This guide provides a detailed look at the properties of 347 Stainless Steel and the dimensional specifications for Long Radius Reducing Elbows.
347 Stainless Steel and Long Radius Reducing Elbow
347 Stainless Steel is a stabilized austenitic chromium-nickel alloy, distinguished by the addition of columbium at a minimum of 10 times the carbon content.
Combined with its high creep strength and good oxidation resistance up to approximately 870°C, 347 is the material of choice for high-temperature applications such as exhaust systems, heat exchangers, furnace parts, and refinery processing equipment.
Long Radius Reducing Elbow
A Long Radius Reducing Elbow, manufactured to ASME B16.9, is a specialized buttweld fitting designed to simultaneously change the direction of flow by 90 degrees and reduce the pipe diameter within a single component.
The "long radius" designation indicates a center-to-end dimension of 1.5 times the nominal pipe size of the larger end, providing a gentler flow path that minimizes pressure drop, turbulence, and erosion compared to short-radius elbows. This fitting is essential for efficient and compact piping layouts in systems requiring a change in both direction and line size.
347 Stainless Steel Fitting Features
Stabilization: Niobium (columbium) addition binds carbon, preventing sensitization and maintaining corrosion resistance in welded zones.
High-Temperature Performance: Superior oxidation resistance up to 1500°F (816°C) and good creep strength.
Corrosion Resistance: Comparable to 304 in many environments, with enhanced resistance to polythionic acid stress corrosion cracking.
Weldability and Formability: Excellent for butt welding without post-weld heat treatment in most cases.
Long radius reducing elbows provide a gradual change in direction (typically 90°) while transitioning between two different pipe sizes, minimizing turbulence and pressure drop compared to short radius designs.
Long Radius Reducing Elbows per ASME B16.9 Dimensions
In ASME B16.9, the center-to-face dimension (H) for the larger end of a long radius reducing elbow equals that of a standard long radius 90° elbow of the same NPS: H = 1.5 × NPS (larger) in inches.
The outlet (smaller end) aligns with the centerline, and wall thickness matches the corresponding pipe schedule (e.g., Sch 10S, 40S, 80S per ASME B36.19M for stainless steel).
Below is a representative dimension table for common 90° long radius reducing elbows.
|
Larger NPS × Smaller NPS |
Outside Diameter (Large End) |
Outside Diameter (Small End) |
Center-to-Face (H) |
Approximate Weight (lbs, Sch 40S/STD) |
|
3 × 2 |
3.500 |
2.375 |
4.50 |
3.5 |
|
4 × 3 |
4.500 |
3.500 |
6.00 |
6.8 |
|
4 × 2 |
4.500 |
2.375 |
6.00 |
6.0 |
|
6 × 4 |
6.625 |
4.500 |
9.00 |
14.5 |
|
6 × 3 |
6.625 |
3.500 |
9.00 |
13.8 |
|
8 × 6 |
8.625 |
6.625 |
12.00 |
28.0 |
|
8 × 4 |
8.625 |
4.500 |
12.00 |
26.5 |
|
10 × 8 |
10.750 |
8.625 |
15.00 |
48.0 |
|
12 × 10 |
12.750 |
10.750 |
18.00 |
72.0 |
|
14 × 12 |
14.000 |
12.750 |
21.00 |
95.0 |
|
16 × 14 |
16.000 |
14.000 |
24.00 |
130.0 |
|
18 × 16 |
18.000 |
16.000 |
27.00 |
170.0 |
|
24 × 20 |
24.000 |
20.000 |
36.00 |
320.0 |
Conclusion
Specifying 347 Stainless Steel Long Radius Reducing Elbows manufactured to ASME B16.9 provides a dependable solution for demanding piping applications.
The stabilized chemistry of 347 Stainless Steel offers essential protection against intergranular corrosion in high-temperature and welded environments, such as those found in power generation, petrochemical, and refining industries.
Simultaneously, adhering to the ASME B16.9 standard guarantees precise, interchangeable dimensions that facilitate efficient system design, procurement, and installation, ensuring long-term performance and safety.
347 stainless steel long radius reducing elbows have reliable, corrosion-resistant performance in elevated-temperature and corrosive environments. As a trusted supplier, we stock these fittings in seamless and welded forms, with full traceability and mill test reports. Contact us for custom sizes, schedules, or quotations for your project requirements.
