Pioneer Industries is an internationally renowned manufacturer and exporter of Brass Inverted Flare Unions, engineered to join two double-flared tubing lines in-line with an impenetrable metal-to-metal seal in automotive brake, fuel, and transmission fluid circuits.
The Brass Inverted Flare Union manufactured by Pioneer Industries is a high-integrity in-line tube coupling fitting designed to connect two lengths of double-flared steel, copper-nickel, or copper tubing. Featuring two opposing internal female 42°/45° inverted flare conical seats separated by a central hexagonal wrench flat, this fitting provides an ultra-reliable, full-flow connection between tubing segments without requiring brazing, soldering, or open flames.
Manufactured strictly in accordance with SAE J512, SAE J1231, and ASME B16.26 standards, our inverted flare unions are precision-turned from extruded high-tensile brass bar stock (BS 249 / CW614N / ASTM B16 C36000) or hot-forged brass blanks (BS 218 / CW617N). The dense, micro-grain brass microstructure eliminates wall porosity and withstands severe hydraulic pulsation, thermal expansion cycles, and mechanical vibration.
Pioneer Industries exports Brass Inverted Flare Unions to automotive tier-1 suppliers, brake line fabricators, commercial fleet repair facilities, and industrial distributors across more than 85 countries worldwide. With massive inventory stocks in Mumbai, India, we provide rapid international dispatch on standard fractional inch and metric configurations.
Every union is manufactured under an ISO 9001:2015 certified quality management system using high-precision CNC multi-axis machines. Thread concentricity, internal seat surface finish, and orifice diameters are 100% verified. Dispatched consignments are accompanied by EN 10204 Type 3.1 material test certificates.
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In automotive brake line replacement, chassis rust repair, and industrial machinery piping, extending tubing runs or splicing damaged line sections requires an ultra-reliable in-line coupling. Pioneer Industries’ Brass Inverted Flare Union provides an impenetrable metal-to-metal wedge seal on both ends when drawn down by standard SAE male inverted flare nuts. The joint creates a completely smooth internal flow path that minimizes pressure drops and eliminates flow restrictions.
Because the union requires zero soldering flux or brazing heat, there is zero risk of internal oxidation entering the brake or fuel system, protecting sensitive ABS valves and fuel injection components from premature contamination failure. Operating reliably across temperatures from -54°C to +121°C, it is fully rated for pressures up to 2,800 PSI.
Pioneer Industries manufactures Brass Inverted Flare Unions in standard fractional sizes from 1/8" to 3/8" tube OD, with reducing union combinations available upon request. Working pressures up to 2,800 PSI (193 bar). Complies with SAE J512, SAE J1231, ASME B16.26, and ASTM B16 specifications.
Explore comprehensive engineering dimensional configurations for Fractional Inch Series, Metric Series, and Certified Material Specifications. Manufactured according to SAE J512, SAE J1231, ASME B16.26, and international standards.
| Part No. | Tube O.D. (T) | Both Threads (UNF) | Hex Size (F) | Overall Length (L) | Orifice Dia (E) | Weight (approx) | Working Pressure |
|---|---|---|---|---|---|---|---|
| PI-IFU-02 | 1/8" | 5/16-28 UNF | 7/16" | 0.62" | 0.078" | 16 g | 2,800 PSI |
| PI-IFU-03 | 3/16" | 3/8-24 UNF | 1/2" | 0.69" | 0.125" | 22 g | 2,800 PSI |
| PI-IFU-04 | 1/4" | 7/16-24 UNF | 1/2" | 0.75" | 0.188" | 28 g | 2,800 PSI |
| PI-IFU-05 | 5/16" | 1/2-20 UNF | 9/16" | 0.81" | 0.219" | 38 g | 2,400 PSI |
| PI-IFU-06 | 3/8" | 5/8-18 UNF | 11/16" | 0.94" | 0.281" | 56 g | 2,000 PSI |
| Part No. | Tube O.D. (mm) | Thread Profile (UNF) | Hex Size (mm) | Overall Length (mm) | Orifice Dia (mm) | Weight (g) | Working Pressure (bar) |
|---|---|---|---|---|---|---|---|
| PI-IFU-M04 | 4 mm | 5/16-28 UNF | 11 mm | 15.7 mm | 2.0 mm | 16 g | 193 bar |
| PI-IFU-M05 | 5 mm | 3/8-24 UNF | 13 mm | 17.5 mm | 3.2 mm | 22 g | 193 bar |
| PI-IFU-M06 | 6 mm | 7/16-24 UNF | 13 mm | 19.0 mm | 4.8 mm | 28 g | 193 bar |
| PI-IFU-M08 | 8 mm | 1/2-20 UNF | 14 mm | 20.6 mm | 5.6 mm | 38 g | 165 bar |
| PI-IFU-M10 | 10 mm | 5/8-18 UNF | 17 mm | 23.8 mm | 7.1 mm | 56 g | 138 bar |
| Component | Material Specification | Standard Specification | Chemical Composition | Mechanical Properties | Temperature Limits | Key Features |
|---|---|---|---|---|---|---|
| Precision Extruded Union 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 |
| Recessed Inverted Flare Cavities | 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, internal 42°/45° cone seat, micro-inch surface finish |
| Inverted Flare Nut | Extruded Brass / Zinc Plated Steel | SAE J512 / SAE J513 / ASTM B16 | Cu: 58.0–61.0%, Zn: Rem. | Tensile ≥ 400 MPa | -54°C to +121°C | External straight UNF male threads, hex drive, deep pilot nose for tube guidance |
| Tubing Interface | Double Flared Steel / CuNi / Copper | SAE J527 / ASTM A254 / ASTM B88 | Low Carbon Steel / CuNi 90/10 | Soft Annealed Temper | -54°C to +121°C | 100% metal-to-metal seal, zero elastomeric degradation in brake fluids & fuels |
Brass Inverted Flare Union fittings find critical deployment across demanding automotive, mobile fluid power, and fuel delivery circuits:
Joins two sections of hydraulic brake line tubing during vehicle repair or line replacement.
Connects long runs of steel or copper-nickel fuel delivery tubing under vehicle chassis.
Couples hydraulic return tubing across chassis crossmembers.
Splices transmission oil lines running from gearbox to radiator cooling tanks.
Connects copper-nickel tubing sections in heavy-duty truck air brake systems.
Couples hydraulic pilot lines on agricultural and earthmoving equipment.
Connects diagnostic pressure loops on mobile fluid test stations.
Couples copper fuel delivery lines on boat inboard engines with corrosion-resistant brass.
Pioneer Industries’ Brass Inverted Flare Union are widely used in numerous industries like:
Expert engineering insights and technical guidance regarding design specifications, pressure tolerances, internal inverted cone sealing mechanics, double flaring, and installation best practices for industrial Brass Inverted Flare Union.
A Brass Inverted Flare Union is an in-line tube fitting featuring two opposing female 42°/45° inverted flare ports separated by a central hex. Its primary function is to couple two lengths of double-flared steel, copper-nickel, or copper tubing together in a straight, leak-tight line without requiring soldering or brazing.
The union relies on an all-metal 42°/45° mechanical compression seal. Male-threaded inverted flare nuts slide over the tubing before flaring. When threaded into the female union ports, the nuts press the double-flared tube lips against the internal brass cone seats, creating hermetic metal-to-metal wedge seals.
Standard inverted flare unions have equal sizes on both ends (e.g. 3/16" x 3/16" with 3/8-24 threads, or 1/4" x 1/4" with 7/16-24 threads). However, Pioneer Industries also manufactures reducing inverted flare unions (e.g. 1/4" x 3/16") to connect two different tube diameters directly.
No. The threads on an inverted flare union are straight mechanical UNF threads designed exclusively to generate axial clamping force. Sealing occurs entirely on the internal 42°/45° cone seats. Tape or liquid sealant must never be applied to inverted flare threads.
Depending on nominal tube size, working pressure ratings range from 2,000 PSI (138 bar) for 3/8" tubing up to 2,800 PSI (193 bar) for 3/16" and 1/4" tubing, with a minimum 4:1 hydrostatic burst safety factor.
Yes. Inverted flare unions can be loosened and reassembled multiple times without degradation of sealing integrity, making them ideal for systems requiring routine servicing, component replacement, or line splicing.
Always use two wrenches: one open-end wrench to hold the central hexagonal body of the union stationary, and a second wrench (such as a flare nut line wrench) to torque the nut. Never tighten one nut against the opposite nut.
Our unions are precision-machined from BS 249 / CW614N (ASTM B16 C36000) extruded brass bar stock, providing high tensile strength (above 400 MPa), exceptional machinability, and superior corrosion resistance.
Yes. Because the seal is 100% metal-to-metal with no rubber or plastic seals, it is fully compatible with all automotive brake fluids, gasoline, diesel, and transmission oils across temperatures from -54°C to +121°C.
Pioneer Industries provides EN 10204 Type 3.1 Mill Test Certificates verifying chemical composition, mechanical properties, and 100% pneumatic bubble leak testing under water.
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