Numerous considerations come into play when designing custom air filters for OEM applications. The following should be reviewed early in the planning process:
Determine the filtration performance requirements.
Match filters to air-moving (cfm) requirements.
Analyze the space available for filters.
Specify standards and specifications (NEBS, ETSI, CE, UL 60950 (formerly UL 1950), etc.)
Filter Selection Procedure
Many thermal design engineers use the following steps when designing an air filter:
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- Select air filter dimensions (length, width, thickness).
- Calculate airflow velocity in linear ft./min. using air volume rating of fan in cfm divided by surface area of air filter in sq. ft. (i.e. 200 cfm./0.50 sq. ft. = 400 fpm).
- Select disposable or reusable media.
- Use media initial resistance vs. face velocity data/curves for preferred media. Typically, initial resistance is 0.10" wg (water gauge) or less.
- Select appropriate air filter model and frame thickness to accept selected media thickness. For example: Disposable, white UFM-50 media fits in any frame thickness (0.30", 0.43" or 0.50"). The cleanable/reusable Quadrafoam in 0.25 thickness fits 0.30" and 0.43" thick frames and 0.50" thick Quadrafoam fits in 0.50" thick frame.)
- Select a media color. Quadrafoam -green, gray or black. Polyester - white
- Determine if any handles or other fixtures are necessary for installation / removal.
- Prepare air filter drawing.
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