A filter housing connection must match more than a nominal pipe size. Thread form, sealing arrangement, mating component and nozzle location belong in the approved specification. A quotation that says only “2-inch connection” leaves room for a mechanically incompatible product.
This guide is a procurement checklist, not a connection design or installation procedure. Apply it when requesting a single bag housing, multi bag housing or high flow cartridge housing. Availability of any connection option must be confirmed for the quoted model.
Representative multi-bag vessel. The photograph does not identify a connection standard, flange rating, nozzle dimensions or a supplied accessory package.
Thread standard is not the complete end connection
NPT is a tapered pipe-thread family. BSP terminology can refer to parallel or tapered arrangements, so “BSP” alone is incomplete. The end connection also defines where and how sealing occurs. A matching-looking thread does not prove a matching seal.
Swagelok’s identification guide separates thread characteristics from the complete end connection and considers taper, diameter and pitch before identifying the interface. It also warns that some NPT and ISO 7/1 sizes are difficult to distinguish. Use documented identification rather than trying an uncertain fitting to see whether it engages.
| RFQ wording | What remains unresolved | Better information to supply |
|---|---|---|
| 2-inch threaded inlet | Thread family, gender and seal interface | Full designation, mating part and drawing |
| BSP outlet | Parallel/tapered arrangement and sealing detail | Exact connection standard and interface detail |
| DN connection with flange | Standard, rating, facing and mating geometry | Approved flange designation and mating drawing |
| Same as the old housing | Equipment revision and any site modification | Identified existing reference plus measured layout |
For flanges, specify the mating pair
List the applicable standard and edition, nominal designation, rating designation and facing. Include the mating flange information and the gasket arrangement required by the responsible system designer. Where these are not established, mark them as open design inputs rather than allowing an unchecked default.
Ask the supplier to show the proposed flange and nozzle details on the general arrangement drawing. Review the bolt pattern, face-to-face relationship and available installation clearance against the existing piping. Do not assume that similar labels from different standard systems define an interchangeable pair.
A flange designation alone is not a complete housing pressure specification. Keep design conditions, materials, temperature, corrosion considerations and the required vessel documentation as separate procurement fields. Have the responsible engineer approve the pressure boundary and connection assembly.
Include every port, not only inlet and outlet
Create a nozzle schedule with a unique identifier for the inlet, outlet, drain, vent and instrument ports as applicable. Define size, standard, gender or facing, orientation, elevation and intended function. A small gauge or drain connection can delay commissioning just as a mismatched main nozzle can.
For replacements, send photographs with dimensions and reference points, not only close-ups of threads. Identify any existing adapters and tell the supplier whether they are to remain. An adapter proposal also needs review for material, ratings, sealing, added length and access; it is not automatic approval to connect unlike parts.
Keep connection size separate from hydraulic capacity
A larger port does not by itself establish the number of bags or cartridges needed. Confirm the required flow, liquid properties, filtration duty and pressure-drop budget independently. Use the multi bag sizing guide or high flow sizing guide for the wider equipment selection.
Request a general arrangement showing maintenance access as well as piping. Include lid opening or lifting clearance, element-removal space and access to valves or instruments that the project requires. The final layout should be approved before fabrication rather than inferred from a catalog image.
Define supply and approval boundaries
- Identify who supplies mating flanges, gaskets, bolts, adapters and instruments.
- State the applicable drawings and the order of precedence if documents conflict.
- List any proposed deviations explicitly in the quotation.
- Approve the connection schedule and arrangement drawing before manufacture.
- Define receiving checks and the applicable assembly/test procedure with qualified personnel.
Do not force, recut or seal an unidentified thread to make it fit. Installation torque, sealant selection and testing belong to the approved equipment and connection instructions, not a generic SEO guide.
Request a connection-specific housing quote
Send the duty, proposed housing type, complete port schedule, mating connection information, layout drawing, materials and design conditions. Request Engineering Quote or OEM pricing with connection options, accessories and deviations clearly itemized.
Frequently asked questions
Are NPT and BSP interchangeable if the nominal size is the same?
Do not assume interchangeability. Identify the exact thread and end connection, including the sealing interface, before selecting a mating component.
Is flange nominal size enough for an RFQ?
No. Include the standard, rating designation, facing, mating details and the approved gasket arrangement, alongside the housing design conditions.
Does a larger inlet guarantee more filtration capacity?
No. Port size is only one equipment detail. Element area, media, fluid properties, flow and allowable pressure drop must also be evaluated.
Technical reference
Swagelok: Thread and End Connection Identification Guide, MS-13-77 supports interface-identification terminology. It is not an INCE assembly instruction or a substitute for the project’s approved connection and vessel specifications.
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