Mechanical connections
Threaded Flanges
Internal threads connect the flange to a matching threaded pipe end. The thread form, nominal size and mating pipe specification must be stated together.
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.
Bolt circle, hole count, bore and gasket seating must match the equipment or existing flange. A nominal pipe size alone is not enough to identify a suitable companion. Include a drawing or the original equipment connection specification in the enquiry.
Compare flange typesDimensions and connection data
Define Companion 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 Companion Flanges with the related forms or references below. A related product is not necessarily a permissible substitute.
| Related product / reference | Distinction | Check before selection |
|---|---|---|
| Threaded Flanges | Internal threads connect the flange to a matching threaded pipe end. The thread form, nominal size and mating pipe specification must be stated together. | Specify thread standard, size and engagement |
| Lap Joint Flanges | A backing flange works with a separate stub end or lapped pipe end. The stub end provides the gasket seating surface while the backing flange transmits the bolt load. | Specify flange and stub end as separate components |
| Slip-On Flanges | The flange bore slips over the pipe before the connection is secured with fillet welds. Pipe outside diameter and installation clearance govern the fit. | Slip-over bore with project-specified fillet welds |
Inspection, documents and delivery
Define acceptance requirements for Companion 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 companion flanges
Availability, dimensions and pressure-temperature suitability are confirmed against your complete enquiry.
| Item | Requirement |
|---|---|
| Mating component | Provide equipment drawing or flange designation |
| Bolt pattern | State bolt circle, hole quantity and hole diameter |
| Pipe side | Identify threaded, welded or other connection form |
| Facing | Confirm seating profile and gasket arrangement |
| Material & quantity | Exact material designation, quantity and required certification or inspection documents |
Application context
Where this form is considered
- Matching equipment flange interfaces
- Replacement mating connections
- Drawing-led assembly enquiries
Related connections
Compare other flange forms
Mechanical connections
Lap Joint Flanges
A backing flange works with a separate stub end or lapped pipe end. The stub end provides the gasket seating surface while the backing flange transmits the bolt load.
Welded connections
Slip-On Flanges
The flange bore slips over the pipe before the connection is secured with fillet welds. Pipe outside diameter and installation clearance govern the fit.