ITS will participate in soundproofing works for of a large-capacity compressor, of which installation is planned to supply ultra-high-purity gases: Nitrogen (N2), Oxygen (O2), Argon (Ar), Hydrogen (H2), Helium (He), and Carbon Dioxide (CO2) are required in very large quantities for the high-tech processes involved - as part of the construction of a semiconductor manufacturing plant in Western Europe -. The aim is to limit noise emissions to ensure acceptable working conditions for personnel likely to be in the vicinity (employees, external contractors) and to preserve the peace and quiet of the surrounding neighborhood:
- regarding the issue of noise in the workplace, regarding working conditions, European Directive 2003/10/EC concerning the minimum health and safety requirements regarding the exposure of workers to the risks arising from physical agents (noise) is a reference document, fixing:
- 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
- regarding the issue of noise in environment, French regulations, if applied, distinguish between the daytime period (7:00 a.m. to 10:00 p.m. except Sundays and public holidays) and the nighttime period (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 (considered industrial site in operation) and residual noise (in the absence of the considered industrial site, but measured over the period of operation of the considered industrial site) is limited in the Regulated Emergence Zones (REZ), which generally include, near the considered industrial site: 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 considered 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 considered industrial site) 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
Such objectives will necessitate the construction, only for this high-capacity compressor, of a large metal building (footprint exceeding 150 m2, height of approximately 8 m) with a steel frame and with:
- 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
To sufficiently limit the propagation of noise towards the outside of this building, the sound reduction index of the envelope components will be 44 dB for the unique index Rw (the sound insulation performance will be significantly higher for high frequencies). A sound absorption coefficient close to 100% for the soundproofing panels at high frequencies will limit the reverberation of sounds inside, which would otherwise amplify noise levels (inside, and therefore outside - all other things being equal -).
In addition, the ventilation air inlets and outlets will be equipped with ventilation silencers; the aim will be to avoid sound transmission through the openings (on the outlet side, the noise will be further increased due to the presence of the fans - with high noise emissions by nature - required to ensure sufficient air renewal for the evacuation of the very significant heat output of the large capacity compressor by compensating for the total pressure loss induced by the silencers).
The sizing of the ventilation system (including the electrical study, the scope of which will comprise the installation of instrumentation sensors) will be a significant aspect of the project. What is at stake is a low temperature rise as allowed within the building foreseen to soundproof the compressor, what will determine both the safe accessibility for personnel and the proper functioning of heat-sensitive electronic equipment on-site.
Another crucial point for its success will be the development of construction systems compatible with the requirements for dismantling all or part of the building for high-capacity compressor soundproofing for maintenance operations. The absence of dismantled surfaces - sub-assemblies of load-bearing walls and roofing - must not compromise the mechanical stability of the remaining elements, even - and especially - in case of windy conditions, even strong; structural calculations should not miss this critical issue, and the design must allow for such dissassembly/reassembly works with minimal production downtime.
As always, the constraints associated with installation in an industrial setting (e.g. regarding footprint and robustness) will be important: design and manufacturing shall meet the highest quality standards.
The expertise acquired by ITS and its business partners in engineering, construction, and project management of buildings designed for the soundproofing of large-capacity compressors, with numerous and significant challenges - not only in terms of noise reduction - led to the awarding of the contract covered by this article: it will ensure a smooth project execution and the fulfillment of all commitments made, whether regarding cost, schedule, performance, or sustainability.
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