Instrument Union
What are Instrument Unions?
Instrument unions are two-piece fittings used to securely join two tubes or pipes in high-precision fluid systems. These fittings allow for easy disconnection and reassembly without disturbing the overall pipeline, making them ideal for instrumentation, analytical, and control systems.
Asiad Steel Industries is a reputed supplier and exporter of instrument unions known for leak-proof performance, pressure handling, and resistance to vibration or thermal expansion.
Key Features
Leak-Proof
Jointing
Durable
Construction
Easy Installation
& Removal
Wide
Compatibility
Corrosion
Resistant
Specifications
| Specification Category | Parameter / Feature | Details / Options |
|---|---|---|
| Size Range | Tube OD Sizes | 1/8” to 2” (3 mm to 50 mm) |
| Pressure Ratings | Working Pressure | Up to 6000 psi (414 bar) depending on size & material |
| Temperature Ratings | -196°C to 600°C (material-dependent) | |
| Fitting Types | Instrument Fittings | Union (Straight Union, Reducing Union, Bulkhead Union, Union Elbow, Union Tee, Union Cross) |
| Material Options | Stainless Steel | SS 304, SS 304L, SS 316, SS 316L |
| Standards & Certifications | ASME / ANSI | ASME B31.3, ASME B16.11 (applicable for fittings) |
| ASTM | ASTM A276, ASTM A479 (for SS bars/rods), ASTM A182 (for forgings) | |
| European Standards | EN 10272 (SS Bars & Rods), DIN 2353 (applicable for instrumentation) | |
| Certifications | ISO 9001, PED 2014/68/EU, NACE MR0175, IBR Approved | |
| Design Features | Connection Type | Double Ferrule Compression, Single Ferrule (on request) |
| End Connections | Tube OD to Tube OD, Tube OD to Male/Female NPT/BSP Threads | |
| Tolerance | As per ASME / ASTM standards | |
| Coating & Surface Finish | Surface Finish | Machined, Pickled, Polished, Passivated |
| Testing & Inspection | Pressure Testing | Hydrostatic, Pneumatic |
| Non-Destructive Testing | Ultrasonic (UT), Dye Penetrant (DPT) | |
| Destructive Testing | Tensile, Hardness |
Dimensions
| Tube OD (mm / inch) | Thread Size | Across Flats (AF, mm) | Overall Length (L, mm) | Pressure Rating |
|---|---|---|---|---|
| 3 mm (1/8″) | 1/8″ NPT / BSP | 12 – 14 | 25 – 28 | Up to 6000 psi |
| 6 mm (1/4″) | 1/4″ NPT / BSP | 14 – 17 | 30 – 33 | Up to 6000 psi |
| 8 mm (5/16″) | 1/4″ NPT / BSP | 17 – 19 | 32 – 36 | Up to 6000 psi |
| 10 mm (3/8″) | 3/8″ NPT / BSP | 19 – 22 | 35 – 38 | Up to 6000 psi |
| 12 mm (1/2″) | 1/2″ NPT / BSP | 22 – 25 | 38 – 42 | Up to 6000 psi |
| 16 mm (5/8″) | 5/8″ NPT / BSP | 25 – 28 | 42 – 46 | Up to 6000 psi |
| 18 mm (3/4″) | 3/4″ NPT / BSP | 28 – 32 | 45 – 50 | Up to 6000 psi |
| 20 mm (7/8″) | 3/4″ NPT / BSP | 32 – 36 | 50 – 55 | Up to 6000 psi |
| 25 mm (1″) | 1″ NPT / BSP | 36 – 41 | 55 – 60 | Up to 6000 psi |
Mechanical Properties
| Property | Value | Unit / Standard |
|---|---|---|
| Tensile Strength | 515 – 620 | MPa (Stainless Steel 316 / 316L) |
| Yield Strength | 205 – 240 | MPa |
| Hardness | ≤ 200 | HB (Brinell, Annealed Condition) |
| Elongation | ≥ 35 | % |
| Density | 7.9 – 8.0 | g/cm³ |
| Impact Toughness | ≥ 100 | J (Charpy at Room Temp.) |
| Modulus of Elasticity (E) | ~200 | GPa |
| Fatigue Strength | 240 – 300 | MPa |
| Corrosion Resistance | Excellent in chloride, acidic & marine environments | – |
| Thermal Conductivity | 15 – 20 | W/m·K |
| Coefficient of Thermal Expansion | 16 ×10⁻⁶ | /°C |
| Yield Ratio (YS/UTS) | 0.38 – 0.45 | – |
| Poisson’s Ratio | 0.27 – 0.30 | – |
| Brinell Hardness Range | 140 – 200 | HB |
| Surface Finish | Smooth / Passivated / Electropolished (as required) | – |
| Connection Type | Double Ferrule / Compression (threaded or welded ends) | – |
| Operating Temperature Range | -196 to +400 | °C (material-dependent) |
| Pressure Rating | Up to 6000 psi (414 bar) | ASTM / ASME Standards |
Chemical Composition
| Element | SS 304 (%) | SS 304L (%) | SS 316 (%) | SS 316L (%) |
|---|---|---|---|---|
| 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 |
| 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 |
| Molybdenum (Mo) | — | — | 2.0 – 3.0 | 2.0 – 3.0 |
| Nitrogen (N) | — | — | ≤ 0.10 | ≤ 0.10 |
| Iron (Fe) | Balance | Balance | Balance | Balance |
Applications of Instrument Unions
Construction &
Infrastructure
Automotive & Heavy
Equipment
Manufacturing &
Fabrication
Medical & Laboratory
Equipment
Electrical &
Electronics Assembly
Oil, Gas & Petrochemical
Installations
Do you have questions?
Are your unions suitable for high-vibration applications?
Do you offer unions in exotic alloys?
Can unions be reused after disassembly?
Are ferrules and nuts included with each union?
