ASME SA213 T22 Serrated Finned Tube with Carbon Steel Fins For Boilers Banks

ASME SA213 T22 Serrated Finned Tube with Carbon Steel Fins For Boilers Banks

An ASME SA213 T22 Serrated Finned Tube with Carbon Steel Fins is a high-performance heat exchanger tube designed for extreme service, typically in high-temperature and high-pressure environments like boilers, superheaters, and reformers in power plants and petrochemical industries.

In simple terms, it's a high-strength alloy steel core tube with carbon steel fins that are serrated in shape to maximize heat transfer efficiency.

Here are some detailed breakdowns:

1. Base Tube: ASME SA213 T22 seamless tubes

(1). Chemical Composition (Weight %)

The composition is specified in the ASME SA-213 standard. The following table shows the required limits.

Other Notes:

The values are maximum ranges unless otherwise specified.

Elements like Copper (Cu) and Nickel (Ni) may have incidental presence with low limits.

(2). Mechanical Properties

The mechanical properties are required for the material in the normalized and tempered heat treatment condition.

Why T22? The chromium content provides improved resistance to oxidation (scaling) and corrosion, especially at high temperatures. The molybdenum increases the strength of the steel at elevated temperatures (creep strength). This makes T22 an excellent choice for service temperatures up to about 1050°F (565°C).

2. Serrated Fin: This is a specific, high-efficiency fin design.

The long, continuous fin strip is cut at regular intervals to create serrations or grooves.

This design creates turbulence in the gas flow, which breaks up the stagnant boundary layer of gas on the fin surface.

Key Benefit: This turbulence significantly improves the heat transfer coefficient compared to a solid (plain) fin, often by 15-25%.

Fin’s Material: Carbon Steel

Why Carbon Steel? The fins are exposed to the gas side, which, while hot, is often at a lower pressure and a different temperature than the fluid inside the T22 tube. Carbon steel provides a good balance of:

• Cost: It is much less expensive than the T22 alloy.
• Workability: It is easy to form and wrap into the serrated fin shape.
• Adequate Properties: It has sufficient strength and oxidation resistance for the gas-side temperature in many applications. If the gas side is highly corrosive, a more resistant fin material might be chosen.

3. Key Advantages of ASME SA213 T22 Serrated Finned Tube with Carbon Steel Fins

Advantages:

• High Efficiency: Serrated fins provide superior heat transfer.
• High-Temperature Strength: The T22 core tube can withstand intense internal pressure and temperature.
• Cost-Effective: Using carbon steel for the fins keeps the overall cost down without compromising the tube's primary pressure-containing function.
• Robust Construction: The L-foot finning process creates a strong, durable bond resistant to thermal cycling and vibration.

The application of ASME SA213 T22 Serrated Finned Tube with Carbon Steel Fins?

1. Heat Recovery Steam Generators (HRSGs)

Function: HRSGs are the "waste heat boilers" located behind gas turbines in combined-cycle power plants. They capture the energy from the hot turbine exhaust to generate steam.

Why Used Here: The gas turbine exhaust is large in volume and relatively low in pressure, but very hot. The T22 core tube is strong enough to handle the high-pressure steam, while the extensive serrated carbon steel fins efficiently capture heat from the large volume of gas. This dramatically improves the plant's overall efficiency.

2. Boilers (Waterwall, Economizer, and Boiler Bank Sections)

Function: In coal-fired or biomass-fired power plants, these tubes are used in sections where the heat flux is high, but not the highest (for which T91 or stainless steels might be used).

Why Used Here: The T22 material offers excellent resistance to the corrosive compounds in flue gas (like sulfur) at these temperatures. The serrated fins maximize heat absorption from the combustion gases, converting water to steam more effectively.

3. Superheaters and Reheaters

Function: These are critical sections in a boiler where saturated steam is further heated to become "superheated" (dry, high-energy) steam, which drastically improves the efficiency of the steam turbine.

Why Used Here: This is one of the most demanding services.

T22 Core Tube: It withstands the high internal pressure of the steam and the high metal temperatures (typically up to ~565°C / 1050°F) without creeping (deforming over time).

Serrated Fins: They efficiently transfer heat from the very hot flue gases to the steam inside. The improved heat transfer is crucial for achieving the target steam temperature.

4. Process Heaters & Reformers (Petrochemical & Refining Industries)

Function: In oil refineries and chemical plants, fired heaters are massive furnaces that heat process fluids (e.g., crude oil, hydrogen) to very high temperatures to drive chemical reactions (like in a Steam Methane Reformer).

Why Used Here: The environment inside these furnaces is aggressive, with high temperatures and potentially corrosive process streams. The T22 tube provides the necessary strength and corrosion resistance, while the fins ensure efficient and uniform heat transfer from the furnace flames to the process fluid inside the tubes.

5. Waste Incineration & Cogeneration Plants

Function: These plants burn waste or biomass to generate power and/or heat. The flue gases can be highly corrosive due to the presence of chlorides and other aggressive elements.

Why Used Here: The chromium content in T22 provides a baseline resistance to this corrosive environment. Using serrated finned tubes allows for a more compact boiler design, which is beneficial in these often space-conscious plants, while still handling the high pressures and temperatures.