Choose a pneumatic filter's micron rating from the air-quality requirements of the equipment it supplies. XMC HDAF20, HDAF30 and HDAF40 use 25 μm filtration as standard, with 5 μm and 50 μm options. A 5 μm element is the finer option, not an automatic upgrade for every machine. Confirm filtration, flow performance and drainage together; a micron rating alone does not establish dry or oil-free air.
What does a pneumatic filter micron rating tell you?
One micron, written μm, is one thousandth of a millimetre. The number describes a particle-size filtration grade: 5 μm is finer than 25 μm, and 25 μm is finer than 50 μm. It is not the connection size or a flow rating. The HDAF catalogue lists these three grades but does not state an absolute retention efficiency or a complete outlet-air purity class. [1] If your specification requires a particular removal efficiency or test method, request supporting performance data rather than treating the micron number as a guarantee that every larger particle is removed.
Compare the 5, 25 and 50 μm HDAF options
The following table explains the available choices, not a universal filtration rule for every industry. Standard describes the catalogue configuration; it does not mean that 25 μm meets the requirement of every valve, cylinder or instrument connected downstream. [1] Record the required element grade explicitly on the quotation and purchase order.
| Element grade | HDAF catalogue configuration | What to confirm before choosing |
|---|---|---|
| 5 μm | Optional; the finest of these three choices | Does the downstream specification call for this grade, and can the selected unit supply the required flow? |
| 25 μm | Standard configuration | Does the complete machine circuit accept this filtration grade under the intended conditions? |
| 50 μm | Optional; coarser than the standard element | Does the downstream equipment explicitly permit this grade? Do not substitute it only to address low pressure. |
Start with every air user on the branch
List the directional valves, cylinders, grippers, pressure instruments and other devices supplied by the filter. Find their air-quality requirements before selecting an element. Festo's air-preparation guidance treats particle contamination, water and oil as separate requirements, alongside adequate pressure and flow. [2] For a machine specification, write down which requirement comes from which component. A broad description such as packaging machine or assembly line is not enough to assign one micron rating. Also distinguish air that operates an actuator from air that contacts the product being made.
HDAF20, HDAF30 or HDAF40: select the body separately
All three reviewed HDAF body sizes list the same standard and optional filtration grades. Their available ports differ, and some overlap. For example, both HDAF20 and HDAF30 offer a 1/4-inch connection. That shared connection does not establish equal flow performance. Use the specification table on printed page 52 and the applicable flow graph on page 53; confirm the plotted port and operating conditions before applying a curve to your selection. [1] Ask XMC for data for the exact element and configuration if the catalogue does not identify them.
| Body size | Model and port options | Filter-element choices |
|---|---|---|
| HDAF20 | HDAF20-01: 1/8 inch; HDAF20-02: 1/4 inch | 25 μm standard; 5 μm or 50 μm optional |
| HDAF30 | HDAF30-02: 1/4 inch; HDAF30-03: 3/8 inch | 25 μm standard; 5 μm or 50 μm optional |
| HDAF40 | HDAF40-03: 3/8 inch; HDAF40-04: 1/2 inch | 25 μm standard; 5 μm or 50 μm optional |
Check pressure drop during the working cycle
Filters introduce flow resistance, so selection needs to consider the required flow and available pressure. [2] When reviewing an existing machine, record the inlet and outlet pressures while the same operating cycle runs, plus which air users operate simultaneously. If a problem appears after an element change, check the exact replacement, installation and measured conditions before assigning a cause. Do not bypass required filtration or fit a coarser element just because the actuator becomes slow. If the requirement is 5 μm, review a suitable unit and the complete supply path while retaining that requirement.
Particle filtration is not the same as drying or oil removal
Do not translate 5 μm into oil-free, dry or sterile air. Manufacturer air-treatment ranges distinguish ordinary air filters from mist separators; SMC, for example, lists them as separate product functions. [3] Festo also describes drying and oil-vapour treatment separately from particle filtration. [2] Review the actual water and oil limits at the point of use. If water keeps collecting in the bowl, check the condensate load and drain operation. Changing the particle grade alone does not establish that the moisture requirement has been met.
A selection example: the same port, two different questions
Consider a hypothetical assembly fixture with a 1/4-inch air connection. Its valve documentation requires 5 μm filtration. The first decision is to specify a suitable 5 μm option, not to assume that a standard HDAF configuration is sufficient. The second decision is body size: both HDAF20-02 and HDAF30-02 appear in the catalogue, so the thread size cannot settle the choice. Request a review using the operating pressure, peak air demand and allowable pressure loss. If the fixture later gains an air nozzle, reassess the demand while keeping the valve's air-quality requirement. This example illustrates the decision process; it is not a tested sizing recommendation for either model.
Specify the element, drain and service details together
Send the complete model code or a clear label photo, required element grade, downstream equipment requirements, port and thread, working pressure, flow with its reference conditions, and drain preference. Add bowl/protective-cover requirements and installation space. The HDAF ordering example on page 52 shows body, port, drain and bowl options; do not invent a micron suffix that is absent from that example. [1] Have XMC state the agreed filtration grade and compatible replacement element on the quotation. Follow the component's service instructions; before opening a bowl or changing an element, isolate and depressurize the circuit under the machine's approved procedure.
Catalogue and technical references
XMC model codes, port choices and element options are taken from the 21 June 2025 catalogue. The Festo and SMC references support general air-treatment distinctions only; their product ratings and approvals are not transferred to HDAF. The example above is hypothetical. Confirm the final configuration against the requirements of the equipment being supplied.
Questions buyers ask.
Is a 5 micron pneumatic filter better than a 25 micron filter?
It provides a finer particle-filtration grade, but the correct choice depends on the downstream equipment requirements and the selected unit's performance. Confirm those requirements before changing the element; smaller is not a universal selection rule.
What is the standard filtration grade for XMC HDAF20, HDAF30 and HDAF40?
The 21 June 2025 catalogue lists 25 μm as standard, with 5 μm and 50 μm available. State the required grade explicitly when requesting a quotation, and confirm the configuration supplied.
Can I choose HDAF20 or HDAF30 from a 1/4-inch port alone?
No. Both sizes offer that connection. Compare the exact configuration against the required flow, operating pressure, permitted pressure loss and available installation space. A shared port size does not establish equal performance.
Can a 5 micron air filter replace a dryer or an oil-removal stage?
The micron rating alone does not establish those functions. Water and oil requirements need a separate review of the air-treatment system and its performance at the point of use.
Can I identify the fitted element grade from the HDAF product photograph?
No. Use the order specification and the confirmed replacement-element identification. A photograph of the housing or its base model label is not sufficient evidence of the installed filtration grade.
Technical references
- [1] XMC Huayi product catalogue, 21 June 2025: printed page 52, HDAF20-40 ordering and specifications; printed page 53, flow characteristics. Catalogue table visually checked on 22 September 2026.
- [2] Festo, Compressed air preparation in pneumatics, 2015 white paper: air-quality requirements, flow and pressure, filtration and separate treatment functions. Accessed 22 September 2026.
- [3] SMC, Elements Part No. List: separate air-filter and mist-separator product functions. Accessed 22 September 2026.
Put the guide to work.
Choose the relevant XMC series, download its product PDF and include the application details with your inquiry.