Loose Bronze Flanges Manufacturer & Exporter
Loose flanges, also called backing or ring flanges, sit loosely on a pipe or collar and clamp a stub end, collar or flared pipe end against the mating face.
Product Overview
Because the flange is not joined to the pipe, it can rotate to match bolt holes and can be removed and reused. The sealing face is on the collar, stub end or lapped pipe end, so the flange acts as the bolting ring. In marine and shipbuilding copper-alloy pipework, loose flanges are commonly paired with a brazed or welded collar on the pipe end.
Product specification
SM-PRD-LOO| Parameter | Specification |
|---|---|
| Product | Bronze loose (backing / ring) flange |
| Materials | UNS C93200, C95400, C95500, C95800, C63000, C83600, C84400 |
| Mates with | Collar, stub end or lapped pipe end, per drawing |
| Dimensions | Bore, OD, thickness and PCD per drawing or class table |
| Bolt pattern | ASME, EN/PN, JIS or custom |
| Facing | Flat both sides; sealing on collar or stub end |
| Pressure | Per piping specification and collar / stub end |
| Marking | Customer requirement or MSS SP-25 pattern |
| Documentation | MTC and inspection documents as applicable |
Technical Description
The same family as the lap joint flange, loose flanges are specified by bore, thickness and bolt pattern. The bore must clear the collar or stub-end OD at its largest point, and any bore radius or chamfer must clear the collar’s fillet. Mixed-metal systems are possible: the flange alloy can differ from the collar alloy, subject to galvanic compatibility in the service environment.
Construction
- Plain ring, flat on both faces
- Bore sized to clear the collar, stub end or pipe OD
- Bore chamfer or radius matched to the collar fillet
- Drilling per class pattern, EN/PN or custom
- Free to rotate on the pipe or collar
Available Materials
Available materials
SM-MAT-LOO| Grade | Alloy | Stock and specification | Fit for this flange |
|---|---|---|---|
| UNS C93200 | Leaded tin bronze (SAE 660) | Cast: ASTM B584 / B271 / B505 | General service; fast machining |
| UNS C95400 | Aluminium bronze | Cast: ASTM B148 / B271 / B505 | General marine and pump flanges |
| UNS C95500 | Nickel aluminium bronze | Cast: ASTM B148 / B271 / B505 | Higher-strength ring flanges |
| UNS C95800 | Nickel aluminium bronze (NAB) | Cast: ASTM B148 / B271 / B505 | Seawater piping paired with collars or stub ends |
| UNS C63000 | Wrought nickel aluminium bronze | Bar, forging, plate: ASTM B150 / B124 / B283 / B171 | Wrought rings from bar or plate |
| UNS C83600 | Leaded red brass / gunmetal | Cast: ASTM B62 / B584 | Water and general-service systems |
| UNS C84400 | Leaded semi-red brass | Cast: ASTM B584 | General valve-composition service |
Stock form and the governing specification depend on grade and size. Mechanical properties are in the data page for each grade.
Dimensions and Sizes
Dimensions to supply are listed below. A drawing or standard for the collar or stub end is needed so the bore clears it.
Dimensions to confirm
SM-DIM-LOO| Dimension | Basis |
|---|---|
| Bore diameter | Clearance over collar or stub-end OD |
| Bore radius / chamfer | Matched to collar fillet |
| Outside diameter, thickness | Per drawing or class table |
| Bolt circle (PCD) | ASME, EN/PN, JIS or custom |
| Bolt holes | Count and diameter per drawing |
| Face finish | Per drawing |
Sizes
Sizes follow your drawing or the class table; give the bore, OD, thickness and bolt pattern, or the NPS and class.
Pressure Classes
The pressure capability of the joint is set by the collar or stub end and the gasket as much as by the loose flange. We machine the flange to the drawing; class and allowable pressure come from the piping specification.
Facing Options
Loose flanges are normally flat on both faces; the sealing surface is on the collar or stub end. Special recesses or spigots can be machined on request.
Applications
- Marine and shipbuilding copper-alloy pipework
- Seawater circuits with collar or stub-end joints
- Systems that need rotating flanges for alignment
- Piping with frequent dismantling
Manufacturing
Rings are turned and bored from cast, continuous-cast or wrought stock, then drilled to pattern. Bore chamfers and radii are formed to match the collar.
Inspection and Documentation
Bore, OD, thickness, PCD and hole pattern are verified against the drawing; surfaces are examined visually. Material verification and MTC are provided as required.
Custom Requirements
Matched flange-and-collar sets, special bore forms, non-standard drilling and customer marking.
Loose Flanges: common questions
What is the difference between a loose flange and a lap joint flange?
They belong to the same family. A lap joint flange has a radiused bore for a stub end. A loose flange is typically a plain ring that clamps a collar, stub end or lapped pipe end.
Where are loose flanges used?
They are common in marine and shipbuilding copper-alloy pipework, paired with brazed or welded collars, and wherever rotating flanges simplify alignment.
What information do you need to make a loose flange?
The bore, outside diameter, thickness and bolt pattern, plus the collar or stub-end drawing so the bore and chamfer clear it.
Related Information
Have a Drawing or Flange Specification?
Send your drawing, material grade, dimensions and quantity to our technical sales team.