A filter bag micron rating chart helps compare particle sizes, but a micron number alone is not a complete performance specification. One micrometre, written µm, is one thousandth of a millimetre. The purchasing question is how effectively the assembled bag retains the relevant particles under stated test conditions.
Filter bag micron rating chart
The chart below converts the ratings in the keyword database into millimetres. It is a unit-conversion reference, not a statement that every grade is available in every material, or that a bag removes every particle at its labelled size.
| Rating (µm) | Equivalent size (mm) |
|---|---|
| 0.5 | 0.0005 |
| 1 | 0.001 |
| 2 | 0.002 |
| 3 | 0.003 |
| 5 | 0.005 |
| 10 | 0.01 |
| 15 | 0.015 |
| 20 | 0.02 |
| 25 | 0.025 |
| 30 | 0.03 |
| 40 | 0.04 |
| 50 | 0.05 |
| 75 | 0.075 |
| 100 | 0.1 |
| 150 | 0.15 |
| 200 | 0.2 |
| 250 | 0.25 |
Nominal, absolute and mesh opening are different claims
A nominal rating needs the supplier’s definition and supporting efficiency data. Do not assume all nominal bags share one removal percentage. An absolute-rated claim also needs a stated efficiency, test method and test conditions; the word alone is insufficient for comparing products.
A mesh opening describes a geometric feature of the media. Shape, flexibility and operating conditions can affect how actual contaminants behave. Verify performance at the application level when the quality requirement is critical.
What a beta ratio tells you
For particle-count testing, a beta ratio compares upstream and downstream particle counts at a specified size. Capture efficiency is calculated as (1 − 1/β) × 100%. Thus a hypothetical beta ratio of 200 corresponds to 99.5% efficiency at the stated size under that test. Parker’s filtration handbook explains this relationship in its hydraulic filtration context. Read the beta-ratio explanation.
That calculation is not evidence that a particular liquid filter bag achieved the result. Request the bag manufacturer’s own data and check whether the reported test represents the application. Do not transfer a hydraulic element’s qualification to an unrelated bag.
How to choose a trial grade
- Define the outlet-quality problem and the particle sizes responsible.
- Request the candidate bag’s efficiency data and clarify rating terminology.
- Check material compatibility, flow and clean pressure drop.
- Trial the bag and compare inlet and outlet samples using the agreed method.
- Record throughput and change-out frequency before choosing the production grade.
As a purchasing example, if two proposed 10 µm bags use different rating definitions, do not approve a substitution based only on the shared number. Ask both suppliers to answer the same retention requirement. If one cannot provide comparable evidence, record that limitation in the trial decision.
Avoid unnecessary restriction
Choosing a finer grade can change the pressure-drop and loading behaviour of the assembly. Measure the effect rather than assuming that the finest option provides the best operating outcome. A staged arrangement may be worth evaluating, but its benefit must be established from the actual contamination profile.
For the full process checklist, use how to select a liquid filter bag. Review confirmed grades within liquid filter bag options rather than assuming the entire chart is a supply catalogue.
Use the chart as a starting point
A filter bag micron rating chart converts and organizes size designations. It does not replace the supplier’s retention definition or tell a buyer which finished construction is suitable for the liquid.
Frequently asked questions
Is 1 µm finer than 5 µm?
Yes as a size designation, but compare the rating definitions and efficiencies before claiming one finished bag will meet a specific quality target.
Does a micron rating prove bacterial removal?
No. Microbial removal requires relevant validation; an ordinary particle-rating label is not a sterilizing claim.
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