Introduction
Heat exchangers play a critical role in maximizing thermal performance across industries such as geothermal energy, petrochemical, and power generation. Among the different tube designs, low finned tubes stand out as a proven solution to increase the surface area and improve heat transfer efficiency without requiring more installation space. Recently, a customer presented us with a highly technical requirement for duplex steel low finned tubes — an excellent example to illustrate how advanced materials and precision manufacturing meet the needs of demanding projects.
Typical Customer Requirement for Low Finned Tubes
The customer requested the following specification:
- Material: ASME SA789 S32205 Duplex
- Outside Diameter (OD): 19.05 mm
- Minimum Wall Thickness: 1.65 mm
- Fin Thickness: 0.33 mm
- Fin Height: To be optimized based on operating conditions
- Fins per Unit Length: 1023.6 fins/meter
- Tube Length: 17,500 mm
- Unfinned Ends: 113 mm at each side
- Quantity: 3,500 pieces
This configuration highlights how customers are focusing on both durability and efficiency in high-pressure and high-corrosion environments.
Why Low Finned Tubes?
Low finned tubes are manufactured by mechanically forming fins from the base tube material, resulting in:
- Increased Heat Transfer Area: More fins per unit length maximize efficiency without additional tube bundles.
- Compact Design: Higher output per unit volume, reducing overall equipment footprint.
- Durable Construction: As the fins are integral with the tube, there is no risk of detachment under thermal cycling.
- Operational Cost Savings: Enhanced efficiency leads to reduced energy consumption and improved system performance.
For environments where heat duty is critical — such as geothermal brine cooling or condenser units — this design ensures long service life and consistent performance.
Why Choose Duplex S32205?
Duplex stainless steel S32205 was selected by the customer due to its unique properties:
- High Resistance to Chloride Stress Corrosion Cracking
- Excellent Pitting Resistance (PREN ≥ 35)
- Superior Mechanical Strength compared with standard austenitic stainless steels
- Cost-Effectiveness: Requires thinner walls while maintaining strength, optimizing weight and price per unit length
These qualities make S32205 especially suitable for aggressive environments where seawater, geothermal brine, or chemical exposure are expected.
Technical Challenges and DLSS Solutions
Meeting this kind of requirement is not straightforward. Manufacturing thin-wall, long-length finned tubes requires precision and advanced quality control:
- Precision Fin Forming: Ensuring consistent fin thickness (0.33 mm) and density (1023.6 fins/m).
- Length and Straightness: For tubes up to 17.5 m, DLSS applies cold drawing and straightening processes to guarantee alignment.
- Surface Treatment: Acid pickling and passivation for corrosion resistance, optional bright annealing for enhanced cleanliness.
- Quality Assurance:
- EN 10204 3.1 or 3.2 certificates
- 100% Eddy Current + Hydrostatic Testing
- PMI (Positive Material Identification) for every heat batch
- Full ITP (Inspection & Test Plan) documentation
- Packaging: End caps, nitrogen purging, and seaworthy wooden cases to ensure safe transportation.
Application Insights
Low finned tubes like these are not limited to one sector. They are commonly applied in:
- Geothermal Power Plants
- Petrochemical Condensers and Coolers
- Seawater Desalination Units
- Refinery Heat Exchangers
By combining low fin geometry with duplex material performance, operators benefit from both thermal efficiency and long service life.
Conclusion – Partner with DLSS
This customer case demonstrates how specific and demanding requirements are becoming the new norm in heat exchanger design. DLSS specializes in supplying precision-engineered tubes — including low finned tubes in duplex, super duplex, titanium, CuNi, and high-alloy steels — backed by rigorous quality control and global project experience.
Contact us at info@dlsspipe.com or visit www.dlsspipeline.com to discuss your upcoming projects.
