Loose lap-joint flanges designed for use with compatible lap-joint stub ends to create detachable and easily aligned flanged connections. Suitable for piping systems where frequent dismantling, inspection or flange rotation is beneficial.
A lap-joint flange is a loose flange designed to be used together with a lap-joint stub end. Unlike a weld neck or slip-on flange, the lap-joint flange is not welded directly to the pipe.
The flange fits over the stub end and can rotate around it. This allows the bolt holes to be easily aligned during assembly and can simplify dismantling and maintenance of the piping joint.
Lap-joint flange assemblies are commonly used in piping systems where frequent disassembly is required or where improved bolt-hole alignment is beneficial.
Rhevon can source lap-joint flanges in different nominal sizes, pressure classes, facing configurations and material grades according to project requirements.
Loose flange supplied for use with a compatible lap-joint stub end.
A lap-joint flange assembly consists of a loose flange, matching stub end, gasket and bolting. Each component must be selected to suit the piping specification.
The lap-joint flange is a loose component that fits over the stub end. It can rotate around the stub end, allowing easier orientation and alignment of the bolt holes during assembly.
The stub end is butt-welded to the pipe and provides the gasket seating surface. The loose lap-joint flange fits over the stub end and is used for bolting.
The flange and stub end are assembled with the specified gasket and bolting to form the complete lap-joint connection.
Flange material should be selected according to operating temperature, pressure, process media, corrosion requirements and the applicable piping specification.
| Material | Typical Specification | Typical Application |
|---|---|---|
| Carbon Steel | ASTM A105 | General Process · Oil & Gas |
| Low-Temperature Carbon Steel | ASTM A350 LF2 | Low-Temperature Service |
| Stainless Steel 304 | ASTM A182 F304 | Corrosive / Process Service |
| Stainless Steel 316 | ASTM A182 F316 | Corrosive / Process Service |
Class 150 and Class 300 lap joint backing-flange dimensions, bores and drilling.
Swipe horizontally to view every column.
| NPS | O(mm) | CLJmin(mm) | P(mm) | n × h(mm) | dbolt(mm) | W(mm) | Y3LJ(mm) | B3LJ(mm) | rLJ(mm) |
|---|---|---|---|---|---|---|---|---|---|
| ½ | 88.90 | 11.18 | 60.45 | 4 × 15.75 | 12.70 | 30.23 | 15.75 | 22.86 | 3.05 |
| ¾ | 98.55 | 12.70 | 69.85 | 4 × 15.75 | 12.70 | 38.10 | 15.75 | 28.19 | 3.05 |
| 1 | 107.95 | 14.22 | 79.25 | 4 × 15.75 | 12.70 | 49.28 | 17.53 | 35.05 | 3.05 |
| 1 ¼ | 117.35 | 15.75 | 88.90 | 4 × 15.75 | 12.70 | 58.67 | 20.57 | 43.69 | 4.83 |
| 1 ½ | 127.00 | 17.53 | 98.55 | 4 × 15.75 | 12.70 | 65.02 | 22.35 | 50.04 | 6.35 |
| 2 | 152.40 | 19.05 | 120.65 | 4 × 19.05 | 15.88 | 77.72 | 25.40 | 62.48 | 7.87 |
| 2 ½ | 177.80 | 22.35 | 139.70 | 4 × 19.05 | 15.88 | 90.42 | 28.45 | 75.44 | 7.87 |
| 3 | 190.50 | 23.88 | 152.40 | 4 × 19.05 | 15.88 | 107.95 | 30.23 | 91.44 | 9.65 |
| 3 ½ | 215.90 | 23.88 | 177.80 | 8 × 19.05 | 15.88 | 122.17 | 31.75 | 104.14 | 9.65 |
| 4 | 228.60 | 23.88 | 190.50 | 8 × 19.05 | 15.88 | 134.87 | 33.27 | 116.84 | 11.18 |
| 5 | 254.00 | 23.88 | 215.90 | 8 × 22.35 | 19.05 | 163.58 | 36.58 | 144.53 | 11.18 |
| 6 | 279.40 | 25.40 | 241.30 | 8 × 22.35 | 19.05 | 192.02 | 39.62 | 171.45 | 12.70 |
| 8 | 342.90 | 28.45 | 298.45 | 8 × 22.35 | 19.05 | 246.13 | 44.45 | 222.25 | 12.70 |
Swipe horizontally to view every column.
| NPS | O(mm) | CLJmin(mm) | P(mm) | n × h(mm) | dbolt(mm) | W(mm) | Y3LJ(mm) | B3LJ(mm) | rLJ(mm) |
|---|---|---|---|---|---|---|---|---|---|
| ½ | 95.25 | 14.22 | 66.55 | 4 × 16.00 | 12.70 | 38.10 | 22.35 | 22.86 | 3.05 |
| ¾ | 117.35 | 15.75 | 82.55 | 4 × 19.05 | 15.88 | 47.75 | 25.40 | 28.19 | 3.05 |
| 1 | 123.95 | 17.53 | 88.90 | 4 × 19.05 | 15.88 | 53.85 | 26.92 | 35.05 | 3.05 |
| 1 ¼ | 133.35 | 19.05 | 98.55 | 4 × 19.05 | 15.88 | 63.50 | 26.92 | 43.69 | 4.83 |
| 1 ½ | 155.45 | 20.57 | 114.30 | 4 × 22.35 | 19.05 | 69.85 | 30.23 | 50.04 | 6.35 |
| 2 | 165.10 | 22.35 | 127.00 | 8 × 19.05 | 15.88 | 84.07 | 33.27 | 62.48 | 7.87 |
| 2 ½ | 190.50 | 25.40 | 149.35 | 8 × 22.35 | 19.05 | 100.08 | 38.10 | 75.44 | 7.87 |
| 3 | 209.55 | 28.45 | 168.15 | 8 × 22.35 | 19.05 | 117.35 | 42.93 | 91.44 | 9.65 |
| 3 ½ | 228.60 | 30.23 | 184.15 | 8 × 22.35 | 19.05 | 133.35 | 44.45 | 104.14 | 9.65 |
| 4 | 254.00 | 31.75 | 200.15 | 8 × 22.35 | 19.05 | 146.05 | 47.75 | 116.84 | 11.18 |
| 5 | 279.40 | 35.05 | 234.95 | 8 × 22.35 | 19.05 | 177.80 | 50.80 | 144.53 | 11.18 |
| 6 | 317.50 | 36.58 | 269.75 | 12 × 22.35 | 19.05 | 206.25 | 52.32 | 171.45 | 12.70 |
| 8 | 381.00 | 41.15 | 330.20 | 12 × 25.40 | 22.23 | 260.35 | 61.98 | 222.25 | 12.70 |
Lap joint flanges back a matching stub end and do not provide the sealing face themselves.
B3 and r must clear the selected stub end. Confirm the supplier's lap-joint length pattern.
Flange requirements can be reviewed against the applicable material specification, dimensional standard, pressure class, facing and purchase order requirements before supply.
Common questions about lap-joint flange specifications, stub ends, pressure classes, materials and applications.
A lap-joint flange is a loose flange designed to be used with a matching lap-joint stub end. Unlike a slip-on or weld neck flange, it is not welded directly to the pipe.
The flange is loose and fits over the stub end, allowing it to rotate around the pipe axis. This makes bolt-hole alignment easier during assembly and can simplify maintenance and dismantling.
Yes. A lap-joint flange is normally used together with a compatible lap-joint stub end. The stub end is welded to the pipe, while the loose flange provides the bolting interface.
Provide the NPS, pressure class, facing type, material grade, quantity and applicable flange standard. If the stub end is also required, provide its material, schedule, pattern and applicable specification.
Yes. Rhevon can source the lap-joint flange together with the matching stub end and, where required, compatible gaskets, studs, nuts and washers as part of a mixed piping requirement.
Share the NPS, pressure class, facing, material, quantity and applicable specification. Include the matching stub-end requirement if required.
