Lap Joint Flange
What is Lap Joint Flange?
A Lap Joint Flange is a type of pipe flange comprising two parts: a flat, circular disc (the “stub end”) and a ring or hub (the “lap joint”). The stub end is typically welded to the pipe or fitting, while the lap joint rotates freely around it. This design facilitates easy alignment during assembly.
These flanges are commonly used in piping systems where frequent dismantling and reassembly are necessary, such as those handling corrosive or abrasive fluids or in systems with thermal expansion considerations. They offer versatility, allowing for adjustments and disassembly without disturbing the entire piping system.
Lap joint flanges come in various materials, sizes, and facings to suit different applications and operating conditions. They are available with flat face (FF), raised face (RF), or ring type joint (RTJ) facings, depending on sealing requirements.
Features of Lap Joint Flange:
- Two-Piece Design:
- Consists of a flange and a stub end.
- The flange is free to rotate around the stub end, allowing for easy bolt alignment during assembly.
- Material Compatibility:
- The flange itself can be made from a lower-grade material, as it does not come into contact with the fluid. The stub end, which makes the connection, is made from a material compatible with the piping material.
- Easy Alignment:
- The rotating feature ensures that bolt holes can be aligned without the need for precise adjustments to the piping.
- Cost-Efficiency:
- Reduces cost by enabling the use of economical materials for the flange when high-grade materials are used only for the stub end.
- Low-Pressure Applications:
- Primarily used in low-pressure applications and systems that do not experience extreme mechanical stress.
- Ease of Maintenance:
- Simplifies disassembly and reassembly, making it ideal for applications requiring frequent cleaning or inspection.
Lap Joint Flange Dimensions Class 150
| Size in Inch | Size in mm | Outer Diameter | Flange Thick. | Lapped Thick. | Lapped ID | PCD | Lapped Thick. | Lapped Radius | No of Bolts | Bolt Size UNC | Machine Bolt Length | RF Stud Length | Hole Size | ISO Stud Size | Weight in kg |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| A | B | C | D | E | G | ||||||||||
| 1/2 | 15 | 90 | 30 | 16 | 22.9 | 60.3 | 11.2 | 3 | 4 | 1/2 | 50 | 55 | 5/8 | M14 | 0.8 |
| 3/4 | 20 | 100 | 38 | 16 | 28.2 | 69.9 | 12.7 | 3 | 4 | 1/2 | 50 | 65 | 5/8 | M14 | 0.9 |
| 1 | 25 | 110 | 49 | 17 | 34.9 | 79.4 | 14.3 | 3 | 4 | 1/2 | 55 | 65 | 5/8 | M14 | 0.9 |
| 1 1/4 | 32 | 115 | 59 | 21 | 43.7 | 88.9 | 15.9 | 5 | 4 | 1/2 | 55 | 70 | 5/8 | M14 | 1.4 |
| 1 1/2 | 40 | 125 | 65 | 22 | 50 | 98.4 | 17.5 | 6 | 4 | 1/2 | 65 | 70 | 5/8 | M14 | 1.4 |
| 2 | 50 | 150 | 78 | 25 | 62.5 | 120.7 | 19.1 | 8 | 4 | 5/8 | 70 | 85 | 3/4 | M16 | 2.3 |
| 2 1/2 | 65 | 180 | 90 | 29 | 75.4 | 139.7 | 22.3 | 8 | 4 | 5/8 | 75 | 90 | 3/4 | M16 | 3.2 |
| 3 | 80 | 190 | 108 | 30 | 91.4 | 152.4 | 23.9 | 10 | 4 | 5/8 | 75 | 90 | 3/4 | M16 | 3.7 |
| 3 1/2 | 90 | 215 | 122 | 32 | 104.1 | 177.8 | 23.9 | 11 | 8 | 5/8 | 75 | 90 | 3/4 | M16 | 5 |
| 4 | 100 | 230 | 135 | 33 | 116.8 | 190.5 | 23.9 | 11 | 8 | 5/8 | 75 | 90 | 3/4 | M16 | 5.9 |
| 5 | 125 | 255 | 164 | 36 | 144.4 | 215.9 | 23.9 | 11 | 8 | 3/4 | 85 | 95 | 7/8 | M20 | 6.8 |
| 6 | 150 | 280 | 192 | 40 | 171.4 | 241.3 | 25.4 | 13 | 8 | 3/4 | 85 | 100 | 7/8 | M20 | 8.6 |
| 8 | 200 | 345 | 246 | 44 | 222.2 | 298.5 | 28.6 | 13 | 8 | 3/4 | 90 | 110 | 7/8 | M20 | 13.7 |
| 10 | 250 | 405 | 305 | 49 | 277.4 | 362 | 30.2 | 13 | 12 | 7/8 | 100 | 115 | 1 | M24 | 19.5 |
| 12 | 300 | 485 | 365 | 56 | 328.2 | 431.8 | 31.8 | 13 | 12 | 7/8 | 100 | 120 | 1 | M24 | 29 |
| 14 | 350 | 535 | 400 | 79 | 360.2 | 476.3 | 35 | 13 | 12 | 1 | 115 | 135 | 1 1/8 | M27 | 41 |
| 16 | 400 | 595 | 457 | 87 | 411.2 | 539.8 | 36.6 | 13 | 16 | 1 | 115 | 135 | 1 1/8 | M27 | 54 |
| 18 | 450 | 635 | 505 | 97 | 462.3 | 577.9 | 39.7 | 13 | 16 | 1 1/8 | 125 | 145 | 1 1/4 | M30 | 59 |
| 20 | 500 | 700 | 559 | 103 | 514.4 | 635 | 42.9 | 13 | 20 | 1 1/8 | 140 | 160 | 1 1/4 | M30 | 75 |
| 24 | 600 | 815 | 663 | 111 | 616 | 749.3 | 47.9 | 13 | 20 | 1 1/4 | 150 | 170 | 1 3/8 | M33 | 100 |
Lap Joint Flange Weight Chart
| Flange Size (inches) | Class 150 (lbs) | Class 300 (lbs) | Class 400 (lbs) | Class 600 (lbs) | Class 900 (lbs) | Class 1500 (lbs) | Class 2500 (lbs) |
|---|---|---|---|---|---|---|---|
| ½ | 1 | 2 | 2 | 2 | 6 | 6 | 7 |
| ¾ | 2 | 3 | 3 | 3 | 6 | 6 | 8 |
| 1 | 2 | 3 | 3.5 | 4 | 7.5 | 8 | 12 |
| 1¼ | 3 | 4.5 | 4.5 | 5 | 10 | 10 | 17 |
| 1½ | 3 | 6.5 | 6.5 | 7 | 14 | 14 | 24 |
| 2 | 5 | 7 | 8 | 9 | 21 | 25 | 37 |
| 2½ | 8 | 10 | 11 | 12 | 25 | 35 | 53 |
| 3 | 9 | 14.5 | 14 | 15 | 29 | 47 | 80 |
| 3½ | 11 | 17 | 20 | 20 | 51 | 75 | 122 |
| 4 | 13 | 24 | 25 | 36 | 81 | 140 | 204 |
| 5 | 15 | 28 | 29 | 63 | 105 | 170 | 314 |
| 6 | 19 | 39 | 42 | 78 | 190 | 286 | 471 |
| 8 | 30 | 58 | 64 | 112 | 277 | 485 | 897 |
| 10 | 43 | 91 | 110 | 195 | 371 | 749 | 1262 |
| 12 | 64 | 140 | 152 | 240 | 415 | 890 | – |
| 14 | 105 | 190 | 210 | 290 | 488 | 1250 | – |
| 16 | 140 | 234 | 280 | 400 | 670 | 1475 | – |
| 18 | 160 | 305 | 345 | 469 | 868 | 1775 | – |
| 20 | 195 | 375 | 420 | 604 | 1659 | 2825 | – |
| 22 | 245 | 435 | 455 | 670 | – | – | – |
| 24 | 275 | 550 | 615 | 866 | – | – | – |
Types of Lap Joint Flanges
- Standard Lap Joint Flange
- Used with a stub end
- Allows rotational alignment of bolt holes
- Common in low-pressure applications
- Stub End Lap Joint Flange
- Stub end fits inside the flange
- Available in different types based on the length and shape of the stub end:
- Type A: Used with standard lap joint flanges
- Type B: Used with slip-on flanges
- Type C: Shorter stub end for light-duty applications
- Raised Face Lap Joint Flange
- Has a raised face for better sealing
- Used in applications where improved gasket compression is required
- Flat Face Lap Joint Flange
- Designed for systems with flat face stub ends
- Used where flange faces need to be in full contact
- Ring-Type Joint (RTJ) Lap Joint Flange
- Features a grooved face for metal-to-metal sealing
- Suitable for high-pressure applications
Grades of Lap Joint Flanges
1. Carbon Steel Lap Joint Flanges
- ASTM A105 (Forged Carbon Steel)
- ASTM A350 LF2 (Low-Temperature Carbon Steel)
- ASTM A694 (High-Strength Carbon Steel)
2. Stainless Steel Lap Joint Flanges
- ASTM A182 F304 / 304L
- ASTM A182 F316 / 316L
- ASTM A182 F321
- ASTM A182 F347
- ASTM A182 F904L
3. Alloy Steel Lap Joint Flanges
- ASTM A182 F11
- ASTM A182 F22
- ASTM A182 F5
- ASTM A182 F9
- ASTM A182 F91
4. Duplex & Super Duplex Steel Lap Joint Flanges
- ASTM A182 F51 / F60 (Duplex 2205)
- ASTM A182 F53 / F55 (Super Duplex 2507)
5. Nickel Alloy Lap Joint Flanges
- ASTM B564 UNS N06600 (Inconel 600)
- ASTM B564 UNS N06625 (Inconel 625)
- ASTM B564 UNS N08825 (Incoloy 825)
- ASTM B564 UNS N10276 (Hastelloy C276)
- ASTM B564 UNS N04400 (Monel 400)
6. Titanium Lap Joint Flanges
- ASTM B381 Gr. 2
- ASTM B381 Gr. 5
Advantages of Lap Joint Flanges
- Easy alignment during installation.
- Reusability, as the flange does not come into direct contact with the fluid.
- Reduced material costs, as the flange can be made from a less expensive material compared to the stub end.
Pressure Ratings
- Class 150 Lap Joint Flange (PN 20)
- Class 300 Lap Joint Flange (PN 50)
- Class 400 Lap Joint Flange (PN 64)
- Class 600 Lap Joint Flange (PN 100)
- Class 900 Lap Joint Flange (PN 150)
- Class 1500 Lap Joint Flange (PN 250)
- Class 2500 Lap Joint Flange (PN 420)
Applications:
- Petrochemical and chemical processing industries.
- Food and beverage processing plants.
- Water treatment facilities.
- Pharmaceutical manufacturing.
- Systems requiring easy dismantling, such as temporary piping layouts or inspection points.
