Why Your UF/Donaldson Filter Elements May Be Costing You More Than They Should
UF (formerly UF, now part of Donaldson) compressed air filtration systems are installed across thousands of industrial facilities throughout Europe. If your plant runs on UF housings — whether the classic P-SRF coalescing series, the P-MF particulate range, or the older P-AC adsorption elements — you already know the challenge: replacement elements are expensive, lead times can stretch, and the OEM lock-in feels unavoidable.
It is not. This guide explains how to cross-reference your existing UF/Donaldson elements to dimensionally and performance-equivalent alternatives available from R+F FilterElements, and what to check before making the switch.
Understanding the UF/Donaldson Element Numbering System
UF element part numbers encode the filter type and size. The most common series you will encounter in the field are:
- P-SRF — coalescing elements (oil and water aerosol removal)
- P-MF — particulate/dust elements
- P-AC — activated carbon adsorption elements
- P-SRF-S — high-temperature coalescing (S-type, up to 200 °C)
The numeric suffix typically encodes the element length and inner diameter. For example, a P-SRF-12057 indicates a 120 mm inner diameter, 570 mm length element. This dimensional convention maps directly onto the R+F FilterElements coding system, making cross-referencing straightforward once you know the key dimensions.
For a full overview of the R+F compressed air filter element range, see the filter elements product page.
Key Performance Parameters to Match
When selecting a replacement element, four parameters must align with the original specification:
Beyond dimensions, the replacement element must match the original's filtration grade (coalescing, particulate, or adsorption), the temperature rating, and the seal material. Most UF housings use NBR seals as standard; if your application runs above 100 °C or involves aggressive gases, FKM/Viton seals are required.
Cross-Reference: UF/Donaldson to R+F FilterElements
The table below covers the most commonly encountered UF/Donaldson element series and their R+F equivalents. All R+F elements listed are manufactured to borosilicate glass microfibre construction for coalescing grades, and meet or exceed ISO 8573-1 purity class requirements.
| UF/Donaldson Series | Type | R+F Equivalent | Notes |
|---|---|---|---|
| P-SRF (coalescing) | Coalescing | RF-C (matching size code) | Direct dimensional match; 99.99% @ ≥ 0.1 µm |
| P-MF (particulate) | Particulate | RF-P (matching size code) | 99.99% @ ≥ 0.3 µm; sintered option available |
| P-AC (adsorption) | Activated carbon | RF-AC (matching size code) | Residual oil < 0.003 mg/m³; ISO 8573-1 Class 1 |
| P-SRF-S (high-temp) | Coalescing, 200 °C | RF-C S-type | FKM seals; rated to 200 °C |
| P-SRF-K (sour gas) | Coalescing, H₂S service | RF-C K-type | Sour gas / H₂S compatible materials |
For point-of-use applications where a full housing replacement is not practical, the RF-DIL disposable inline filter provides a compact, tool-free alternative that can be inserted directly into instrument tubing or sample lines.
Need help selecting the right replacement element?
How to Identify Your Element Size
If the element label is worn or missing, you can determine the size from the housing itself. UF/Donaldson housings are typically stamped with the model number on the bowl or head. The housing model number encodes the flow capacity and element size. Alternatively, measure the element directly:
- Inner diameter (ID): measure the bore of the end cap
- Length: measure overall element length including end caps
- End-cap style: flat face-seal, O-ring groove, or threaded centre rod
Once you have these three measurements, the R+F FilterElements team can confirm the correct replacement code. Use the Engineering Sizing Tool to cross-check flow rates and pressure drop at your operating conditions, or visit the compressed air filter range for full technical specifications.
Use our free Engineering Tool to get a filtration recommendation for your specific application in under 2 minutes.
Performance Equivalence and ISO 8573-1 Compliance
A common concern when switching from OEM elements is whether the replacement will maintain the same ISO 8573-1 purity class. R+F FilterElements are tested and rated to the same standard as the original UF/Donaldson elements:
- RF-C coalescing elements: ISO 8573-1 Class 1 for oil aerosol (≤ 0.01 mg/m³ residual oil)
- RF-P particulate elements: ISO 8573-1 Class 1 for solid particles (≥ 0.1 µm)
- RF-AC adsorption elements: ISO 8573-1 Class 1 for total oil (≤ 0.003 mg/m³ residual oil vapour)
For applications requiring validated purity — food and beverage, pharmaceutical, electronics — R+F FilterElements can supply test certificates on request. See the ISO 8573-1 compressed air quality guide for a full breakdown of purity classes and what they mean for your process.
When to Consider a Full Housing Upgrade
If your UF/Donaldson housings are more than 10–15 years old, it may be worth evaluating a full housing replacement rather than continuing to source elements for ageing equipment. Signs that a housing upgrade is warranted include:
- Visible corrosion or pitting on the bowl or head
- Repeated seal failures or bowl thread wear
- Pressure drop higher than the original specification even with new elements
- Flow requirements that have grown beyond the original housing capacity
The R+F process gas filter range includes the RF-H-150 (100 bar, 316L stainless steel) for demanding process gas duties, as well as the full compressed air housing range for standard industrial applications. For vacuum pump exhaust filtration, the vacuum pump exhaust filter range covers flows from 5 to 765 m³/h.
- UF element part numbers encode the filter type and size.
- When selecting a replacement element, four parameters must align with the original specification:
- The table below covers the most commonly encountered UF/Donaldson element series and their R+F equivalents.
- If the element label is worn or missing, you can determine the size from the housing itself.
Ordering Replacement Elements
To order R+F replacement elements for your UF/Donaldson housings, you will need:
- The UF/Donaldson element part number (from the element label or housing documentation)
- The quantity required
- Any special requirements (high-temperature, sour gas, food-grade seals)
R+F FilterElements holds stock of the most common element sizes for rapid despatch. For less common sizes or large-volume orders, lead times are typically 5–10 working days from Hildesheim, Germany.
Related Reading
- Coalescing vs Particulate Filter Elements — Which Do You Need?
- ISO 8573-1 Compressed Air Quality — A Practical Guide
- Oxygen Filtration Safety — What Every Engineer Should Know
Try our Engineering Sizing Tool → or discuss your requirements with our team.
