Mechanical connections
Companion Flanges
A companion flange is selected to mate with a particular flanged connection. The term describes its role in an assembly, so the actual connection form and dimensions must be identified.
Construction & special designs
Square Flanges
A square flange has a square external form and a connection-specific bolt arrangement. The outer shape alone does not identify its bore, seal or pressure rating.
Square connection systems can use different pipe attachments and gasket or seal arrangements. Provide the equipment designation or a controlled drawing of both mating components. Do not treat a square four-bolt form as an ASME B16.5 circular flange or an interchangeable hydraulic connection.
Compare flange typesIdentify the connection system
State the governing equipment or flange standard and any manufacturer interface designation. An O-ring recess, flat gasket or other seal requires its own dimensions and compatible mating surface.
Match the complete pattern
Provide centre distances in both directions, bolt-hole diameters, flange thickness and bore. Verify clearance to surrounding equipment as well as the nominal connection size.
Dimensions and connection data
Define Square 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 Square Flanges with the related forms or references below. A related product is not necessarily a permissible substitute.
| Related product / reference | Distinction | Check before selection |
|---|---|---|
| Companion Flanges | A companion flange is selected to mate with a particular flanged connection. The term describes its role in an assembly, so the actual connection form and dimensions must be identified. | Provide equipment drawing or flange designation |
| Plate Flanges | A plate flange is a ring-shaped component made from plate, with an open bore and a bolt pattern specified for the mating connection. Plate construction is distinct from a flat gasket facing. | State the plate specification, grade and thickness |
| 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 |
Inspection, documents and delivery
Define acceptance requirements for Square 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 square flanges
Availability, dimensions and pressure-temperature suitability are confirmed against your complete enquiry.
| Item | Requirement |
|---|---|
| Interface | Equipment designation or approved mating drawing |
| Bolt pattern | Horizontal and vertical centres, hole count and diameter |
| Seal | Gasket or seal geometry, material and surface requirements |
| Design basis | Applicable connection standard, loads and pressure-temperature conditions |
| Material & quantity | Exact material designation, quantity and required certification or inspection documents |
Application context
Where this form is considered
- Drawing-defined square equipment connections
- Specified hydraulic or utility interfaces
- Replacement square flange pairs
Related connections
Compare other flange forms
Construction & special designs
Plate Flanges
A plate flange is a ring-shaped component made from plate, with an open bore and a bolt pattern specified for the mating connection. Plate construction is distinct from a flat gasket facing.
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.