Union
What is a Socket Weld Union?
A Socket Weld Union is a forged pipe fitting used to join two pipes while allowing future disassembly without cutting. It features two socket weld ends and a threaded center nut, enabling the joint to be opened and reassembled easily—ideal for pipelines that require frequent maintenance, cleaning, or inspection.
Socket weld unions are widely used in chemical processing, instrumentation, steam systems, and petrochemical plants, providing high-pressure integrity along with ease of maintenance.
Key Features
- Easy Assembly and Disassembly – Eliminates need for cutting or re-welding.
- Leak-Proof Design – Metal-to-metal sealing under high pressure.
- Reusable – Maintains seal integrity after multiple installations.
- Compact & Durable – Space-saving design suitable for tight layouts.
- Pressure Class Options – Available in Class 3000 and 6000 ratings.
Types of Socket Weld Union
- Flat Seat Union
- Beveled Seat Union
- Male-Female Union
- Hex Union
- Union with Blow-Out Proof Seal
Specifications
Mechanical Properties
Chemical Composition
Equivalent Grades
Weight Chart
Specifications
| Parameter | Details |
|---|---|
| Sizes | ½" to 2" (DN15 to DN50) |
| Pressure Ratings | Class 3000 / 6000 |
| Material Options | A105, A182 F304/316, Duplex, Inconel |
| Standards | ASME B16.11, MSS-SP-83 |
| End Connection | Socket Weld |
| Property | Typical Value |
|---|---|
| Tensile Strength | 485 – 700 MPa |
| Yield Strength | 250 – 450 MPa |
| Elongation | 20% – 30% |
| Temperature Range | -46°C to +600°C |
| Element | Composition (%) |
|---|---|
| Carbon (C) | 0.08 – 0.35 |
| Manganese (Mn) | 0.60 – 1.65 |
| Silicon (Si) | 0.15 – 0.80 |
| Chromium (Cr) | 18.0 – 20.0 (SS only) |
| Nickel (Ni) | 8.0 – 10.5 (SS only) |
| Molybdenum (Mo) | 2.0 – 3.0 (For 316) |
| Phosphorus (P) | ≤ 0.035 |
| Sulfur (S) | ≤ 0.040 |
| Iron (Fe) | Balance |
| Standard | Equivalent Grade |
|---|---|
| ASTM | A105, A182 F304/316, A350 LF2 |
| ASME | B16.11 |
| MSS-SP | SP-83 |
| DIN | 2950, 2975 |
| Union Type | Size (inches) | Weight per 100 pcs (kg) |
|---|---|---|
| Flat Seat Union | ½" | 9.80 |
| Beveled Seat Union | 1" | 13.40 |
| Hex Union | 1½" | 17.20 |
Applications of Socket Weld Union
Construction &
Infrastructure
Automotive & Heavy
Equipment
Manufacturing &
Fabrication
Medical & Laboratory
Equipment
Electrical &
Electronics Assembly
Oil, Gas & Petrochemical
Installations
Do you have questions?
How is a socket weld union different from a coupling?
Unlike a coupling, a union allows pipe disconnection and reconnection without cutting, making it ideal for maintenance access.
Do unions affect system pressure ratings?
No, they’re rated for the same Class 3000 / 6000 pressures as other socket weld fittings.
Can unions be reused after disassembly?
Yes, they’re built for multiple installation cycles without losing sealing strength.
Are socket weld unions suitable for gas lines?
Yes. With proper material and certification, they’re suitable for compressed gases and fluid lines.
