Kaifil

Metal Filter End Connections: DOE, SOE, 222, 226, Threads and Flanges

Define the filter-to-housing joint by its sealing surface, locating feature and load path. Compare common cartridge ends and prepare an interface drawing for a reliable replacement.

Metal filter cartridges with several end configurations — The photograph shows metal filter cartridges with different end fittings and end-cap arrangements.

Published: Oct 28, 2026

Updated: Oct 28, 2026

Published by: Kaifil Mesh Products Co., Ltd.

Treat the connection as three linked functions

An end connection locates the element, separates the clean and dirty sides, and transfers assembly and operating loads. These functions may use different surfaces. A locating ring can center a cartridge while a separate gasket provides the seal. Draw the filter end together with its mating seat so every contact has a defined role.

DOE and SOE describe the end arrangement

DOE means double open end: both ends are open, commonly with axial gaskets compressed between the element and housing seats. SOE means single open end: one end is closed and the open end connects to the matching housing seat. The assembly drawing defines the service flow direction. The closed end can include a locating or retaining feature. State the total length, compressed sealing stack and closure arrangement; these determine how the element is seated.

222 and 226: record the actual spigot and seal engagement

222 and 226 identify common cartridge connection families. A push-in spigot uses O-rings against the mating bore; locating or retaining features distinguish particular end designs. For a 226 end with locking lugs, show their position and engagement with the housing. Provide spigot diameters, groove sections, insertion depth, lead-in and the mating bore. The code is an identification field; the interface drawing supplies the dimensions and tolerances.

Threads and flanges need a defined sealing face

For a threaded end, specify thread form, size, pitch, engagement and the point where sealing occurs. A shoulder gasket or radial O-ring seals at its designed surface; an intended thread seal needs its own sealing method. For a flange, record face geometry, gasket seat, bolt arrangement and alignment. Keep a removable cartridge flange distinct from a pressure-vessel or pipe flange designation.

Match the seal to its groove and exposure

A radial O-ring seals between the spigot and bore; an axial gasket or face O-ring seals between opposed faces. Record O-ring free-state inside diameter and cross section, compound, hardness and position. Groove depth, width, clearance and lead-in control seating. Select the exact seal compound for process fluid, cleaning chemicals and temperature cycle, including installation lubricant. The metal alloy and the seal compound are separate order fields.

Inspect fit, bypass and load as separate questions

Dimensional inspection checks concentricity, sealing surfaces, groove edges and insertion or clamping depth. An assembly bypass or leak test checks the sealing boundary under its defined conditions. A pore-integrity test checks the porous medium and its joints. A structural differential-pressure test loads the element in a stated direction with the intended support. A connection code alone supplies none of these acceptance results.

A replacement example: keep the housing seat in the drawing

When replacing a pleated metal element, measure the housing bore or gasket seat as well as the old cartridge. Record the closed-end locator, available insertion space and removal clearance. Compare the porous length separately from the overall assembly length. A worn or swollen service seal helps identify the position, while an unused seal or groove drawing defines the replacement size.

Prepare the interface in four steps

1. Identify the installed arrangement

Record DOE or SOE, end code if present, open/closed ends and flow direction.

2. Measure both mating parts

Show element and housing datums, sealing surfaces, grooves, engagement and assembly clearances.

3. Specify the seal set

Give size, compound, hardness, quantity and position for every O-ring or gasket.

4. Agree assembly and acceptance

Define insertion or clamping procedure, clean handling and separate fit, seal, integrity and structural checks.

Product gallery

Technical cutaway of DOE gasket seating, SOE O-ring engagement, a threaded shoulder and a flange seal — Technical schematic showing sealing and locating functions. Interface dimensions and fitting details follow the element and mating-housing drawing; the schematic is not to scale.

Connection and sealing comparison

End arrangement	Primary seal	Locating / retention	Drawing focus
DOE	Axially compressed end gaskets	Housing seats and closure	Both seats, compressed length and alignment
SOE push-in / 222 family	O-rings on the mating spigot/bore	Spigot and closed-end locator	Grooves, bore, lead-in and insertion depth
226 with locking features	O-rings on the mating interface	Lugs and matching housing engagement	Seal geometry, lug location and lock travel
Threaded end	Defined shoulder, radial or thread seal	Thread engagement and seating shoulder	Thread specification plus sealing datum
Flanged end	Gasket or face-seal arrangement	Flange face and fasteners	Seat, bolt arrangement and clamping path

Interface acceptance record

Check	Define before inspection	Record
Fit	Drawing datums, tolerances and assembly position	Measured dimensions and engagement
Seal / bypass	Fluid, pressure, direction, duration and limit	Leak or bypass result for the assembled joint
Pore integrity	Wetting liquid or test procedure and acceptance	Result for the medium and permanent joints
Structural load	Differential pressure, temperature, support and direction	Element behavior under the specified load

End-connection questions

Is a 222 or 226 code enough to order a replacement?

Add the end drawing and mating-seat details. Seal grooves, engagement, locating features and overall length complete the fit specification.

Can an O-ring be replaced by matching its outside diameter?

Use free-state inside diameter and cross section together with compound and hardness. Check the groove and mating part; a used ring may have stretched, swollen or taken a compression set.

Does a flange or thread identify the element pressure capability?

The complete element has a load path through media, support, joints, connection and housing seat. Specify operating and cleaning differential pressure, direction and temperature for that construction.