Pioneer Industries is a globally trusted manufacturer and exporter of Brass Flare Long Union Nuts, engineered with an extended cylindrical barrel that damps high-amplitude vibration and reduces tube fatigue in automotive, marine, refrigeration, and industrial compressor systems.
The Brass Flare Long Union Nut from Pioneer Industries is an engineered mechanical fastening component designed to clamp 45° flared tubing securely against mating flare cones while providing critical mechanical strain relief. Unlike standard short nuts, the long union nut features an elongated cylindrical sleeve extending backward along the tubing axis. This extended barrel acts as a rigid vibration damper, distributing cyclic bending stresses away from the vulnerable tube flare radius and preventing mechanical fatigue failure.
Manufactured strictly in compliance with SAE J512, SAE J513, and ASME B16.26 standards, our long union nuts are precision CNC-machined from extruded high-tensile brass alloy (BS 249 / CW614N / ASTM B16 C36000). The internal threads are cleanly single-point cut or precision-tapped to class 2B tolerances, ensuring smooth makeup and preventing thread galling even under heavy repeated torque cycles.
Pioneer Industries exports Brass Flare Long Union Nuts to leading industrial compressor builders, mobile HVAC manufacturers, commercial refrigeration assemblers, and hydraulic specialists worldwide. Our central distribution warehouse in Mumbai maintains extensive inventory reserves across all standard fractional inch and metric tube sizes.
Every long union nut undergoes automated multi-point dimensional checking, including thread pitch diameter verification, internal 45-degree shoulder bevel inspection, and concentricity testing between the bore and thread. EN 10204 Type 3.1 material test certificates are provided with every dispatched production lot.
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In applications subjected to continuous reciprocating vibration—such as diesel engine fuel delivery lines, tractor hydraulic connections, and large refrigeration semi-hermetic compressor heads—standard short nuts allow the tubing to flex directly at the flare neck, leading to work hardening and premature hairline fractures. Pioneer Industries’ Brass Flare Long Union Nut eliminates this failure mode by supporting the outer circumference of the tube over a significantly greater length.
The internal clamping shoulder is machined with a precision 45° angle matching the back contour of standard flared tubing. This design ensures uniform clamping pressure around the 360-degree perimeter of the flare, producing an ultra-reliable, bubble-tight metal-to-metal seal capable of withstanding working pressures up to 5,000 PSI without loosening or leaking.
Pioneer Industries manufactures Brass Flare Long Union Nuts in tube OD sizes from 1/8" to 3/4" with SAE UNF straight female threads. Operating pressures up to 5,000 PSI (345 bar). Complies with SAE J512, SAE J513, ASME B16.26, and ASTM B16 standards.
Explore comprehensive engineering dimensional configurations for Fractional Inch Series, Metric Series, and Certified Material Specifications. Manufactured according to SAE J512, SAE J513, ASME B16.26, and international standards.
| Part No. | Tube O.D. (T) | Straight Thread (UNF) | Hex Size (F) | Overall Length (L) | Bore Dia (D) | Weight (approx) | Working Pressure |
|---|---|---|---|---|---|---|---|
| PI-FLN-02 | 1/8" | 5/16-24 UNF | 3/8" | 0.75" | 0.130" | 18 g | 5,000 PSI |
| PI-FLN-03 | 3/16" | 3/8-24 UNF | 7/16" | 0.81" | 0.193" | 24 g | 5,000 PSI |
| PI-FLN-04 | 1/4" | 7/16-20 UNF | 9/16" | 0.94" | 0.256" | 38 g | 5,000 PSI |
| PI-FLN-05 | 5/16" | 1/2-20 UNF | 5/8" | 1.06" | 0.318" | 48 g | 4,500 PSI |
| PI-FLN-06 | 3/8" | 5/8-18 UNF | 3/4" | 1.19" | 0.382" | 72 g | 4,000 PSI |
| PI-FLN-08 | 1/2" | 3/4-16 UNF | 7/8" | 1.44" | 0.507" | 115 g | 3,500 PSI |
| PI-FLN-10 | 5/8" | 7/8-14 UNF | 1-1/16" | 1.62" | 0.632" | 168 g | 3,000 PSI |
| PI-FLN-12 | 3/4" | 1-1/16-14 UNS | 1-1/4" | 1.88" | 0.758" | 260 g | 2,500 PSI |
| Part No. | Tube O.D. (mm) | Thread Profile (UNF) | Hex Size (mm) | Overall Length (mm) | Bore Dia (mm) | Weight (g) | Working Pressure (bar) |
|---|---|---|---|---|---|---|---|
| PI-FLN-M06 | 6 mm | 7/16-20 UNF | 14 mm | 23.8 mm | 6.2 mm | 38 g | 345 bar |
| PI-FLN-M08 | 8 mm | 1/2-20 UNF | 16 mm | 27.0 mm | 8.2 mm | 48 g | 310 bar |
| PI-FLN-M10 | 10 mm | 5/8-18 UNF | 19 mm | 30.2 mm | 10.2 mm | 72 g | 276 bar |
| PI-FLN-M12 | 12 mm | 3/4-16 UNF | 22 mm | 36.5 mm | 12.3 mm | 115 g | 241 bar |
| PI-FLN-M16 | 16 mm | 7/8-14 UNF | 27 mm | 41.1 mm | 16.3 mm | 168 g | 206 bar |
| PI-FLN-M18 | 18 mm | 1-1/16-14 UNS | 32 mm | 47.8 mm | 18.4 mm | 260 g | 172 bar |
| Component | Material Specification | Standard Specification | Chemical Composition | Mechanical Properties | Temperature Limits | Key Features |
|---|---|---|---|---|---|---|
| Precision Extruded Nut Body | Forging Brass (BS 218 / CW617N) | BS EN 12165 / ASTM B283 C37700 | Cu: 57.0–59.0%, Pb: 1.6–2.5%, Zn: Rem. | Tensile ≥ 440 MPa, 110–150 HB | -54°C to +121°C | Contoured grain flow, dense wall structure, zero porosity, high shock resistance |
| Internal 45° Thrust Shoulder | Free Cutting Brass (BS 249 / CW614N) | IS 319 Gr. 1 / ASTM B16 C36000 | Cu: 58.0–60.0%, Pb: 1.5–3.0%, Zn: Rem. | Tensile ≥ 400 MPa, 100–140 HB | -54°C to +121°C | Precision CNC machining, exact 45° cone angle, micro-inch surface finish |
| SAE Flare Nut | Extruded Brass / Forged Brass | SAE J512 / SAE J513 / ASTM B16 | Cu: 58.0–61.0%, Zn: Rem. | Tensile ≥ 380 MPa | -54°C to +121°C | Short and long skirt options, internal 45° beveled shoulder for tube support |
| Tubing Interface | Flared Copper / Brass Tube | ASTM B88 / ASTM B280 / ASTM B135 | Cu ≥ 99.9% (DHP) | Soft Annealed Temper | -54°C to +121°C | 100% metal-to-metal seal, zero elastomeric degradation in refrigerants/LPG |
Brass Flare Long Union Nut fittings find deployment across demanding thermal, fluid, and gas piping circuits:
Installed on compressor discharge and suction stubs subject to intense mechanical vibration.
Secures high-pressure fuel lines against continuous engine pulse resonance and thermal cycles.
Provides heavy-duty strain relief for copper air brake tubing running along heavy truck chassis.
Clamps hydraulic pilot lines against hydraulic pump pulsation and high fluid hammer events.
Protects fuel and cooling fluid lines from structural marine hull vibrations in sea vessels.
Maintains zero-leak flare joint integrity on high-pressure cryogenic liquid vaporizer skids.
Connects condenser coil headers in rooftop air conditioning units exposed to heavy wind and motor vibration.
Secures high-frequency lube lines on CNC machining spindle heads and reciprocating slides.
Pioneer Industries’ Brass Flare Long Union Nut are widely used in numerous industries like:
Expert engineering insights and technical guidance regarding design specifications, pressure tolerances, flare cone sealing mechanics, tubing compatibility, and installation best practices for industrial Brass Flare Long Union Nut.
The primary difference is the overall length of the cylindrical body behind the hex head. A Long Union Nut extends significantly farther along the tubing, providing an elongated internal guide bore that dampens vibration and prevents the tube from flexing right at the flare root, whereas a Short Nut is compact and intended for low-vibration or space-constrained areas.
When copper tubing vibrates, bending stress concentrates at the abrupt cross-sectional change where the tube flares outward. The extended sleeve of the Long Union Nut cradles the tube outer diameter for nearly an inch, transferring the bending pivot point to the rigid un-flared section of the tube and dramatically reducing flare neck fatigue.
Pioneer Industries manufactures these nuts with Unified National Fine (UNF) straight threads conforming to SAE J512 and SAE J513 standards. These straight mechanical threads are designed solely to generate axial clamping force when threaded onto male flare fittings.
Do not use PTFE tape or liquid pipe sealant on flare nut threads, as sealing occurs exclusively on the 45-degree metal-to-metal flare face. A tiny drop of clean refrigeration oil applied to the threads and the back face of the flare can reduce friction, allowing accurate torque transmission without twisting the tube.
Our long union nuts are machined from premium BS 249 / CW614N (ASTM B16 C36000) free-cutting brass bar stock. This high-density alloy delivers exceptional tensile strength (up to 440 MPa) and resistance to stress cracking under heavy wrenching torque.
Yes. As long as the internal threads are undamaged, the hex flats are not stripped, and the internal 45-degree shoulder is free from gouges or cracks, the nut can be reused repeatedly across multiple tubing assemblies.
Standard tightening torque values: 1/4" tube: 10–15 ft-lbs (14–20 N-m); 3/8" tube: 20–30 ft-lbs (27–41 N-m); 1/2" tube: 35–50 ft-lbs (47–68 N-m); 5/8" tube: 50–65 ft-lbs (68–88 N-m); 3/4" tube: 75–90 ft-lbs (102–122 N-m).
Yes. Pioneer Industries Brass Flare Long Union Nuts are completely interchangeable with any standard 45° SAE male flare fitting manufactured according to SAE J512, SAE J513, or ASME B16.26 specifications.
Pioneer Industries manufactures metric-compatible long union nuts with precise bore diameters matched to standard metric OD sizes (6mm, 8mm, 10mm, 12mm, 16mm) while retaining standard SAE flare threads, facilitating seamless integration with metric refrigeration tubing.
Every order is accompanied by EN 10204 Type 3.1 Mill Test Certificates detailing chemical analysis, tensile testing, dimensional conformance, and batch traceability from certified raw material to finished product.
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