Introduction

At Mcneil Instruments India, we specialize in the engineering, manufacturing, and global export of Stainless Steel 347 Pipe Fittings — precision-built components crafted to endure high temperatures, aggressive environments, and complex process conditions.
Designed for industries where thermal stability, corrosion resistance, and weld reliability are non-negotiable, our SS 347 and SS 347H fittings are trusted across refineries, petrochemical complexes, thermal plants, and power generation networks.

Each fitting — whether elbow, tee, reducer, bend, stub end, or end cap — is produced to ASTM A403 WP347 / WP347H, ASME B16.9, and ANSI/DIN standards. We engineer them with dimensional accuracy, smooth internal finish, and optimum strength-to-weight ratio, ensuring leak-free performance and mechanical endurance in every system.

What is Stainless Steel 347?

Stainless Steel 347 (UNS S34700 / Werkstoff Nr. 1.4550) is an austenitic chromium-nickel stainless steel stabilized with niobium (columbium) and tantalum to prevent carbide precipitation during welding and prolonged high-temperature exposure.
This stabilization makes SS 347 particularly suited for applications where materials like 304 or 316 might lose strength or suffer intergranular corrosion after thermal cycling.

For higher heat resistance, the 347H variant (UNS S34709) incorporates a higher carbon content (0.04–0.10%), which improves creep strength and stress-rupture resistance, making it ideal for continuous service above 900°C.

Stabilization Advantage

The niobium-tantalum combination forms stable carbides instead of chromium carbides, preserving chromium content in the matrix — which in turn maintains a protective passive film, ensuring corrosion protection even in sensitizing temperature ranges (450°C–850°C).

Chemical Composition (% by weight)

Mechanical Properties (Typical Minimum Values)

Key Performance Characteristics

• Resists Sensitization: Niobium stabilization prevents intergranular corrosion in weld heat-affected zones.
  
• Superior Creep Strength: Withstands prolonged stress at elevated temperatures better than SS 304/316.
  
• Excellent Weldability: Performs well under TIG, MIG, or manual arc welding with minimal distortion.
  
• High Oxidation Resistance: Retains surface stability even under cyclic heating up to 870°C.
  
• Non-Magnetic in Annealed Condition: Useful in applications sensitive to magnetic interference.
  
• Stable Mechanical Properties: Maintains toughness and ductility in both cryogenic and high-heat environments.
  

Types of Stainless Steel 347 Pipe Fittings

At Mcneil Instruments India, we manufacture a complete portfolio of SS 347 & 347H fittings, designed to integrate seamlessly into critical process pipelines.

1. SS 347 Elbow

Used to change the flow direction (45°, 90°, or 180°). These elbows are ideal for high-pressure steam, gas, and superheated systems where strength and corrosion protection are essential.

2. SS 347 Tee

Used for fluid branching or mixing applications. Equal and reducing tees are designed to maintain pressure balance and uniform flow velocity even under cyclic loads.

3. SS 347 Reducer

Available in concentric and eccentric designs, reducers connect pipes of different diameters while minimizing flow turbulence and pressure drop.

4. SS 347 Buttweld Fittings

Designed for permanent joints, these fittings are welded directly to pipes — providing smooth, leak-proof, and corrosion-resistant connections suitable for high-pressure operations.

5. SS 347 Stub Ends

Used with lap joint flanges to allow easy disassembly for inspection or cleaning in refineries and process plants.

6. SS 347 End Caps

Protect pipe ends from mechanical damage or environmental corrosion; essential for pressurized line terminations.

7. SS 347 Bends

Custom-fabricated bends with long or short radii ensure optimized fluid dynamics and reduced erosion at directional changes.

Available Range:

• Size: ½″ NB to 36″ NB
  
• Type: Seamless, Welded, ERW, Fabricated
  
• Schedules: SCH 10 to SCH 160 & XXS
  
• Standards: ASTM A403 WP347 / 347H, ASME B16.9 / B16.28 / MSS-SP-43
  

Applications of Stainless Steel 347 Pipe Fittings

Owing to their thermal endurance and resistance to intergranular corrosion, SS 347/347H fittings serve in diverse industrial sectors:

• Power Plants: Superheaters, reheaters, and high-pressure steam lines.
  
• Oil & Gas Refineries: Hydrocarbon transport, catalytic cracking, and furnace lines.
  
• Chemical & Petrochemical Industries: Heat exchangers, reactor vessels, and process piping for sulfuric and nitric acid environments.
  
• Food & Beverage Plants: Steam sterilization systems and high-temperature fluid transport.
  
• Pharmaceutical & Biotech: Cleanroom-compatible fittings for high-temperature sterilized systems.
  
• Marine Engineering: Seawater and exhaust systems resisting scaling and oxidation.
  
• Aerospace & Thermal Systems: High-performance exhaust manifolds, turbines, and heat-treatment chambers.
  

Advantages of Using SS 347 Pipe Fittings

✅ Enhanced Thermal Resistance: Maintains stability at 870°C continuous service.
✅ Excellent Weld Integrity: Niobium prevents weld decay and cracking.
✅ Corrosion & Scaling Resistance: Ideal for environments exposed to oxidizing gases.
✅ Long Service Life: Reduced maintenance frequency and operational downtime.
✅ Precision Engineering: Manufactured under ISO-certified quality systems for tight tolerances.
✅ Versatile Fabrication: Easily machinable, formable, and weldable across industrial setups.

Quality Assurance & Testing

Each SS 347 pipe fitting manufactured by Mcneil Instruments India undergoes rigorous testing and inspection to meet international quality standards.

Tests Conducted:

• Hydrostatic Pressure Test
  
• PMI (Positive Material Identification)
  
• Ultrasonic & Radiographic Examination
  
• Intergranular Corrosion (IGC) Test
  
• Dimensional Accuracy Check
  
• Tensile & Hardness Tests
  
• Surface Finish & Visual Inspection
  

All fittings are supplied with EN 10204 3.1 / 3.2 certification, heat numbers, and traceable mill test reports (MTRs).

Why Choose Mcneil Instruments India

• ISO 9001:2015 Certified Manufacturing Facility
  
• In-house Machining, Forging & Welding Units
  
• Strict Compliance with ASTM, ASME, ANSI, and DIN
  
• 100% Pressure & Dimensional Testing
  
• Global Export Expertise to 40+ Countries
  
• Customization Available in Thickness, Radius, and End Connection
  
• Secure Export Packaging & Timely Logistics Support
  

Our legacy of precision, consistency, and customer trust makes Mcneil Instruments India one of the most dependable SS 347 Pipe Fittings manufacturers and exporters globally.

Maintenance & Care Guidelines

• Inspect periodically for stress cracks or scaling, especially in high-temperature zones.
  
• Avoid cleaning with chloride-based agents; use mild alkaline solutions.
  
• Maintain controlled welding parameters during installation.
  
• Ensure uniform alignment to prevent mechanical fatigue at joints.
  
• Store in dry environments to avoid surface oxidation before installation.
  

Conclusion

Stainless Steel 347 Pipe Fittings represent the pinnacle of high-performance metallurgical design — balancing strength, weldability, and corrosion resistance for extreme service conditions.
At Mcneil Instruments India, every fitting reflects engineering excellence — from raw material selection to final inspection — ensuring performance that stands the test of pressure, temperature, and time.

Contact our technical team today to discuss customized solutions or request a quotation for your next project.

Frequently Asked Questions (FAQ)

1. What makes SS 347 better than SS 304/316 for high-temperature service?
SS 347 is stabilized with niobium, preventing intergranular corrosion and ensuring better mechanical strength at high temperatures — something 304/316 can’t sustain beyond 800°C.

2. What is the difference between 347 and 347H fittings?
The 347H grade has a higher carbon content for superior creep strength and high-temperature resistance, making it ideal for continuous exposure above 900°C.

3. What testing standards does Mcneil Instruments India follow?
We comply with ASTM A403 WP347/WP347H, ASME B16.9, and ISO 9001 quality management, performing full hydro, NDT, and PMI tests on each batch.

4. In what sizes and types are SS 347 fittings available?
From ½″ NB to 36″ NB, in seamless, welded, and fabricated forms — across all schedules from SCH 10 to XXS.

5. How do I request a quotation?
Visit www.Mcneilinstruments.com and fill out our inquiry form — our technical team will respond promptly with a detailed quote and specifications.