The design and construction of noise reducing-structures for industry encompasses a variety of activities:
- studies and design tasks:
- in terms of acoustics, as regards noise propagation, in enclosed spaces (taking into account the reverberation phenomenon) or outdoors (the distance - and, when it is significant between a noise source and a given observation point where the sound level must be assessed: atmospheric absorption -, as well as obstacles in the path of sound waves (with their screening effect) count when it comes to predicting the impact of noisy equipment, and a fortiori of a complete installation, considering the effectiveness of different soundproofing means, more or less appropriate depending on the context (e.g. sound-absorbing linings, acoustic screens, enclosures or even soundproofed buildings, silencers of different types) and aiming at objectives linked in particular to the fight against noise at work and/or environmental protection, which are the subject of regulations:
- 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
- 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 (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
- 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:
- in terms of aeraulics, when the heat dissipated by enclosed equipment must be evacuated using a more or less sophisticated ventilation system, most often involving fans (to, depending on the context, create a negative or positive pressure in a room), noise attenuators, with or without anti-rain louvers and filters
- in terms of structures, with regard to regulations (often with specificities linked to the location) regarding consideration of climatic (e.g. rain, snow, wind) and seismic risks for the site in question
- in other related fields (depending on the context):
- ergonomics, when it comes to soundproofing workstations and habitability for personnel protection cabins (e.g. in relation to thermal and visual comfort)
- fluid mechanics, in relation to noise reduction in gas networks under pressure
- electrical (even if only with regard to mechanical ventilation systems) or even pneumatic or hydraulic for the moving parts of certain machine enclosures for which safety aspects are therefore of concern
- in terms of acoustics, as regards noise propagation, in enclosed spaces (taking into account the reverberation phenomenon) or outdoors (the distance - and, when it is significant between a noise source and a given observation point where the sound level must be assessed: atmospheric absorption -, as well as obstacles in the path of sound waves (with their screening effect) count when it comes to predicting the impact of noisy equipment, and a fortiori of a complete installation, considering the effectiveness of different soundproofing means, more or less appropriate depending on the context (e.g. sound-absorbing linings, acoustic screens, enclosures or even soundproofed buildings, silencers of different types) and aiming at objectives linked in particular to the fight against noise at work and/or environmental protection, which are the subject of regulations:
- construction:
- in the field of boilermaking, for silencers
- in the field of metalworking for other means of noise reduction
In fact, a large number of noise-reducing structures for industry can - as far as envelopes intended for sound transmission are concerned - be carried out using, in a contextualized manner, more or less standardized construction systems, obtained by more or less industrialized processes, based on the use of a metal frame (i.e. a framework) and of different elements:
- 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 are equipped with ventilation silencers (to to ensure the necessary continuity of sound insulation).
ITS participated in the design and construction of noise-reducting structures for industry, the site in question being in Central Asia.
As this is a cogeneration plant, i.e. a combined heat and power plant, with a capacity of around 250 MW based on the operation of two combustion turbines, each with a generator, it was necessary to design and construct:
- two buildings for the turbines
- two enclosures for the generators
The difference in designation between "buildings" and "enclosures" is (apart from their respective dimensions and certain details such as a caged ladder for access to the roofs of the buildings equipped with guardrails around the perimeter) somewhat artificial, since these structures:
- share their design and construction principles (as mentioned above); these are therefore metallic structures, with similar specific acoustic characteristics (on the one hand concerning the limitation of sound levels due to internal amplification, and on the other hand transmission through partitions and other elements), which are both removable and very robust to adapt to the constraints of the industrial sector
- achieve a sound pressure level of less than 85 dB(A) at 1 meter, which both addresses the problem of noise exposure for site workers and prevents noise pollution for the neighborhood, within the industrial property limits and - even more so - over longer distances
- are equipped with ventilation systems (which are also soundproofed using baffle silencers and equipped with sensors for control) to maintain an acceptable temperature for personnel and for some sensitive hardware installed inside
Of course, at the time they were studied, they benefited from the know-how of an experienced multidisciplinary engineering team that paid attention to the smallest detail. They were manufactured in a workshop using the best manufacturing and assembly techniques mastered by a highly qualified workforce, with a love of a job well done, and they were subject to rigorous quality control throughout the production cycle to meet the standards expected by Customers who entrust ITS and its business partners with the design and consytruction of noise-reducing structures for industry, from which they expect a delivery on time, a level of performance that meets their specifications, and a maximum durability (in short: everything that makes the good reputation of ITS and its business partners).
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Noise reducing structures for industry similar to those covered by this article |
In addition to soundproof buildings, sound enclosures and noise-barrier walls, ITS markets, in terms of noise-reducing structures for industry (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 | |