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ABSTRACT
A localized air delivery system can be used as a protection against airborne pollutants when solid barriers are not practicable. Very clean air is delivered only in the close vicinity of the products to be protected. The main difficulty resides in maintaining a robust protection (i.e. ensuring that ambient air will not mix with clean air), against ordinary or exceptional disturbances, as there is no material separation between the two airs. This article first presents the physical principles used to design this method. It then illustrates the method with real industrial examples of localized air delivery systems.
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Read the articleAUTHORS
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Johan CARLIER: Irstea research engineer, PhD in mechanics from Lille University of Science and Technology - Irstea – UR OPAALE ACTA team, Rennes, France
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Lionel FIABANE: Research engineer, Irstea, Doctor of Engineering Sciences, École Polytechnique - Irstea – UR OPAALE ACTA team, Rennes, France
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Dominique HEITZ: Irstea researcher, ACTA team leader, qualified to direct research in mechanics at the University of Rennes 1, PhD in fluid mechanics from the University of Poitiers. - Irstea – UR OPAALE ACTA team, Rennes, France
INTRODUCTION
Only the localized control of clean air flows can claim to ensure high levels of air cleanliness around products sensitive to airborne contamination. It is of course possible to achieve good overall particle protection in large volumes such as production workshops, even if they are open to internal contamination (operators, machines, raw materials, etc.). But localized control, also known as "unidirectional flow" or "directed flow", makes it possible to achieve "class 5" levels of cleanliness in local operations (from the ISO 14644-1 ), or "class 100" (from the former FED-STD-209 E standard) in environments that can hardly reach cleanliness classes 100 times lower in clean rooms disturbed by activity ("class 7" from ISO 14644-1 or "class 10,000" of FED-STD-209 E).
This observation is now shared by a large number of food manufacturers, for whom the issue of cold and working conditions is added to that of ultra-cleanliness. Good localized control of clean, cold air flows enables a constantly low temperature of around 4°C to be maintained at the level of the food products being processed (worktops, packaging machines, conveyor belts, etc.), while ensuring a much higher temperature of around 15°C in contact with people located nearby.
This article will begin by defining what is meant by localized protection by clean air blowing, and then describe the physical phenomena involved in environmental separation devices. In particular, the effects of entrainment, mixing and buoyancy will be discussed, as will the dynamics of particle transport. Finally, concrete localized protection technologies will be presented and described.
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KEYWORDS
Airflows | Clean air | Particulate matters
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Localized airflow protection
Localized ambient protection by air flow
Bibliography
Events
ContaminExpo – Exhibition and conference on contamination control and cleanrooms, held every two years in Paris (odd-numbered years):
Standards and norms
ISO
- Classification de la propreté particulaire de l'air, NF EN ISO 14644-1 (février 2016). - ISO 14644-1 - 2015
- Ergonomics of thermal environments – Analytical determination and interpretation of thermal comfort by calculating PMV and PPD indices and local thermal comfort criteria. - ISO 7730 - 2005
- Filtres à air à haute...
AFNOR
Regulations
World Health Organization (WHO) – Ambient air quality and health. Fact Sheet No. 313 (2016).
http://www.who.int/mediacentre/factsheets/fs313/fr/
Directive 2008/50/EC of the European Parliament and of the Council of May 21, 2008 on ambient air quality and cleaner air for Europe.
...
Patents
Device for protecting an operating area and corresponding method (FR3008782).
Air flow diffusion system (FR2973100).
Filtered air diffuser (FR2900718).
Method and device for close protection of a work surface by means of a clean air flow (FR2750199).
Directory
Organizations – Federations – Associations (non-exhaustive list)
Anses (Agence nationale de sécurité sanitaire de l'alimentation, de l'environnement et du travail) :
ASPEC (French reference organization for all those involved in contamination control in cleanrooms and controlled-atmosphere zones):...
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