Noise reduction of industrial compressors (in oil refineries, facilities with gas pipelines, chemical plants, natural gas processing plants, refrigeration plants but also in air separation units - ASU -) aims to limit sound impact:
- of air intake (often with the implementation of a filtration system, of variable efficiency depending on the application)
- of machinery i.e. the set of mechanical components
It is a necessity:
- for the health of workers on the industrial site (it comes to the preservation of their hearing and to the prevention of accidents which could result from the failure to perceive audible warning signals or the noise of traffic from vehicles and machinery in the case ambient sound levels that are too high); European directive 2003/10/EC sets 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 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
- for the peace of the neighborhood:
- in France, the regulations distinguish between 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 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 the day and 60 dB(A) ) during the night. Emergence i.e. the difference between the equivalent A-weighted continuous pressure levels of ambient noise (industrial site in operation) and residual noise (in the absence of noise generated by the industrial site, but measured over the period of operation of the industrial site) is limited in Regulated Emergence Zones (REZ), which generally include, nearby: homes, building zones and areas occupied by third parties e.g. Public Acces Buildings, other industrial establishments. If the ambient noise level in the REZ (including noise from the industrial site) 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 REZ (including noise from the industrial site) 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 an Installation 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
ITS participated in the noise reduction of industrial compressors of a gas separation site in Northern Europe.
With regard to a large capacity turbomachine (its power is around 1.8 MW), it was necessary to consider a very large soundproof building with a ventilation system specially designed to evacuate the significant heat power inherent in its operation.
Techniques and means for noise reduction of industrial compressors
In the context of the project that is the subject of this article (as is often the case in such cases), the techniques and means of reducing the noise of industrial compressors were as follows:
- for the envelope of the soundproofed building: a metal frame (steel) and:
- for fixed or parts easily removable, by elements: industrial soundproofing panels with an absorbing face (modular). To meet the upkeep and maintenance constraints of turbomachines, large removable elements have been provided, both for the walls and for the roof (handling being possible with a crane); were decisive for the success of such a construction:
- their careful location, for access to enclosed equipment
- their careful design and manufacturing, to allow easy and durable dismantling and reassembly while ensuring the required sealing and stability of the construction even in the absence of these elements
- for acces for employees and some hardware: (rotating) acoustic doorsets with, for translucent parts (with glazing guaranteeing residual safety in the event of accidental breakage): acoustic window sets
- for fixed or parts easily removable, by elements: industrial soundproofing panels with an absorbing face (modular). To meet the upkeep and maintenance constraints of turbomachines, large removable elements have been provided, both for the walls and for the roof (handling being possible with a crane); were decisive for the success of such a construction:
- for the air renewal and cooling system, ventilation silencers for air inlets and air outlets (equipped with fans); were decisive for the development of an efficient ventilation concept:
- the choice of locations and sizing of ventilation openings
- the selection of fans according to the admissible temperature rise, and their noise level
- the development of noise reduction devices with appropriate insertion loss, sufficiently low self-noise and compactness appropriate to the limited space available
The engineering relating to such a project was multidisciplinary, including:
- structural calculations: for very large metal constructions, exposed to bad weather (rain, snow, wind), seismic risks
- an acoustic study: for the selection of construction elements (modular soundproofing panels, door blocks, silencers) with appropriate performance and for the calculation of the sound pressure level in specified locations
- aeraulic calculations: regarding the ventilation system
- an electrical study: in relation to the installation of fans and sensors
The manufacturing had to be careful, to meet the highest level of requirements in terms of quality and durability of a construction for which the (near in time) completion date was not the least of the challenges that had to be met.
Everything has been done to implement the best possible means of noise reduction of industrial compressors, meeting a very ambitious objective of obtaining a sound pressure level as low as 67 dB(A). ref. 20 µPa at 1 meter while the sound power level of some noise sources was reaching 132 dB(A) ref. 1 pW.
This project made it possible, once again, to illustrate the mastery by ITS and its commercial partners of issues of all kinds in relation to the soundproofing of turbomachines (industrial compressors, but also combustion turbines).
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Structures for noise reduction of industrial compressors similar to those covered by this article |
In addition to soundproofed buildings for noise reduction of industrial compressors (and noise barrier-walls), ITS markets air intake systems (also: for gas turbines) as well as Vent silencers for pressurized gas | |