ITS will contribute to noise mitigation for industrial turbines, pumps, and compressors being particularly noisy pieces of equipment frequently installed to ensure fluid circulation under varying operating conditions, particularly regarding the fluid's nature, temperature, and pressure.
The limitation of noise emissions of the considered chemical site, located in Northern Europe, shall meet various requirements:
- those concerning noise emissions within the perimeter of the plant in question. 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
- those concerning noise emissions outside the perimeter of the plant in question. 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 establishment in operation) and residual noise (in the absence of the considered industrial establishment, but measured over the period of operation of the considered industrial establishment) is limited in the Regulated Emergence Zones (REZ), which generally include, near the noisy 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 establishment) 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 establishment) 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
Turbines, pumps, and compressors associated with a particularly noisy manufacturing process will be enclosed within a special metal housing featuring a framework 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
These are the two inseparable features of a high-performance sound-insulating enclosure for noise mitigation (not only for industrial turbines, pumps and compressors): such construction systems must simultaneously limit noise levels inside the created space (achievable with sound-absorbing panels offering an absorption coefficient greater than 95%) and limit sound transmission to the outside (achievable with a sound reduction index exceeding 40 dB at medium and high frequencies).
This enclosure, designed to mitigate noise by limiting its propagation, must be fitted with openings to control the temperature rise resulting from heat emission by the enclosed turbomachinery. Therefore, to ensure a sufficient level of acoustic performance for the entire structure, the air inlets and outlets will be equipped with ventilation silencers; fans will allow for the removal of dissipated thermal power (specifically, with an air exchange rate of 12 times the acoustic enclosure volume per hour) to maintain a thermal environment suitable for personnel access (for monitoring proper operation and for maintenance) and to ensure temperatures remain below the limit beyond which the functionality of certain sensitive electronic components would be severely compromised.
Furthermore, cutouts for routing the piping of the relevant fluid systems - which will be numerous and of varying sizes in this instance - must not be a weackness of the soundproofing system, due to a lack of airtightness which would inevitably lead to unwanted sound transmission. These openings require careful sealing, as do the cutouts for the structural steel elements supporting the platforms where turbines, pumps, and compressors are to be installed (at significant heights). The implications of this entanglement and the resulting interfaces must not be underestimated, lest the project fail to meet its objectives (e.g. regarding the feasibility of installing acoustic enclosure components in a harsh environment and the effectiveness of noise control for the enclosed noisy machinery and equipment).
Another major challenge for the project will be reconciling the need to attenuate noise from turbines, pumps, and compressors with an industrial environment - typical of chemical plants - characterized by limited space for the implementation of soundproofing equipment (namely the subsets - even when minimized - of the ventilation system) and the clearance required for large doors and removable assemblies - necessary for replacing bulky equipment - without encroaching on pedestrian or vehicle traffic lanes. Requirements for rapid disassembly and reassembly during production line maintenance operations will pose yet another challenge.
Unlike projects where site visits are possible to assess contextual factors (interventions at industrial sites are frequent for ITS human ressource, not only to perform souns level measurements but also to evaluate the feasibility of installing noise-mitigation hardware - and also for acceptance testing after soundproofing works -), the project to which the present post is relating will rely exclusively on a study based on drawings, as none of what could afterward be recognized as an overwhelming accumulation of obstacles of all kinds (when it comes to the installation of an acoustic enclosure) currently exist: an entire factory is to be built from scratch.
interventions at industrial sites are frequent for ITS human ressource, not only to perform sound levels measurements but also to evaluate the feasibility of installing noise-mitigation hardware |
In this instance, meticulous, multi-criteria 3D design work will be required, where every detail counts. Although the structure is modest in size (a footprint of just under thirty square meters and a height of less than 5 meters), the complexity of the project will severely test the personnel at ITS and its commercial partners. They must - within the allotted timeframe - account for all technical constraints regarding the site while designing and constructing an enclosure that provides sufficient noise attenuation (targeting a 40 dB(A) reduction) and meets all specifications. The experience gained over recent decades by the teams at ITS and its commercial partners will prove invaluable in this context. This is precisely what one of the most demanding Clients relied upon when awarding this project to secure a well-designed, robust, and high-performance noise mitigation equipment for industrial turbines, pumps, and compressors.
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