Lap Joint Bronze Flanges Manufacturer & Exporter
A lap joint flange rotates freely on a stub end that carries the sealing face. Rotation makes bolt-hole alignment easy at assembly and suits systems that are dismantled often.
Product Overview
The lap joint flange is a ring with a radiused corner at the bore. It slides over the pipe, sits behind a stub end, and is drawn up against the stub end’s lap when bolted. Since the flange can turn, the bolt holes are lined up with the mating flange without rotating the pipe.
Product specification
SM-PRD-LAP| Parameter | Specification |
|---|---|
| Product | Bronze lap joint flange |
| Materials | UNS C93200, C95400, C95500, C95800, C63000, C83600, C84400 |
| Mates with | Stub end or lapped pipe end, per drawing |
| Dimensional basis | Applicable standard or customer drawing |
| Pressure class | Class 150 / 300 or per drawing, as applicable |
| Bore | Clearance over stub-end OD; corner radius to drawing |
| Facing | Stub end carries the seal; flange face FF / RF if required |
| Marking | MSS SP-25 pattern or customer requirement |
| Documentation | MTC and inspection documents as applicable |
Technical Description
In a lap joint, the sealing face and the wetted surface are the stub end, not the flange. That lets the flange be specified separately from the stub end. The flange bore and corner radius must clear the stub end’s outside diameter and lap radius, so stub-end dimensions are confirmed before machining.
Construction
- Flat-faced ring with a radiused corner at the bore
- Bore sized to clear the stub-end OD and lap radius
- Drilling to class pattern or drawing
- No joint made to the pipe at the flange: it is loose on the pipe
- Back-face and OD machined for bolting seat
Available Materials
Available materials
SM-MAT-LAP| Grade | Alloy | Stock and specification | Fit for this flange |
|---|---|---|---|
| UNS C93200 | Leaded tin bronze (SAE 660) | Cast: ASTM B584 / B271 / B505 | General service; easy machining of bore radius |
| UNS C95400 | Aluminium bronze | Cast: ASTM B148 / B271 / B505 | General marine and pump-system flanges |
| UNS C95500 | Nickel aluminium bronze | Cast: ASTM B148 / B271 / B505 | Higher-strength flanges at heavier classes |
| UNS C95800 | Nickel aluminium bronze (NAB) | Cast: ASTM B148 / B271 / B505 | Seawater lines paired with matching stub ends |
| UNS C63000 | Wrought nickel aluminium bronze | Bar, forging, plate: ASTM B150 / B124 / B283 / B171 | Wrought bar or plate-derived rings |
| 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 that control fit are listed below. Please supply the stub-end drawing or standard so the bore diameter and radius are machined to clear it.
Dimensions to confirm
SM-DIM-LAP| Dimension | Basis |
|---|---|
| Bore diameter | Clearance over stub-end OD, per drawing |
| Bore corner radius | Matched to stub-end lap radius |
| Flange OD, thickness | Class table or drawing |
| Bolt circle (PCD) | Class pattern or drawing |
| Bolt holes | Count and diameter per class or drawing |
| Back-face finish | Bolting seat per drawing |
Sizes
Sizes follow the class tables or your drawing. State the NPS, class and stub-end type or drawing in the RFQ.
Pressure Classes
Lap joint flanges are specified by class (commonly Class 150 or Class 300) with the allowable pressure governed by the alloy and the stub end. The stub-end face carries the gasket, so the stub end is part of the pressure design.
Facing Options
The sealing face is on the stub end; the flange back face and the bolting seat are machined flat and square. Where a flange face is required as well, specify FF or RF on the RFQ.
Applications
- Seawater and cooling-water piping
- Systems that are dismantled regularly
- Pipework where bolt-hole alignment is difficult
- Large-diameter lines with matching stub ends
Manufacturing
Rings are turned from cast or wrought stock, with the bore radius formed to drawing, then drilled. The OD and back face are finished flat. Bore radius is checked against a template or gauge where specified.
Inspection and Documentation
Bore diameter and radius, thickness, OD, PCD and hole pattern are checked dimensionally; surfaces are examined visually. Material verification and MTC are supplied where required; other tests only when the purchase order lists them.
Custom Requirements
Non-standard bore radii, special thickness, matching sets of flange and stub end, customer marking and special drilling.
Lap Joint Flanges: common questions
What is a lap joint flange?
A lap joint flange is a ring that rotates freely on a stub end or lapped pipe end. The stub end carries the sealing face, so the flange can turn to line up the bolt holes.
What information is needed to make a lap joint flange?
Send the stub-end drawing or standard, the nominal size and class, and the bolt pattern, so the bore diameter and corner radius are machined to clear the stub end.
Which grades are used for seawater lap joint flanges?
C95800, C95500 and C95400 are the aluminium bronze grades most often specified for seawater piping, depending on the project specification.
Related Information
Have a Drawing or Flange Specification?
Send your drawing, material grade, dimensions and quantity to our technical sales team.