Basically, the cleanliness of a production environment is determined by three parameters: airborne particulate cleanliness class (e.g. class 3 according to ISO 14644-1), personnel hygiene, equipment. From this it follows that these parameters also have to be controlled in order to be able to create the necessary cleanliness conditions for the respective processes or products in the production environment. The achieved product quality corresponds with these parameters. According to the current state of the art, the first air quality and the personnel hygiene can be controlled and are available for all cleanliness requirements. However, as there are no measurement regulations, the contamination potentials (e.g. electrostatic charge, sedimented particles ³ 0,2 µm) emanating from equipment cannot be monitored to such a degree as to provide a scientifically proven result. If one wants to establish a production environment in which all contamination risks for the product can be controlled, one needs a sound scientific measuring procedure with the help of which one can generate reproducible results for all contamination factors emanating from the equipment. This was in fact the stipulation for the body that elaborated the VDI Guideline 2083 Sheet 8 "Cleanroom Suitability of Operating Materials."

The approach described in the Guideline is fundamentally based on the distinction between the cleanroom suitability and the cleanliness suitability of equipment. In the evaluation of the cleanroom suitability of a piece of equipment, one finds out the highest concentration of airborne particles emitted into the cleanroom environment. This is due to the fact that, independently of product-specific requirements, in almost all areas that demand manufacture under "clean" conditions, the concentration of airborne particles must not exceed certain limits. For all kinds of "clean" manufacture, the emission of airborne particles constitutes the same standard that makes it possible to compare the contamination behaviour of the most different kinds of equipment. Cleanroom suitability is one integral part of cleanliness suitability. The classification as belonging to a specific airborne particulate cleanliness class is done after a statistical analysis of the measured data. The concentration of particles of the different size classes measured in the system environment of the equipment is compared to the limits fixed in the regulation for air cleanliness in question. Depending on the limits defined in the corresponding regulation for air cleanliness, the statistical analysis is based either on the Poisson distribution or on the Student's t distribution. By the way, any regulation that contains limits for the particulate concentration in a defined air volume can serve as a basis for this comparison.

The evaluation of cleanliness suitability must take into consideration all cleanliness-relevant parameters that could influence the product quality. This includes the whole range of factors from the air flow, via particulate emission (sedimented, airborne, media-transported), vibrations, electrostatic material qualities to the evaluation of the cleanability. In essence, these product-specific measurement parameters depend on the cleanliness requirements of the product to be manufactured. A comparison of the measured values with the requirements on the product in question shows for which manufacturing processes and products the equipment can be used.

The evaluation of the cleanroom and cleanliness suitability as laid down in VDI 2083 Sheet 8 renders all hygiene-relevant qualities of equipment transparent. If you take these evaluations as a basis, you can benefit from a number of advantages for the qualification or validation of a production process. As early as in the design qualification stage, the suitable equipment can be planned for and procured - also from a hygienic point of view. Moreover, the risk of experiencing "surprises" during operational qualification is minimised significantly. This guarantees that you can keep to schedule and that you have to invest less time and money in additional analyses.

The new state of the art established by the VDI Guideline 2083 Sheet 8 helps to further reduce the risk of product contamination and to optimise the qualification processes.

Source:
Fraunhofer Institut IPA

If you would like to order the VDI Guideline 2083 Sheet 8, you can do this via the website www.beuth.de. Type "VDI 2083" into the input field and click on "Suche." You will find Sheet 8 towards the end of the result list.