MICRON STRING WOUND FILTER CARTRIDGE TECHNICAL DETAILS
String wound filter cartridges utilize polypropylene inner cores as a base. This base is nominally 10" long (actual length = 9 27/32") and the final filter cartridge length fits standard 10" filter housings sold by a variety of manufacturers. MICRON also supplies 10" filter housings which utilize MICRON string wound filter cartridges.
Special FDA compliant polypropylene filter yarn (typically called string,) is carefully wound onto the core in a specific pattern and density to meet the micron particle size requirements of that particular filter cartridge. String wound filter cartridges are referred to as “depth" filters since particulate is trapped within the full volume or “depth" of the cartridge. The lower the micron rating of the filter cartridge, the smaller the contaminating particle size it will remove from the liquid being filtered. Cartridges wound to very low micron ratings such as 1 or 5 micron utilize a phenomenon called “Van Der Walls" attraction forces to capture and hold the contaminant. Micron ratings of string wound filters are nominal (see FAQ for detail).
String wound polypropylene filter cartridges, as with any filter cartridge, will create a pressure drop in a flowing liquid system. A clean filter cartridge will create a minimal pressure drop depending on the liquid flow rate. The higher the flow rate, the higher the pressure drop. As the filter becomes clogged with contaminants, the pressure drop will gradually increase and flow will, correspondingly, decrease. Typically, a maximum pressure drop of 20 PSI is allowed for string wound filter cartridges as higher pressure drops may overcome the Van Der Walls holding forces allowing contaminating particles to release again from the surface of the polypropylene filter media. Given the strength of the polypropylene core, crushing of string wound filter cartridges due to a high clog condition is almost non-existent at low operating temperatures. At higher temperatures, collapsing may occur at about a 50 to 70 PSI pressure drop.
Typical flow rates for string wound filter cartridges vary from 3 Gallons Per Minute (GPM) for cartridges rated at 1 micron to 6 GPM for cartridges rated at 50 micron. The larger the micron rating, the larger the filter pores are, which allow for higher flow rates.
Safe operating temperatures for polypropylene filter cartridges are up to 150° F. MICRON recommends operating temperatures be kept below 140°F to maintain a margin of safety.
MICRON polypropylene filter cartridges are compatible with a wide variety of liquids to be filtered, including, but not limited to:
- Acetic Acid
- Caustic Soda
- Potable Water
- Compressed Air
- Citric Acid
- Milk
- Alcohol
- Diesel Fuel
- Mineral Oil
- Cane and Beet Sugar Liquors
- Fruit Juices
- Salt Water
- Carbonated Water
- Glycerin
- Vinegar
- Bio Diesel Fuels
Contact Us for a complete chemical compatibility listing.