ITS participated in the limitation of the sound emergence of noisy industrial equipment in an energy production plant in South-East Asia, based on the use of a combustion turbine coupled to a steam turbine and a generator. This combined cycle gas plant - the largest in the country, with a power of more than 580 MW - will provide electricity to more than 680,000 inhabitants. The main sources of noise to be considered in such cases were:
- the turbine itself
- a compartment for the load
- a plenum for an air intake duct and for an exhaust duct
- a generator
- a steam turbine
The first 3 sub-assemblies listed above were entirely enclosed using ventilated soundproof buildings (each: with 4 walls and a roof), while the last 2 sub-assemblies listed above required the construction of noise-proof walls (distinguished from soundproof buildings by the absence of a roof and forced ventilation systems).
Design and construction of structures to limit the sound emergence of noisy industrial equipments
The design and the construction of structures to limit the sound emergence of noisy industrial equipment for this energy production plant were carried out in a manner analogous to many other similar projects, within the framework of comparable facilities, with notably :
- structural calculations: to guarantee the stability and durability of very large metal structures such as those to be considered, unfavorable site conditions must be taken into account (risks of bad weather potentially of high intensity, seismic risks), what is more by ensuring stability during the dismantling of some sub-assemblies (with large areas) during maintenance or repair work on enclosed equipment
- acoustic studies: to respect, near the walls of structures dedicated to soundproofing, sound levels as low as 85 dB(A) at 1 meter (which is not nothing when some noise sources have an overall weighted sound power level greater than 135 dB(A)), for what concerns:
- noise protection for personnel (e.g. dedicated to the supervision, maintenance) of the power plant; their hearing health, the limitation of the risks of accidents at work due to inaudible warning signals are conditioned by compliance with sound level limits, which, when based on the European directive 2003/10/EC can be listed in the following way:
- limit exposure values to noise for workers: 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 to noise for workers triggering 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 to noise of worker triggering action: exposure level L EX, 8h = 80 dB (A) and a peak sound pressure ppeak = 112 Pa or 135 dB(C) ref. 20 μPa
- neighborhood quietness ; when based on French regulations, 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) are treated differently. In some cases, a prefectural decree (when it is not ministerial) sets the noise levels not to be exceeded at the property line: this is particularly the case for Installations Classified for Environmental Protection (ICEP) e.g. 70 dB(A) during the day and 60 dB(A) during the night. Emergence i.e. the difference between the equivalent A-weighted continuous pressure levels of the ambient noise (plant in operation) and the residual noise (in the absence of the noise generated by the plant, but measured over the period of operation of the plant) is limited in Regulated Emergence Zones (REZ), which generally include, near the industrial establishment: homes, building zones and areas occupied by third parties e.g. Public Establishments (ERP), other industrial establishments . If the ambient noise level in the REZ (including plant 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 ZER (including plant noise) is greater than 45 dB(A) then the admissible emergence is 5 dB(A) during daytime periods and 3 dB(A) during periods nocturnal. In the case of an Installation Classified for Environmental Protection (ICEP), 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.
- noise protection for personnel (e.g. dedicated to the supervision, maintenance) of the power plant; their hearing health, the limitation of the risks of accidents at work due to inaudible warning signals are conditioned by compliance with sound level limits, which, when based on the European directive 2003/10/EC can be listed in the following way:
- aeraulic studies: to ensure the renewal of air and the evacuation of the (very significant) heat power dissipated inside soundproofed buildings
- electrical study: for components such as fans, sensors
It was therefore foreseen a metal frame (steel) and:
- for fixed or easily removable parts, by sub-assemblies: industrial soundproofing panels with an absorbing face (modular)
- for employees access: (rotating) acoustic doorsets with, for translucent parts (with glazing guaranteeing residual safety in the event of accidental breakage): acoustic window sets
In addition, the openings provided for the air inlet and outlet (the latter: with fans) of the soundproof buildings have been equipped with ventilation silencers (otherwise the overall acoustic performance would be degraded).
All the elements constituting the various ventilated acoustic enclosures and noise walls for limiting industrial noise in this energy production plant were the subject of all possible attention from the beginning (supply of raw materials and components of first class quality) to the end of the production cycle (careful welding and pre-assembly works, rigorous control and careful packaging in maritime containers, without forgetting the preparation of exhaustive and precise documentation to facilitate on-site assembly which the Customer will manage).
This limitation of sound emergence from industrial equipment was, once again, an opportunity for ITS and its commercial partners to take advantage of their long experience in carrying out such projects, particularly in the energy sector, as part of the construction of works such as those illustrated in the picture below.
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Structures for the limitation of sound emergence from noisy industrial equipment in a power plant similar to those covered by this article |
In addition to ventilated soundproof buildings and noise barrier walls, ITS markets, for the limitation of sound emergence from noisy industrial equipment in power generation plants (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 | |