Intended to limit noise emissions from industrial facilities e.g. in energy sector, an exhaust vent silencer is a highly technical hardware marketed by ITS.
It must meet technical specifications of different kinds:
- in terms of acoustics, since it is a question of obtaining a sound pressure level below a certain limit, in specified locations (e.g. at a short distance to protect site employees and/or at longer distance to ensure the tranquility of the neighborhood)
- in terms of fluid mechanics, since the upstream process should not be adversely affected by an inappropriate total pressure loss
- in terms of mechanical resistance, since it is necessary that the design and construction are in line with the thermodynamic constraints of the fluid which is transported, linked to pressures being (sometimes: very) high at the inlet of the silencer (e.g. 100 bars or more), which can be accompanied (depending on the case) by very low (e.g. - 60 °C or less) or very high (e.g. + 500 °C or more) temperatures
In general, the upstream part of an exhaust vent silencer consists of perforated elements (constituting a single-stage or multi-stage diffuser), which must be carefully calculated with regard to the requirements mentioned above: relating to acoustic, fluids dynamic, resistance of materials and assemblies (often: a building code dedicated to pressure vessels is applicable).
Downstream, the fluid - at a pressure much closer to the atmosphere, but which nevertheless differs from atmospheric pressure by the pressure drop of the dissipative part of the silencer - circulates in perforated channels between walls lined with an absorbent material (and an anti-erosion cover), the geometry of which is variable as required, and also depending on the engineering and manufacturing uses, specific to each supplier, e.g. parallel tubes, concentric annular ducts, almost rectangular slots between splitters.
In all cases, on the occasion of the sizing operations of an exhaust vent silencer, the flow of depressurized gas is of course a fundamental parameter to be taken into account, influencing in particular the size of the soundproofing device (for a given mass flow rate can correspond very different volumetric flow rates depending on the temperature and pressure conditions, which influences the size of the pressure reducer and that of the dissipative stage, as well as the self-noise, linked to the flow of the fluid at more or less high speed).
Accessorization (drain for condensate evacuation, support appropriate to possible installation conditions, anti-bird mesh, rain cap) is an aspect not to be neglected in the context of an exhaust vent silencer, any imperfection in this field being likely to have unfortunate consequences on site.
ITS will participate in the implementation of an exhaust vent silencer within the confines of a petrochemical site located in the United Kingdom, in the context of an industrial soundproofing project.
It will be a question of limiting, downstream of a valve, the noise caused by the discharge to the atmosphere of nitrogen under pressure, in relation to a fluid circuit associated with the operation of a natural gas processing and refining unit producing Natural Gas Liquids (NGL).
The principles, recalled above, which should govern the right choices in terms of design and construction will, once again, be put into practice in the context of this project aimed at implementation (outdoors, therefore: subject to inclement weather and physico-chemical influences resulting from proximity to the sea) of a noise attenuator whose lifespan must not be less than 20 years, what is an ordinary specification when it comes to hardware intending to limit noise emissions in energy sector.