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Using a separate stub end and a loose backing ring, carbon steel lap joint flanges are designed to enable easier alignment during pipe installation. The flange is usually made according to ASTM A105 standards, and it is available in Class 150 and Class 300 versions, as per ASME B16.5. The backing ring is not welded to the pipe like the weld neck and slip-on flanges; instead, it sits on top of the stub end. Since the ring can rotate, it helps line up the bolt holes without having to rotate the entire pipe. The stub end is welded onto the pipe and also serves as the sealing surface for the gasket. The backing ring, on the other hand, provides the clamping pressure needed to hold the joint in place. Solitaire Overseas manufactures and supplies carbon steel lap joint flanges with full mill test certification, and hydrostatic testing or third-party inspection can be arranged on request.
| Parameter | Specification |
|---|---|
|
Standard |
ASTM A105, ASME B16.5, MSS SP44 |
|
Size Range |
NPS 1/2 inch to 24 inch |
|
Pressure Class |
Class 150, Class 300 |
|
Facing |
Raised Face or Flat Face |
|
Construction |
Forged backing flange, used with a separately welded stub end |
|
Testing |
Hydrostatic test, third party inspection on request |
|
Certification |
Mill Test Certificate EN 10204 3.1, 3.2 on request |
| Grade | C max | Mn | P max | S max | Si |
|---|---|---|---|---|---|
|
A105 |
0.35 |
0.60 to 1.05 |
0.035 |
0.040 |
0.10 to 0.35 |
| Grade | Tensile Strength min | Yield Strength min | Elongation min (%) |
|---|---|---|---|
|
A105 |
485 MPa (70 ksi) |
250 MPa (36 ksi) |
22 |
| Class | Approx. Rating at Ambient (psi) | Approx. Rating at Ambient (bar) | Approx. Rating at 400°F (psi) | Approx. Rating at 750°F (psi) |
|---|---|---|---|---|
|
150 |
285 |
19.6 |
200 |
95 |
|
300 |
740 |
51.0 |
635 |
505 |
| NPS | Outside Diameter (mm) | Bolt Circle (mm) | Number of Bolt Holes | Bolt Hole Diameter (mm) | Flange Thickness (mm) |
|---|---|---|---|---|---|
|
1/2" |
89 |
60 |
4 |
16 |
11 |
|
1" |
108 |
79 |
4 |
16 |
14 |
|
2" |
152 |
121 |
4 |
19 |
19 |
|
4" |
229 |
190 |
8 |
19 |
24 |
|
6" |
279 |
241 |
8 |
22 |
25 |
|
8" |
343 |
298 |
8 |
22 |
29 |
|
12" |
483 |
432 |
12 |
25 |
32 |
A: It is a two piece flange connection made up of a loose backing flange and a separate stub end. The stub end is welded to the pipe and forms the seal face, while the backing flange rotates freely and simply clamps the joint together with bolts.
A: A weld neck flange is welded directly to the pipe and its bolt holes are fixed once installed. A lap joint flange is not welded at all, it slides over the stub end and rotates freely, which makes bolt hole alignment much faster and lets the joint be dismantled without cutting the pipe.
A: Solitaire Overseas supplies carbon steel lap joint flanges in Class 150 and Class 300. For Class 600 and above, a weld neck flange from our Carbon Steel High Pressure Flanges range is the correct specification.
A: ASTM A105 is the standard grade for lap joint flanges. A694 high-yield subgrades are supplied for other flange types but are not typically specified for lap joint flanges, since this type is used for lower-pressure, easily dismantled service rather than high-pressure duty.
A: Choose a lap joint flange when the joint needs to be taken apart often, when bolt hole alignment is difficult, or when the stub end needs to be a different material from the flange. Choose a slip on flange for general piping that stays assembled for the life of the system.
Contact Solitaire Overseas for expert guidance and the right flange solution for your application.
Related products:Carbon Steel Flanges, Carbon Steel Pipe Flanges, Carbon Steel High Pressure Flanges, Carbon Steel Plate Flanges, and Carbon Steel Stub End.