In many installations in the chemical industry and in some power plants, aerodynamic noise is emitted by control valves in various industrial processes.
This noise is partially transmitted through the walls of the valves and also (and mainly) propagates downstream of the valves, being then transmitted by the pipes walls of networks, of more or less complex geometry (depending on the site constraints), sometimes leading to the atmosphere, where noise is then also emitted by vents.
This noise is so powerful (overall sound power level sometimes above 150 dBA) that it is potentially causing noise pollution for personnel of the operator operating in the vicinity as for the neighborhood (including long distance), a fortiori in case of nozzles located in altitude e.g. on roofs of high buildings. It is often necessary to use in such cases a soundproofing equipment of high technology to ensure compliance of the installation of one hand with respect to the legislation on noise at work and on the other hand with respect to the regulation in terms of environmental protection.
The dimensioning of the silencers to be enviaged requires a sufficiently accurate knowledge of the sound power levels per frequency band to be considered for the sound source to be takled, which are highly dependent:
- of valves types,moreover: single-stage or not
- geometrical characteristics of the valves
- valves operating conditions i.e. nature and thermodynamic conditions of the transported fluid
Thus, the parameters able to influence the intrinsic mechanical steam power of the considered flow, the acoustic efficiency of the valve or the peak frequency noise emissions and therefore the total internal sound power level of a valve are numerous.
Thereby, it is rarely possible to get from industrial processes control valves manufacturers sound power measurements results reflecting accurately a particular situation for which a soundproofing device is considered (or even for which a simple sound impact evaluation is wished) as a part of a project, which is a serious obstacle to the analysis and design works to be conducted.
In some cases, data being fragmented and based on unspecified methodologies are made available, however being not suitable for sizing a silencer or pipe lagging or even for the performance of sound decay calculations in good conditions.
ITS has integrated the prediction of control valves aerodynamic noise to the simulation software SILDIS® (cf. acoustics simulation software).
Calculation routines have been implemented to calculate the level of total internal sound power level per frequency band (1/3 octave and 1/1 octave).
Following the operations of modification of software SILDIS®, comparison of simulation results with bibliographic data (measurement results, results of calculation by others, ...) showed good agreement for many combinations of the parameters influencing the noise emissions of industrial processes control valves.
The consequence expected from the improvements made to the software SILDIS® is the possibility of using the output data obtained on the occasion of the prediction of the aerodynamic noise of industrial process control valves as input data for other software modules in the context of protection of workers, and/or preservation of the environment (thus especially for soundproofing projects in the energy production sector):
- Module 1: prediction of acoustic and aeraulic performance of silencers
- Module 1A: prediction of acoustic and aeraulic performance of silencers with discontinued splitters
- Module 8: prediction of the sound impact of duct systems