APPLICATION: for reducing noise from pressure reducing systems on natural gas and process plant.

Noise is generated at pressure-reducing stations by shock waves and turbulence downstream of the valve. Without a silencer, fluid-borne noise is free to travel further downstream, and may result in high noise levels radiated from pipework. In-line silencers should be installed close after the valve, in order to absorb sound energy as soon as it is created.


These silencers are designed and constructed to pressure vessel codes such as BS5500 and ASME VIII.

Carbon steel construction in used for standard duty. Construction can also be of stainless steel or other specified material. Inlet and outlet sizes are tailored to the customer's existing installation. The acoustic packing is determined by the application. The silencer shell is fully lined to minimise noise radiation.


Noise generated in the pressure let-down has high frequencies, and the silencers are of absorptive type to provide attenuation across the 500 Hz, 1 kHz, 2 kHz, 4 kHz and 8 kHz octave bands.

The principle of noise control downstream of the valve is to contain the mixing process in a much smaller space, then to provide an absorptive silencer to attenuate the resulting noise. Gas enters through an inlet diffuser which breaks a single large solid jet into a number of much smaller jets. This has two effects. The first is mixing of high and low velocity gases within a smaller space. The second effect is that reduction of jet size shifts sound energy from the low frequency region to high frequencies, where absorption is more effective. Dissipation of high-freqency energy is further improved by the multitubular constuction. Length of silencer is determined by the required attenuation.


Noise and Pulsation Control Ltd. model LVS silencers are guaranteed to meet the customer's specified performance and integrity for a period of one and a half years after initial operation, or two and a half years after shipment.

Application data

For a specific recommendation on silencer, a customer should provide the following information:

  • Gas
  • Molecular weight and ratio of specific heats
  • Inlet connection size and type
  • Outlet connection size and type
  • Flow rate
  • Operating pressure
  • Operating temperature
  • Design pressure
  • Design temperature
  • Construction code
  • Unsilenced sound pressure level at a specified distance
  • Required silenced sound pressure level at a specified distance
  • Allowable pressure drop
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