BIZOMAT MAKEOS · Maintenance
Filter Beta Ratio and Capture Efficiency
What beta ratio and capture efficiency does this filter achieve, and what will pass downstream?
Filtration (beta) ratio of a filter element from upstream and downstream particle counts at a given size, the capture efficiency, and the downstream count expected from a known beta ratio and upstream contamination.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Calculation | choice | Calculate beta from counts, or the downstream count from a rated beta. |
| Upstream particles at the size | per mL | Particle count upstream of the filter at the stated size. |
| Downstream particles at the size | per mL | Particle count downstream at the same size. |
| Beta ratio (rating mode) | Rated beta ratio at the size of interest (from the filter maker’s ISO 16889 / ISO 4572 multipass test). |
What each input means
Open an input to see what it is, its units, the worked example and the common mistakes, with a small diagram.
What this means: Calculation
- What it is
- What to work out: the beta ratio from measured particle counts before and after the filter, or the count passing downstream from a filter’s rated beta ratio.
- Units and format
- Choose one of 2 options from the list: Beta from upstream and downstream counts; Downstream count from a beta ratio.
- Example
- The form opens with “Beta from upstream and downstream counts” selected as a worked example. Choose the option that matches your case.
- Get it right
- Counts mode uses the upstream and downstream counts; rating mode uses the upstream count and beta.
What this means: Upstream particles at the size
- What it is
- The number of particles of the stated size and larger per millilitre in the fluid flowing into the filter. Used in both modes.
- Units and format
- Enter a number in per mL: per mL. The form accepts 0.000001 per mL or more. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 5000 per mL as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Upstream and downstream counts must be at the same particle size and taken at the same time.
What this means: Downstream particles at the size
- What it is
- The number of particles of the stated size and larger per millilitre in the fluid leaving the filter, used in counts mode.
- Units and format
- Enter a number in per mL: per mL. The form accepts 0 per mL or more. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 25 per mL as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Halving the downstream count doubles the beta ratio.
- Get it right
- It must be above zero and not larger than the upstream count.
What this means: Beta ratio (rating mode)
- What it is
- The filter’s rated beta ratio at the particle size of interest: upstream count divided by downstream count in the maker’s multipass test. Used in rating mode.
- Units and format
- Enter a plain number with no unit. The form accepts 1 to 10000000. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 200 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- The downstream count is the upstream count divided by beta.
- Get it right
- A beta rating applies only at its stated particle size; quote it as, for example, beta at 10 µm(c).
Method and formulas
- β_x = upstream count ÷ downstream count at particle size x.
- Efficiency = (1 − 1 ÷ β) × 100%.
- Downstream count = upstream ÷ β.
- Example: 5000 upstream and 25 downstream particles per mL is β = 200 (99.5% efficient).
Limitations
- Beta ratios apply at one particle size and test condition; flow surges and cold starts reduce real efficiency.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Compare filter elements by their tested beta ratio
- Estimate downstream cleanliness from a filter rating
- Check a filter’s performance from before-and-after counts
Who it is for
- Reliability engineers
- Lubrication technicians
- Maintenance engineers
What you get
- Beta ratio
- Capture efficiency
- Particles passing
Interpreting the result
- β 200 captures 99.5%; going from β 75 to β 200 cuts particles passing by more than half.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 2441–2442. Topic reference; no source tables or recommended settings are reproduced.
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Open the Filter Beta Ratio and Capture Efficiency calculator