KOSA Filtration · Application Engineering
How to Select Filter Cartridge Micron Rating
Micron rating sets the particle size a cartridge removes. Match it to the duty: 0.2 µm sterile vents, 0.5–5 µm final polish, 10–50 µm pre-filtration. Specify absolute vs nominal and verify against the downstream protection need.
Key Takeaways
- Micron rating is the particle size a cartridge retains — tighter = cleaner but higher pressure drop.
- Typical map: sterile vent 0.2 µm, final polish 0.5–5 µm, pre-filter 10–50 µm.
- State absolute vs nominal rating — absolute is a tested cut point, nominal is approximate.
- Stage filters: coarse pre-filter protects the finer, costlier polish element.
- Confirm the rating against the downstream equipment or product clarity you must protect.
Map application to micron rating
The right micron rating protects downstream equipment and meets product clarity without overspending pressure drop. Use the duty, not a rule of thumb, to pick the cut point.
| Application | Recommended micron range | Why |
|---|---|---|
| Sterile vent / tank breather | 0.2 µm | Hydrophobic sterile barrier against bacteria ingress |
| Final polish (filling / WFI protect) | 0.5–5 µm | Documented clarity before sensitive equipment |
| Membrane / pump protection | 1–10 µm | Removes abrasive solids before the asset |
| Beverage / solvent clarification | 5–25 µm | Clarity with acceptable flow and life |
| Pre-filter / bulk solids | 10–50 µm | Cheap coarse stage extends polish-element life |
Absolute vs nominal, and staging
An absolute rating is a tested, single-particle cut point (e.g. 99.98% at 0.2 µm); a nominal rating is an approximate average. For validated or protective duty, always write the absolute rating into the spec.
At SuZhou KoSa we size cartridge trains so a coarse 10–50 µm pre-filter carries the bulk load and a 0.5–5 µm polish element delivers the final cut — this balances element life against clarity. Going too tight too early just wastes pressure drop and shortens cartridge life; going too coarse risks fouling membranes, pumps or filling heads. Media type matters too: pleated polypropylene or glass-fibre gives far more area than a string-wound depth cartridge at the same micron, extending run time between change-outs. Confirm the rating against what you must protect, not the catalogue headline number.
Selection checklist
1. What must the filter protect or achieve?
Membrane/pump → 1–10 µm; sterile vent → 0.2 µm; product clarity → 0.5–5 µm.
2. How much solids load is upstream?
Heavy load → add a 10–50 µm pre-filter before the polish element.
3. Is the cut point validated?
Specify absolute rating and request the beta-ratio / removal-efficiency data.
Micron ranges above are typical engineering practice. Always state absolute vs nominal rating and verify against your fluid, flow and the equipment you must protect.
Need a specification for your line?
Send your fluid, flow and hygiene class — we return a documented recommendation.
Contact KOSA KosafiltrationSuZhou KoSa · +86 512 57501864 · [email protected]
Frequently asked questions
How do I choose a filter cartridge micron rating?
Match the rating to the duty: 0.2 µm for sterile vents, 0.5–5 µm for final polish before filling or sensitive equipment, and 10–50 µm for pre-filtration of bulk solids. The rating should protect the downstream asset, not follow a generic number.
What is the difference between absolute and nominal micron rating?
An absolute rating is a tested single-particle cut point (for example 99.98% removal at 0.2 µm), while a nominal rating is an approximate average. For validated or protective duty, specify the absolute rating and request the beta-ratio data.
Should I use one cartridge or stage two?
Staging is usually best: a coarse 10–50 µm pre-filter removes bulk solids and extends the life of a finer 0.5–5 µm polish element, balancing pressure drop and element cost.
What happens if I specify too tight a micron rating?
Going too tight too early raises pressure drop, shortens cartridge life and adds cost without benefit; going too coarse risks fouling membranes, pumps or filling heads. Size to the actual protection need.