The cause of the pneumatic valve vibration

Pneumatic valve actuator pneumatic valve type _ _ pneumatic valve vibration cause the vibration of the pneumatic valve generally divided into two states, one is the overall vibration of pneumatic valve, namely the pneumatic valve in the pipe or frequent vibration. Another is the vibration of the pneumatic valve core, the frequent movement can be seen from the stem and the following are the two vibration causes and treatment measures are as follows: 1. The pneumatic valves on the pipeline vibration causes roughly as follows: pipe or base violent vibration, easy to cause the entire pneumatic valve vibration; Also related to the frequency, that is, when the frequency of the external and the system is equal or close to the natural frequency of forced vibration energy reached maximum, produce resonance. These two factors influence each other, sometimes can make the vibration of the vibration intensity, the pipeline pumping, loose accessories or components, and the thrum of the man, serious still can cause stem fracture, seat falls off, the system will not work. Based on this kind of situation, to cause vibration of the pipeline and base for reinforcement, it also helps to eliminate the influence of external frequency. 2. Valve core vibration measured medium flow rate has increased dramatically, sometimes making pneumatic valve differential pressure before and after a sharp change, when more than valve stiffness, the stability of the valve is worse, it can also cause the entire pneumatic valves have serious oscillation. But this kind of oscillation is not necessarily a valve opening is small. This kind of vibration generally accompanied by a shrill scream. Poor stability of pneumatic valve, once has the internal or external interference of unbalanced force and stiffness than the pneumatic valve, pneumatic valve and yourself and don't have the ability to eliminate the interference, the oscillation is produced. The need to increase the stiffness of pneumatic valves, such as 20 ~ 100 kpa spring, or increase the stability of its work, there is a benefit. Pneumatic valve installation position should be far away from the vibration source, such as inevitable, preventive measures should be taken. This whole pneumatic valve vibration, in has not yet reached resonance case, pneumatic valve is basically can be adjusted according to the outside of a given signal. Because the relative displacement of a given signal to the valve core, does not change because of the pneumatic valve vibration or change is very small, the reason for this is that they are a whole. Pneumatic valves are globe valves at the ends of the hard drive or hard, can make the rapid flow of medium produces strong reflected shock wave, reflected wave impact pneumatic valve core. When the force is greater than the diaphragm downward pressure on the valve core, make up valve core, produces vibration, especially under the condition of small signal, because the pre-tightening force is small, are more likely to make the valve core produces fibrillation. Pneumatic valve opening is too small, make the pneumatic valve differential pressure is too great, before and after to make in throttling inlet velocity increase, pressure decrease rapidly. If the pressure drops to the liquid when the temperature of saturated vapor pressure, can make the liquid produce gasification, flash, generate bubble, bubble burst pressure and shock wave formation, air hammer, the pressure generally up to tens of mpa. Pneumatic hammer shock valve core, the valve core to form voids zhuang pits and make the valve core vibration. Valve core vibration reason commonly roughly as follows: the controller output signal is not stable. Rapid change of high and low, such as valve positioner sensitivity is too high, the regulator output small changes or drift, locator will converted into output signal is very large. The valve of oscillation. Pneumatic valve of the friction force is too small, such as pneumatic valve packing with too little, or gland loose, external input signal has small changes or drift, immediately passed to the valve core, the valve core vibration, noise and giggles. Instead, such as the friction pneumatic valve is too large, such as packing too much, gland and twist too tight, or gland aging, dry, in small signal when the action is, once the action is generated and produced large signal phenomenon, pneumatic valve causes sluggish oscillation, the vibration curve approximation shows square wave. Encounter this kind of situation, should reduce the damping to solve the corresponding part of the pneumatic valve, such as replacement of packing, etc. Air fluctuations make the positioner output, some rust or locator activity, is not flexible, make not corresponding to the input and output signal generated by leaps and bounds. At this time should be open air cleaning of the pressure reducing valve locator, and apply grease to the activities section, to eliminate friction. Due to the effect of unbalanced force of the pneumatic valve itself, the result of the pneumatic valve core often produce oscillation. Zero spring tension is too small, the ability to resist interference is small, the outside world signals under the condition of small, easy to make the valve core produces vibration. To sum up, according to practical experience, the author diagnosis, in general, the medium to be measured valve core of the oscillation is always greater than the influence of the pneumatic valve vibration on the impact of measured medium, and the causes and the prophylactic measures of valve core oscillation than the entire complex pneumatic valve vibration causes and preventive measures. In practice and it can be seen that both the cause of the vibration is not likely to get so clear, sometimes also is mixed intertwined.