Why are control valves sometimes very noisy?
Control valves regulate flow by increasing or decreasing the fluid pressure drop across an element. These pressure drop adjustments are usually accompanied by noise generation.
The potential of vibration and noise exist whenever there is a disturbance in the flow such as a change in piping configuration causes turbulence in the system. When the flow is disturbed it generates an acoustic pressure fluctuation.
The acoustic field generated by the turbulent pipe flow persists and creates externally radiated noise. This fluctuating internal wall pressure excites the vibration in the pipe wall depending upon the pipe diameter, material, pipe wall fitness. Some noise frequency will radiate through the pipe wall and create sound waves that people can hear.
The mechanical noise produced by the control valves is the result of random pressure fluctuations within the valve body and/or the impact of fluid from the internal parts of the valve that come into mechanical contact with the fluid flow. The sound produced by this type of vibration is normally found in the frequency range of 1,500 Hz.
Noise can be generated in three basic ways: by the mechanical vibration of the valve components, by the turbulent gas flow (aerodynamic noise), or by cavitation of the liquid flow (hydrodynamic noise). For more details please go through: https://automationforum.in/t/what-are-the-different-problems-in-control-valve/2948
If the control valve noise is not addressed, it may introduce process control problems, present safety hazards to workers or require costly repairs to valves, pipes, other instruments, and surrounding equipment.
The two basic approaches to controlling the noise of the valve are the treatment of the source and the path. The source treatment avoids the excessive noise that would otherwise be generated within the control valve, while the path treatment reduces the noise after it has been generated.