In France, a limitation of the noise impact is required for an industrial facility, especially if it comes to a Facility Classified for Environmental Protection (FCEP):
- to comply with Directive 2003/10/EC of the European Parliament and of the Council, of February 6, 2003, concerning the minimum safety and health requirements relating to the exposure of workers to risks due to physical agents (noise):
- for the level of daily exposure to noise L EX, 8h: 80 dB(A) and 85 dB(A) are the thresholds, respectively lower and upper, triggering action; 87 dB(A) is the authorized limit value
- for the peak sound pressure ρpeak: 112 Pa i.e. 135 dB(C) and 140 Pa i.e. 137 dB(C) are the thresholds, respectively lower and upper, triggering the action; 200 Pa i.e. 140 dB(C) is the authorized limit value
- so as not to exceed the limits of admissible noise levels at the property line - often 70 dB(A) during the day and 60 dB(A) during the night -
- to satisfy the emergence criterion i.e. the difference between the equivalent A-weighted continuous pressure levels of the ambient noise (industrial facility in operation) and the residual noise (in the absence of the noise generated by the industrial facility, but measured on the period of operation of the industrial facilty) which is limited in Zones with an Regulated Emergence (ZRE), which generally include, when located nearby: homes, building areas and areas occupied by third parties e.g. Public Acess Buildings (PAB), other industrial establishments
- if the ambient noise level in the ZRE (including industrial facilty 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 ZRE (including indyutrial facility noise) is greater than 45 dB(A) then the admissible emergence is 5 dB(A) during the day and 3 dB(A) at night
- to avoid causing unwanted 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, when it exceeds 10 dB in the frequency range 50 Hz-315 Hz or 5 dB in the frequency range 400 Hz-8000 Hz
ITS will contribute to the limitation of the noise impact of an industrial facilty classified for environmental protection (FCEP) in Nice region (French region Provence Alpes Côte d'Azur). The noise sources whose soundproofing constitutes the project which motivated this article are quite commonly widespread in the industrial sector, nevertheless distinguishing themselves in the present case by their unusual size, since they include:
- a very large capacity compressor
- a huge electric motor (its power is greater than 15 MegaWatt)
- a powerful cooling system
Techniques and means for the limitation of the noise impact of an industrial facility classified for environmental protection (FCEP)
Taking into account the objectives for limiting the noise impact of the industrial facility being concerned, which is classified for environmental protection (FCEP), as recalled above - both with regard to site personnel and with regard to the neighborhood - led to the consideration of grouping together the various noisy equipment mentioned above in a single large building (length greater than 30 m, width of around 15 m, height of around 10 m) with a ventilation system to limit an unwanted rise in temperature due to the operation of machines, when the temperature outside can supposedly reach 38°C in summer. Namely, are expected:
- that the sound pressure level does not exceed 85 dB(A) ref. 20 µPa at 1 meter from the partitions (facades and roof of the building, including for openings intended for ventilation)
- that the temperature rise is, in relation to the ambiance outside the building, limited to 2°C
As part of this project to limit the noise impact of the industrial facility being concerned, which is classified for environmental protection (FCEP), a metal frame (steel) and:
- for fixed or easily removable parts, by elements: industrial soundproofing panels with an absorbing face (modular); the constraints linked to maintenance and possible replacements of voluminous mechanical parts and harware inside building will impose the dismantling of some parts of the facades and a large proportion of the roof, by craning very large sub-assemblies equipped with lifting rings and with a special peripheral sealing system
- for acces for employees and some hardware: (rotating) acoustic doorsets with, for translucent parts (with glazing guaranteeing residual safety in the event of accidental breakage): acoustic window sets
In addition, ventilation silencers will be installed:
- for the air inlets and outlets of the building (the latter being equipped with fans whose noise must be reduced)
The technical scope to be considered for such work to limit the noise impact of the industrial facility being concerned, which is classified for environmental protection (FCEP), includes in particular:
- a fairly complex structural study since it involves very large metal constructions, which must:
- be durably watertight (to protect from rain) including for the removable elements of the roof
- remain stable, particularly during the dismantling of sub-assemblies - walls and roof - while exposed to wind and seismic risks (French legislation imposes specific designs and manufacturing, for the prevention of major accidents involving substances or dangerous preparations in the context of a project such as the one considered)
- aeraulic engineering: with regard to the evacuation of the thermal power dissipated by the equipment enclosed inside the building (including the study of the pressure loss of dissipative silencers)
- electrical study: in relation to the installation of fans and sensors for temperature control inside the building
- a careful acoustic study:
- selection of construction elements (ventilation silencers, modular soundproofing panels, acoustic door sets, etc.) with an appropriate insertion loss/sound reduction index/sound absorption coefficient in the entire frequency band of interest e.g. using, as necessary, Module 1 - prediction of the acoustic and aeraulic (aerodynamic) performance of silencers [1] - and Module 2 - prediction of the acoustic performance of plane partitions [2] - of SILDIS® software (developped and marketed by ITS)
- modeling of the overall performance of the partitions of the building e.g. using Module 10 - prediction of sound emissions from buildings and other constructions - [3] of the SILDIS® software as for the simulation of sound transmission outside of the building envisaged as part of the project described in this article, at the pre-study stage (cf. figure 1). For each of the 5000 mesh cells of the model specially created, considering the geometry and properties of the wall elements, the contribution to the sound pressure level in the middle of the length of the facade, at 1 m from the wall, at a height of 1.5 m from the ground is calculated in dB(A) ref. 20 µPa taking into account the noise of the different equipment inside the building; in the lower part of the sound map, the rectangular surfaces relate - from left to right - to a 1-leaf door, an air inlet silencer, a 2-leaf door, an air inlet silencer, illustrating an inhomogeneity of performance of the construction elements which is not detrimental to the achievement of the objective of noise limitation at all the specified locations, including at the openings intended for ventilation (equipped with silencers)
Figure 1 Simulation of sound transmission outside the building envisaged as part of the project described in this article (at the pre-study stage)
The context of the limitation of the noise impact of this industrial facility will be for ITS and its commercial partners an additional opportunity to overcome various technological and organizational challenges, in relation to a building with high acoustic performance with a silent ventilation system which must be well thought out and built - with a short production cycle - in compliance with the highest standards in terms of quality and durability.
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Structures for the limitation of the noise impact of an industrial facility similar to those covered by this article |
In addition to industrial buildings with high acoustical performance and silent ventilation system), ITS markets, for noisy industrial equipment soundproofing (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 | |
[1] Prediction of acoustic and aerodynamic performance of silencers - software SILDIS® Module 1
[2] Prediction of acoustic performance of plane partitions and walls - software SILDIS® Module 2