Talk about the valve "run by"

First, on the valve leakage, leakage prevention measures. 1. All valves must be subjected to different levels of pressure test after entering the factory. 2. There is a need to disassemble the valve must be grinding. 3 in the process of overhaul must carefully check whether to add packing, packing gland is tightened. 4 valve before installation must check the valve for dust, sand, iron oxide and other debris. If the above debris must be cleaned before installation. 5. All valves must be installed before installation of the appropriate level of gasket. 6. In the installation of the flange door fasteners must be tightened, when tightening the flange bolts must be fastened in the direction of symmetry. 7. In the valve installation process, all valves must press the system, the pressure is properly installed, non-loaded, mixed. For this purpose, all valves must be numbered by the system before installation and documented. Second, on the prevention of coal dust leaks. 1. All flanges must be fitted with sealing material. 2. Leakage prone area is the coal mill import and export valves, coal feeders, manufacturers Flanges, and all have flange connection parts. To this end, we will conduct a comprehensive inspection of all manufacturers and equipment can leak powder parts, without the installation of sealing materials we will be a second refit and tighten the fasteners. 3. Coal seam welding mouth is willing to happen leakage phenomenon, we will take some measures. 3.1 In the weld before the weld area must be carefully polished metal luster and polished out of the groove required for welding. 3.2 pairs of mouth must be reserved before the gap, forbidden to force counterparts. 3.3 welding consumables must be used correctly, in the cold weather, as required, preheating and so on. Third, on the oil system leaks, running oil and other preventive measures. 1. Good oil system leaks, running oil and other work is very important. 2. The system with the fuel tank must be carefully checked and cleaned before installation. 3. Oil cooler equipment must be hydrostatically tested. 4. For oil pipeline system also need to do hydraulic test and pickling work. 5. During the installation of oil pipelines, all flanged joints or union joints with screws must be equipped with oil-resistant rubber pads or oil-resistant asbestos pads. 6. Leaking oil system mainly in the flange and threaded joints, so the flange must be installed in the bolt fastening evenly. Prevent leak tight or not tight situation occurs. 7. In the process of oil filter, the construction workers must always stick to the job, is strictly forbidden to go out and post. 8. In the filter paper is to replace the oil filter must be shut down. 9. In the installation of temporary oil filter connection pipe (high-strength plastic transparent hose), the connector must be tied firmly with lead wire to prevent the oil filter running after a long time to run off the phenomenon of running oil. 10. Deployment of highly responsible construction staff to take care of the work of the oil filter. 11. Before auxiliary oil system starts oil circulation, a special technical explanation will be given by the engineering department to the personnel responsible for auxiliary oil circulation. Fourth, put an end to equipment and pipe fittings surface bubble, take, drip, leak, the following preventive measures: 1.2.5Mpa flange gasket above, are used metal wound mat. 2.1.0Mpa-2.5Mpa flange gasket, using asbestos pad, and brushing black lead powder. 3.1.0Mpa following water pipe flange gasket rubber pad, and brushing black lead powder. 4. Pump packing are used PTFE composite packing. 5, smoke, coal seam sealing parts, the use of asbestos rope twisting a good, smooth join the joint surface, it is strictly prohibited to tighten the screws after the force to join. Fifth, the elimination of valve leakage following measures: (for the valve leak we should do the following measures) 1 pipeline installation and construction, we must establish a good sense of quality, consciously clean the oxide scale and the pipe wall, leaving no debris, Ensure that the pipe wall clean. 2. First to ensure that the valve into the scene must be 100% hydrostatic test. 3. Valve grinding should be carried out seriously, requiring all valves (except for imported valves) should be sent to the grinding group disintegration inspection grinding and maintenance, and the implementation of the responsibility, consciously make records and identification, easy to trace. Important valves should be listed in detail secondary inspection, so that "playing a seal, there is a test, record" requirements. 4. The first boiler door and discharge door to be determined in advance, in the hydrostatic test process only allows the opening of these valves, other valves are not free to open, so as to protect the valve core. 5. Pipeline to open a large wash, light off, to prevent damage to the door core. If missing, the reason is? (1) the contact between the opening and closing member and the valve seat sealing surface; (2) the fitting of the packing and the stem and packing box; (3) the leakage at the previous place where the valve body and the valve cover are connected is called Internal leakage, which is commonly referred to as lax, it will affect the ability of the valve to cut off the medium. After the two leaks called leakage, that is, the medium leaked from the valve to the valve. Leakage will result in material loss, pollute the environment, serious accidents will result. In fact, the analysis of internal leakage, internal leakage is generally: the valve according to their different caliber, the pressure difference of the system, and the system is not the same as the medium, there is an allowable leakage standards. In a strict sense, a truly '0' leak valve does not exist. In general, small-diameter shut-off valves are prone to invisible leaks (not zero leaks), whereas large-sized gate valves make invisible leaks difficult. In the event of internal leakage of the valve, we should first try to understand the specific amount of leakage, access to allowable leakage of the valve standard, the leakage of the system when the work environment and other factors a comprehensive analysis to correctly judge the valve leakage problem . (1) Parallel gate valve leakage problem, the principle of parallel gate valve is based on the system of differential pressure on the outlet side of the spool and seat sealing surface compression, the system pressure is very low, the valve back A slight internal leakage may occur. Encounter such internal leakage, it is recommended to continue to observe the system inlet pressure to the design pressure or normal working pressure check the valve seal, if there is still excessive leakage, it should be disassembled and the sealing surface of the valve grinding . (2) internal leakage of wedge gate valve is sometimes due to the different control methods of the valve, as the manufacturer in the design selection, the corresponding stem and stem nut strength design is not considered the way torque control, and use The travel control mode, if forced to close the position of the stroke control mode to torque control, valve stem nut may result in damage, etc., while leading to the electric head open when a fault occurs, open torque fault alarm. Encounter this valve leakage problem, usually after the electric shut down and then manually shut again, you can close, if there is still leakage after manual shut-off, then there is a problem sealing the valve, then the need to disintegrate grinding. (3) Check valve leakage, check valve seal is also dependent on the system of pressure, when the check valve inlet pressure is very low, the outlet pressure will have a slight increase in the phenomenon, then should be integrated Factor analysis, determine the amount of leakage, according to the analysis of the structure to decide whether to take the body maintenance work. (4) Large-caliber disc valve leakage, large-caliber disc valve leakage standards are generally large, when the inlet pressure increases, the outlet pressure will increase, this problem should be judged first Out of the amount of leakage, according to the amount of leakage for maintenance of the decision. (5) The internal leakage of the control valve, due to the different form of the control valve, the standard of internal leakage is not the same, while the control valve generally use the travel control, (not using torque control), and therefore generally exist Leakage phenomenon. The regulation valve leakage problem should be treated differently, there are special requirements of the leakage control valve should be considered in the design and manufacture. XX nuclear power plant there are many such contradictions, many have forced the valve has been replaced by torque control, which is the work of the control valve is not good. To be more specific: (1) valve trim material selection and heat treatment is poor, not enough hardness, easily washed by high-speed fluid. (2) Due to the structure of the valve, the energy (velocity) of the fluid is not effectively consumed when passing through the valve, and the impact on the sealing surface is large; the excessive pressure causes the pressure behind the valve to be too small and below the saturation pressure to cause cavitation, Cavitation bubbles in the process of cavitation all the energy concentrated at the rupture point, resulting in several thousand Newton's impact force, the shock wave pressure up to 2 × 103Mpa, greatly exceeded the existing metal material fatigue failure limit. Extremely hard disc and seat will also be destroyed in a very short time, a leak. (3) the valve for a long time in the small opening state of work, the flow rate is too high, the impact of large, easy to damage the valve trim.

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