The noise reduction of electricity production equipment often concerns large capacity turbomachines (e.g. combustion and/or steam turbines coupled to generators) and related equipment (gas module, lubrication module) which have numerous common points regarding their soundproofing:
- a very high unit unilenced sound power level i.e. possibly reaching or exceeding 140 dB(A) even in the case of a medium mpower combustion turbine (e.g. 140 MW)
- a targeted sound pressure level at the end of soundproofing works being quite low, e.g. possibly being 85 dB(A) - or less - at 1 m, conditioning both:
- the protection of personnel (e.g. working on supervision, maintenance) of the site (this involves preventing them from auditory trauma with hearing loss, and preventing work accidents when warning signals are not not heard); European directive 2003/10/EC stipulates noise exposure limit values for this purpose:
- limit exposure values for workers to noise: exposure level L EX, 8h = 87 dB (A) and peak sound pressure ppeak = 200 Pa or 140 dB(C) ref. 20 μPa
- higher exposure values of workers to the noise triggering the action: exposure level L EX, 8h = 85 dB (A) and peak sound pressure ppeak = 140 Pa or 137 dB(C) ref. 20 μPa
- lower exposure values of workers to the noise triggering the action: exposure level L EX, 8h = 80 dB (A) and a peak sound pressure ppeak = 112 Pa or 135 dB(C) ref. 20 μPa
- preserving the tranquility of the neighborhood:
- French regulations distinguish 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) and, 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 Environmental Protection (FCEP) e.g. 70 dB(A) during daytime periods and 60 dB(A) during nocturnal. Emergence i.e. the difference between the equivalent A-weighted continuous pressure levels of ambient noise (electricity production facility in operation) and residual noise (in the absence of noise generated by the electricity production facility, but measured over the period of operation of the electricity production facility) is limited in Regulated Emergence Zones (REZ), which generally include, nearby: homes, building areas and areas occupied by third parties e.g. Public Acces Buildings (PAB), other industrial establishments. If the ambient noise level in the REZ (including electricity production facility 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) during the night. If the ambient noise level in the ZER (including electricity production facility 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 Environmental Protection (FCEP), 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 adjacent frequency bands, is considered undesirable if it exceeds 10 dB in the frequency interval 50 Hz-315 Hz or 5 dB in the frequency interval 400 Hz-8000 Hz.
- cooling requirements when they are installed in an enclosed space: this involves ensuring temperature control both for the personnel who have to work there and for some sensitive components
- above-average design, performance and quality requirements
ITS participated in the noise reduction of electricity production equipment in a gas power plant located in Western Europe, by marketing soundproofing hardware intended to limit the impact of gas turbine noise sources, generators and related equipment other than air intakes and exhausts (which nevertheless constitute areas of interest for ITS within the framework of other projects).
Design and construction of structures for noise reduction works for electricity production equipment
The design and construction of works for noise reduction of electricity production equipment concerned very large enclosures, similar to industrial buildings, with exceptional acoustic insulation, involving:
- structural calculations: taking into account site conditions (rain, snow, wind, seismic activity), to ensure the necessary stability, including in the event of partial dismantling during maintenance or repair work on enclosed equipment
- acoustical engineering: to determine the sound reduction index required for the partitions of the envelope (fixed, removable or with openings), the insertion loss of the silencers - taking into account the regenerated noise), targeted sound pressure level being 80 dB(A) at 1 m -
- aeraulic sizings: for a ventilation system (with filtration) suitable for the evacuation of the (very significant) heat power dissipated by enclosed equipment and machines
- electrical studies: for components such as fans, sensors
A metal frame (in steel) was therefore foreseen and:
- for fixed or easily removable parts, by elements: industrial soundproofing panels with an absorbing face (modular), without roof for the generator, delivered with a canopy (the effectiveness of which in terms of noise reduction at specified locations has been supplemented by the implementation of a noise barrier wall)
- for acces for employees: (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, except for generator - hot air being evcuated by natural convection -) have been equipped with ventilation silencers (without which too much acoustic power would be transmitted through the openings).
Such a project of noise reduction of electricity production equipment mobilized, at ITS and its commercial partners, resources of the highest level both for the design and for the manufacturing of enclosures designed to be functional and to last, while satisfying the numerous constraints (e.g. technical, normative, calendar) inherent to such constructions. It completes the already long list of references in this field.
Spread the word !
Structures for noise reduction of electricity production equipment similar to those covered by this article |
In addition to sound enclosures and noise-barrier walls, ITS markets, for noise reduction of electricity production equipment (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 | |