Fisher noise-attenuation trims for control valves help provide the necessary degree of noise reduction for your application.
Valves controlling high pressure drop liquids and gases can contribute substantially to ambient noise levels. The noise can be generated in three basic ways: by the mechanical vibration of valve components, by turbulent gas flow (aerodynamic noise), or by cavitating liquid flow (hydrodynamic noise). If control valve noise is left untreated, it can introduce process control issues, pose safety risks to workers, or require costly repairs to valves, pipes, other instrumentation, and surrounding equipment.
Fisher Whisper NXG trim for globe control valves allows you to use smaller valves where previously capacity limited without reduction in noise abatement, providing 20% more flow capacity than the market.
Fisher Vee-Ball Series control valves (V150, V200, V300) with Whisper NXV trim combine the efficiency of a rotary valve with the acoustical attenuation capability of Whisper technology to provide improved performance in applications where aerodynamic noise is a concern.
The two basic approaches for controlling valve noise are source treatment and path treatment. Source treatment prevents excessive noise that would otherwise be generated within the control valve, while path treatment reduces the noise after it has been generated.
Common source treatments include noise-attenuation control valve trims, inline diffusers, and vent diffusers that minimize turbulence. Typical path treatments include increasing the pipe thickness, adding acoustical or thermal insulation, or adding inline pipe silencers.
Hydrodynamic noise occurs in liquid flows and is predominately caused by cavitation. Cavitation consists of the formation and collapse of vapor cavities in the flowstream.
This noise occurs over a wide frequency range and is often described as sounding like gravel flowing through the pipe.
Aerodynamic noise is primarily generated by the turbulent expansion or compression of gases. It results from the shear forces created as the gas hits obstructions in the flow stream, decelerates, expands, or changes flow direction.
There are several locations where turbulence can be a problem: the throttling region, the region between the control valve trim and the body wall, and downstream of the control valve trim.
Emerson engineers analyze acoustic sources—from control valves and trim to diffusers and spargers—so you don’t have to risk worker safety, costly fines, or operating restrictions.
We utilize the International Electrotechnical Commission (IEC) 60534-8-3 standard for noise prediction and are actively involved in improving it. We leverage our flow labs and testing facilities to provide accurate noise predictions, validated through tests in compliance with the IEC standard.
Proper valve sizing is critical for controlling valve noise. An inappropriately sized valve can introduce noise issues. Emerson has standardized valve sizing techniques and selection criteria to account for factors that contribute to valve noise, so you can trust our products will work in your plant, as advertised.
Exit jet independence is crucial for avoiding jet coalescence, which will lead to additional noise. All Emerson noise technologies are designed with this critical factor as standard.
Pressure management utilizes the expanding area principle to allow for volumetric expansion of depressurizing gas and safe pressure reduction of potentially cavitation liquids.
Unique flow passage shapes reduce turbulence to minimize shock-associated noise and place turbulent shear layers away from solid boundaries to reduce noise. The multi-stage pressure reduction, utilized with sound engineering principles, controls jet size, formation, interaction, and accommodates fluid expansion.
Reduce noise with a specially designed silencer that causes acoustic wave reflection and destructive interference of noise.
The silencer design consists of various sized cavities around a perforated tube. Acoustic waves enter the cavities and interact. Wave reflections off the internal body surfaces cause a cancellation effect, called destructive interference, resulting in reduced noise propagation downstream.
