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A forged fitting union is a mechanical joint used to connect two pipes and allow easy disconnection without cutting the pipes. Unlike couplings, which are permanent, unions are designed for applications where frequent dismantling or maintenance is required. They consist of three parts: a male end, a female end, and a nut that pulls the ends together to form a tight, leak-proof seal.
Forged unions are made using the hot forging process, ensuring high strength, excellent pressure handling, and long service life. They are available in socket weld and threaded (NPT/BSP) types, and typically made from carbon steel, stainless steel, or alloy steel.
Specifications
| Specification | Details |
|---|---|
| Type | Forged Union (Three-piece: Male, Female, Nut) |
| Connection Types | Threaded (NPT/BSP), Socket Weld (SW) |
| Pressure Ratings | Class 2000 (Threaded), Class 3000 & 6000 (Socket Weld) |
| Size Range | 1/8” to 4” NPS |
| Design Standards | ASME B16.11, MSS SP-83, BS 3799 |
| Forming Process | Hot Forged and Machined |
| Temperature Range | Varies by material (suitable for high-temperature applications) |
| Material Grades | Carbon Steel (ASTM A105), Stainless Steel (ASTM A182 F304, F316), Alloy Steel (ASTM A182 F5, F9) |
| Sealing | Metal-to-metal seating or gasketed, depending on design |
| Applications | Oil & Gas, Power Generation, Petrochemical, Water Treatment, Chemical Plants |
Grades
| Material Type | Grade | Description |
|---|---|---|
| Carbon Steel | ASTM A105 | General use, good strength, suitable for high-pressure applications. |
| Stainless Steel | ASTM A182 F304 | Good corrosion resistance, widely used in chemical and food industries. |
| ASTM A182 F316 | Superior corrosion resistance, ideal for marine and harsh chemical environments. | |
| Alloy Steel | ASTM A182 F5 | Chromium alloy, suitable for high-temperature and pressure services. |
| ASTM A182 F9 | Higher performance alloy for boilers and high-temp piping. | |
| Duplex Steel | ASTM A182 F51 | High strength and excellent resistance to stress corrosion and pitting. |
| Low Temp Carbon | ASTM A350 LF2 | Used in low-temperature applications such as cryogenic systems. |
Dimenstion Chart
| Size (NPS) | Threaded Union (NPT/BSP) - Length (inches) | Socket Weld Union - Length (inches) | Outside Diameter (inches) | Pressure Class (Class) |
|---|---|---|---|---|
| 1/8" | 1.00 | 1.00 | 0.405 | 2000, 3000, 6000 |
| 1/4" | 1.10 | 1.10 | 0.540 | 2000, 3000, 6000 |
| 3/8" | 1.20 | 1.20 | 0.675 | 2000, 3000, 6000 |
| 1/2" | 1.40 | 1.40 | 0.840 | 2000, 3000, 6000 |
| 3/4" | 1.60 | 1.60 | 1.050 | 2000, 3000, 6000 |
| 1" | 1.80 | 1.80 | 1.315 | 2000, 3000, 6000 |
| 1 1/4" | 2.00 | 2.00 | 1.660 | 2000, 3000, 6000 |
| 1 1/2" | 2.20 | 2.20 | 1.900 | 2000, 3000, 6000 |
| 2" | 2.50 | 2.50 | 2.375 | 2000, 3000, 6000 |
| 2 1/2" | 3.00 | 3.00 | 2.875 | 2000, 3000, 6000 |
| 3" | 3.50 | 3.50 | 3.500 | 2000, 3000, 6000 |
| 4" | 4.00 | 4.00 | 4.500 | 2000, 3000, 6000 |