Filter Cartridge End Caps and Seals: A Practical Guide.
Recognize DOE, 222 and 226 interfaces, understand where sealing happens, and collect the details needed for a replacement that fits.
By FiltruneOn this page
A replacement cartridge has to do two jobs: provide the required filtration and connect correctly to its housing. End caps, gaskets and O-rings are part of that connection. The names DOE, 222 and 226 are useful starting points, but the complete adaptor and housing detail determine the fit.
Start with Both Ends of the Cartridge
DOE means double open end: the central passage is open at both ends. Common gasketed versions seal against matching surfaces in the housing. SOE means single open end: one end connects to an outlet seat and the opposite end is closed. The closed end may be flat, finned or otherwise located by the housing design. [1]
Photograph the connection end and the opposite end separately. A view of the cylindrical body does not show how it is retained or sealed. Record visible markings and the housing model before taking measurements; a matching manufacturer drawing is more useful than identifying a shape by eye alone.
| Description | What to look for | What to confirm |
|---|---|---|
| DOE, gasketed | An open central passage at each end, with end sealing surfaces. | Gasket geometry, both housing seats and the specified compression/retention arrangement. |
| SOE, 222-style O-ring connection | An open spigot carrying O-rings; the other end is closed. | Spigot dimensions, O-ring specification, insertion depth and the closed-end location. |
| SOE, 226-style O-ring connection | An O-ring spigot, commonly with a locking arrangement. | Tab geometry and engagement, seat dimensions and the opposite-end form. |
Why 222 or 226 Is Not a Complete Order Code
The same O-ring family can appear with different opposite ends and locating features. For example, product catalogues list both flat and fin-ended 222 configurations, and multiple 226 configurations. An adaptor number used in one supplier’s ordering system should not be assumed to mean the same complete geometry in another. [2]
Request a dimensional drawing of the proposed connection and compare it with the housing requirement. Nominal cartridge length alone does not establish installed length, seating depth or seal compression. The retention method also matters: do not assume that pushing an element into a seat is the complete installation procedure.
Describe the interface in three parts
Connection1Opposite end2Seal3
Actual cartridge dimensions, housing identification and the liquid/cleaning conditions.
- 1Open-end adaptor
Identify the complete adaptor style and its dimensional drawing, including any locking features.
- 2Location and support
Record a flat end, fin or other locating feature and how the housing retains it.
- 3Size and compound
Specify the gasket/O-ring dimensions and the actual material compound required.
Where the Seal Protects the Flow Path
The intended path takes liquid through the filter medium before it reaches the clean outlet. The cartridge-to-housing seal separates those regions. If that connection is not established as intended, fluid can travel around the medium instead of through it. A finer filter grade does not compensate for an incorrect seal.
Treat the seat, adaptor and seal as one interface. Check for a damaged or contaminated seating surface, the wrong ring, a twisted ring or an element that has not reached its specified position. Follow the housing and cartridge installation instructions for insertion, locking, retention and any permitted lubricant; a generic sketch cannot provide those product-specific steps.
Choose the Seal Compound for the Exposure
The material abbreviation describes an elastomer family, not a universal approval. Review the actual compound against the full liquid composition, concentration, temperature and cleaning exposure. A cartridge may encounter a different chemical or temperature during cleaning than during normal production. [3]
| Family | Useful starting context | Question to resolve |
|---|---|---|
| EPDM | Often considered for water and suitable cleaning duties; petroleum oils are an important limitation. | Does the actual compound suit the complete fluid and cleaning cycle? |
| NBR / nitrile | Often considered where petroleum-oil resistance is relevant. | What do the fluid additives, temperature and ageing conditions require? |
| FKM / fluoroelastomer | Often considered for selected oils, fuels and chemical exposures. | Is the exact chemical compatible with this FKM compound? Do not generalize across solvents. |
| Silicone / VMQ | Available in a range of compounds with different service and handling properties. | Are chemical exposure, mechanical handling and any required contact documentation addressed? |
Use this table to organize a supplier discussion, not to approve a liquid from its category name. Colour is also an unreliable material identifier. Where documentation is required for contact use, extractables or a cleaning regime, request it for the actual selected seal and cartridge rather than borrowing a statement from another option.
Collect a Replacement Identification Set
Label the measurements clearly so a supplier can distinguish the body, adaptor, fin and sealing surfaces. Ask which features must be measured against the drawing and which tolerances apply. Where the installed assembly is uncertain, resolve that uncertainty before selecting a replacement from a photograph.
Before Returning the Assembly to Service
Use the housing’s documented procedure and suitable trained personnel for opening and restarting pressure equipment. Cartridge dimensions and a good-looking seal are not a substitute for the assembly checks required by that procedure.
The pleated filter cartridge category is a useful starting point for media options. Confirm the proposed PDP configuration and housing interface together.
Melt-blown vs. pleated filter cartridges explains the separate construction and performance questions to resolve once the interface is understood.
