Abstract: In some hydropower stations that depend on the weight for the self-closing of the butterfly valve, after the butterfly valve is operated for several years, the failure of the butterfly valve to close the full-closing position occurs during the closing process. Aiming at this problem, a reliable automatic butterfly valve closing procedure is proposed. This procedure not only ensures the normal closing of the butterfly valve but also provides the safety guarantee for the overhaul and operation of the hydropower station. It also protects the butterfly valve spindle and bearing and prolongs The use of butterfly valve time. Key words: butterfly valve; closing fault; cause analysis; treatment method 1 faulty butterfly valve profile Qinshan Hydropower Station adopts PDF130-WZ-280 butterfly valve, which is a horizontal double flat flap structure. Butterfly valve assembly, including the valve body, the valve, the main seal work, bearings, revolving arm, relay, locking device, hammer and bypass valve. The butterfly valve body adopts the overall structure of the cast welding, and the contact part between the valve body and the working seal ring is made of stainless steel, which prolongs the service life of the seal ring and improves the sealing performance. The valve seal is located on the downstream side, the sealing surface with a bevel structure, which has good sealing performance. The bottom of the valve body has eight anchor bolts used as a fixed valve body, can withstand the upward thrust of the relay and the action of moving water in the valve up force, but can not withstand the full throttle when the water thrust. In order to increase the self-closing moment of the valve when the water is closed, the valve and the valve body are biased. The geometric center and the rotation center are offset by 50mm, which increases the reliability of closing. The main work of the valve seal with solid shaped rubber around the valve, with pressure ring and the compression screw fastened on the valve, in order to ensure the seal ring adjustable and positioning, with locking screws to be fixed. Valve shaft 40Cr forged steel, and bearing and shaft seal contact with chrome protection, and the valve inserted by the fixed pin. The bearing consists of a steel sleeve and a copper tile, the bronze tile material is cast aluminum bronze (ZCuAl1OFe3), the end seal adopts the U-shaped support ring seal, the sealing force is adjustable, and the replacement is convenient. The valve arrangement of two 200mm diameter straight swing type relay, the relay piston rod connected to the valve shaft through the boom, the piston rod surface chrome treatment. Piston and cylinder seal using O-ring and PTFE seal; Receptacle cylinder with two shut-off devices and throttling buffer structure, the external high-pressure hose connection. Control System. The opening of the butterfly valve adopts the FYZ valve hydraulic control device to supply oil, and drives the relay to fully open the valve and the heavy hammer to adopt the hydraulic locking ingot. The lock cylinder oil source comes from the governor hydraulic device. When the unit is in an accident or need to stop normally, switch the lock cylinder oil source to disengage. The butterfly valve relies on the two heavy hammer (each 3.5 t) configured by itself and the hydraulic action to the valve closed, which can cut off the water flow and protect the unit . 2 Symptom Qingshan Hydropower Station was put into operation in March 2000 and operated until March 2002 and found that when the butterfly valve was closed to about 95% of the full stroke during butterfly valve closing, the butterfly valve arm (weight) stopped Whereabouts, the butterfly valve can not reach the full close position. This and the butterfly valve can only be fully open or fully closed 2 positions contradictory position of the butterfly valve is in indefinite state, resulting in a larger amount of leakage, causing a strong noise, overhaul to the hydropower station has brought greater security risks. 3 Analysis of the reasons 3.1 oil pipelines This phenomenon may be due to poor return oil line oil caused by the oil side of the shut-off side of the reservoir is not drained, resulting in the relay piston can not be fully restored to the full position, resulting in butterfly valve Rotary arm can not reach the maximum travel whereabouts, causing the butterfly valve closed to the full off position. In this regard the operation of the oil pipeline inspection, the pipeline for the oil valve decomposition inspection to ensure that the oil pipeline unobstructed. 3.2 The structure of the relay In order to reduce the speed and pressure at the bottom of the relay piston impact relay oil during the closing process, there are two shut-off devices in the operation of the relay cylinder, namely the throttling buffer structure. On the relay throttling buffer structure and the relay throttles to adjust, increase the throttle opening, so that the oil return flow becomes larger, the throttle before and after the pressure becomes smaller, is conducive to the relay Piston's whereabouts. At the same time, the inspection found that the piston rod surface of the relay chromium plating layer intact, no signs of corrosion card astringent. The above two methods have no obvious effect, which means the reason why the butterfly valve can not reach the fully closed position has nothing to do with the operating system (operating pipe and relay device). 3.3 in the process of closing the butterfly valve butterfly valve torque required to bear less than the friction resistance at the bearing moment In order to prevent sediment silting impede the opening of the valve, the lower edge of the butterfly valve against the flow of water closed, moving water moment M always tends to close the valve, the valve on the move Water pressure along the flow direction of the force p along the water flow direction, vertical component P1 upward direction. When the valve is closed, the water is completely still and the valve is subjected to hydrostatic pressure. Due to the difference between the position of the valve and the valve, the center of hydrostatic pressure is below the center line of the valve. In this way, for the butterfly valve of the horizontal axis, there is a hydrostatic torque for turning the valve. In Qinshan hydropower station, the butterfly valve can not be closed normally close to full position. In the valve operation, there are friction and friction torque at the turning pin of the operating mechanism. Among them, the friction between the valve shaft and the bearing and the torque is the main, the value of the total friction to take up friction most of the friction torque. According to the design conditions, the friction coefficient of the valve shaft and cast aluminum bronze generally take μ = 0.15, so when the maximum head 121.5m, the butterfly valve can be automatically shut down by its own weight. However, the condition that the butterfly valve can not be closed automatically must be μ> 0.27. Therefore, the following conclusions can be drawn: After 2 years of operation, butterfly valves # 1 and # 2 of Qinshan Power Station have been shut down with varying degrees of closing to the full close position. Our analysis suggests that this situation occurs for the following two reasons: (1) after more than two years of operation of the butterfly valve, sedimentation may occur between the valve shaft and the bearing, resulting in a gap between the valve shaft and the bearing Reduce, bearing friction factor increases. In the process of closing the valve, when the valve approaches the fully closed position, a pressure difference is formed between the valve and the downstream, and this pressure difference will produce a torque on the valve shaft that hinders the closing. This resistance moment is proportional to the friction coefficient of the bearing Proportional, when the resistance torque is greater than the valve closing torque occurs when the above phenomenon. (2) bearing after a period of operation, the bearing lubrication surface may be corrosive, bearing wear, friction factor increases, can also lead to the above phenomenon. 4 approach (1) to change the operating procedures to close the butterfly valve. While closing the butterfly valve, open the bypass valve and close the bypass valve after the valve is closed. In this way, the butterfly valve can be balanced before and after the closing process, eliminating the pressure difference between the upper and lower ends of the butterfly valve in the process of closing the valve, greatly reducing the frictional resistance during closing and enabling the valve to be smoothly operated, and Can reduce the bearing lubrication surface wear and increase butterfly valve bearing life. (2) There are 4 M30 screw holes reserved on the side of the two weight hammers. You can add some steel plates to the hammer and fasten it with screws. This increases the weight of the hammer, which increases the weight moment when the butterfly valve is closed, allowing the butterfly valve to close smoothly as the bearing friction coefficient increases. In the above two methods, if using the second method of transformation, the butterfly valve in a period of time can be more smoothly shut itself down, but after a long run, with sediment in the valve shaft and bearing precipitation and bearing Further wear lubrication surface, the friction coefficient increases frictional resistance increases, the butterfly valve may not be able to shut down, and even need to replace the new bearing. Therefore, taking into account the difficulty of dealing with the above problems and the safe and economical operation of the power station, a method of modifying the butterfly valve closing flow is adopted, as shown in FIG. 1 (gray in the figure for improving and adding a flow part). Figure 1 Improved butterfly valve closing process 5 Practical application Qingshan Hydropower Station butterfly valve closing process is improved, at the same time open the bypass valve closed, the valve after the water. Butterfly valve in the upper and lower water pressure off the case closed. During this process, the hydrostatic torque acting on the valve is basically eliminated, meanwhile, the friction torque on the valve shaft is greatly reduced. Practice shows that the modified butterfly valve is stable, shut down properly and shut down well. At the same time taking into account the unit over-speed, due to governor valve with the main valve refused to move, the butterfly valve to be closed to prevent unit over-speed. In this way, in order to prevent the opening of the bypass valve caused by closing the butterfly valve, the speed of the unit is increased. In the operating oil line of the over-speed protection device, an oil pipe is also connected to the governor accident solenoid valve. When the over-speed protection device action, the accident solenoid valve also action, governor main pressure valve quickly toward the side of the action, turn off the guide vane to prevent the unit flee. 6 Conclusion The closure process of the butterfly valve, because the butterfly valve in the closure before and after the water pressure balance, by the hydrostatic pressure smaller, greatly reducing the friction torque of the valve shaft, but also reduces the butterfly valve spindle and bearing wear and tear, extended Butterfly spindle and bearing inspection cycle, but also to ensure the stable operation of the butterfly valve to ensure the safe and economical operation of the hydropower station. If the use of butterfly valves in hydropower stations with large sediment load, it is best not to use the kind of butterfly valve with self-closing device, because the use of butterfly valves with self-closing device, after a long run, with the sediment in the valve shaft and bearings Between the precipitation and the bearing lubrication surface wear, bearing friction factor increases the friction resistance increases, the butterfly valve will eventually not be closed. This will definitely increase the number of butterfly valve overhaul and reduce the service life of the butterfly valve, which is not conducive to the safe and economical operation of the hydropower station. (Full text) Address: Valve Gate Valve Globe Valve Ball Valve Hydraulic Control Valve Butterfly Valve Check Valve Plug Valve Regulator Trap Reducer Filter