Welded connections
Reducing Flanges
A reducing flange combines a larger mating-flange interface with a smaller pipe connection or bore. Both the mating size and the reduced connection must be identified.
Welded connections
Expander Flanges
An expander flange incorporates a transition between a smaller pipe-side connection and a larger flanged bore. The transition geometry is part of the component design.
Identify both connection sizes, the transition length and the wall profile. Expander terminology is not sufficient to establish whether the requirement is an integral component or a fabricated assembly. The mating flange standard does not automatically validate the transition or its load capacity.
Compare flange typesDefine the transition
Specify pipe-side bore and wall, the larger flanged opening and the required overall length. Include weld-end preparation and any internal profile or flow-path requirements.
Confirm the design and manufacture
Agree whether the proposed construction is integral or fabricated, with the applicable design calculation, fabrication requirements and inspection scope. A bolt-pattern match is only one part of that review.
Dimensions and connection data
Define Expander Flanges as part of the complete joint. These fields identify required engineering data; they are not universal dimensions or a declaration of available sizes.
| Parameter / designation | Technical information | Selection requirement |
|---|---|---|
| Nominal size and bore | State the nominal connection size separately from the actual bore or pipe outside diameter. | A matching size label does not establish matching internal geometry. |
| Outside diameter and thickness | Identify the finished flange diameter, minimum thickness and any hub or collar projection. | Include the drawing datum and units for replacement measurements. |
| Bolt circle and holes | Record pitch-circle diameter, hole quantity, hole diameter and any special orientation. | Check against the mating flange; do not infer a bolt pattern from pressure class alone. |
| Gasket-contact surfaces | Specify face form, seating dimensions and surface finish on the assembled joint. | Include gasket designation; a visually similar surface is not evidence of compatibility. |
| Pipe-side interface | Identify weld preparation, socket, thread, collar or other attachment geometry as applicable. | Provide pipe schedule/wall thickness and the connection-specific standard. |
| Design conditions | State design pressure, minimum/maximum temperature, fluid and mechanical loads. | Pressure class is not a pressure value in bar or psi. Use the material-specific rating basis. |
Compare related options
Compare Expander Flanges with the related forms or references below. A related product is not necessarily a permissible substitute.
| Related product / reference | Distinction | Check before selection |
|---|---|---|
| Reducing Flanges | A reducing flange combines a larger mating-flange interface with a smaller pipe connection or bore. Both the mating size and the reduced connection must be identified. | State flange nominal size, rating and facing |
| Weld Neck Flanges | A tapered hub carries the connection from the flange body to a butt-welded pipe end. The pipe bore and wall thickness are important parts of the flange specification. | Butt-weld end; specify pipe schedule and bore |
| Long Weld Neck Flanges | An extended neck combines a flanged connection with a longer nozzle section. Neck length, bore and end preparation must be specified for the intended equipment connection. | Provide required projection, wall and bore |
Inspection, documents and delivery
Define acceptance requirements for Expander Flanges in the purchase order. Required examinations and documents depend on the material, design and project specification.
| Review stage | Information to confirm | Order requirement |
|---|---|---|
| Material identity and traceability | Specification, grade, heat/lot identification and the required material certificate. | Agree documentation and marking before manufacture; visual appearance cannot verify alloy identity. |
| Dimensional verification | Critical dimensions from the selected standard or controlled drawing. | Identify inspection points, tolerances, units and drawing revision. |
| Surface and end condition | Gasket-contact surface, attachment end, edges and any coating exclusions. | State finish and visual acceptance criteria; agree protection of machined surfaces. |
| Supplementary examinations | Any specified PMI, NDE, hardness, impact, corrosion or other tests. | Define the method, sampling and acceptance criteria; tests are not automatically included. |
| Assembly compatibility | Adjoining components, weld or mechanical interface and project service conditions. | Design approval and correct assembly remain separate from a dimensional inspection report. |
| Packing and order release | Quantity, identification, surface protection, documents and delivery destination. | Agree preservation, packaging and release requirements with the order. |
Specification checklist
Define your expander flanges
Availability, dimensions and pressure-temperature suitability are confirmed against your complete enquiry.
| Item | Requirement |
|---|---|
| Connection sizes | Pipe-side size and larger flange-side bore |
| Profile | Transition length, wall thickness and internal contour |
| Construction | Integral or fabricated form and approved drawing |
| Design review | Material, loads, pressure-temperature basis and inspection |
| Material & quantity | Exact material designation, quantity and required certification or inspection documents |
Application context
Where this form is considered
- Size transitions at equipment connections
- Space-constrained flange-to-pipe changes
- Engineered transition components
Related connections
Compare other flange forms
Welded connections
Weld Neck Flanges
A tapered hub carries the connection from the flange body to a butt-welded pipe end. The pipe bore and wall thickness are important parts of the flange specification.
Welded connections
Long Weld Neck Flanges
An extended neck combines a flanged connection with a longer nozzle section. Neck length, bore and end preparation must be specified for the intended equipment connection.