Reasons for oscillation in control valves
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We have a control valve that keeps oscillating; the oscillation is severe when the valve is adjusted, and the nuts on the pressure adjustment cap often become loose as a result, leading to leakage from the valve. Is there any good solution?
The control valve was selected to be too large; additionally, the diaphragm may be leaking.
1. Improper setting of control parameters, such as excessive differentiation. 2. As mentioned on the 2nd floor, it is a problem with the control valve itself.
The oscillation of control valves is generally caused by two reasons: 1) Issues with the control valve itself – the selection problem mentioned earlier can be addressed by checking the inlet valve and increasing its opening degree to see if oscillation occurs at that setting; it’s also important to check whether the flow direction of the control valve is reversed, as well as whether there are any leaks in the gas circuit and its actuator. 2) Problems with the positioner. Sometimes, improper adjustment of the positioner can also lead to such issues. For smart positioners, consult the corresponding manual, clean them first, then perform a self-check; if oscillation persists after this, adjust the tuning knob on the electrical conversion unit until an appropriate setting is reached. Another possible cause is a problem with the circuit board, in which case it’s necessary to replace it and try again.
1. First, it is necessary to check whether there are any issues with the control valve itself and take appropriate action. 2. Adjust the system parameters. 3. Is the pressure difference too high? Consider using a double-seat valve. 4. If the flow capacity chosen is too high, then consider reducing the opening range of the control valve, as well as adjusting the shut-off valves before and after it
1. The control valve vibrates when it is near the fully closed position; the valve size chosen is too large, and it is used at low opening degrees. 2. The flow direction of the medium is the same as the direction in which the valve is closed, causing vibration at any opening degree of the valve; 1) the support is unstable; 2) there is a source of vibration in the vicinity; 3) wear on the valve core and sleeve
What was said on the sixth floor refers to problems with the valve itself; basically, a preliminary assessment should be made from these two aspects. Additionally, the selection parameters should also be checked to see if there are any issues with the selection calculations, such as the shutdown pressure difference. Debugging can also cause such problems; for example, the issues related to the positioners mentioned on the fourth floor, or failures of the positioners can lead to similar phenomena.