Regulating system, the mechanical noise generated by the control valve comes mainly from the spool, the stem and some can move parts. Part vibrations can be caused either by fluid pressure fluctuations, by fluid, or by large gaps between the sleeve skirt and the valve body guide. For example, the lateral movement of the spool relative to the guide surface, the collision between the spool and the valve seat. If there is a gap between the parts, even if the force is not transmitted, the vibration can also generate friction and impact. These collisions are all rigid collisions that produce a noticeable metal and percussion sound. The noise excited by the collision is a continuous spectrum with a wide frequency range. The magnitude of the noise is determined by the energy of the collision, the mass, stiffness, and damping of the vibrating body. This vibration frequency is generally less than 1500HZ. Resonance can occur if the frequency of vibration is close to or the same as the natural frequency of the structure. Resonance not only produces a great deal of mechanical noise, the frequency is as high as 3000-7000HZ, and it will produce a great destructive stress, which will lead to the fatigue damage of vibrating parts. Valve components that vibrate easily at their natural frequencies are plunger style spools, cylindrical thin-walled window-style spools, and flexible components such as ball valve metal seal rings. In the mechanical noise, will produce a dry friction sound. When the interaction of the two surfaces (such as the valve core and valve seat) to produce relative motion, the effect of one surface on the other surface of the block, is the friction effect. Due to the intercalation of the surface asperities and the agglomeration of the molecules, the adhesion between the surfaces causes loss of energy as well as wear of the surface, resulting in part heating, plastic deformation, vibration and noise. The noise produced by dry friction to produce vibrations is high frequency noise that sounds sharp and jarring, making it uncomfortable. Dry friction can be reduced if there is good lubrication in both friction surfaces, improved surface finish and geometric accuracy. The noise caused by the mechanical part is still difficult to predict. However, once this noise has occurred, it can be measured in the field with the instrument. The main method to reduce the mechanical noise is to improve the structure of the valve itself, especially the structure of the valve core, the valve seat structure and the guide portion, so as to increase the rigidity and reduce the mass of the movable component.
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