Threaded Union
What is a Threaded Union?
A Threaded Union is a forged pipe fitting that connects two pipes using threaded ends while allowing easy future disassembly without cutting or welding. It consists of three parts: two threaded ends and a central nut that holds the connection together, providing easy access for maintenance, cleaning, or replacement.
Threaded unions are widely used in high-pressure piping systems that require frequent servicing, such as chemical plants, gas lines, pump systems, and HVAC pipelines.
Key Features
- Reusable Design – Easy to assemble, disassemble, and service.
- Secure Seal – Threaded joint with central nut ensures tight connection.
- Thread Compatibility – Fits BSP, BSPT, NPT, and ISO standards.
- Versatile Use – Works with both liquid and gas applications.
- Seal Options – Available in flat seat, beveled seat, and metal-to-metal types.
Types of Threaded Unions
- Flat Seat Union
- Beveled Seat Union
- Hex Union
- Male-Female Thread Union
Specifications
Mechanical Properties
Chemical Composition
Equivalent Grades
Weight Chart
Specifications
| Parameter | Details |
|---|---|
| Sizes | ⅛" to 4" (DN6 – DN100) |
| Thread Standards | NPT, BSP, BSPT, ISO Metric |
| Pressure Ratings | Class 2000 / 3000 / 6000 |
| Material Options | Carbon Steel, SS 304 / 316, Alloy Steel |
| Standards | ASME B16.11, MSS-SP-83, BS 3799 |
| Manufacturing | Forged, Precision Machined |
| Property | Typical Value |
|---|---|
| Tensile Strength | 485 – 700 MPa |
| Yield Strength | 250 – 450 MPa |
| Elongation | 20% – 30% |
| Hardness | 125 – 250 HB |
| 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 (Stainless Steel) |
| Nickel (Ni) | 8.0 – 10.5 (SS 304/316) |
| Molybdenum (Mo) | 2.0 – 3.0 (for F316 only) |
| Phosphorus (P) | ≤ 0.035 |
| Sulfur (S) | ≤ 0.040 |
| Iron (Fe) | Balance |
| Standard | Equivalent Grade |
|---|---|
| ASTM | A105 (CS), A182 F304/F316 (SS) |
| ASME | B16.11 |
| MSS-SP | SP-83 |
| BS | 3799 |
| 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 Threaded Union
Construction &
Infrastructure
Automotive & Heavy
Equipment
Manufacturing &
Fabrication
Medical & Laboratory
Equipment
Electrical &
Electronics Assembly
Oil, Gas & Petrochemical
Installations
Do you have questions?
What is the benefit of using a threaded union over a coupling?
A union allows disassembly without cutting the pipe, while a coupling is permanent once installed.
Are unions pressure-rated like other fittings?
Yes, we offer Class 2000 / 3000 / 6000-rated unions for high-performance applications.
Can threaded unions be used for gas lines?
Absolutely. With proper material and sealing, unions are safe for natural gas, air, and fuel lines.
What materials are available for corrosion resistance?
Unions are available in SS 304, SS 316, Duplex, and alloy steels for harsh environments.
