Displaying items by tag: filter

Between rooms of different cleanroom classes, pressure differences between 5 and 20 Pa must be ensured from cleaner room to less clean room. The minimal positive pressure of the cleanroom ensures that no air flows back into the cleaner area from the unclean area when doors are opened. The lowest contamination-level cleanroom itself is also accessed via airlocks for personnel and materials, where strong air currents stir up the particles present and extract them via filter systems. According to DIN EN ISO 14644-3, the pressure difference of a cleanroom to the personnel and material airlocks, to any cleanrooms of other purity classes as well as to the surroundings, must be tested. A test of differential pressure at the filter should also be carried out.

Contamination control depends on a reliable filter system. A malfunctioning filter can introduce contaminants into a controlled environment. Filters need to remove impurities from the process stream but avoid transferring impurities that could wind up on a device’s or product’s surface. The filters themselves must be manufactured and packaged in a controlled environment.

Repairing or replacing inadequate filters can be costly. In particular, custom filters can be expensive and may take weeks or months to be delivered, so adequate planning is a must. Following good protocols will keep filters working right and minimize premature change-outs, with the associated expenses for parts and labor as well as disruption and potential contamination.

Preventive maintenance is obviously the first step to ensure that a cleanroom’s filters function properly, and that the amount of time and money spent on them is minimal.

HEPA filters, as defined by the United States Department of Energy (DOE) standard adopted by most American industries, remove at least 99.97% of airborne particles 0.3 micrometers (µm) in diameter. The filter's minimal resistance to airflow, or pressure drop, is usually specified around 300 pascals (0.044 psi) at its nominal flow rate.

Air Flow Rates

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