What is the reason for the vibration of the control valve?

Vibration and noise of control valve can be roughly divided into mechanical vibration, cavitation vibration and hydrodynamic vibration according to their inducing factors.

2. 1 mechanical vibration

Mechanical vibration can be divided into two States according to its manifestations. One state is the whole vibration of the control valve, that is, the whole control valve vibrates frequently on the pipeline or base, which is caused by the violent vibration of the pipeline or base. In addition, it is also related to frequency, that is, when the external frequency is equal to or close to the natural frequency of the system, the energy of forced vibration reaches the maximum, resulting in * * * vibration. The other state is the vibration of the control valve disc, mainly due to the sharp increase of medium flow, which makes the pressure difference between the front and rear of the control valve change sharply, causing serious oscillation of the whole control valve.

2.2 Cavitation vibration

Cavitation vibration mostly occurs in the regulating valve of liquid medium. The fundamental cause of cavitation is the liquid vaporization caused by the acceleration of fluid contraction and the drop of static pressure in the control valve. The smaller the opening of the regulating valve, the greater the pressure difference between the front and back, the greater the possibility of fluid acceleration and cavitation, and the smaller the corresponding pressure drop of choke flow.

2.3 hydrodynamic vibration

The throttling process of medium in the valve is also a process of friction, resistance and disturbance. Turbulent fluid will form vortex when it passes through the regulating valve with poor flow around the fluid, and the vortex will fall off with the wake of the fluid continuing to flow. The formation and influencing factors of this vortex shedding frequency are very complicated and random, and it is very difficult to calculate quantitatively, but objectively there is a dominant shedding frequency. When this dominant shedding frequency (including higher harmonics) is close to or consistent with the structural frequency of the control valve and its accessories, * * vibration will occur, and the control valve will vibrate with noise. The intensity of vibration depends on the intensity of dominant shedding frequency and the consistency of higher harmonic direction.