A custom metal filter element is defined by three things: the filter media, the end-cap interface code (222, 226, 215, DOE), and the seal material. If any one of these is wrong, the cartridge either will not seat, bypasses unfiltered fluid, or fails under temperature and chemical load. This guide explains sintered metal, wedge wire and mesh media, the interface codes buyers search for most, and how to specify seals that survive in service.
Filter Media: Sintered Metal, Wedge Wire and Woven Mesh
The media decides what the element can capture, how it handles temperature and viscosity, and whether it can be cleaned and reused. Tanqi Industry supplies three main media types from Anping workshops, each suited to different industrial applications.
Sintered Metal Filters
Sintered metal filters in stainless steel (304, 304L, 316, 316L, 310S, 317L) and specialty alloys (titanium, Hastelloy, Inconel, Monel) are pressed and sintered into porous sheets or tubes. Micron ratings from 0.1 µm to 100 µm. Rigid structure means they resist collapse under high differential pressure and can be backflushed, ultrasonically cleaned or baked to remove captured solids. Used in hydraulic return-line and pressure-line filtration, polymer and melt service, petrochemical process streams, and high-temperature gas filtration.
Selection rule: choose sintered metal when the fluid is hot, viscous, or the element must survive hundreds of cycles without replacement.
Wedge Wire Screens
Wedge wire screen filters use V-shaped profile wire welded to longitudinal support rods, creating a continuous slot opening from 25 µm upwards. The V geometry means particles contact the wire at two points only, reducing blinding. Suitable for water intake, resin traps, sugar and syrup, starch, in-line strainers and self-cleaning filter housings. Slot size is fixed by wire profile, common sizes are 0.05 mm, 0.1 mm, 0.2 mm, 0.5 mm, 1.0 mm and above.
Selection rule: choose wedge wire when the contaminant is large, fibrous, or sticky, and you need mechanical strength with clean-in-place capability.
Pleated Woven Wire Mesh
Wire mesh filter elements use 316L or 304 stainless steel mesh pleated around a perforated core to increase surface area in a compact housing. Micron ratings from 5 µm to 2000 µm depending on weave (plain, twill, Dutch). Lower cost than sintered media, easier to produce in short runs, but less rigid and harder to clean thoroughly. Used for general liquid and gas pre-filtration, hydraulic suction lines, and compressor intake.
Selection rule: choose pleated mesh when budget matters and the fluid is relatively clean or the element is disposable.
End-Cap Interface Codes: 222, 226, 215, DOE and the Rest
Interface codes describe the shape of the end cap, how the cartridge locks into the housing and where the O-ring sits. These codes are trade shorthand, not a single global standard. Two suppliers may label the same physical part differently. Always confirm dimensions against a drawing before ordering.
SOE vs DOE: The Two Families
Most codes fall into two groups:
- SOE (Single Open End): one end closed, the other carries the sealing boss or fin. Used in hydraulic, lube, polymer, pharma and process housings.
- DOE (Double Open End): both ends open; sealing happens through housing gaskets or compression plates. Common in bag-filter conversions and simple water housings.
Filter Element Interface Codes at a Glance
| Code | Family | What It Means | Typical Use |
|---|---|---|---|
| SOE | Single Open End | One end closed, O-ring or fin at open end | Hydraulic, process, pharma |
| DOE | Double Open End | Both ends open, sealed by housing gaskets | Water, bag-filter conversions |
| 215 | SOE insert | ~33 to 34 mm boss class, push-in | Compact hydraulic, instrument loops |
| 220 | SOE fin | ~35 mm boss class, fin plus O-ring | General liquid filters |
| 222 | SOE fin | ~45 mm O-ring circle, single fin, push-in | Hydraulic, lube oil, water, polymers |
| 226 | SOE bayonet | ~58 mm circle, double or tri-fin, twist-lock 90 degrees | Food, pharma, process, higher flow |
| 34 / 37 | Boss class | 34 mm / 37 mm O-ring circle | European hydraulic housings |
| 4M | SOE large head | External O-ring, large closed top | Polymer, melt, high-viscosity |
| 19H | Small boss SOE | ~19 mm boss class | Instrument, special process |
| A / A22 / A222 | Triangle fin | Triangle profile plus 222 O-ring circle | Anti-rotation hydraulic housings |
| B / B222 | Tail fin | Bat wing fin locks under flow reversal | Vibrating lines, lube systems |
| C | Flat BOE | Plain open end, gasket compression | Low-pressure water, large-diameter |
| D | Small boss SOE | Compact boss plus O-ring | Hydraulic samplers, small elements |
| DH116NC / DHKC | Vendor SOE | No-collar / key-collar variants | OEM cross-reference elements |
| IS116 | Insert SOE | IS-series housing insert | Process cross-reference |
| PT34-44 | Threaded or expanded | 34 to 44 mm connection | Steam, special process housings |
| SK / SKNC | Skirt type | Skirt plus O-ring / no collar | Water treatment, OEM clone elements |
Note: boss diameters are nominal class ranges. O-ring groove dimensions vary between housing manufacturers. Dimensions are confirmed against your drawing before production, not guessed from the code.
222 vs 226: The Most Common Confusion
These two codes cause more returns than any other. A 222 element uses a smaller O-ring circle (nominally ~45 mm) and pushes straight into the housing. A 226 uses a larger circle (nominally ~58 mm) and locks with a bayonet twist, usually 90 degrees. Forcing a 226 into a 222 housing tears the O-ring. Forcing a 222 into a 226 housing leaves it unseated and bypassing.
If you are not certain which one your housing takes, send a photo of the existing element on top of a ruler, or the housing model number.
Vendor-Specific Codes
Codes like DH116NC, DHKC, IS116, PT34-44 and SKNC are vendor shorthand. They appear in cross-reference requests for HYDAC, Pall, Parker, CJC and Donaldson replacements. Catalogs disagree on what these mean. Tanqi maintains a working cross-reference list, but treats every vendor code as a drawing item, not a dropdown item.
Seal Materials: NBR, EPDM, FKM, Silicone, PTFE
The interface code decides whether the element fits. The seal material decides whether it survives. A perfect 222 cartridge with the wrong O-ring will leak or crack in service. Fluid compatibility is the governing factor.
| Seal Material | Temp Range | Chemical Resistance | Typical Application |
|---|---|---|---|
| NBR (Buna-N) | -20 to 100°C | Mineral oils, hydraulic fluid; poor ozone resistance | Hydraulic fluid, lubrication systems |
| EPDM | -40 to 120°C | Hot water, steam, mild acids and alkalis; poor oil resistance | Water treatment, food and beverage, steam |
| FKM (Viton) | -20 to 200°C | Solvents, fuels, aggressive chemicals | Petrochemical, solvents, high-temp process |
| Silicone | -60 to 200°C | Food-grade, FDA compliant; poor oil and tear resistance | Food and beverage, pharmaceutical |
| PTFE | -200 to 260°C | Almost all chemicals, strong acids and bases | Chemical processing, pharmaceutical, high-purity |
When requesting a quote, specify the seal compound. If you are not sure, tell us the fluid name and operating temperature. We will recommend the compound.
Common Mistakes When Specifying Filter Elements
- Assuming 222 equals 226. Different O-ring circle diameter, different locking mechanism. Measure the housing boss before ordering.
- Buying DOE when the housing needs SOE. The element will drop through or bypass completely.
- Specifying interface code but ignoring seal material. The right fin with the wrong O-ring fails within weeks.
- Trusting a cross-reference table that does not list dimensions. Catalogs disagree. Your drawing is the authority.
- Reusing an old part number after the housing was retrofitted. The housing may now take a different interface. Check physically.
What to Send for a Quotation
To source OEM-compatible replacement cartridges for HYDAC, Pall, Parker, CJC, Donaldson or any other branded element, send as many of the following as available:
- Housing model number and original element part number
- Photo of the existing element (top, bottom, side) with a ruler
- Outside diameter and overall length
- Micron rating and media type (if known)
- End-cap interface code (from the old element or housing plate)
- Seal material
- Operating fluid, temperature and pressure
Tanqi verifies material grade, dimensions, ISO 4406 code, connection interface and seal compound against your drawing before release. Photos and test reports are provided on request.
Frequently Asked Questions
1. How do I choose the right media for a custom filter element?
Choose the media according to the fluid, temperature, pressure, contaminant type, micron rating, and cleaning requirements. Sintered metal is suitable for high-temperature, high-pressure, or reusable applications; wedge wire works well for larger, fibrous, or sticky contaminants; pleated woven mesh is a cost-effective option for general pre-filtration.
2. What is the difference between 222, 226, SOE, and DOE interfaces?
These codes describe the end-cap design and how the filter element fits and seals inside the housing. SOE elements have one open end, while DOE elements have two open ends. A 222 interface typically uses a smaller O-ring circle and push-in connection, whereas a 226 interface uses a larger O-ring circle and bayonet-style locking. They are not interchangeable.
3. What if my interface code is not listed in the table?
Seal selection depends mainly on the operating fluid, temperature, and chemical environment. NBR is commonly used with mineral oils and hydraulic fluids, EPDM suits hot water and steam, FKM is preferred for fuels, solvents, and higher-temperature service, while PTFE offers broad chemical resistance for demanding process applications.
4. What information is needed to manufacture a custom filter element?
Provide the housing model or original element part number, element dimensions, media type and micron rating, interface code, seal material, operating fluid, temperature, and pressure. Photos of the existing element and a dimensional drawing are also helpful for confirming fitment and preventing bypass or sealing problems.
Interface codes look like small details, but they decide whether a filter element works in your housing. For custom stainless steel filter elements and OEM-compatible replacements, Tanqi treats the end cap as a drawing item, not a dropdown selection. Material grade, micron rating, dimensions, seal compound and interface shape are all confirmed before production.
If you are replacing an element and only have a code like 226, 4M or SKNC, send us your custom specifications. We will tell you what can be cloned and what must not be changed.