Methods to eliminate resonance noise of regulating valves
Only when hand-operated valves resonate, can energy accumulate to produce a strong noise of over 100 decibels. Some symptoms show strong vibration but low noise, some have weak vibration but extremely high noise, and some have both strong vibration and noise. This type of noise creates a single tone, with a frequency generally between 3,000 to 7,000 hertz. Obviously, eliminating resonance naturally eliminates noise as well.
Methods to eliminate cavitation noise of regulating valves
Cavitation is a major source of fluid dynamic noise. During cavitation, high-speed impacts occurs when bubbles burst, creating strong turbulence locally, resulting in cavitation noise. This type of noise has a wide frequency range, producing a crackling sound similar to the sound of sand and stone in fluid. Eliminating and reducing cavitation is an effective way to eliminate and reduce noise.
Methods to use thick-walled pipelines for regulating valves
Thick-walled pipelines are one of the methods of acoustic treatment. Using thin-walled pipes increases noise by 5 decibels, but using thick-walled pipelines can reduce noise by 0 to 20 decibels. The thicker the wall, the larger the diameter for the same wall thickness, the better the noise reduction effect. Of course, the thicker the wall, the higher the cost.
Methods to use sound-absorbing materials for regulating valves
This is a common and effective method of acoustic treatment for hand-operated valves. Sound-absorbing materials can be used to surround noise sources and piping behind valves. It must be pointed out that because noise can be carried long distances by fluid flow, the effectiveness of noise elimination stops where the sound-absorbing material is applied or where the thick-walled pipeline is used. This method is suitable for situations with relatively low noise and short piping, but is more expensive.
Methods to connect silencers in series with regulating valves
This method is suitable for the reduction of aerodynamic noise, effectively eliminating noise inside fluids and suppressing noise levels transmitted to the solid boundary layer. This method is most effective and economical for places with high mass flow or a high-pressure ratio on both sides of the valve. Using absorbing-type serial silencers can significantly reduce noise. However, economically speaking, it is generally limited to attenuating about 25 decibels.
Methods to use soundproof boxes for regulating valves
Using soundproof boxes, houses, and buildings to isolate the noise source inside, reduces external environmental noise to an acceptable level for human beings.
Methods to connect throttling elements in series with regulating valves
In occasions with a high pressure ratio of regulating valves, the series throttling method can be used to disperse the total pressure drop on the regulating valve and fixed throttling elements behind the valve. Using diffusers and porous limiting plates makes it the most effective way to reduce noise. In order to achieve the best diffuser efficiency, the diffuser must be designed according to the installation situation of each piece so that the sound level produced by the valve and the diffuser are the same.
Methods to choose low-noise regulating valves
Low-noise regulating valves, based on the gradual speed reduction of fluid flowing through the valve core and valve seat through curved flow paths (multi-porous or multi-slotted channels), avoid generating supersonic flow at any point within the flow path. There are various forms and structures of low-noise valves (some specially designed for specific systems) for selection. When the noise is not too significant, using low-noise sleeve valves can reduce noise by 10 to 20 decibels, which is the most economical low-noise valve.
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