How to Choose String Wound Filter Cartridges?

Filtration Requirement	Typical Contaminant	Recommended String-Wound Configuration	Common Nominal Micron Range	Selection Considerations
Removal of visible sediment from process or utility water	Sand, rust, silt, pipe scale and other coarse particles	Polypropylene or polyester yarn wound on a rigid, compatible core	10–50 µm	Use a larger micron rating for high solids loading or as a prefilter. Confirm that the cartridge dimensions match the housing.
Fine particulate protection for downstream equipment	Fine silt, fine rust particles and suspended solids	Tightly wound polypropylene or cotton yarn with controlled winding density	1–10 µm	Finer cartridges generally create higher pressure drop and may require more frequent replacement. Check the filter’s stated rating method.
Protection of reverse-osmosis or membrane systems	Suspended solids that can foul or block membrane surfaces	Low-shedding polypropylene string-wound prefilter	1–5 µm	Select a rating appropriate to the membrane supplier’s pretreatment requirements and maintain adequate flow at the expected differential pressure.
Removal of oil-containing or hydrocarbon-bearing particles	Oil-wetted solids and particulate matter in industrial fluids	Polyester or another chemically compatible yarn; hydrophobic media may be appropriate	5–25 µm	String-wound cartridges remove particles, not dissolved oil. Verify media, core and gasket compatibility with the specific hydrocarbon.
Filtration of acidic or alkaline process liquids	Suspended process solids in fluids with non-neutral pH	Chemically resistant polypropylene or suitable synthetic yarn and core	5–50 µm	Review chemical compatibility, operating temperature and exposure time. Compatibility can vary with concentration and temperature.
Use with potable-water treatment equipment	Sediment, rust and suspended particles	Materials certified or approved for the intended potable-water application	1–20 µm	Verify applicable drinking-water contact requirements for the installation location. A sediment cartridge does not remove dissolved chemicals or microorganisms unless specifically designed and certified to do so.
High dirt-loading applications	Large quantities of suspended solids, including silt and scale	Gradient-density or progressively tighter winding pattern	5–50 µm	A larger cartridge or a staged filtration arrangement can extend service life. Ensure the housing has enough space for the selected length and diameter.
Low extractables and low fiber-shedding requirements	Particles or fibers released by unsuitable filter materials	Melt-spun or high-quality synthetic yarn with a robust core	1–25 µm	Request extractables, cleanliness and integrity information when the filtered fluid is sensitive or requires controlled contamination levels.

Parameter	Why It Matters	Practical Check
Micron rating	Indicates the approximate particle size the cartridge is intended to retain.	Determine whether the rating is nominal or absolute; these terms are not interchangeable.
Flow rate and pressure drop	Affects pump demand, process capacity and replacement timing.	Compare clean pressure-drop data at the required flow and fluid viscosity.
Cartridge dimensions	Determines whether the cartridge seals correctly inside the existing housing.	Confirm length, outside diameter, inside diameter, end configuration and gasket or O-ring type.
Media and core compatibility	Prevents swelling, degradation, shedding or structural failure.	Check fluid chemistry, concentration, temperature and exposure duration.
Operating temperature	Temperature can change material strength, chemical resistance and flow behavior.	Use the manufacturer’s maximum operating temperature for the complete cartridge assembly, not only the yarn.
Replacement endpoint	A loaded cartridge can restrict flow and increase energy consumption.	Set a differential-pressure limit based on the housing and process requirements, and replace the cartridge before bypass or damage occurs.