YUHONG GROUP HFW Finned Tube: TP347H Stainless Base Tube + Carbon Steel Fins for Power Boiler Heat Exchangers

This case covers a completed export shipment of high-frequency welded (HFW) finned tubes with a hybrid “TP347H stainless steel base tube + carbon steel fin” construction, exported from China to Pakistan for high-temperature, high-pressure and corrosive heat exchange duty — most typically boiler equipment in the power generation industry.

Technical highlights: produced to ASTM A376 with NPS 40, 141.3 mm OD, 6.55 mm average wall and 3,288 mm tube length, contracted in Ningbo and shipped by sea freight to the customer’s project site in Pakistan.

Power boiler heat exchangers operate under a combination of conditions that punish conventional tube selection:

• High metal temperature — radiant and superheater zones push tube metal well beyond the creep range of ordinary carbon and low-alloy steels.
• High internal pressure — the pressure boundary must hold design pressure with adequate wall thickness for the full service life.
• Corrosive flue gas and steam-side attack — oxidation, intergranular corrosion and ash-related attack shorten tube life.
• Heat transfer efficiency — a bare tube gives limited area per unit length, meaning a larger, heavier, costlier exchanger.

A single-material answer forces a trade-off: all-stainless solves corrosion but multiplies cost; all-carbon-steel is cheaper but fails the temperature and corrosion requirement.

The pressure boundary is built from TP347H austenitic stainless steel to ASTM A376. The niobium-stabilised grade resists oxidation and intergranular corrosion at elevated temperature, with service capability approaching 815 °C. The 6.55 mm wall on the 141.3 mm OD tube provides the structural margin for continuous service under severe boiler conditions.

Carbon steel fins are high-frequency welded onto the TP347H base tube. The HFW process produces a true metallurgical bond along the full helix, giving low contact resistance and consistent fin efficiency compared with tension-wound or embedded fins. The finned surface expands the effective heat transfer area to more than 8 times that of the bare tube, so a shorter, lighter and lower-cost exchanger achieves the same duty. Using carbon steel for the fin rather than stainless keeps material cost under control, because the fin works as a heat transfer surface, not as a pressure boundary.

Fins are HFN carbon steel, metallurgically bonded along the full helix of the TP347H base tube.

• Material traceability — mill certificates for TP347H tubes and CS fin strip, matched to heat numbers.
• Weld integrity — HFW parameters monitored inline; fin-to-tube bond checked by destructive pull tests on coupons from each production run.
• Pressure testing — hydrostatic test on every base tube before finning and after welding, at the specified hold time and pressure.
• Dimensional and visual inspection — OD, wall, fin pitch, fin height, straightness and length verified piece by piece.
• Export packing — bundled tubes, protected fin edges, capped ends, export-marked for container shipment from Ningbo to Pakistan.

• Reliable pressure boundary — TP347H base tubes resist oxidation and intergranular corrosion in severe boiler service.
• More than 8× the heat transfer area of an equivalent bare tube, enabling a compact, low-pressure-drop exchanger layout.
• Controlled total cost — stainless is used only where it is functionally required, and carbon steel where it is cost-efficient.
• Predictable export delivery — produced to ASTM A376, export-packed and shipped as one consolidated lot from Ningbo to Pakistan, ready for site fabrication.

Alongside the TP347H HFW finned tube, the same line also supplies ASME A335 P22 studded fin tubes. Studs welded to the tube surface resist ash deposition, erosion and mechanical cleaning better than a continuous helical fin, which suits boiler water walls, furnace walls and heat recovery sections. The Cr-Mo P22 base tube gives good high-temperature strength at lower cost than austenitic stainless.

This TP347H + carbon steel HFW finned tube configuration is widely applied in power plant boiler economisers, superheaters and reheaters, waste heat recovery and other high-temperature, high-pressure, corrosive heat exchange services where long service life and heat transfer efficiency must be achieved within a controlled budget. This shipment was supplied for power boiler service in Pakistan.