ASTM A376 TP347H HFW Solid Finned Tube with Carbon Steel Fins For HRSGs

ASTM A376 TP347H HFW Solid Finned Tube with Carbon Steel Fins For HRSGs

This tube is a high-performance heat exchanger tube designed for extreme service in high-temperature and high-pressure environments, such as boilers, superheaters, and reformers in power plants and petrochemical industries. Its core purpose is to transfer heat very efficiently from hot gases to a fluid (usually water or steam) inside the tube.

Here are some component breakdowns:

1. Base tube: ASTM A376 TP34H Seamless tubes

(1). Chemical Composition Requirements

Note: *Cb is the historical symbol for Niobium, commonly used in ASTM standards. This composition range is key to distinguishing TP347H from standard TP347, optimizing high-temperature creep resistance.

(2). Mechanical Property Requirements

2. Fin Type: HFW (High-Frequency Welded) Solid Fin

HFW is a precise, automated process where strips of steel (skelp) are formed into a cylindrical shape and the longitudinal seam is welded using a high-frequency electric current. It is not seamless, but it produces a very strong, consistent, and cost-effective weld. For high-pressure service, the weld area is often heat-treated and meticulously inspected to ensure integrity equal to the base metal.

While the tube itself is made of high-alloy stainless steel (TP347H), the fins are made from carbon steel. This is a common and economical design choice because:

• The fins operate at a slightly lower temperature than the tube wall in contact with the hot steam.
• Carbon steel provides good heat transfer, strength, and is significantly less expensive than stainless steel.
• The corrosion/oxidation resistance is provided primarily by the stainless steel tube. In high-temperature service, carbon steel fins will form a stable oxide layer.

3. Why This Specific Combination is Used?

This tube is engineered to solve a specific set of demanding conditions:

• High Internal Pressure & Temperature: The ASTM A376 TP347H HFW base tube withstands the high-pressure steam (e.g., in a superheater) and resists creep (slow deformation under stress at high heat).
• Corrosion/Oxidation Resistance: The TP347H stainless steel offers excellent resistance to oxidation (scaling) in the hot flue gas environment and is particularly resistant to sulfidation and chloride stress corrosion cracking in certain conditions.
• Efficient Heat Transfer: The solid carbon steel fins maximize heat absorption from the combustion gases and transfer it to the tube wall.
• Mechanical Durability: The solid finned construction resists damage from soot blowing, ash erosion, and thermal cycling.
• Cost Optimization: Using expensive stainless steel only for the pressure-bearing tube and cheaper carbon steel for the fins is an optimal balance of performance and cost.

Primary Applications & Industries

1. Power Generation (Coal-Fired, Biomass, Waste-to-Energy)

This is the most common application.

• Superheaters & Reheaters: The primary application. These are sections of the boiler where saturated steam is further heated to become superheated steam (e.g., 540°C to 600°C / 1000°F to 1112°F). The TP347H base tube withstands the high-pressure, high-temperature steam inside, while resisting oxidation and corrosion from the aggressive flue gas outside. The carbon steel fins efficiently absorb heat from the gas.
• Economizers (in corrosive environments): In plants burning fuels with high sulfur or chlorine content (e.g., certain coals, waste), the economizer (which preheats feedwater) can fall into a corrosive acid dew point temperature range. TP347H offers better resistance to acid dew point corrosion than standard carbon or low-alloy steel tubes.

2. Petrochemical & Refining

• Hydrogen Plant & Ammonia Plant Reformers: In the fired heater (reformer furnace) where the reforming reaction occurs, the process gas inside the tubes is at very high temperature and pressure in a hydrogen-rich environment. TP347H offers excellent resistance to creep and hydrogen embrittlement. The external fins absorb radiant and convective heat from the furnace burners.
• Chemical Process Heaters: Used in cracking furnaces (e.g., ethylene production) and other direct-fired heaters where process tubes are exposed to high heat flux and potentially corrosive combustion products.

3. Heat Recovery Steam Generators (HRSGs) in Combined Cycle Plants

• High-Pressure Superheater Sections: While the gas turbine exhaust is cleaner than coal flue gas, it is still at high temperature. In larger, more advanced HRSGs designed for higher steam parameters, TP347H tubes may be specified for the final superheater stages to ensure long-term reliability and higher efficiency.