Valve Trim Selection for Noise Reduction

Sources of Valve Noise

Control valves generate noise through aerodynamic turbulence, cavitation, and flashing. In gas and steam service, high-velocity jets create acoustic noise that can exceed 85 dB(A) at the pipe wall—damaging to personnel and equipment.

Noise Reduction Trim Technologies

• Multi-stage pressure reduction: cascaded orifice plates drop pressure gradually

• Tortuous path cage trims: fluid follows multiple 90-degree turns, dissipating energy

• Drilled hole cages: multiple small holes distribute flow and reduce jet velocity

• Low-noise characterized plugs: shaped to minimize turbulent jet formation

IEC 60534-8 Noise Prediction

IEC 60534-8-3 (aerodynamic noise) and IEC 60534-8-4 (hydrodynamic noise) provide prediction methods for control valve noise. Engineers calculate predicted noise levels at 1 meter from the pipe and apply trim modifications to achieve targets below 85 dB(A).

Downstream Attenuation Methods

• Pipe silencers or inline diffusers after the valve

• Heavy-wall pipe schedules (Sch 80 or Sch 160) near the valve

• Acoustic insulation lagging on downstream piping

• Expansion into larger-bore pipe immediately downstream

Selection Guidance

Specify noise-attenuating trim when predicted levels exceed 85 dB(A). For very high pressure drops in gas service, multi-stage trim is the most effective solution. For liquid cavitation noise, anti-cavitation trim addressing the root cause is preferred over downstream attenuation alone.