“Is a 10-micron filter better than a 12-micron filter?” As printed on most boxes, that question has no answer. Filtration ratings only mean something when you also know the capture efficiency — the Beta ratio — and the test standard behind it. This guide explains the ISO 16889 system and shows how two big manufacturers print different numbers on physically identical grades.
The micron number is a particle size; Beta is the capture odds at that size
In the ISO 16889 multipass test, contaminated oil is circulated through the element while an online particle counter measures contamination upstream and downstream. At each particle size the counts produce the filtration ratio:
βx = (particles larger than x µm upstream) ÷ (particles larger than x µm downstream)
Translated into capture efficiency:
| Beta | Efficiency | Plain meaning |
|---|---|---|
| βx = 2 | 50% | coin-flip capture |
| βx = 20 | 95% | nominal-class territory |
| βx = 200 | 99.5% | commonly quoted as the “nominal rating” point |
| βx = 1000 | 99.9% | the modern hydraulic default |
| βx = 2000 | 99.95% | high-performance media (e.g. Pall Supralon) |
So a filter’s real performance is always a pair: a micron size and a Beta at that size. “10 µm” alone might mean β10=2 or β10(c)=1000 — different elements, different worlds.
Why the same cartridge gets printed “10 µm” and “12 µm”
No grade has a single sharp cut-off. Glassfiber media capture particles across a range of sizes; efficiency rises smoothly as particles get larger. A single element therefore passes several meaningful points:
- at 10 µm, it might capture 99% (β10 ≈ 200)
- at 12 µm, it captures 99.9% (β12(c) ≥ 1000)
Both statements are true for the same cartridge. Manufacturers choose which point to print, and they do not choose the same one.
The documented HYDAC ↔ Pall example
Pall publishes an official interchange list mapping Red1000 elements into HYDAC Betamicron housings. For every element size it prints these paired ratings:
| HYDAC grade code | HYDAC-printed class | Pall Red1000 grade | Pall prints (βx(c) > 1000) |
|---|---|---|---|
| 003 | 3 µm | P | 5 µm |
| 005 | 5 µm | N | 7 µm |
| 010 | 10 µm | S | 12 µm |
| 020 | 20 µm | T | 22 µm |
Aftermarket data sheets for the same 0240 R 010 BN4HC element spell it out directly: 10 µm @ β≥200 and 12 µm(c) @ β≥1000. Same pleated media, two reporting conventions. Pall states the elements fit directly into the HYDAC housings without adaptors — see the HC2218FCS6H page for the full mapping and sources.
This is why the cross-reference tables on this site grade these pairs full on fit and grade, while quoting both micron conventions in the note. A naive comparison (“10 beats 12”) would reject the manufacturer’s own declared equivalent.
How to compare ratings correctly
- Find the Beta statement on both data sheets. Look for the format βx(c) ≥ N per ISO 16889.
- Compare at the same efficiency point. β1000 against β1000, not nominal against absolute.
- Watch the “(c)” marker. Ratings marked βx(c) come from the continuous injection method; older prints without it use the earlier test method and are not exactly interchangeable.
- Treat dirt-holding capacity and Δp separately. Two β1000 grades can differ substantially in service life and clean pressure drop — the multipass test measures those too.
- Ignore marketing words. “Absolute”, “high efficiency” and “nominal” are not standardized labels across brands; the Beta table is.
Why this matters for substitution buying
Procurement tables built on a single micron column systematically mis-pair elements:
- A buyer demanding “10 µm or finer” rejects the catalog-declared 12 µm β1000 replacement — which is the same physical grade as the 10 µm β200 original.
- A buyer accepting “5 µm” without a Beta point might receive an element rated β5=2, which is far coarser in protection than a 12 µm β1000 cartridge.
When a cross-reference on this site is tagged partial with a micron difference, the note states which test point each number represents. When it is tagged verify, the aftermarket listing did not include a Beta statement at all — request the data sheet before committing.
FAQ
Is β1000 the same as 99.9% efficiency? Yes: efficiency = (β − 1) / β, so β1000 = 99.9% capture at the stated size in a single pass.
Which Beta should a modern hydraulic system target? Most modern microglass elements are rated βx(c) ≥ 1000; premium media reaches 2000. The required cleanliness code (ISO 4406), set by the most sensitive component, determines the micron point.
Does “absolute rating” mean 100% capture? Historically “absolute” meant the largest hard spherical particle that passes under test — not 100% capture of that size. Compare Beta numbers instead of relying on the word.
Where can I see the HYDAC–Pall grade mapping? It is extracted from Pall’s Red1000 interchange document and linked on every HYDAC Betamicron R-series model page and Pall Red1000 series page; the raw citations are in the editorial policy.