I. Preliminary preparation 

 1. Safety preparation: 

 Ensure the safety of the operating environment, close the corresponding fluid system, release pressure, and take necessary safety measures, such as wearing protective equipment. 

 Cut off the power supply, air source, hydraulic oil circuit associated with the overhaul valve, and clean the gas circuit, oil circuit and components to ensure compliance with safe operation regulations. 

 2. Preparation of tools and materials: 

 Prepare the required repair tools and materials, such as wrenches, screw drivers, gaskets, sealants, cleaning agents, etc., and ensure the quality and applicability of these tools and materials. 

 3. Program development: 

 For large-caliber valves or important valves, a repair plan should be prepared, a repair process should be developed, and approved by the relevant departments. 

 II. Fault observation and preliminary inspection 

 1. Observation of phenomena: 

 Observe abnormal conditions during the opening, closing or adjustment of the valve, such as leakage, jams, vibration, etc. 

 2. Preliminary inspection: 

 Check the appearance of the valve, sealing surface, connection parts, etc. for damage, wear or looseness. 

 Check whether the valve's operating mechanism is flexible and the instructions are accurate. 

 III. Selection of professional diagnosis and repair methods 

 1. Professional diagnosis: 

 If the preliminary examination fails to find the cause of the failure, a professional diagnosis is required. Use professional testing tools and equipment to conduct more in-depth inspection and analysis of valves to determine the specific cause and location of the failure. 

 2. Choose the right repair method: 

 Select the appropriate repair method based on the results of troubleshooting. Common repair methods include replacing damaged parts, repairing seals, adjusting the operating mechanism, etc. 

 IV. Disassembly and repair 

 1. Disassembling the valve: 

 Remove the relevant parts of the valve according to the maintenance needs. During the disassembly process, pay attention to record the position and order of each part for subsequent assembly. 

 2. Cleaning and inspection: 

 Use appropriate cleaning agents and tools to remove impurities and污垢 inside the valve and ensure that the valve is clean and unobeded. 

 Check the sealing surface and operating mechanism of the valve to ensure that it is intact. 

 3. Repair or replace parts: 

 Repair or replace damaged or worn parts according to the results of troubleshooting. Use appropriate tools and materials to repair or replace according to the manufacturer's requirements. 

 V. Assembly and testing 

 1. Reassembling the valve: 

 Reassemble the valves according to the location and order recorded during disassembly. Make sure that each component is installed correctly and tightly connected. 

 2. Manual operation test: 

 After assembly is completed, a manual operation test is carried out first. Manually switch the valve to check whether its operation is flexible and the instructions are accurate. 

 3. Sealability test: 

 Close the valve and observe if there is any leakage at the connection between the valve and the pipeline. If a leak is found, the cause should be found in time and corresponding remedial measures should be taken. 

 4. Functional test: 

 Functional testing is carried out on the basis of ensuring that the valve is well sealed. According to the process flow of the system, simulate the actual operating conditions and test whether the valve's switching performance, adjustment performance, etc. meet the requirements. 

 VI. Records and archiving 

 1. Record maintenance data: 

 During the repair process, repair data should be recorded in detail, including troubleshooting results, repair methods, replaced parts, etc. These data are important for subsequent troubleshooting and maintenance. 

 2. Filing and maintenance reports: 

 After the repair is completed, the repair report should be prepared and submitted to the user for archiving. The repair report should include the maintenance process, replaced parts, test results and other information. 

 VII. Precats 

 1. The inspection valve shall be listed with the inspection number, working pressure, working temperature and medium. 

 2. Disassembly and assembly shall be carried out according to the process procedure, using special tools and tools, and fore-force disassembly and assembly is strictly prohibited. 

 3. The disassemated valves should be stacked separately and checked or marked with direction and position requirements. 

 4. Cleaning and descaling should be thorough to ensure that there are no impurities and dirt inside the valve. 

 5. When asmbling, ensure that each component is installed correctly, tightly connected, and free of leakage. Through the above steps, the valve overhaul can be carried out smoothly and the normal operation of the valve can be restored.