive shaft 134 Transmission Mechanism 135 drive shaft 136 motor 14 Nut Cleaning Components 141 motor 142 nozzles 15-bolt cleaning assembly 151 drive motor 152 sliders 153 lead screw pair 154 guide rod 155 supports 156 Wind Blade 157 connecting rod 158 camera components 159 spray boom 16 Gas-Water Separator 161 Steam-Water Separator 162 fan 2 box cover assembly 3 High-pressure water units 31 Sedimentation Tank 32 centrifugal pump 33 Filter 34 plunger pump 35 accumulator 36 valve group 4 consoles 5 main bolts 6 main nuts Detailed Implementation

[0028] The structural and working principles of the present invention will be described in detail below with reference to the accompanying drawings: See Figure 1 The present invention provides a high-pressure water jet cleaning robot for nuclear power plant main bolts and its working method, including a housing assembly 1, a housing cover assembly 2, a high-pressure water unit 3 and a control console 4.

[0029] See Figure 2 The housing assembly 1 mainly includes a water tank assembly 11, a nut removal assembly 12, a roller assembly 13, a nut cleaning assembly 14, a bolt cleaning assembly 15, and a steam-water separation assembly 16.

[0030] See Figure 3 The water tank assembly 11 serves as the main support structure for the entire tank assembly 1, supporting and securing the remaining functional components. It primarily comprises a water tank 111, a water tank frame 112, and anchor bolts 113. The water tank frame 112 is a double-layer welded structure, with the water tank 111 installed within the upper frame. The entire water tank frame 112 is placed on the ground using the anchor bolts 113. The bottom of the water tank 111 is designed with an inclination angle of 3° to 10° relative to the horizontal plane, allowing wastewater generated during the cleaning process to automatically flow to the drain outlet by gravity, effectively preventing localized water accumulation.

[0031] See Figure 4The nut removal assembly 12 is located inside the water tank 111 and is used for automatically removing and installing the main nut 6. It mainly includes a guide rod 121, a chuck frame 122, a clamping cylinder 123, a double-acting cylinder 124, a sprocket mechanism 125, and a sprocket motor 126. The chuck frame 122 is mounted on the guide rod 121 and can slide axially along the guide rod 121; multiple sets of clamping cylinders 123 are evenly arranged circumferentially along the chuck frame 122 to clamp the main nut 6; the double-acting cylinder 124 is mounted on one side of the chuck frame 122, its cylinder barrel is connected to the chuck frame 122, and its piston rod is connected to the main nut clamping end, used to apply axial tension during the main nut removal process. The disassembly process of the main nut 6 is as follows: When the chuck frame 122 moves to the disassembly station of the main nut 6, the clamping cylinder 123 clamps and fixes the main nut 6, the double-acting cylinder 124 applies axial force, and at the same time the roller assembly 13 drives the main bolt 5 to rotate in the opposite direction, thus achieving the loosening and disassembly of the main nut 6. Subsequently, the sprocket motor 126 drives the chuck frame 122 to move through the sprocket mechanism 125, transferring the main nut 6 to the cleaning station for automatic thread cleaning and drying.

[0032] The sprocket mechanism 125 can be replaced by a belt drive mechanism, and the sprocket motor 126 can be replaced by a cylinder, hydraulic cylinder or other drive components.

[0033] See Figure 5 The roller assembly 13 is located inside the water tank 111 on the right side, and its function is to radially support the main bolt and drive the main bolt to rotate. The roller assembly 13 mainly includes a roller 131, a bracket 132, a transmission shaft 133, a transmission mechanism 134, a drive shaft 135, and a motor 136. Multiple brackets 132 are arranged side by side inside the water tank 111, and the rollers 131 are mounted on the brackets 132 and linked together by the transmission shaft 133; one end of the drive shaft 135 is fixed to the bracket 132, and the other end is connected to the motor 136. The power output by the motor 136 is transmitted to the roller 131 through the drive shaft 135, the transmission mechanism 134, and the transmission shaft 133, thereby driving the main bolt 5 located on the roller 131 to rotate.

[0034] The transmission mechanism 134 can be a gear drive, belt drive, or sprocket drive.

[0035] See Figure 6The nut cleaning assembly 14 is located inside the water tank 111 and is used to spray high-pressure water and compressed air to clean and dry the main nut 6. The nut cleaning assembly 14 mainly includes a motor 141 and a nozzle 142. The nozzle 142 is installed at the output end of the motor 141, and the motor 141 drives the nozzle 142 to rotate. The nozzle 142 has dual fluid channels, which can respectively introduce high-pressure water and compressed air. The switching between the two fluid channels supports both automatic switching (controlled by the console program) and manual switching modes, thereby realizing flexible switching and execution of rinsing and drying processes. The high-pressure water working pressure is steplessly adjustable within the range of 5–30 MPa.

[0036] The motor 141 can be a pneumatic motor, an electric motor, or a hydraulic motor.

[0037] See Figure 7 The bolt cleaning assembly 15 is located inside the water tank 111 on one side and is used to clean and dry the surface of the main bolt 5. It mainly includes a drive motor 151, a slider 152, a lead screw pair 153, a guide rod 154, a support 155, a wind blade 156, a connecting rod 157, a camera assembly 158, and a spray bar 159. The drive motor 151 is connected to the lead screw pair 153. One end of the slider 152 is connected to the lead screw pair 153, and the other end is connected to the guide rod 154. The guide rod 154 is fixedly installed on the support 155 to provide axial guidance for the slider 152. The air blade 156 and the spray bar 159 are installed on the slider 152. The camera component 158 ​​is a radiation-resistant industrial camera, fixed on the air blade 156. It moves along the axial direction of the main bolt 5 with the slider 152 and collects images of the threaded area segment by segment. After cleaning and before the main nut 6 is installed, the control console 4 starts the image acquisition program. The camera component 158 ​​scans the entire threaded section of the main bolt 5 in a moving photography mode. The control console 4 stitches the acquired images to form a complete image of the thread, which can help identify the location of residual contaminants and defects on the threaded surface and provide a basis for judging the quality of the workpiece. The two sets of sliders 152 are synchronously linked through the connecting rod 157 and can move axially linearly along the guide rod 154. Their movement range covers the threaded area of ​​the main bolt 5, achieving cleaning without dead angles. The spray bar 159 sprays high-pressure water with a stepless adjustable pressure in the range of 5 to 30 MPa to clean the threads, while the air blade 156 blows out compressed air to dry the threads.

[0038] The lead screw assembly 153 can be a ball screw or a trapezoidal lead screw.

[0039] The spray bar 159 uses steplessly adjustable high-pressure water jets within the range of 5–30 MPa to clean the threads. The axial movement speed v of the nozzle, the rotation speed n of the main bolt 5, and the bolt pitch p satisfy the following relationship: v_nozzle = n_bolt × p. The control console 4 implements linkage control between the rotation speed of the main bolt 5 and the movement speed of the nozzle to maximize cleaning efficiency. The cleaning efficiency was verified by comparing the cleaning with an M170×4 main bolt simulation body at three pressure gradients of 10 MPa, 20 MPa, and 30 MPa. The thickness of the phosphate layer did not change before and after cleaning. It was confirmed that within the full pressure range of 5–30 MPa, the high-pressure water jet thoroughly cleans the impurities such as anti-seize agent, boron crystals, and corrosion products adhering to the thread surface without damaging the phosphate layer on the workpiece surface. The operator can flexibly adjust the water pressure according to the degree of thread contamination, taking into account both cleaning efficiency and workpiece surface protection.

[0040] See Figure 8 The gas-water separation component 16 mainly includes a gas-water separator 161 and a blower 162. The gas-water separator 161 and the blower 162 are connected to a water tank 111 through a duct to form a closed gas circulation loop. The gas-water separation steps are as follows: First, circulating air containing water vapor flows into the gas-water separator 161 through the duct for gas-liquid separation. After processing, it flows into the blower 162 through the duct. The blower 162 drives the airflow to continuously circulate in the closed loop. The heat generated during operation can assist in heating the circulating air, achieving continuous drying of the circulating air. The continuous operation of the blower 162 creates a negative pressure environment of -50 to -100 Pa inside the tank, effectively suppressing the escape of radioactive waste such as radioactive aerosols. The wastewater separated by the gas-water separator 161 is returned to the sedimentation tank 31 without the need for an additional drainage device, achieving closed-loop control of waste.

[0041] The cover assembly 2 is located above the body assembly 1. The two together form a sealed working cavity. The cleaning of the main bolts 5 and the main nuts 6 is carried out in the sealed cavity, which can effectively prevent water vapor from leaking out.

[0042] See Figure 9The high-pressure water unit 3 mainly includes a sedimentation tank 31, a centrifugal pump 32, a filter 33, a plunger pump 34, an accumulator 35, and a valve group 36. The main function of the high-pressure water unit 3 is to provide high-pressure water for the entire cleaning equipment. The high-pressure water circulation process is as follows: water from the sedimentation tank 31 is pressurized by the centrifugal pump 32, flows through a multi-stage filter 33 to remove impurities, and then enters the plunger pump 34 for secondary pressurization, forming a high-pressure water flow. This high-pressure water is distributed to each execution terminal via the valve group 36. To stabilize pressure fluctuations in the high-pressure circuit, an accumulator 35 is connected in series in the circuit. It can store some energy when the system pressure rises and release the stored energy when the pressure drops, thereby effectively suppressing pressure pulsations and maintaining stable system pressure. The sedimentation tank 31 has a staged filtration function; wastewater flows sequentially through filter screens with progressively increasing mesh sizes, thereby achieving step-by-step interception of particles of different sizes, effectively improving the filtration effect and water purification efficiency.

[0043] The control console 4 sends control commands to each actuator and receives execution results and system status feedback signals in real time, forming a closed-loop control. It integrates dedicated digital twin software, whose main functions include real-time status monitoring (key monitoring parameters include high-pressure water pressure, flow rate, plunger pump speed, fan speed, motor current, chuck position, clamping cylinder pressure, internal negative pressure, circulation loop temperature, vibration, etc.), fault warning, visual inspection, operation simulation exercises, and cleaning parameter recording, realizing comprehensive operation control and dynamic operation status display of the cleaning robot for the main bolts and nuts of the nuclear power plant pressure vessel.

[0044] This invention includes the following steps: Step 1 (Lifting and Positioning): Lift the main bolt 5 horizontally to the equipment operating area and place it on the roller assembly 13. Close the box cover assembly 2 to form a sealed operating chamber.

[0045] Step 2 (Initial Cleaning): The bolt cleaning assembly 15 starts from the initial position, the spray bar 159 sprays high-pressure water, and the slider 152 moves to the right along the guide rod 154 to clean the right section of the thread of the main bolt 5 with high-pressure water jet.

[0046] Step 3 (parallel nut removal and left section cleaning): The chuck frame 122 moves along the guide rod 121 to the main nut 6 removal station and aligns with the main nut 6. The clamping cylinder 123 clamps the main nut 6 evenly in the circumferential direction. The double-acting cylinder 124 applies a pulling force in the axial direction. At the same time, the roller assembly 13 drives the main bolt 5 to rotate in the opposite direction. The combined forces loosen the main nut 6 and complete the removal. Simultaneously, the bolt cleaning assembly 15 moves to the left to clean the left section thread of the main bolt 5, realizing the parallel operation of nut removal and bolt cleaning, effectively reducing the process time.

[0047] Step 4 (Parallel Cleaning of Mid-Section and Nut): After the main nut 6 is disassembled, the sprocket motor 126 drives the chuck frame 122 through the sprocket mechanism 125 to move the main nut 6 to the cleaning station; the nut cleaning component 14 is started, the motor 141 drives the nozzle 142 to rotate, and the high-pressure water flow thoroughly cleans the internal threads of the main nut 6; simultaneously, the bolt cleaning component 15 continues to advance to clean the mid-section threads of the main bolt 5. The two components operate in parallel to maximize work efficiency.

[0048] Step 5 (Overall Air Drying): The bolt cleaning assembly 15 switches to the air drying mode, and the air blade 156 reciprocates along the thread section of the main bolt 5, blowing out compressed air to thoroughly dry the thread surface; the nut cleaning assembly 14 switches the fluid channel to compressed air to simultaneously dry the internal thread of the main nut 6; the steam-water separation assembly 16 continues to operate, and the fan 162 drives the water vapor-containing gas to circulate through the steam-water separator 161 to accelerate the drying of the environment inside the chamber.

[0049] Step Six (Image Acquisition and Quality Inspection): After air drying, the console 4 starts the image acquisition program. The camera component 158 ​​moves along the thread segment axially with the slider 152, acquiring thread images segment by segment. The console 4 stitches the acquired images to form a complete image of the main bolt 5 thread. The operator uses the images to help confirm the cleaning quality, identify residual contaminants and potential defects on the thread surface, and provide a basis for judging the quality of the workpiece.

[0050] Step 7 (Nut Reinstallation): After the quality is confirmed to be qualified, the nut removal assembly 12 moves the main nut 6 back to the installation position. The chuck frame 122 aligns the main nut 6 with the main bolt 5. The roller assembly 13 drives the main bolt 5 to rotate in the forward direction. The double-acting cylinder 124 assists in applying force to tighten the main nut 6 and install it in the designated position of the main bolt 5.

[0051] Step 8 (Final Drying and Lifting): The bolt cleaning assembly 15 is activated to perform final drying on the outer surface of the main nut 6 and the area mating with the main bolt 5, ensuring that there is no residual moisture on the workpiece surface. Open the cover assembly 2 and lift out the main bolt 5. This completes the fully automated disassembly, cleaning, and quality inspection of the main bolt 5 and the main nut 6.

[0052] The above-described specific embodiments are only used to explain the design concept of the present invention, and are intended to facilitate understanding and implementation by those skilled in the art, rather than to limit the scope of protection of the present invention. Therefore, equivalent changes made using the design concept of the present invention still fall within the scope of protection of the present invention.

Claims

1. A high-pressure water jet cleaning robot for main bolts in nuclear power plants, characterized in that, include: The tank assembly includes a water tank assembly, a nut removal assembly, a roller assembly, a nut cleaning assembly, a bolt cleaning assembly, and a steam-water separator assembly; the water tank assembly has a sealing structure around its opening; the nut removal assembly is used for automatically removing and installing the main nut; the roller assembly is used to radially support the main bolt and drive its rotation; The lid assembly is installed above the box assembly and presses the sealing structure with its own weight, forming a sealed working cavity with the box assembly. The high-pressure water unit includes a sedimentation tank, a centrifugal pump, a filter, a plunger pump, an accumulator, and a valve group. After being pressurized and filtered by the centrifugal pump, the filter, and the plunger pump in sequence, the water is distributed to each execution terminal by the valve group. The accumulator is connected in series in the loop to smooth out pressure pulsations and realize closed-loop water circulation. The control console is connected to the housing assembly, the cover assembly and the high-pressure water unit by signal. It is used to send control commands and receive feedback signals in real time. The control console implements linkage control of the main bolt rotation speed and the nozzle axial movement speed. The nut cleaning assembly and bolt cleaning assembly both use high-pressure water jet as the cleaning medium to perform non-contact cleaning of the internal threads of the main nut and the external threads of the main bolt, respectively; the working pressure of the high-pressure water jet is steplessly adjustable in the range of 5 to 30 MPa. The nut removal assembly includes a guide rod, a chuck frame, a clamping cylinder, a double-acting cylinder, a sprocket mechanism, and a sprocket motor; the nut removal assembly is mainly used for the fully automatic removal and transfer of the main nut to the cleaning station and the reinstallation of the main bolt; The bolt cleaning assembly includes a drive motor, a slider, a lead screw pair, a guide rod, a support, an air blade, a connecting rod, a spray bar, and a camera assembly; the drive motor drives the slider to move axially linearly along the guide rod via the lead screw pair, the spray bar moves with the slider and sprays high-pressure water to clean the main bolt threads, and the air blade moves with the slider and blows out compressed air to dry the main bolt threads; The vapor-water separation component includes a vapor-water separator and a fan; the vapor-water separation component is mainly used to separate water vapor from the box assembly, and its continuous operation maintains a negative pressure environment inside the box. The heat generated by the fan operation also assists in heating the circulating air to suppress the escape of radioactive aerosols and accelerate drying. During air drying, the air blades reciprocate along the threaded section, blowing out compressed air, which works in conjunction with the negative pressure hot air circulation generated inside the chamber by the air-water separation component to dry the threads of the main bolt.

2. The high-pressure water jet cleaning robot according to claim 1, characterized in that, The water tank assembly includes a water tank, a water tank frame, and anchor bolts; the water tank frame has a double-layer structure, the water tank is installed on the upper layer of the water tank frame, and the water tank frame is fixed to the ground by the anchor bolts; the bottom of the water tank has an inclination angle of 3° to 10° with the horizontal plane, so that the cleaning wastewater flows automatically to the drain outlet by gravity.

3. The high-pressure water jet cleaning robot according to claim 1, characterized in that, The roller assembly includes rollers, brackets, transmission shafts, transmission mechanisms, drive shafts, and motors; multiple sets of brackets are arranged side by side inside the water tank, and the rollers are mounted on the brackets and linked together through the transmission shafts; the power of the motor is transmitted to the rollers through the drive shafts, transmission mechanisms, and transmission shafts to drive the main bolts to rotate.

4. The high-pressure water jet cleaning robot according to claim 1, characterized in that, The nut cleaning assembly includes a motor and a nozzle; the nozzle is installed at the output end of the motor, and the motor drives the nozzle to rotate; the nozzle has dual fluid channels for introducing high-pressure water and compressed air respectively. The switching between the two fluid channels supports both automatic and manual switching modes controlled by the console program. When high-pressure water is introduced, the working pressure of the high-pressure water is infinitely adjustable within the range of 5 to 30 MPa to achieve non-contact high-pressure cleaning of the internal threads of the main nut; when compressed air is introduced, the internal threads of the main nut are dried.

5. The high-pressure water jet cleaning robot according to claim 1, characterized in that, The lid assembly consists of a frame, a nitrogen spring, and a hinge seat; the nitrogen spring provides support when the lid is open, and the lid assembly is hinged to the body assembly via the hinge seat.

6. The high-pressure water jet cleaning robot according to claim 1, characterized in that, The sedimentation tank has a staged filtration function, in which sewage flows through filter screens with progressively increasing mesh sizes, achieving step-by-step interception of particles of different sizes.

7. The high-pressure water jet cleaning robot according to claim 1, characterized in that, The control console implements linkage control between the main bolt rotation speed and the nozzle axial movement speed, and the two satisfy the following relationship: v_nozzle = n_bolt × p Where: v_nozzle is the axial movement speed of the nozzle (mm / min), n_bolt is the rotation speed of the main bolt (r / min), and p_main bolt pitch (mm). This allows the nozzle to advance axially by one thread pitch for each revolution of the main bolt, achieving continuous cleaning of the entire thread and ensuring thorough and complete cleaning.

8. A method for operating a high-pressure water jet cleaning robot as described in any one of claims 1 to 7, characterized in that, The process includes the following steps: Step 1: The main bolt is hoisted to the equipment operating area and placed horizontally on the roller assembly. The cover assembly is closed to form a sealed operating chamber. Step 2: The bolt cleaning assembly starts from its initial position. The spray bar sprays high-pressure water, and the slider moves to the right along the guide rod to clean the right section of the main bolt's thread. Step 3: The chuck frame moves along the guide rod to the main nut disassembly position and aligns with the main nut. The clamping cylinder clamps the main nut, and the double-acting cylinder applies axial tension. Simultaneously, the roller assembly drives the main bolt to rotate in the opposite direction, collaboratively completing the main nut disassembly. Simultaneously, the bolt cleaning assembly moves to the left to clean the left section of the main bolt's thread. Step 4: After the main nut is disassembled, the sprocket motor drives the chuck frame through the sprocket mechanism to move the main nut to the cleaning position. The nut cleaning assembly starts to clean the internal thread of the main nut. Simultaneously, the bolt cleaning assembly cleans the main bolt's thread. Step 5: The bolt cleaning assembly switches to air-drying mode, and the reciprocating motion of the air blades air-dries the threaded section of the main bolt; the fluid channel of the nut cleaning assembly switches to compressed air to air-dry the internal thread of the main nut; the air-water separation assembly continues to run, accelerating the drying of the environment inside the chamber; Step 6: The control console starts the image acquisition program, and the camera assembly moves along the threaded section with the slider, acquiring images segment by segment and stitching them into a complete thread image. The operator uses this image to help confirm the cleaning quality and to help identify residual contaminants and potential defects on the thread surface; Step 7: The nut removal assembly moves the main nut back to the installation position, the roller assembly drives the main bolt to rotate forward, and the double-acting cylinder assists in applying force to install the main nut onto the main bolt; Step 8: The bolt cleaning assembly performs final air drying on the outer surface of the main nut, the chamber cover assembly is opened, the main bolt is lifted out, and the fully automated disassembly, cleaning, and quality inspection operation is completed.

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