1) Elimination of resonance noise method
Only when the regulating valve resonates, there is energy superposition and a strong noise of more than 100 decibels. Some of them show strong vibration, low noise, some vibrations are weak, and the noise is very large; some vibrations and noise are large. This noise produces a single-tone sound with a frequency of typically 3000 to 7000 Hz. Obviously, the resonance is eliminated and the noise naturally disappears. For methods and examples, see 4), 5), and 6) in 4.5 above.
2) Elimination of cavitation noise method
Cavitation is the main source of hydrodynamic noise. When cavitation, the bubble burst produces high-speed impact, causing strong turbulence in the local area, resulting in cavitation noise. This noise has a wide frequency range that produces a gig sound similar to that of a fluid containing sand. Eliminating and reducing cavitation is an effective way to eliminate and reduce noise.
3) Use thick wall pipeline method
The use of thick-walled tubes is one of the sound path treatment methods. The use of thin walls increases noise by 5 decibels, and the use of thick-walled tubes reduces noise by 0 to 20 decibels. The thicker the same pipe diameter wall, the larger the pipe diameter of the same wall thickness, the better the noise reduction effect. For example, when the wall thickness of the DN200 pipeline is 6.25, 6.75, 8, 10, 12.5, 15, 18, 20, 21.5mm, the noise can be reduced to -3.5, -2 (ie increase), 0, 3, 6, respectively. 8, 11, 13, 14.5 decibels. Of course, the thicker the wall, the higher the cost of the rotor pump Castel red wine.
4) Using sound absorbing materials
This is also a more Common and effective way to handle sound paths. The noise source and the post-valve line can be wrapped with sound absorbing materials. It must be pointed out that since the noise will travel long distances through the fluid flow, where the sound absorbing material is wrapped, where the thick wall pipe is used, the effectiveness of eliminating the noise is terminated. This method is suitable for situations where the noise is not very high and the pipeline is not very long, because it is a more expensive method.
5) Series silencer method
This method is applicable to the muffling as aerodynamic noise, which can effectively eliminate the noise inside the fluid and suppress the noise level transmitted to the solid boundary layer. This method is most effective and economical in places where the mass flow rate is high or the pressure drop ratio before and after the valve is high. Noise can be drastically reduced with an absorbing series silencer. However, from an economic point of view, it is generally limited to attenuation to about 25 decibels.
6) Sound insulation box method
Use soundproof boxes, houses and buildings to isolate the noise source inside, so that the noise of the external environment is reduced to an acceptable level.
7) Series throttling method
In the case where the pressure ratio of the regulating valve is high (Î”P/P1 â‰¥ 0.8), the series throttling method is adopted, that is, the total pressure drop is dispersed on the fixed throttle element behind the regulating valve and the valve. If a diffuser or a porous restrictor is used, this is the most effective way to reduce noise. In order to get the best diffuser efficiency, the diffuser (solid shape, size) must be designed according to the installation of each piece, so that the noise level generated by the valve is the same as the noise level generated by the diffuser.
8) Select low noise valve
The low-noise valve is gradually decelerated according to the flow of the fluid through the regulating valve spool and the tortuous flow path (porous channel, multi-channel) of the regulating valve seat to avoid supersonic speed at any point in the flow path. A variety of low-noise valves of various configurations (designed for specialized systems) are available for use. When the noise is not very large, use a low-noise sleeve valve to reduce noise by 10 to 20 decibels, which is the most economical low-noise valve.
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