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Regulating valve common fault handling four
Control valve vibration solution 1) increase the stiffness of the oscillation and slight vibration, increase the rigidity to eliminate or reduce, such as the use of large stiffness of the spring, the use of piston actuators and other options are feasible. 2) Increase the damping method to increase the damping that is to increase the vibration of the friction, such as sleeve valve spool can be used "O" ring seal, with a larger friction graphite filler, which to eliminate or reduce the slight vibration or Have a role 3) to increase the size of the guide to reduce the gap with the general orientation of the shaft valve size are small, all valves are generally larger with the gap, there are 0.4 ~ lmm, which produces mechanical vibration is helpful. Therefore, when a slight mechanical vibration occurs, the vibration can be weakened by increasing the guide size and reducing the mating clearance. 4) to change the throttle shape, eliminating the resonance method due to the control valve so-called vibration occurred in the high-speed flow, rapid changes in pressure orifice, changing the shape of the throttle can change the vibration source frequency, the resonance is not strong comparison Easy to solve. The specific method is to be within the scope of the opening of the valve core turning 0.5 ~ 1.0mm. For example, a self-operated pressure regulating valve is installed near the factory area of ​​a factory. The whistle of the resonance causes the worker to rest. After the 0.5mm spool surface is dropped, the resonance whistle disappears. 5) replace the throttling pieces Eliminate the resonance method with 4.5 in 4), but the replacement of throttling pieces. The methods are: ①replacement of flow characteristics, log linear, linear change logarithm; ② replace the spool form. Such as the shaft plug into a "V" shaped spool, the two-seat valve shaft type into a sleeve-type; will open the window sleeve to play a small hole sleeve. If a nitrogen fertilizer plant a DN25 two-seater valve, the valve stem and spool connections often broken, we confirmed that the resonance, the linear characteristics of the spool to the logarithmic spool, the problem is solved. Another example is an aeronautical institute laboratory with a DN200 sleeve valve, the valve plug can not be cast with a strong rotation, the opening of the sleeve to a small hole to the sleeve, the rotation disappeared immediately. 6) Change the type of control valve to eliminate resonance Resonant valves with different structures naturally have different natural frequencies. Changing the type of control valve is the most effective way to eliminate the resonance fundamentally. A valve resonates very strongly during use - strongly vibrates (can damage the valve in severe cases), rotates strongly (even the valve stem is shaken and broken) and produces strong noise (up to over 100 dB) Valve, as long as it replaced a valve with a large difference in structure, immediate effect, strong resonance miraculously disappear. Such as a vinylon plant expansion project selected a DN200 sleeve valve, the above three phenomena exist, DN300 pipe followed by the valve plug rotation, the noise 100 dB, the resonance opening 20 ~ 70%, consider the resonance open Degree, use a double seat valve, the resonance disappears, put into operation normally. 7) to reduce the cavitation vibration method due to cavitation bubble rupture and cavitation vibration, should naturally reduce cavitation on the way. ①Let the bubble burst impact energy does not act on the solid surface, especially the spool, but to liquid absorption. Sleeve valve has this feature, so you can change the spool plug sleeve type. ② to reduce the cavitation all the ways, such as increasing the throttling resistance, increasing the pressure of systolic orifice, grading or * decompression. 8) to avoid the wave wave hit the external source wave vibration caused by the valve vibration, which is obviously the normal operation of the control valve should be avoided, if such a vibration, it should take appropriate measures when the poor stability of the control valve Solution 1) to change the role of unbalanced direction method In the stability analysis, it is known that the role of unbalance force with the same direction as the valve closing, that is, when the valve closure trend, the valve stability is poor. Work on the valve in the unbalanced conditions, the choice of changing the direction of its method, the flow is usually closed to open type, generally can easily solve the problem of valve stability. 2) to avoid valve instability zone valve some of its working structure of its own restrictions on the work in certain degree of stability when the poor stability. ①double-seat valve, the opening of less than 10%, due to the ball on the open at the ball Department at the closure, bringing instability; ② unbalanced force change slope near the alternating, its stability is poor. Such as butterfly valve, alternating point at about 70 degrees; double seat valve in the 80 ~ 90% opening. In case of such valve, the inevitable stability in the work of unstable areas, to avoid the work of unstable areas. 3) replace the valve with good stability and good stability of the valve change in its unbalance small, good guidance. Ball valve commonly used, the sleeve valve has this great feature. When a single, double seat valve stability is poor, the replacement of sleeve valve stability will be improved. 4) increase the spring stiffness Act enforcement agencies to resist load changes on the impact of the ability to rely on the spring stiffness, the greater the stiffness, the smaller the impact on the trip, the better valve stability. Increase the spring stiffness is to improve the stability of the valve common simple method, such as the spring range of 20 ~ 100KPa into a 60 ~ 180KPa spring of large stiffness, this method is mainly used with a retainer valve, otherwise, the use of Valve to be additionally equipped with locator. 5) to reduce the response speed method When the system requirements regulator valve response or adjustment speed should not be too fast, the valve response and adjustment speed but fast, such as the flow needs to be fine-tuned, and the control valve flow regulation varies greatly, or The system itself is a quick response system and a regulating valve but with a positioner to speed up the valve action, which are both detrimental. This will produce overshoot, vibration and so on. In this regard, should reduce the response speed. There are ways: ①the linear characteristics of the logarithmic characteristics; ② with the locator can be changed to the converter, the relay. 6) to change the flow to solve the problem of promoting the Commissioner to eliminate Surge Law two-type valve to improve the shut-off effect, usually used as a closed flow. The liquid medium, due to the role of flow closed unbalanced force is the spool closed, there is the role of promoting the Commissioner, also known as pumping action to speed up the valve spool speed, resulting in a slight water hammer, causing the system surge. The solution to the above phenomenon is that as soon as the flow direction is changed to flow, surge can be eliminated. A similar problem that may affect the valve's inability to work properly may also be considered in this way. 7) The most typical valve to overcome the fluid destructive method is the double-seat valve, the fluid enters from the middle, the spool is perpendicular to the inlet, and the fluid is divided into upper and lower two streams to flow around the spool. The fluid impinges on the spool, causing it to lean toward the outlet side, causing friction and damaging the spool and bush guide surfaces, resulting in maladjustment. High flow rates may also cause the spool to flex, erode, or even rupture in severe cases. The solution: ①improve the hardness of the guide parts of the material; ② increase the spool up and down the middle of the ball size, so that was rough; ③ alternative use of alternative valves. As with the sleeve valve, the flow of fluid around the sleeve, the lateral thrust of the valve plug greatly reduced. 8) to overcome the fluid rotation force to make the valve core rotation method of the "V" -shaped port of the valve spool, due to the media inflow asymmetry, acting on the "V" port on the spool tangential force inconsistencies, resulting in a so that Rotating rotation force. Especially for DN ≥ 100 valve is more intense. As a result, it is possible to cause disengagement of the valve and actuator ram connection, which may cause the diaphragm to distort. The solution is: ①anti-rotation of the spool at an angle to balance the role of the tangential force on the spool; ② further lock the stem and the push rod connection, if necessary, add a piece of anti-rotation of the splint; ③ the "V" -shaped opening of the spool to replace the spool-shaped spool; ④ adopt or change to a sleeve-type structure; ⑤ If the resonance caused by rotation, the elimination of resonance can solve the problem. 9) Adjust the disc valve disc friction to overcome the open beating method using "O" ring, seal ring, liner and other soft-sealed butterfly valve, the valve is closed, due to the deformation of the soft seal, the valve plate in place and wrap valve Board, can achieve very good cut off effect. However, when the valve is to be opened, the actuator's force to open the valve plate increases. When the frictional force of the soft seal to the valve plate increases, the valve plate starts. Once activated, this friction decreases drastically. To achieve the balance of power, the valve plate open violently, this force with the corresponding opening degree of the role of the media unbalanced moment and the opening torque of the actuator balance, the valve stops at this opening. This violent and sudden take-off opening can be as high as 30 to 50%, which will have a series of problems. At the same time, due to the closure of the soft seal to produce greater changes, easy to produce permanent deformation or squeeze the valve plate damage, such as strain, affect life expectancy. The solution is to adjust the soft seal on the valve plate to start the friction, which can not only ensure the required cut off requirements, but also make the valve more normal start. The specific measures are: ①adjust the amount of interference; ② limit or adjust the actuator preload, the output force approach to reduce the valve plate to open over the open to bring the difficulties.