Helical Finned Tube — Continuously Welded Spiral ND Steel Fin Tube for Boiler Economizers

Material
A high-frequency resistance welded helical/spiral finned tube produced with an ND steel (09CrCuSb) base tube and optional ND/carbon/stainless fin strip. ND steel is a Cu–Sb–Cr–alloyed low-alloy steel engineered to resist low-temperature sulfuric-acid dew-point corrosion and chloride attack in flue-gas paths, making it ideal for boiler economizers and air preheaters.

Specifications

• Tube OD (bare): 19–63.5 mm (3/4"–2-1/2"); other sizes on request

• Wall thickness: 2.0–8.0 mm

• Fin type: Solid or serrated helical fin, continuous wrap, HFERW bond

• Fin material & thickness: ND steel / carbon steel / stainless; 0.8–3.0 mm typical

• Fin height: 8–20 mm (±1.0 mm after welding)

• Fin pitch (fins per meter): as specified; tolerance +5%/−2%

• Tube straightness (finished finned tube): max deviation 5 mm per 3 m (scaled for shorter lengths)

• Ends: Plain or beveled; specified bare ends length tolerance ±6 mm or one fin spacing, whichever is greater

• Typical base-tube alternatives: SA210 A-1 / GB 20G (carbon), A213 T11/T12 (Cr-Mo), EN 10216-2 P235GH / 16Mo3.

Key Features

• High corrosion resistance at dew point

• Efficient, durable fin-to-tube bond (HFERW)

• Geometric consistency for performance

• Material traceability to ordered standards

Our Advantages

1. Straightness & fit-up — ≤5 mm/3 m finished tube; ≤3 mm/3 m bare tubes

2. Dimensional tolerances — Bare OD ≤±1.0 mm; fin height ±1.0 mm; fin pitch +5%/−2%

3. Weld integrity — Min weld width ≈90% of fin thickness or ≥170 MPa weld tensile; controlled weld interruptions; no PWHT required

4. Right material for flue gas — ND steel specifically targets acid dew-point service in economizers

5. Standards-based alternatives — SA210 A-1 / GB 20G; A213 T11/T12; EN P235GH

Chemical Composition (wt.%)

• 09CrCuSb (ND steel): C ~0.09; Cr 0.30–0.60; Cu 0.20–0.40; Sb 0.05–0.10

• GB 20G: C 0.17–0.23; Si 0.17–0.37; Mn 0.35–0.65; P ≤0.025; S ≤0.015–0.020; residual Cr ≤0.25; Cu ≤0.20

• SA210 A-1: C ≤0.27; Si ≤0.10; Mn ≤0.93 (adjustable with C); P ≤0.035; S ≤0.035

• A213 T11: C ≤0.15; Si 0.50–1.00; Mn 0.30–0.60; P ≤0.025; S ≤0.025; Cr 1.00–1.50; Mo 0.44–0.65

• A213 T12: C ≤0.15; Si 0.50–1.00; Mn 0.30–0.60; P/S ≤0.025 (T12S option S ≤0.045); Cr 1.00–1.50; Mo 0.44–0.65

Mechanical Properties

• SA210 A-1: Tensile ≥415 MPa; Yield ≥255 MPa; Elongation ≥30%

• A213 T11/T12: Tensile ≥415 MPa; Yield ≥205 MPa; elongation per A213 table (size dependent)

• GB 20G: Typical plate/tube levels ~Tensile 410–500 MPa; Yield ≥235 MPa; Elongation ≥24% (verify on MTC)

• 09CrCuSb: Supplier-qualified per order; certified on MTC

Execution Standards

• ASTM/ASME: A213/SA213 (T11, T12), A210/SA210 (A-1)

• EN: EN 10216-2 (P235GH, 16Mo3)

• JIS: G3461 (carbon), G3462 (alloy)

• GOST: 8731/8732 (seamless), 8734 (precision cold-formed)

• Fin-weld reference: International HFERW fin dimensions/tolerances/tests

Application Fields
Power-plant economizers, air preheaters, waste-heat recovery, flue-gas condensers, and industrial heat exchangers in SOx/Cl−-bearing service.

Q: Are you trading company or manufacturer ?

A: manufacturer,also can do trading.

Q: How long is your delivery time?

A: Generally speaking,it is 10-15 days if the goods are in stock,or it is 30-40 days if the goods are not in stock,

it is according to quantity.

Q: Do you provide samples? is it free or extra ?

A: Yes, we could offer the sample for free charge but need pay the cost of freight.

Q: What is your terms of payment ?

A: Payment<=2000USD, 100% in advance. Payment>=2000USD, 30% T/T in advance ,balance before shippment.

If you have another question, pls feel free to contact with me.