Construction of an exhaust silencer for an industrial genset

… no worry about the delivery and the quality of construction ...
C.G. Project Coordinator (Provence Alpes Côte d'Azur region, France)

 

ITS has participated in the construction of an exhaust silencer for an industrial genset, in order to reduce noise emissions (related to the evacuation of flue gases) from a heat engine used for energy production.

The soundproofing device has been inserted into the exhaust line, making it possible to reduce the noise upstream of the chimney of the thermal power station, so as to avoid any noise nuisance for the neighborhood which, otherwise, could have been caused by a excessive sound power level at the outlet.

Such an establshment, classified for environmental the protection (ECEP), is subject to a strict regulation for the prevention of neighborhood noise, based on emergence i.e. on the difference between the A-weighted equivalent continuous pressure levels of ambient noise (establishment in operation) and residual noise (in the absence of noise generated by the establishment, but measured over the operating period of the establshment): 3 dB (A) is the permissible emergence for the period 22h - 7h, as well as Sundays and public holidays, for Zones with Regulated Emergence (ZRE) when the ambient noise level (including the noise of the establshment) is greater than 45 dB (A).

A careful dimensioning must therefore be carried out in the case of an exhaust silencer for an industrial genset, because its acoustic performance must not generate a total pressure loss that is too high, affecting the efficiency of the facilityCareful sizing must therefore be carried out in the case of an exhaust silencer for an industrial generator set, because its acoustic performance must not generate an excessively high total pressure loss, affecting the efficiency of the energy production facility. For such a noise limitation device, the following therefore requires special attention:

  • the reactive part (in general: constituting the upstream stage), based on changes in the section of tubes (perforated or not), e.g. connecting chambers - often: multiple -, which are often accompanied by a significant point pressure drop, especially at usually high gas passage speeds
  • the dissipative part, for which the effects of the friction of the transported fluid (taking into account its viscosity) on the rough surfaces of a sound-absorbing lining protected by a perforated sheet are not necessarily negligible (especially if it is not not a straight-through silencer, but a sound attenuator with a sound-absorbing central pod, or with concentric or transverse splitters) and, of course, all the more so as the considered length is important

The ITS human resource has the appropriate simulation resources, for some: developed in-house [1], for others: being commercial software, based on finite elements [2].

In addition to a good design, which is absolutely necessary, careful selection of materials and meticulous construction (the assemblies are made by welding) are also required to obtain a quality exhaust silencer: durability is a criterion of choice for an exhaust silencer for an industrial genset.

Finally, meeting deadlines (often restrictive for the supplier because the exhaust silencers for an industrial generator set are supplied just in time) is a key factor for Customer satisfaction.

[1] cf. https://www.its-acoustique.fr/en/acoustic-aeraulic-construction-cad-calculation-software.html

[2] cf. https://www.its-acoustique.fr/en/updates/acoustic-aerodynamic-finite-element-modeling-silencer.html

Construction of a large sized noise barrier wall

(height approximately 35 m, area approximately 1500 m2) around a Heat Recovery Steam Generator (HRSG) in a high capacity gas-fired power plant.

I would like to take this opportunity to thank you and your team for your active contribution in meeting this important milestone… We all can be proud of our collaboration, and the constructive spirit inspired between the teams to face all challenges during the erection.
C.B. Subcontracting Manager (Nord-Pas-de-Calais region, France)

 

The construction of a large sized noise barrier wall is required when it comes to limiting the environmental noise impact of noise sources as large as a Heat Recovery Steam Generator (HRSG) of which hundreds of m2 of walls are subjected to major vibro-acoustic sollicitations, with respect to which their capacity to limit the sound transmission is insufficient.

The implementation of an acoustic screen based on metal acoustic insulation panels with an absorbing face (noise source side) makes it possible to limit the spread of noise towards residents who could otherwise be disturbed, even at great distances a fortiori in the case of an uninterrupted installation (this is the case of a power plant), especially during the night.

The application of the regulations in force, based on the emergence criterion i.e. the difference between the A-weighted equivalent continuous pressure levels of the ambient noise (instalation in operation) and the residual noise (in the absence of the noise generated by the installation, but measured over the period of operation of the installation) imposes a specific soundproofing action.

The presence of many singularities (structural elements for support of ancillary equipment, pipes, ducts) makes it necessary a careful study allowing the prefabrication of sub-assemblies of metal construction whose installation (with specific lifting means: crane and lfting plaforms) will be facilitated neither by the height of the construction nor by the co-activities with other fitting companies, in the case of the construction of a thermal power station.

The construction of a large sized noise barrier wall is a project whose technical and organizational challenges are major and require the expertise of business partners such as those that ITS can find.

Improvement of acoustic comfort of an activity room for children

... we are really satisfied with the works done. The job was done with care and the result is fully revolutionary!
A.T. Nursery Director (Rhône-Alpes region, France)

 

Improving the acoustic comfort of an activity room for children is a recurring problem in a nursery, especially if the construction is based exclusively on sound-reflecting materials such as concrete or glass. For then ambient sound levels are usually too high, which is causing the occupants, young and older a nuisnace whose consequences are stress and excessive fatigue. As a result, children do not have favorable conditions for learning, and supervisory staff have difficulty in performing the tasks they are required to perform in their professional activities: they all suffer from an unfavorable sound environment.

ITS can help improve the acoustic comfort of a children's activity room by marketing absorbent materials that reduce the harmful effects of excessive reverberation. The selection of these absorbing materials in terms of quality (which absorption coefficient to retain at the frequencies corresponding to the envisaged sound emissions ?) and in quantity (which surfaces to cover e.g. for the ceiling and on the walls ?) is the subject of a study based on on the measurement [1] of an indicator of the acoustic quality of the considered space, in the state where it is when ITS has been requested: the reverbetaion time (duration), which can be subject to a result guarantee after works, illustrating the quality of the soundproofing performed.

In general, performance simulations (which can be carried out by ITS) of different possible solutions for improving the acoustic comfort of a nursery make it possible to review what is technically possible and to allow the best choice (taking into account the possible modalities for works, and financial considerations) of actions in terms of limitation of reverberation and noise, for what the experience of the human resource of ITS in this matter counts.

An absorbing ceiling or suspended baffles, a wall absorbing lining are (as sound absorbing screens) common components (if they have an acoustic absorption coefficient close to 100% at mid-high frequencies i.e. in the 1/1 octave frequency bands centered on 500 Hz, 1 kHz, 2 kHz) of any soundproofing system envisaged for the improvement of acoustic comfort of an activity room for children.

The major challenge, for a successful project, is a good use of these components and their optimized combination in a context always unique, even if often presenting similarities with other projects for which the feedback of experience is always a way to progress.

When the scope of work marketed by ITS includes on-site works, the careful preparation of the erection operation, the careful assembly - in safe and clean conditions without imperfection - of soundproofing equipment, by a highly qualified workforce, having a love for a job well done is a key success factor for improving the acoustic comfort of a children's activity room.

[1] involving electroacoustic hardware (noise generator with loudspeakers and sound system with microphone) that ITS owns