Talk about the issues of \"overheating, vaporization, dripping, and leakage\" in equipment”

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I. Preventive measures against valve leakage of water and steam. 1. After entering the factory, all valves must undergo hydrostatic tests of different levels. 2. Valves that require disassembly for repair must be ground. 3. During the reconditioning process, it is necessary to carefully check whether any packing has been added and whether the packing gland is tightened. 4. Before installation, it is necessary to check whether there are any impurities such as dust, sand, or iron oxide inside the valve. If there are any such debris, it must be thoroughly cleaned up before installation. 5. All valves must be fitted with gaskets of the appropriate grade before installation. 6. When installing the flanged door, the fasteners must be tightened. When tightening the flange bolts, they must be tightened sequentially in a symmetrical manner. 7. During the valve installation process, all valves must be installed correctly according to the system and pressure requirements; random or mixed installation is strictly prohibited. To this end, all valves must be numbered according to the system before installation, and records must be kept. II. Preventive measures against coal dust leakage. 1. Sealing material must be installed on all flanges during installation. 2. Areas prone to powder leakage are the coal inlet and outlet valves of the coal grinder, the coal feeder, the manufacturer’s flanges, and all parts connected by flanges. To this end, we will conduct a comprehensive inspection of all areas on manufacturers’ equipment where powder leakage might occur. For those areas where no sealing material has been applied, we will apply it a second time and tighten the fasteners. 3. There is a possibility of powder leakage at the welds of the coal powder pipes, and we will take the following measures. 3.1 Before welding, the weld area must be carefully polished to achieve a metallic shine, and the groove required for welding must be created. 3.2 A gap must be reserved before alignment; forced alignment is strictly prohibited. 3.3 For welding materials, it is necessary to use the correct ones; in cold weather, preheating must be carried out as required, etc. III. Preventive measures against oil system leaks and oil spills, etc. 1. It is very important to properly handle issues such as leaks and oil spills in the oil system. 2. Systems with oil tanks must be carefully inspected and cleaned before installation. 3. Equipment equipped with oil coolers must undergo a hydrostatic test. 4. For the oil pipeline system, hydrostatic testing and acid cleaning must also be carried out. 5. During the installation of oil pipelines, all flange connections or threaded unions must be fitted with oil-resistant rubber gaskets or oil-resistant asbestos gaskets. 6. Leaks in the oil system are mainly found at flanges and threaded unions; therefore, the bolts must be tightened evenly when installing the flanges. Prevents situations where it leaks or isn’t tightly sealed. 7. During the oil filtration process, construction workers must remain at their posts at all times; leaving their posts or moving to other posts is strictly prohibited. 8. It is necessary to shut down the oil filter mechanism when replacing the oil filter paper. 9. When installing the temporary connection hose for oil filtration (a high-strength transparent plastic hose), the joints must be securely tied with wire to prevent any disconnection or oil leakage after the oil filter has been in operation for an extended period. 10. Assign highly responsible construction workers to oversee the operation of the oil filter. 11. Before the auxiliary oil system begins to circulate oil, the Engineering Department shall organize a detailed technical briefing for the personnel responsible for the oil circulation in this system. IV. To prevent bubbling, escaping, dripping, and leaking at the joints of equipment and pipe fittings, the following preventive measures are taken: Flange gaskets with a pressure rating of 1.2.5 Mpa or higher all use metal wound gaskets. Flange gaskets with a pressure range of 2.1.0 Mpa to 2.5 Mpa use asbestos gaskets coated with lead black powder. For water pipeline flange gaskets below 3.1.0 Mpa, rubber gaskets are used, coated with lead black powder. 4. The packings for the water pumps are all PTFE-fiber composite packings. 5. For the sealed joints of flue and coal-dust ducts, the asbestos rope used must be twisted once and then smoothly placed onto the mating surfaces; it is strictly prohibited to force it in after the screws have been tightened. V. The following measures can be taken to eliminate internal leakage in valves: (To prevent leakage in valves, we should take the following actions) 1. During pipeline installation, it is essential to have a strong sense of quality; iron oxide scale and other debris on the inner walls of the pipes must be removed carefully to ensure that the inner walls remain clean. 2. First, ensure that all valves brought to the site must undergo a 100% hydrostatic test. 3. Valve grinding must be carried out meticulously. It is required that all valves (except inlet valves) be sent to the grinding workshop for disassembly, inspection, grinding, and maintenance. Responsibilities must be clearly defined, and proper records and markings should be made conscientiously to facilitate traceability. Important valves should be listed in detail for secondary acceptance, ensuring compliance with the requirements of \"applying stamps, verifying the stamps, and keeping records\". 4. The water filling valve and the drain valve of the boiler should be determined in advance; only these valves are allowed to be opened during the hydrostatic test, and no other valves should be opened arbitrarily, thereby protecting the valve cores. 5. When flushing the pipeline, open it wide and close it gently to prevent damage to the door core. If it’s missing, what’s the reason? (1) The contact area between the moving part and the two sealing surfaces of the valve seat ； (2) The fit between the packing and the valve stem as well as the packing box ； (3) The junction between the valve body and the valve cover. The leakage at the former location is referred to as internal leakage, which is commonly known as “inability to seal properly.” This affects the valve’s ability to block the flow of the medium. The leaks in the latter two locations are called external leaks, that is, the medium leaks from inside the valve to outside it. Leakage can result in material loss, environmental pollution, and in severe cases, accidents. In practice, internal leakage is analyzed; generally, depending on the valve’s diameter, the system pressure difference, and the type of fluid in the system, there is a specified standard for acceptable internal leakage. In a strict sense, there are no valves that truly have ‘0’ leakage. Generally, it is easy to achieve imperceptible leakage (not zero leakage) in small-diameter globe valves, whereas it is very difficult to do so in large-diameter gate valves. When internal leakage is detected in a valve, it is first necessary to determine the exact amount of leakage as accurately as possible, consult the allowable leakage standards for that valve, and conduct a comprehensive analysis of factors such as the operating conditions of the system at the time of leakage, in order to properly assess the issue of internal leakage in the valve. (1) The internal leakage problem of parallel gate valves: The working principle of parallel gate valves relies on the pressure difference in the system to press the valve element on the outlet side against the sealing surface of the valve seat; when the system pressure is very low, slight internal leakage may occur behind the valve. In cases of such internal leakage, it is recommended to continue monitoring the situation. When the inlet pressure of the system reaches the design or normal operating pressure, check the valve’s sealing performance. If there is still excessive leakage, the valve should be disassembled and its sealing surfaces ground to restore proper sealing. (2) Internal leakage in wedge gate valves is sometimes caused by differences in the valve’s control method. When designing such valves, manufacturers choose components such as the valve stem and valve stem nut in a way that focuses on strength, without taking into account torque control; instead, stroke control is used. If the stroke control mechanism at the closed position is forced to be changed to torque control, it may cause damage to the valve stem nut, and it can also lead to faults in the electric actuator, resulting in error alerts related to the opening torque. When encountering internal leakage issues with such valves, it is usually sufficient to close them manually after closing them electrically to ensure they are tightly shut. If internal leakage persists even after manual closure, it indicates a problem with the valve’s sealing surfaces, and in such cases, the valve needs to be disassembled and ground for repair. (3) Internal leakage of the check valve: The sealing of the check valve also relies on the pressure difference in the system. When the inlet pressure of the check valve is very low, the outlet pressure will also increase slightly. In such cases, it is necessary to analyze various factors to determine the amount of internal leakage, and then decide whether maintenance work is required based on the analysis results. (4) Internal leakage in large-diameter disc valves: The standard for internal leakage levels in such valves is generally high. As the inlet pressure increases, the outlet pressure also rises. To address this issue, it is first necessary to determine the extent of internal leakage, and then decide whether maintenance is required based on that level of leakage. (5) Internal leakage of control valves: Due to the various types of control valves, the standards regarding internal leakage also vary. Additionally, control valves generally utilize stroke control (rather than torque control); therefore, internal leakage is a common occurrence. The issue of internal leakage in control valves should be addressed differently; control valves with specific requirements regarding internal leakage should be taken into account during their design and manufacturing. There are many such contradictions at the XX nuclear power plant; many valves had to be changed to torque control, which is detrimental to the operation of the control valves. To be more specific: (1) The material selection and heat treatment of the valve internals are inadequate; the hardness is not sufficient, making them prone to being damaged by high-speed fluids. (2) Due to the limitations of the valve structure, the energy (velocity) of the fluid is not effectively dissipated as it passes through the valve, resulting in high impact wear forces on the sealing surfaces ； Excessive speed results in too low a pressure behind the valve, below the saturation pressure, which leads to cavitation. During cavitation, when the bubbles burst, all the energy is concentrated at the point of rupture, generating an impact force of several thousand newtons; the pressure of these shock waves can reach 2×103 Mpa, **which exceeds the fatigue failure limit of existing metal materials. The extremely hard valve discs and seats can also be damaged in a very short time, resulting in leaks. (3) When the valve operates for a long time at a partially open position, the flow velocity is too high and the impact force is great, making the valve trim prone to damage.