Reducing the noise impact of an industrial site is a major concern, both in terms of preventing nuisances that could be caused by excessive noise levels, and in terms of corrective actions, when they are required (designers, equipment suppliers and operators are interested parties in this issue).
With regard to the interior of the site, a major challenge is to protect employees and external personnel passing through (visitors, service providers) from the risks of hearing trauma that can cause deafness for people overexposed to noise. In this regard, European Directive 2003/10/EC has achieved consensus well beyond the member states, establishing:
- limit exposure values for workers to noise: exposure level L EX,8h = 87 dB (A) and peak sound pressure pcrête = 200 Pa or 140 dB (C) ref. 20 μPa
- lower exposure values for workers to noise triggering action: exposure level L EX,8h = 80 dB (A) and peak sound pressure pcrête = 112 Pa or 135 dB (C) ref. 20 μPa
- higher exposure values for workers to noise triggering action: exposure level L EX,8h = 85 dB (A) and peak sound pressure pcrête = 140 Pa or 137 dB (C) ref. 20 μPa
With regard to the outside space, it comes not to cause noise disturbance for local residents, e.g. at the property boundary or at a greater distance. French regulations, if applied, distinguish between daytime (7:00 a.m. to 10:00 p.m. except Sundays and public holidays) and nighttime (10:00 p.m. to 7:00 a.m. as well as Sundays and public holidays):
- in some cases, a prefectural decree (when it is not ministerial) sets the noise levels not to be exceeded at the property boundary: this is particularly the case for Facilities Classified for the Protection of the Environment (FCPE) e.g. 70 dB(A) during the day and 60 dB(A) at night
- emergence i.e. the difference between the equivalent continuous A-weighted pressure levels of ambient noise (industrial site in operation) and residual noise (in the absence of industrial site noise, but measured over the period of operation of the industrial site) is limited in the Regulated Emergence Zones (REZ), which generally include, near the technical facility: homes, building zones and areas occupied by third parties e.g. Public Access Buildings (PAB), other industrial establishments. If the ambient noise level in the REZ (including the industrial site noise) is between 35 dB(A) and 45 dB(A) then the admissible emergence is 6 dB(A) during the day and 4 dB(A) at night. If the ambient noise level in the REZ (including industrial site noise) is greater than 45 dB(A) then the admissible emergence is 5 dB(A) during the day and 3 dB(A) during the night.
- in the case of a Facility Classified for the Protection of the Environment (FCPE), the marked tone, the presence of which is linked to the difference between the sound pressure level in a given 1/3 octave frequency band and the adjacent frequency bands, is considered undesirable if it exceeds 10 dB in the frequency range 50 Hz-315 Hz or 5 dB in the frequency range 400 Hz-8000 Hz
ITS participated in the reduction of noise impact of an industrial site located in the Middle East.
In the power plant in question, the main sources of noise were a combustion turbine (of medium power, less than 90 MW) and a generator - very noisy, since the sound power level of the whole exceeded 140 dB(A), which is considerable.
Study and fabrication of equipment for the reduction of the noise impact of an industrial site
The study and manufacturing of hardware for the reduction of the noise impact of this industrial site involved metal constructions (similar to industrial buildings - one for the gas turbine and another for the generator - with exceptional acoustic performance) with a metal frame and:
- for fixed or easily removable parts, by elements: industrial soundproofing panels with an absorbing face (modular)
- for acces: (rotating) acoustic doorsets with, for translucent parts (with glazing guaranteeing residual safety in the event of accidental breakage): acoustic window sets
In addition, the ventilation air inlets and outlets (the latter: with fans of which noise must be also attenuated) have been equipped with ventilation silencers (without which there would be a highly undesirable weakness in limiting sound propagation)
The study of such constructions to reduce the noise impact of an industrial site involves:
- structural calculations: the stability of the buildings must be ensured regardless of site conditions (rain, snow, wind, and seismic risks may combine), allowing for the dismantling of very large wall surfaces during repair/replacement operations of enclosed equipment, which is itself large
- predictive acoustic calculations: to size the building's structural elements and quantify noise propagation at various locations of interest, such as near the walls for the protection of personnel - a sound pressure level below 80 dB(A) at 1 meter is often required - such as at the edge of industrial property or even beyond to ensure the peace and quiet of neighbors
- aeraulic (aerodynamic) calculations: to size a ventilation system required to evacuate the heat dissipated by the turbine and the generator, and to control the temperature inside the buildings
- electrical study: for the installation of fans, sensors
The factory prefabrication of all subassemblies involved the sourcing of top-quality raw materials and components, as well as careful construction and equipment integration, subject to stringent quality control and the highest standards.
In the context of such a soundproofing project, where the challenges (achieving guaranteed acoustic performance, meeting ambitious deadlines, and avoiding imperfections of any kind) are important, a wide range of skills and expertise must be combined.
This project for the reduction of the noise impact of an industrial site was an opportunity - once again - for ITS and its business partners to leverage the extensive experience acquired through similar projects to develop high-performance and robust construction systems that will provide long-term satisfaction.
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Buildings for the reduction of the noise impact of an industrial site: in a power plant similar to those covered by this article |
In addition to sound enclosures and noise-barrier walls, ITS markets, for the reduction of the noise impact of industrial sites (visible in the photo opposite but not delivered as part of the project subject of this article) soundproofed air intake systems for combustion turbines / gas turbines, exhaust silencers for combustion turbines / gas turbines, and also Vent silencers for pressurized gas | |