Isolation Technologie Services (ITS) participated in the noise reduction of an industrial facility, in South-East Asia, with a view to bringing it into compliance :
- with regard to the prevention of risks related to noise in the workplace (i.e. to prevent an alteration in the auditory perception of personnel subjected to excessive noise levels, whether they are site employees or external maintenance technicians) [1]
- with regard to the protection of the environment (i.e. to avoid disturbing the neighborhood by excessive acoustic emissions) [2]
It was a thermal power station, using - for the production of electricity - a combination of fuel oil, liquefied natural gas and biofuels. The equipment of this industrial facility to be the subject of noise reduction were thus generators and turbines, constituting major sound sources in such a context since the sound power level of several parts of such machines exceeds 130 dB(A) ref. 1 pW.
For generators (delivered by their manufacturer with an enclosure intended to limit sound production), noise reduction was based on the implementation of noise barrier walls, while for turbines it was achieved through construction of complete soundproof buildings.
In the context of the noise reduction of this industrial facility, the contract with the end customer provided for the supply not only of sound insulation hardware, but also of additional equipment such as piping, overhead crane, and also, as regards turbines, soundproof ventilation systems (the evacuation of the heat power dissipated in an enclosed space - a fortiori when the enclosure has thermal insulation properties - required overpowered and noisy fans, whose sound emissions had to be reduced by specific devices (i.e. by silencers).
The studies having been carried out took into account the climatic conditions and the seismic risks of the site, and the realization of the means of noise reduction was based on metal constructions with:
- a metal frame, which must be self-stable even in the event of partial dismantling (for maintenance and repair operations, for equipment changes)
- sound insulation panels in (high density) rock wool surfaced by a glass cloth and protected by a perforated sheet (the exterior facing being made of steel); doors for the movement of personnel, as well as hatches and removable elements for access when replacing equipment have been provided (where required to be useful) with, as regards filling, the same constitution supplemented by peripheral gaskets guaranteeing the tightness needed for good performance in terms of soundproofing
- ventilation silencers made up of a peripheral steel casing and dissipative elements (which is what makes the silencers effective in terms of noise reduction) with a metal frame and filling in mineral fibrous absorbent material, with surfacing and perforated sheet
As part of this noise reduction project for an industrial installation, careful design and manufacture, by a (long-standing) commercial partner of ITS, made it possible to provide, on time, noise-reducing hardware giving full satisfaction in terms of quality; durability will meet expectations :
- everything has been designed and manufactured avoiding all concepts, construction stages and assemblies inducing fragility and failure risks (especially for moving parts and electrical hardware)
- the anti-corrosion treatment of structural elements, metallic acoustic insulation panels and silencers was foreseen for an extreme degree of corrosivity - C5 according to standard ISO 12944 - to take into account the combined effect of the atmosphere and of the sea water, as anticipated for a facility located near the coast
Such problems of noise reduction of industrial facilities (sometimes very different as regards the sector of activity and the machines and equipment concerned, e.g. thermal or electric motors, compressors, refrigeration and air conditioning equipment, ovens, waste suction or air filtration systems, crushers) constitute a recurring activity for ITS, whose human resources adapt their knowledge and professional methods to market adapted, efficient, sustainable and cost-effective solutions.
[1] the normative or regulatory requirements are often variable according to the country considered; according to European Directive 2003/10/ EC, for the daily noise exposure level L EX, 8h: 80 dB(A) and 85 dB(A) are the thresholds, respectively lower and upper, triggering the action; 87 dB(A) is the authorized limit value
[2] what an industrialist is bound to is depending on the location in the world; in France, a limit is set by a prefectural decree e.g. 60 dB(A) at the property line and the concept of emergence is applied. The emergence, which is the difference (using the A weighting) between the noise level of the ambient noise (installation in operation) and the residual noise level (in the absence of the noise produced by the installation), is regulatory limited - depending on the case to 5 or 6 dB(A) during the daytime and to 3 or 4 dB(A) during the night period in zones with regulated emergence (ZRE)