A silencer for superheated steam circuit is necessary when its downstream part opens into the atmosphere, because the expansion of the pressurized fluid is then accompanied by noise emissions characterized by an acoustic power whose level currently reaches or exceeds 150 dB (A), which would be of a nature (if nothing was done) to cause severe auditory trauma to workers operating nearby and a serious disturbance to the neighborhood.
ITS will participate in the construction of a silencer for a superheated steam circuit for an industrial site in the area of Marseille (France, Provence Alpes Côte d'Azur region).
It will be a question of replacing a noise reduction device because of its state of deterioration due to the time (after about thirty years of service), in the context of a project of renovation of the installations of a petrochemical process.
This silencer for superheated steam circuit will be (in a cylindrical envelope slightly more than 5 m long and nearly 2 m in diameter) made up of:
- upstream: a multi-stage expander (diffuseur), made with concentric perforated ferrules where the Mach number associated with the state of the flow can reach the value of 1 (corresponding to the speed of sound under the local thermodynamics conditions of the fluid); a first acoustic attenuation will be associated with the presence of this component
- downstream: a sound-absorbing filling (porous medium covered by a perforated protection), on the one hand peripheral and on the other hand in the form of a central splitter of circular front section, between which the fluid will flow, the noise decreasing progressively when the sound propagates in such a channel, this mechanism thus causing a second acoustic attenuation
- the sound pressure level values at distances corresponding to those of the possible presence of operators (in particular: supervision and maintenance technicians) will be limited to below the regulatory limits
- the emergence i.e. the difference between the level of the ambient noise (installation in operation) and the level of the residual noise (in the absence of the noise generated by the installation, but measured over the period of operation of the installation) will be as respecting the tranquility of the local residents.
In connection with its pressurized parts, this silencer for a superheated steam circuit will be subject to specific design, construction and testing steps (in addition to those related to the acoustic and aerodynamic performance of this unit); special care will be taken (by the choice of building materials for certain subassemblies and by the selection of a corrosion protection system of the highest level for other subassemblies) for its longevity (taking into account the fact that the fluid-related humidity, imposed by the service conditions, will be added to the saline atmosphere resulting from the very close proximity to the sea).
This silencer for a superheated steam circuit can then effectively fulfill its function of protecting the sound environment for several decades.