In modern industrial piping design, lap joint flanges are used in a wide range of industries due to their superior strength, durability and flexibility. These characteristics make them ideally suited for a wide range of applications, from piping systems to structural assemblies, especially where reliable, hermetically sealed connections are required. The design of lap joint flanges allows for easy assembly and disassembly, which is especially important in industries where frequent maintenance, repairs and inspections are required.
ZIZI specializes in the generation of flanges in various materials and types, in strict compliance with international standards (e.g. EN 1092-1, ASME B16.5, etc.), and provides high-quality piping connection solutions to customers all over the world.
What Is Lap Joint Flange (LAPJ)？
Lap joint Flange is a type of flange used for pipe connection, which usually consists of two parts: the flange and the pipe connecting part are connected by a loose connector (such as a bolt, nut, or sleeve) instead of being fixed directly. This design allows the connecting part of the lap joint fange to be easily removed and replaced without dismantling the entire pipe or system.
They’re used in a two-part assembly consisting of a Stub End which is butt welded to the pipe and a lap joint flange which is slid onto the pipe before welding the Stub End.
Lap Joint Flange Application Areas：
1. Chemical Processing Plants
Lap joint flanges enables reduced downtime and increased productivity when parts need to be cleaned, inspected, or replaced.
2. Oil and Gas Industry
Piping systems on offshore platforms require regular maintenance and inspection,lap joint flanges making repairs and replacements more efficient.
3. Marine and Shipbuilding
During the shipbuilding process, lap joint flanges is used to connect the internal piping of the hull to external equipment.
4. Water Treatment Industry
Lap joint flangesDisassembly and easy replacement make regular cleaning and maintenance work more efficient.
5. Heating, ventilation, and air conditioning (HVAC) systems
In systems that require regular cleaning and inspection, the easy disassembly feature of lap joint flanges makes it convenient to perform these tasks.
Lap Joint flange Material Selection：
| Carbon Steel | ASTM A105/A105N |
| low temperature steel | ASTM A350 LF2/LF3 |
| Pipeline steel | ASTM A694 F42/46/52/56/65/70 |
| Alloy steel | ASTM A182 F5/F9/F11/F12/F22/F91/F92 |
| Stainless steel | ASTM A182 F304/304L/304H、F316/316L、F317、F310S、F321、F347、F904L |
| Duplex stainless steel | ASTM A182 F51/53/55/60 |
ASME B16.5 LAPJ Flange Dimension:
Lap joint flange is divided into seven grades: 150#, 300#, 400#, 600#, 900#, 1500#, 2500#.
Class 150 Lap Joint Flange:
| Nominal Pipe Size | A | B | C | D | R | F | H | I | J | Weight | |
| inch | mm | mm | mm | mm | mm | mm | mm | Holes | mm | mm | kg / piece |
| 1/2 | 21.30 | 88.90 | 22.90 | 11.20 | 15.70 | 3.000 | 30.20 | 4 | 15.70 | 60.45 | 0.38 |
| 3/4 | 26.70 | 98.60 | 28.2 | 12.70 | 15.70 | 3.000 | 38.10 | 4 | 15.70 | 69.85 | 0.55 |
| 1 | 33.40 | 108.0 | 35. 10 | 14.20 | 17.50 | 3.000 | 49.30 | 4 | 15.70 | 79.25 | 0.76 |
| 11/4 | 42.20 | 117.3 | 43.70 | 15.70 | 20.60 | 4.800 | 58.70 | 4 | 15.70 | 88.90 | 1.01 |
| 11/2 | 48.30 | 127.0 | 50.00 | 17.50 | 22.40 | 6.400 | 65.00 | 4 | 15.70 | 98.60 | 1.30 |
| 2 | 60.30 | 152.4 | 62.50 | 19. 10 | 25.40 | 7.900 | 77.70 | 4 | 19.10 | 120.7 | 2.03 |
| 21/2 | 73.00 | 177.8 | 75.40 | 22.40 | 28.40 | 7.900 | 90.40 | 4 | 19.10 | 139.7 | 3.25 |
| 3 | 88.90 | 190.5 | 91.40 | 23.90 | 30.20 | 9.700 | 108.0 | 4 | 19.10 | 152.4 | 3.81 |
| 31/2 | 101.6 | 215.9 | 104.1 | 23.90 | 31.75 | 9.700 | 122.2 | 8 | 19.10 | 177.8 | 4.76 |
| 4 | 114.3 | 228.6 | 116.8 | 23.90 | 33.30 | 11.20 | 134.9 | 8 | 19.10 | 190.5 | 5.25 |
| 5 | 141.3 | 254.0 | 114.5 | 23.90 | 36.60 | 11.20 | 163.6 | 8 | 22.40 | 215.9 | 6.02 |
| 6 | 168.3 | 279.4 | 171.5 | 25.40 | 39.6 | 12.70 | 192.0 | 8 | 22.40 | 241.3 | 7.40 |
| 8 | 219. 1 | 342.9 | 222.3 | 28.40 | 44.50 | 12.70 | 246. 1 | 8 | 22.40 | 298.5 | 12.1 |
| 10 | 273.0 | 406.4 | 277.4 | 30.20 | 49.30 | 12.70 | 304.8 | 12 | 25.40 | 362.0 | 16.4 |
| 12 | 323.8 | 482.6 | 328.2 | 31.75 | 55.60 | 12.70 | 365.3 | 12 | 25.40 | 431.8 | 26.1 |
| 14 | 355.6 | 533.4 | 360.2 | 35. 10 | 79.25 | 12.70 | 400. 1 | 12 | 28.40 | 476.3 | 34.5 |
| 16 | 406.4 | 596.9 | 411.2 | 36.60 | 87.40 | 12.70 | 457.2 | 16 | 28.4 | 539.8 | 44.6 |
| 18 | 457.2 | 635.0 | 462.3 | 39.60 | 96.80 | 12.70 | 505.0 | 16 | 31.75 | 577.9 | 48.7 |
| 20 | 508.0 | 698.5 | 514.4 | 42.90 | 103.1 | 12.70 | 558.8 | 20 | 31.75 | 635.0 | 61.6 |
| 24 | 609.6 | 812.8 | 616.0 | 47.80 | 111.3 | 12.70 | 663.4 | 20 | 35.10 | 749.3 | 86.6 |
Advantages of Lap Joint Flange:
✅Lower maintenance costs: reduces downtime and maintenance costs.
✅Good sealing: Provide solid sealing performance to avoid leakage.
✅Resistant to high pressure and high temperature: Suitable for high pressure and high temperature working environment.
✅Highly adjustable: suitable for parts of the piping system that require frequent adjustment.
Frequently Asked Questions (FAQs)：
What Are the Sealing Surfaces of Lap joint flanges?
Flat Face (FF)
Raised Face (RF)
Ring Type Joint (RTJ)
Tongue and Groove (T&G)
Male and Female (M&F)
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