Choosing the ideal cleanroom floor
When choosing a suitable cleanroom floor, it is necessary to take the process-specific demands into consideration and ensure that the material meets the required cleanliness standards.
When choosing a suitable cleanroom floor, it is necessary to take the process-specific demands into consideration and ensure that the material meets the required cleanliness standards. Here, the planning focus needs to be aimed at the production process.1
Author: Kathrin Kutter, Market Segment Manager Industry, Nora Systems GmbH, Weinheim
The first indicators for choosing suitable materials for cleanrooms are to be found in the internationally acknowledged ISO 14644 rule codes and the GMP guidelines. ISO 14644-4 stipulates that surfaces such as floor coverings must have a low particle emission behaviour and a non-porous surface. They have to be slip-resistant and impervious to static and dynamic loads as well as the utilised process media, cleaning agents and disinfectants. In addition, they should have the appropriate electrostatic properties.2 The GMP guidelines supplement the requirements profile by stipulating a smooth surface with no cracks or open joints, and that the surfaces must be both easy to clean and disinfected as required.3 However, this characteristics profile can only serve as an orientation aid. The distinction between the cleanroom and cleanliness suitability of materials as laid down in VDI 2083 Sheet 17 takes other relevant criteria into account.
Cleanroom and cleanliness suitability of materials
The cleanroom suitability solely takes the particulate contamination of materials and products into account. However, this does not suffice for cleanrooms in the life science industry. Other criteria such as cleanliness suitability have to be heeded here. These criteria also include molecular contamination, cleanability, chemical resistance and the metabolic potential of cleanroom-compatible materials.
The relevant criteria are defined individually taking into consideration the specific manufacturing process and product in question. The drafted catalogue of requirements is to be taken into account right from the planning stage of the cleanroom. Different priorities with regard to critical forms of contamination are set depending on the industry concerned.
Choosing the ideal floor
In the life science industry, the wall perimeter trim of the floor has to be designed so that proper cleaning can be guaranteed, for example with a coved skirting. Similarly, open joints are to be avoided as they represent a hygiene risk.
A key selection criterion for the floor is also the nature of the surface. Additional surface coatings, sealants or finishes are generally to be critically regarded because they represent a weak spot. Under the influence of tribological stress (e.g. rolling transport containers, heavy employee traffic), these usually become detached from the substrate and cause airborne particulate contamination.
In the case of partially detached or damaged coatings, there is also a risk of pockets of germs developing in poorly accessible places that cannot be adequately cleaned and disinfected. Rubber floor coverings from nora do not require a coating. The production process endows them with an extremely dense surface that is extremely abrasion-proof and offers a permanently high standard of hygiene. They can be thoroughly disinfected and be cleaned without leaving any residues.
ESD protection for ultra-sensitive products
In the semiconductor industry and microsystems technology sector, ESD protection is a critical factor. In the case of floor coatings that are prepared on site, the conductive additives are mixed in during the processing of the compound. A sustained reliably functioning floor system also depends to a great extent on the technical skills of the flooring installer. With other floor systems, conductive additives are physically or chemically embedded into the material during the production process. They are evenly distributed in the floor and remain sustainably effective. Concludingly applied surface sealers or finishings of any kind are to be avoided because they have a decisive influence on the functionality of the system. Extended warranties on the electrostatic properties, such as those provided for non-coated rubber floor coverings from nora systems GmbH, offer decision-makers sustained functional reliability.
1. Dr. Ing Dipl-Phys. Udo Gommel, Dipl.-Ing. (FH) Frank Bürger: VDI-Gesellschaft Bauen und Gebäudetechnik: Reinraumtechnik: 14th VDI Congress, Nürtingen, 26th and 27th November 2011, Düsseldorf: VDI-Verlag, 2011 (VDI Reports 2125)
2. DIN EN ISO 14644-4:2003-06
3. EU GMP Guidelines (Guidelines on Good Manufacturing Practice) Part 1: 2006
Comparability of floor coverings
To facilitate a reliable comparison of materials, the Fraunhofer Institute for Manufacturing Engineering and Automation, together with industry representatives, has developed test methods and rating schemes within the framework of the CSM industry association. Materials are tested for their cleanroom and cleanability suitability under uniform conditions. Identical test conditions and standardised documentation make it easier for decision-makers to compare the offered systems and, together with the catalogue of requirements defined at the planning stage, also offer functional reliability at the installation site.