Stainless Steel 347 and 347H Instrumentation Tubes are widely used in high-temperature and corrosive environments where excellent mechanical properties and resistance to intergranular corrosion are essential. These grades, part of the austenitic stainless steel family, are stabilized with niobium, making them ideal for demanding instrumentation applications in industries such as oil and gas, petrochemicals, power generation, and more.
This article delves into the unique features, chemical composition, mechanical properties, and key applications of SS 347/347H instrumentation tubes.
Understanding Stainless Steel 347 and 347H
Stainless Steel 347 is a niobium-stabilized austenitic stainless steel developed to offer resistance against intergranular corrosion after exposure to temperatures in the chromium carbide precipitation range (800–1500°F or 427–816°C).
Stainless Steel 347H, on the other hand, is a high-carbon version of 347, typically used for enhanced creep resistance and higher strength at elevated temperatures. The higher carbon content (minimum 0.04%) makes 347H better suited for applications involving prolonged exposure to high heat.
Chemical Composition
Element SS 347 (%) SS 347H (%)
Carbon ≤ 0.08 0.04–0.10
Chromium 17.0–19.0 17.0–19.0
Nickel 9.0–13.0 9.0–13.0
Niobium (Cb + Ta) ≥10xC ≥10xC
Manganese ≤ 2.0 ≤ 2.0
Silicon ≤ 1.0 ≤ 1.0
Phosphorus ≤ 0.045 ≤ 0.045
Sulfur ≤ 0.030 ≤ 0.030
Key Features of SS 347/347H Instrumentation Tubes
Excellent Intergranular Corrosion Resistance: The addition of niobium prevents carbide precipitation, offering superior resistance in corrosive environments.
High-Temperature Stability: Ideal for use in environments up to 1000°C without scaling or deformation.
Creep Strength: The high carbon content in 347H enhances creep and stress rupture resistance.
Good Weldability and Formability: Can be easily fabricated using standard welding methods.
Long Service Life: Durable even under harsh chemical and thermal conditions.
Common Specifications & Standards
ASTM A213 / A269 – Seamless and welded instrumentation tubes
ASME SA213 / SA269
NACE MR0175
Size Range: 1/8″ OD to 2″ OD (custom sizes available)
Wall Thickness: 0.5mm to 3mm or as specified
Applications of SS 347/347H Instrumentation Tubes
These instrumentation tubes are extensively used in:
1. Oil & Gas Industry
Control lines, hydraulic tubing, and chemical injection systems
Offshore and subsea piping exposed to high pressures and saline environments
2. Chemical and Petrochemical Processing
Tubing for chemical transfer and pressure instrumentation systems
Resistance to organic and inorganic acids makes it ideal for aggressive chemical plants
3. Power Generation
Heat exchangers, boiler tubes, and superheater tubing
Excellent performance in high-pressure and high-temperature systems
4. Aerospace and Defense
Instrumentation lines for hydraulic and fuel systems
Stability under extreme heat cycles and vibrations
5. Pharmaceutical & Food Processing
Cleanability and corrosion resistance make it suitable for sterile environments
Why Choose 347/347H for Instrumentation?
Instrumentation systems are critical for precision measurement and control. The reliability of these systems hinges on the quality of the tubing materials. SS 347/347H instrumentation tubes offer the perfect combination of corrosion resistance, temperature durability, and mechanical strength, which is why they are preferred for instrumentation in harsh environments.
Conclusion
Stainless Steel 347 and 347H Instrumentation Tubes are highly versatile and reliable solutions for industries that demand high-performance tubing under challenging conditions. Their superior corrosion resistance, heat tolerance, and mechanical strength ensure accurate performance and long operational life. Whether you’re working in a high-temperature refinery or an offshore oil rig, these tubing grades can deliver both durability and efficiency in instrumentation systems.
For sourcing premium-quality SS 347/347H Instrumentation Tubes, trust manufacturers and exporters with a proven track record of meeting global quality standards.