A Leader in Silencing for Industry

The major source of regulator or control valve noise is the flow turbulence created by the rapid expansion of high-pressure gas or steam. 

The level of aerodynamic noise and turbulence is primarily a function upstream and downstream pressure ratio. 

In critical flow applications both the gas mass flow and noise level increase until the critical pressure ratio is reached. 

Beyond the critical ratio there is no increase in mass flow yet the noise level will continue to increase with increasing pressure ratio (Mechanical Stream Power). 

A staged expansion ratio below the critical ratio will result in the lowest noise level. 

At critical "sonic" flows, the noise radiates from the downstream piping. 

At below critical "subsonic" flows noise is radiated from the valve/regulator body and upstream and downstream piping. 

Effective treatment of control valve/regulator noise involves both source and path noise control.

Source noise control involves the application of staged pressure expansion with the use of orifices, diffusers, or valve noise trim. Path noise control involves the application of "in-line" silencers, Heavy wall piping and / or acoustic lagging.

A pressure reduction silencer is a special absorptive/diffuser design generally fabricated as an ASME Code pressure vessel. Unsilenced noise levels can exceed 120 dBA; piping radiated noise levels can exceed 110 dBA. Approximately 20 dB noise reductions can be achieved with application of an in-line silencer. The silencer must be located as close to the valve or regulator as possible.