Valve Noise Reduction Techniques and Aerodynamic Trim Design

Valve noise is a significant concern in gas and steam service. Excessive noise indicates energy loss, cavitation or flashing in liquids, or shock waves in gas flow.

Sources of Valve Noise

Noise in control valves originates from turbulent flow, cavitation, flashing, and mechanical vibration. Aerodynamic noise from gas or steam flow is most common in high differential pressure applications.

• Aerodynamic noise: Turbulence and shear layers at high velocity gas flow

• Hydrodynamic noise: Cavitation bubble collapse in liquid service

• Mechanical noise: Valve trim vibration at natural frequency

• Pipe-borne noise: Radiated from pipe walls; treated with insulation or silencers

Noise Prediction Methods

IEC 60534-8 provides standardized methods for predicting valve noise. Manufacturers use these calculations during sizing to flag applications where noise levels will exceed limits.

• IEC 60534-8-3: Aerodynamic noise for gas and steam

• IEC 60534-8-4: Hydrodynamic noise for liquid service

• Sound power level: Calculated in decibels referenced to 10-12 watts

• Pipe sound pressure level: Sound at 1 meter from pipe centerline

Low-Noise Trim Design

Multi-stage pressure reduction trim reduces velocity at each stage, limiting turbulence intensity. Tortuous path trims, cage designs with multiple ports, and diffuser plates are standard solutions.

• Multi-stage cage: Pressure drop distributed across multiple concentric cages

• Tortuous path: Flow forced through long convoluted passages

• Diffuser: Downstream expanding section reduces exit velocity

• Noise reduction up to 20 dBA: Achievable with properly selected low-noise trim

Downstream Treatment

When source treatment is insufficient, downstream silencers and pipe insulation provide additional attenuation.

• Inline silencer: Absorption type reduces broadband noise

• Acoustic insulation: Foam or mineral wool wrapping reduces radiated sound

• Pipe specification upgrade: Heavier wall pipe radiates less sound

• Location: Move valve away from occupied areas if possible