Buying GuidesBy Ningchuan Engineering Team·October 30, 2026
One of the questions we hear most from buyers is: what micron rating filter bag do I need? Pick one that is too fine and it blinds fast; too coarse and your downstream equipment suffers. Here is how to get it right.
What does a micron rating mean?
A micron (micrometre) is one thousandth of a millimetre. A 100 micron bag will stop particles around that size - roughly the width of a human hair. Two kinds of rating exist:
- Nominal rating - the bag catches a large share (typically 80-90%) of particles above the stated size. Most sewn felt bags are nominal, and they hold far more dirt per bag.
- Absolute rating - guarantees a defined removal efficiency at the stated size. Choose absolute when a process specification or downstream membrane demands it.
Practical starting points by liquid
- Raw / river water - 50-100 micron for bulk solids ahead of sand or cartridge filtration.
- RO pretreatment - 5-25 micron, followed by a 1-5 micron cartridge filter as the final guard.
- Food and beverage (juice, syrup, oil) - 25-100 micron for polish; 1-10 micron for final clarity.
- Paints, inks, coatings - 10-50 micron, often nominal felt bags for high dirt holding.
- Chemical process water - 10-50 micron depending on solids load.
Three practical tips
- Go one step coarser first. If 5 micron blinds in a day, try 10 or 25 micron before the fine bag - a two-stage train costs less per cubic metre.
- Match the bag to the housing. Standard sizes 1# (7 inch x 32 inch) and 2# (7 inch x 16 inch) fit most single and multi bag housings; we make both.
- Mind the temperature and chemistry. PP felt handles up to about 90 C; PES and PTFE suit higher temperatures and aggressive chemicals.
We manufacture liquid filter bags in PP, PES and PTFE from 1 to 200 micron, plus the full range of stainless steel bag filter housings - single bag and multi bag - and a complete bag filter housing selection guide.
Tell us the liquid, solids content and the particle size you must remove, and our engineers will recommend the rating and housing combination - free of charge.
Related products: liquid filter bags 1-200 micron · single bag filter housings · multi bag filter housings · bag filter housing selection guide
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