Mitigating Control Valve Noise

by , | Dec 5, 2022 | Valves, Actuators & Regulators | 1 comment

Manufacturing and production facilities tend to be noisy, especially where fluids flow through pipes. Control valves can be one of the sources of noise contributing to these conditions.

Chemical Engineering: Reducing the Noise from Control ValvesIn a Chemical Engineering article, Reducing the Noise from Control Valves, Emerson’s Mark Nord describes ways to reduce noise levels emitted from these control valves. He opens by describing decibels and the dBA scale in how it corrects for loudness at varying frequencies.

Sound is measured in decibels (dB), with each one-tenth of a bel, a unit of sound intensity named after telephone inventor Alexander Graham Bell. Decibels are not a linear scale, but are logarithmic, which mirrors how the human ear perceives sound.

The dBA sound intensity measurements:

…are similar to dB measurements, except the energy at the low and high frequencies is weighted less since those sounds are not heard as well by the human auditory system.

Control valves, like other process equipment such as pumps, compressors, and engines, contribute to the noise intensity. Three ways they create noise include:

…mechanical vibration of internal components, aerodynamic noise from turbulent gas flow, and hydrodynamic noise from cavitation.

Unlike point-source noises, such as from a vent, the noise from control valves radiates down the pipe and loses sound energy more slowly. Control valve damage can occur:

…in valves subjected to noise levels greater than 110-115 dBA.

Two ways to avoid damaging noise levels are:

…using either source control (reducing sound at the source) or path control (keeping sound from radiating to the environment).

Two ways to control noise at the source include pressure-drop staging and flow division.

Pressure-drop staging reduces the overall sound by dividing a single pressure drop into a number of smaller steps.

Flow division breaks up a single flow path into multiple ones, reducing flow-stream turbulence and shifting the frequency of the noise spectrum, and subsequently the sound created.

Path control:

…can be as simple as using thick-walled pipe, adding pipe insulation, or encasing the pipe with acoustic blankets or sound-absorbing materials. Alternately, specially designed silencers or modal attenuators… use resonant chambers to cancel the noise through destructive interference.

Read the article for Mark’s sequential steps to consider when addressing noisy control valves. Visit’s Fisher 6060 WhisperTube Modal Attenuator page for more on this path control technology and the Control Valve Noise Reduction section for more ways to reduce noise levels in your facility.

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The opinions expressed here are the personal opinions of the authors. Content published here is not read or approved by Emerson before it is posted and does not necessarily represent the views and opinions of Emerson.

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