Vibration control valve generally divided into two states, one is the control valve as a whole vibration, that is the entire control valve in the pipe or the base frequency vibration. The other is the regulating valve spool of the vibration, which from the stem can be seen moving up and down frequently, the following two kinds of vibration in this analysis of the causes and treatment measures are as follows.
Vibration of a control valve as a whole
The control valve causes vibration in the pipe is as follows: pipe or severe vibration base could easily cause a vibration of the valve; In addition, with the frequency, that is, when the external frequency and the system natural frequency equal to or close to the energy when the forced vibration reaches its maximum, resulting in resonance. These two factors may sometimes mutual influence will lead to vibration of the more intense vibration, so that pipe beating, accessories or component loosening, and issued clatter clatter of noise, will result in a serious stem fracture, seat off, causing the system not work . Based on this situation, respond to vibration caused by the pipeline and base reinforcement, which also help to eliminate outside frequency interference.
2 spool vibration
Sometimes, the flow rate of a sharp increase in measured media, so that differential pressure regulating valve before and after the drastic changes in the stiffness when over valve, the valve on the deterioration of the stability, which could cause severe oscillations throughout the regulating valve. However, this oscillation is not necessarily a small valve opening caused. This vibration usually associated with ear-piercing screams. Poor stability control valve, if there is internal or external unbalanced force and interference than the stiffness of valve and control valve themselves do not have the ability to eliminate this interference, we generated oscillation. There needs to increase the stiffness of control valve, such as the 20 ~ 100KPa the spring, or to increase the stability of its work, there is a certain advantage.
Regulating valve installation location should be away from the vibration source, such as the inevitable, should take preventive measures.
This vibration of the control valve, before we can achieve the resonance case, with the valve is basically outside the given signal can be carried out adjustments. Because of the given signal the relative displacement of the spool is not due to the vibration of the control valve to change or change little, the reason is that they are a whole.
Regulating valve at both ends of the cut-off valve to open or Meng Meng off, make a sharp movement of the wave-measuring medium produced a strong red reflection wave, reflected wave shock regulator valve core. When the diaphragm is greater than downward pressure on the spool when the spool will move up to generate vibration, especially in the small-signal conditions, due to preload a smaller, easier to spool vibration generated.
Control valve opening is too small, so that before and after the differential pressure regulating valve is too large to make the mouth at the cutting velocity increases, pressure decreases rapidly. If the pressure drops at this time to the liquid at that temperature the saturation vapor pressure, the liquid can produce gasification, the formation of flash, generate bubbles, burst bubbles formed when powerful pressure and shock waves to generate steam hammer, the pressure is generally up to tens of MPa. Pneumatic hammer shock spool to spool the formation of cell surface and to spool vibration Zhuang Ma.
The reasons for the general spool vibration is as follows: regulator output signal instability. Fluctuated rapidly changing at this time, such as valve positioner sensitivity is too high, then the regulator output of small change or drift, it will immediately convert the output signal a great location. Causing valve oscillation. The friction control valve is too small, such as the filler valve installed too little, or did not tighten the gland, external input signals are small changes or drift will be immediately passed to the spool to spool vibration, and issued giggle beep. On the contrary, such as the friction control valve too, such as the filler loading too much, then screw too tight gland or stuffing aging, dry, then the action can not be in the small signal, the signal is large one produced by the action and then generate overshoot phenomenon, would produce hysteresis control valve oscillation, vibration curve was similar to a square wave. In such cases, it should reduce the corresponding part of the damping control valve to solve, such as the replacement of packing and so on. Fluctuations in gas supply to output fluctuations in positioning, or moving parts locator rust, not flexible, so that does not correspond to the input and output signals, resulting in oscillations by leaps and bounds. You should open the gas supply valve cleaning locator to the moving parts coated with lubricating oil, in order to eliminate friction.
As the control valve itself the result of unbalanced force, so that adjustment spool regular oscillation. 12:00 spring-tight edge top is too small, the ability to resist outside interference is small, in the case of a small external signal, easy to make spool vibrate.
To sum up, according to practical experience, the author diagnosed, in general, the spool oscillation of the measured effects of media control valve is always greater than the whole the impact of vibration on the measured medium, and the spool oscillation causes and preventive measures the total oscillation than the entire control valve complex causes and preventive measures. Practice can also be seen, these two causes of vibration and can not share it clear, sometimes mixed intertwined. ball valve Trunnion Mounted Ball Valve Floating Ball Valve Top Entry Ball Valve Three way ball valve V Type Ball Valve
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