TP321H High Frequency Welded Finned Tube with Carbon Steel (CS) Fins for Waste Heat Recovery Systems
In high-temperature waste heat recovery units (WHRU), HRSG economizers, and process heater convection sections, operators face rapid efficiency loss from limited surface area, thermal fatigue, and material degradation under cyclic flue gas exposure (typically 400–750 °C). Our TP321H base tube + CS fin high-frequency welded (HFW) finned tubes deliver metallurgical bonding that multiplies external heat transfer area while maintaining tube-side integrity against creep and intergranular attack. This combination recovers more energy from exhaust streams, reduces fuel consumption, and extends equipment run time between outages.
TP321H Base Tube + CS Fin Structure and High-Frequency Welding Process
The tube consists of a seamless or welded TP321H (UNS S32109) austenitic stainless steel base tube with continuous helical carbon steel fins attached by high-frequency resistance welding. The fin strip is edge-wound under controlled tension while a high-frequency current (typically 200–450 kHz) generates localized resistance heat at the fin root–tube interface. Applied forge pressure creates a continuous metallurgical bond without filler metal. Weld penetration and bond strength are verified by peel tests and metallographic examination, achieving fin-to-tube contact efficiency ≥95 % and eliminating air-gap thermal resistance.
Chemical Composition of TP321H Base Tube and Carbon Steel Fins
TP321H Base Tube (ASTM A312 / ASME SA312)
| Element |
Composition (%) |
| Carbon (C) |
0.04 – 0.10 |
| Manganese (Mn) |
≤ 2.00 |
| Phosphorus (P) |
≤ 0.045 |
| Sulfur (S) |
≤ 0.030 |
| Silicon (Si) |
≤ 1.00 |
| Chromium (Cr) |
17.0 – 19.0 |
| Nickel (Ni) |
9.0 – 12.0 |
| Titanium (Ti) |
4×(C+N) min – 0.70 max |
| Nitrogen (N) |
≤ 0.10 |
| Iron (Fe) |
Balance |
Carbon Steel Fins (typical low-carbon grades such as Q235 / SPCC / equivalent)
| Element |
Typical Composition (%) |
| Carbon (C) |
0.12 – 0.20 |
| Manganese (Mn) |
0.30 – 0.70 |
| Phosphorus (P) |
≤ 0.045 |
| Sulfur (S) |
≤ 0.045 |
| Silicon (Si) |
≤ 0.30 |
| Iron (Fe) |
Balance |
Dimensional Range and Tolerances (TP321H/CS HFW Finned Tube)
| Parameter |
Standard Range |
Typical Tolerance |
| Base Tube OD |
15 – 219 mm |
±0.25 mm or ±0.5 % |
| Base Tube Wall Thickness |
1.0 – 12 mm |
±10 % of nominal |
| Fin Height |
8 – 30 mm |
±0.5 mm / ±1.0 mm |
| Fin Thickness |
0.8 – 3.0 mm |
±0.1 mm |
| Fin Pitch / Density |
3 – 25 mm (1–8 FPI) |
±5 % over 300 mm length |
| Tube Length |
Up to 18–24 m (custom) |
±5–10 mm |
| Unfinned Ends |
50 – 300 mm (as required) |
— |
Custom dimensions outside the above ranges are available upon engineering review.
Performance Advantages in Waste Heat Recovery Service
- Metallurgical HFW bond maintains thermal conductivity under repeated thermal cycling and vibration, preventing fin detachment common with tension-wound designs.
- TP321H titanium stabilization plus controlled carbon provides superior creep-rupture strength and resistance to intergranular corrosion in the 500–750 °C range compared with non-stabilized grades.
- Carbon steel fins deliver high thermal conductivity at lower material cost, optimizing the cost-to-performance ratio for flue-gas side service where oxidation is moderate.
- Increased external surface area (typically 5–12× bare tube) raises overall heat transfer rates, allowing smaller equipment footprints or higher energy recovery from the same gas stream.
- Solid helical fin geometry resists ash fouling better than dense serrated alternatives in many dirty-gas applications while remaining cleanable by soot-blowing.
Application Focus: Waste Heat Recovery, HRSG & Process Heaters
These TP321H/CS HFW finned tubes are engineered for continuous duty in:
- Heat Recovery Steam Generator (HRSG) economizer and evaporator sections recovering gas-turbine exhaust heat.
- Boiler economizers and air preheaters in coal-fired, biomass, and waste-to-energy plants.
- Fired heater convection banks and waste heat boilers in refining and petrochemical units.
- Flue-gas heat recovery systems where tube-side fluid is water, steam, or process fluid under elevated pressure and temperature.
In these services the product directly addresses efficiency shortfalls caused by insufficient surface area and material limitations of plain tubes or lower-grade finned tubes, delivering measurable gains in recovered heat and reduced auxiliary fuel use.
Packaging and Logistics
Tubes are packed in seaworthy plywood cases or steel-frame wooden crates with internal supports to prevent fin deformation. Tube ends are capped with plastic protectors; external surfaces receive temporary anti-rust oil or VCI protection as required. Marking includes heat number, size, material grade, and order reference. Standard export packing supports FCL/LCL shipment; special length or project packaging can be arranged.
Certificates, Quality Control & Procurement Terms
All material is supplied with EN 10204 3.1 Mill Test Certificates covering chemical analysis, mechanical properties, and heat treatment. Production inspections include dimensional verification, weld integrity (peel / visual / NDT as specified), hydrostatic or pneumatic testing of the base tube, and final visual examination. Optional third-party inspection (SGS, BV, Lloyd’s, etc.) is available.
Commercial Terms
- MOQ: 10–50 pieces (or equivalent tonnage) depending on diameter and length; larger project quantities preferred.
- Price basis: FOB Shanghai / Ningbo / other China main ports (CIF or CFR available on request).
- Lead Time: 30–50 days after order confirmation and deposit for standard sizes; 45–60 days for special dimensions or large volumes.
- Payment: T/T or L/C at sight.
Contact us with your design parameters (tube OD, wall thickness, fin height/pitch, length, quantity, and design temperature/pressure) for a project-specific quotation and detailed technical data sheet.
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