3D printing is driving innovative low noise designs.
Control valve noise is created by very high pressure drops across a valve, which generate high vapor velocities as a process fluid moves through the narrowed valve body passages.
Low noise trim designs have been used to address this issue, but these are costly and reduce flow capacity significantly. A new solution uses parts made with 3D alloy printing, as we explain in our InTech Apr 2023 article titled How Additive Manufacturing Leads to Quieter Control Valves.
The article explains how control valve noise comes from both the valve and the pipe:
Some common causes of control valves generated noise includes: mechanical vibration of internal components, aerodynamic noise from turbulent gas flow, and hydrodynamic noise from cavitation. The sound external to the pipe poses a threat to hearing at levels above 85 dBA, and levels above 110 dBA can possibility damage valve components and adjacent piping connections and should thus be avoided.
This problem can be addressed by restricting the sound path or eliminating noise at the source. Sound path solutions include thick pipes, heavy insulation, and/or acoustic blankets to block the noise.
Attacking the source
Quiet valve trims break up the flow into multiple paths, or they take smaller pressure drops across multiple stages, reducing overall flow velocity and attenuating sound. But low noise trim technology has limitations:
- Tends to restrict valve flow capacity significantly, requiring larger valve bodies to pass the same flow rate.
- Is typically much more expensive than standard valve trims since intricate machining is required to produce these designs.
- Limited applicability for rotary valves.
3D printed parts address these and other issues, while maintaining high flow capacity.
Reducing rotary valve noise
Rotary valves typically produce higher noise levels than globe valves due to their trim configuration, so they are typically not used in high pressure drop/high noise applications. However, 3D printing can now be used to produce next generation rotary trim configurations that reduce sound levels significantly, up to 18 dB. Note: subsequent to the article, testing reveals reduced sound levels up to 20dBa.
These trims reduce noise yet maintain the high flow capacities common with rotary valves, saving significantly as compared to globe valve alternatives.
Getting globe valve trim right
Obtaining high noise reduction levels in globe valves has been very expensive, and these solutions have significantly reduced flow. New 3D designs maintain flow, while reducing noise.
Numerous flow passages and more efficient pressure drop stages not only reduce noise, but also shift most of the sound to higher and less destructive frequencies.
Other 3D designs reduce noise even more, albeit with some sacrifice of flow capacity.
A different approach
Modal attenuators are passive devices that use destructive sound resonance to offset and cancel noise. This technology was discovered in the 1980s, but implementation at scale was not possible until now, with 3D printing the enabler.
We explain its operation:
The modal attenuator consists of a series of carefully engineered resonant cavities to provide sound reduction across a wide spectrum of frequencies. The full-bore design allows unrestricted flow, and internal drain channels drain off condensate which could build up in the device and reduce performance. Installed just downstream of the valve, the modal attenuator achieves an overall sound reduction up to 15 dBa, while creating no restriction in flow capacity whatsoever. The device can be used on existing valves or paired with a low noise control valve to achieve even higher levels of noise reduction. Unlike diffusers or silencers, the modal attenuator works consistently across a wide range of flow rates.
End users should evaluate options by consulting with Fisher experts, as they have knowledge of available solutions and how each should be applied.
Visit the Control Valve Noise Reduction section on Emerson.com for more on the technologies and solutions to help you cut control valve noise.
About the Authors
Grady Emswiler is a product marketing manager for Engineered Products at Emerson. She is new to the company, but she has a background in product marketing in different industries. Grady holds a Bachelor of Science degree in Marketing from Iowa State University.
Mike Hoyme is a Product Manager for Fisher Rotary Valves. He is a Certified Functional Safety Professional with 10 years of valve engineering and product management experience, and he strives to create final elements for safety instrumented systems that both improve safety and process uptime. Hoyme holds a Bachelor of Science degree in Mechanical Engineering from the South Dakota School of Mines and Technology.