When it comes to operating in severely corrosive and high-temperature environments, choosing the right material for heat exchanger and condenser tubing is critical. One standout option is Stainless Steel 317/317L Welded U Tubes—engineered for superior corrosion resistance, especially in acidic and chloride-rich conditions.
In this blog, we’ll explore the properties, benefits, applications, and technical specifications of SS 317 and 317L welded U tubes—and why they are a go-to choice for demanding industrial processes.
What Are Stainless Steel 317 and 317L?
Stainless Steel 317 is an austenitic chromium-nickel stainless steel with higher molybdenum content than 316, offering superior resistance to pitting, crevice corrosion, and chemical attack.
Stainless Steel 317L is the low-carbon version of 317, designed to reduce the risk of intergranular corrosion during welding and high-temperature exposure.
Chemical Composition Highlights:
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Molybdenum (3.0–4.0%): For improved corrosion resistance
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Nickel (11.0–15.0%): Ensures excellent strength and ductility
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Low Carbon Content in 317L: Prevents carbide precipitation and enhances weldability
Benefits of Welded U Tubes in 317/317L
Welded U tubes are produced by forming and welding flat strips into tubes, then bending them into a U-shape for efficient heat exchange. When fabricated from 317/317L, these tubes offer both mechanical integrity and superior corrosion resistance, even in sulfuric acid, acetic acid, and chloride-laden environments.
Key Advantages:
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High resistance to localized corrosion (pitting and crevice)
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Excellent performance in aggressive chemical processes
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Low carbon version (317L) reduces weld decay and improves service life
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Cost-effective alternative to high-alloy materials
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U-bend design optimizes thermal expansion handling and space efficiency
Typical Applications of SS 317/317L Welded U Tubes
Due to their enhanced resistance and reliability, 317/317L U tubes are extensively used in:
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Chemical and Petrochemical Processing: Suitable for handling strong acids and corrosive agents
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Pulp and Paper Industry: Resist chemical bleaching agents and high humidity
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Marine Applications: Withstand saline environments and biofouling
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Food and Beverage Plants: Ensure hygiene with non-contaminating surfaces
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Power Plants: Used in boilers, feedwater heaters, and condensers
Standards and Specifications
317/317L Welded U Tubes are typically manufactured to the following standards:
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ASTM A249 / ASME SA249 (for welded austenitic tubes)
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ASTM A213 / ASME SA213 (for seamless and welded tubes in heat exchangers)
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ASTM A688 (for high-performance tubing in nuclear service)
Dimensional Range:
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Outer Diameter: 6.35 mm to 50.8 mm (1/4” to 2”)
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Wall Thickness: 0.5 mm to 3.0 mm
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U-Bend Radius: As per customer specs (typically 1.5x to 2.5x OD)
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Tube Lengths: Up to 30 meters (straight) before bending
