Investment Casting
Union
What is a Union?
A Union is a precision-made pipe fitting manufactured using the investment casting process. It is designed to connect two pipes or components and allows for easy disassembly without disturbing the rest of the system. Unions are ideal for installations that require frequent maintenance, inspection, or replacement.
Unlike permanent joints, unions provide a reusable, leak-proof connection, making them highly suitable for instrumentation systems, food-grade units, chemical pipelines, and marine environments where hygiene, accessibility, and precision matter.
Key Features
Leak-Proof
Jointing
Durable
Construction
Easy Installation
& Removal
Wide
Compatibility
Corrosion
Resistant
Specifications
| Specification Category | Parameter / Feature | Details / Options |
|---|---|---|
| Size Range | Nominal Size | ½” to 4″ (custom sizes available) |
| Pressure Ratings | ANSI / ASME Class | Class 150, 300, 600, 900, 1500, 2500 |
| PN Ratings | PN6, PN10, PN16, PN25, PN40, PN64 | |
| Product Types | Investment Casting Fitting | Union (Full, Reducing) |
| Material Options | Carbon Steel | ASTM A216 WCB |
| Stainless Steel | ASTM A351 CF8 / CF8M / CF3 / CF3M | |
| Alloy Steel | ASTM A351 CK3MCuN, CK20MCuN | |
| Nickel Alloy | Inconel, Monel | |
| Standards & Certifications | ASTM | ASTM A351, ASTM A182 |
| ASME / ANSI | ASME B16.11 | |
| MSS | MSS SP-79, MSS SP-83 | |
| European Standards | EN 10241, EN 10226 | |
| Certifications | ISO 9001, PED 2014/68/EU, NACE MR0175, CE Marked | |
| Design Features | Union Type | Full Union, Reducing Union |
| Wall Thickness | As per ASTM / ASME standards, schedule 40, 80 | |
| End Connections | Female / Male Threaded, Flanged, Socket Weld | |
| Pressure Class | 2000#, 3000#, 6000#, 9000# | |
| Tolerance | Thread Tolerance | As per ASME B1.20.1 / ISO 7-1 |
| Coating & Surface Finish | Anti-Corrosion Coating | Passivation, Nickel Plating |
| Surface Finish | Mill Finish, Polished, Bead Blasted | |
| Testing & Inspection | Pressure Testing | Hydrostatic, Pneumatic |
| Non-Destructive Testing | Dye Penetrant (DPT), Magnetic Particle (MPI) | |
| Destructive Testing | Tensile, Hardness, Torque Test |
Dimensions
| Fitting Type | Nominal Size (NPS) | Outside Diameter (OD) | Union Face to End (F) | Overall Length (L) | Weight per Piece |
|---|---|---|---|---|---|
| Union (Full) | ½” | 21.3 mm | 15 mm | 55 mm | 200g |
| Union (Full) | ¾” | 26.7 mm | 18 mm | 65 mm | 280g |
| Union (Full) | 1″ | 33.4 mm | 20 mm | 75 mm | 360g |
| Union (Full) | 1½” | 48.3 mm | 25 mm | 95 mm | 580g |
| Union (Full) | 2″ | 60.3 mm | 28 mm | 110 mm | 780g |
| Union (Full) | 3″ | 88.9 mm | 35 mm | 140 mm | 1.2kg |
| Union (Full) | 4″ | 114.3 mm | 40 mm | 175 mm | 1.8kg |
| Union (Reducing) | 1″ × ¾” | 33.4 / 26.7 mm | 20 mm | 75 mm | 400g |
| Union (Reducing) | 2″ × 1½” | 60.3 / 48.3 mm | 28 mm | 110 mm | 1.0kg |
Mechanical Properties
| Property | Value | Unit / Standard |
|---|---|---|
| Tensile Strength | 485 – 750 | MPa (Carbon Steel, Stainless Steel, Alloy Steel, Nickel Alloys) |
| Yield Strength | 170 – 450 | MPa |
| Hardness | 120 – 200 | HB (Brinell) |
| Elongation | ≥ 20 – 30 | % |
| Density | 7.8 – 8.0 | g/cm³ (Carbon Steel), 7.9 – 8.0 g/cm³ (Stainless Steel) |
| Impact Toughness | ≥ 27 – 70 | J (Charpy, grade-dependent) |
| Modulus of Elasticity (E) | ~200 | GPa |
| Fatigue Strength | 250 – 450 | MPa |
| Corrosion Resistance | Good to Excellent (SS > CS > Alloy Steel > Nickel Alloys) | – |
| Thermal Conductivity | 15 – 50 | W/m·K |
| Coefficient of Thermal Expansion | 11 – 17 ×10⁻⁶ | /°C |
| Yield Ratio (YS/UTS) | 0.40 – 0.65 | – |
| Poisson’s Ratio | 0.27 – 0.30 | – |
| Brinell Hardness Range | 120 – 200 | HB |
| Surface Finish | Mill Finish, Polished, Bead Blasted | – |
| End Connections | Male / Female Threaded, Flanged, Socket Weld | – |
| Operating Temperature Range | -46 to 600 | °C (material-dependent) |
| Pressure Rating | Class 150, 300, 600, 900, 1500, 2500 | ASME B1.20.1 / ASME B16.11 |
Chemical Composition
| Element | SS 304 | SS 304L | SS 316 | SS 316L |
|---|---|---|---|---|
| Chromium (Cr) | 18.0 – 20.0 | 18.0 – 20.0 | 16.0 – 18.0 | 16.0 – 18.0 |
| Nickel (Ni) | 8.0 – 10.5 | 8.0 – 12.0 | 10.0 – 14.0 | 10.0 – 14.0 |
| Carbon (C) | ≤ 0.08 | ≤ 0.03 | ≤ 0.08 | ≤ 0.03 |
| Manganese (Mn) | ≤ 2.00 | ≤ 2.00 | ≤ 2.00 | ≤ 2.00 |
| Silicon (Si) | ≤ 1.00 | ≤ 1.00 | ≤ 1.00 | ≤ 1.00 |
| Phosphorus (P) | ≤ 0.045 | ≤ 0.045 | ≤ 0.045 | ≤ 0.045 |
| Sulfur (S) | ≤ 0.030 | ≤ 0.030 | ≤ 0.030 | ≤ 0.030 |
| Iron (Fe) | Balance | Balance | Balance | Balance |
| Molybdenum (Mo) | — | — | 2.0 – 3.0 | 2.0 – 3.0 |
Applications of Investment Casting Unions
Construction &
Infrastructure
Automotive & Heavy
Equipment
Manufacturing &
Fabrication
Medical & Laboratory
Equipment
Electrical &
Electronics Assembly
Oil, Gas & Petrochemical
Installations
Do you have questions?
What’s the purpose of using a union over a coupling?
Are unions available with different end connections?
Can unions be pressure tested and certified?
Are unions corrosion-resistant for marine use?
