Noise emissions of pressurized fluids involved in many industrial physico-chemical processes (e.g. air, oxygen, nitrogen, steam and other vapors of all types) must be controlled: on the one hand, to avoid exposing workers to excessive noise levels and on the other hand in a perspective of prevention of any noise pollution for the environment of a facility.

The circulation of a fluid in a network is often accompanied by the creation of aerodynamic noise i.e. caused by a flow e.g. related to the presence of a control valve, sometimes with sound power levels up to 140 or even 150 dB ref. 1pW distributed more or less uniformly from low frequencies to high frequencies (the sound production depends on the characteristics of the valve, on the thermodynamic conditions of the fluid and on its flow rate).

Sound emissions (in particular: downstream of the valve) are then linked to the circulation of the fluid, transporting the acoustic energy in a network of pipes whose walls do not always oppose enough noise transmission, given the material of which the piping is made, its thickness, its geometry and its installation conditions (the internal noise level propagated, this latter relating to the noise level at the inlet of the piping section considered and the conditions of transport of the fluid mentioned above play an important role as well).

In some cases, external insulation (sometimes: when a limitation of thermal losses is desired and then requiring the installation of a lagging) may be a way to reduce the noise transmitted through the walls (i.e. may be a device for limiting the sound emissions of pressurized fluids), but if It must be envisaged over long lengths and with singularities (e.g. elbows, junctions), or at height (thus necessitating scaffolding), its implementation can be complex and expensive (and such a device is in general counterproductive in terms of acoustic performance at the resonance frequency that its presence induces, which is not always trivial).

Perforated plates or other soundproofing devices for pressurized fluids (intended in particular to make the flow laminar and not turbulent, otherwise with the sound production then associated), placed downstream of the control valve, but located upstream of the rest of the piping system, can reduce the noise carried downstream and therefore, all things being equal, reduce the noise transmitted through the walls of the pipes.

When a venting of a pressurized fluid occurs e.g. at a decompression orifices (at the downstream end of a purge network), noise is generated, again with acoustic power very high and with a wide sound spectrum.

A silencer (other device for limiting the sound emissions of pressurized fluids) must then be considered to maintain noise emissions at acceptable levels, depending on the environment of the facility in general, and in particular on its distance from the property lines.

ITS is marketing all types of devices for limiting the sound emissions of pressurized fluids.

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Vent silencer for pressurized gas
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