ASME SA213 T11 Serrated Finned Tube with Carbon Steel Fins For HRSGs
An ASME SA213 T11 HFW Serrated Finned Tube with Carbon Steel Fins is the same high-performance heat exchanger tube as described before, but with a deliberate material choice for the fins to optimize performance and cost. The fins (the external heat-transfer enhancement) are made from carbon steel instead of an alloy like T11.
Key Clarification: The "Base Tube" vs. "The Fins"
1. The Base Tube (Pressure Part): This is the inner tube that carries the high-pressure, high-temperature fluid (water, steam, oil).
ASME SA213 T11 Seamless Tubes’ Chemical Composition:
The composition is specified in ASTM A213/A213M. Requirements are for both heat analysis (from the melt) and product analysis (from the finished product).
| Element | Composition Range (%) |
| Carbon (C) | 0.05 – 0.15 |
| Manganese (Mn) | 0.30 – 0.60 |
| Phosphorus (P) | 0.025 max |
| Sulfur (S) | 0.025 max |
| Silicon (Si) | 0.50 – 1.00 |
| Chromium (Cr) | 1.00 – 1.50 |
| Molybdenum (Mo) | 0.44 – 0.65 |
ASME SA213 T11 Seamless Tubes’ Mechanical Properties:
Mechanical Properties
These are the minimum required properties for tubes in the normalized and tempered heat treatment condition.
| Property | Value |
| Tensile Strength | 415 MPa (60,000 psi) min |
| Yield Strength (0.2% offset) | 205 MPa (30,000 psi) min |
| Elongation in 2 inches (50.8 mm) [*] | 30% min (for walls ≤ 0.07 in / 1.8 mm)
See table below for others |
2. Fins: Carbon Steel Serrated Fins
Why Use Carbon Steel for Fins?
- Cost Reduction: This is the primary reason. Carbon steel is significantly cheaper than alloy steel (like T11). Since the fins make up a substantial volume of the material in the final product, using carbon steel lowers the overall cost.
- Adequate Performance for the Fin's Role: The fins are exposed to the gas/air side of the heat exchanger (e.g., flue gas, exhaust air). This environment is typically at a much lower pressure and often at a lower temperature than the internal fluid in the T11 base tube. Carbon steel can easily withstand these conditions.
- Good Thermal Conductivity: Carbon steel has good thermal conductivity, which is essential for efficiently transferring heat from the fin surface to the base tube.Ease of Fabrication: Carbon steel is easier to roll, cut, and weld (in the case of embedded/L-foot fins) than alloy steel.
3. Why This Specific Combination (T11 Tube + CS Fins) is Common & Logical
This specification represents a classic engineering optimization:
The Base Tube (T11) handles the demanding duty: It contains the high-pressure, often superheated steam or hot water. The 1.25% Chromium content provides the necessary oxidation resistance and strength at the operating temperature.
The Fins (Carbon Steel) handle the less demanding duty: They are in the cooling gas stream. While the gas might be hot, it is not under high pressure, and its temperature is often below the oxidation limits for carbon steel. Using expensive alloy here is an unnecessary cost.
The key assumption is that the gas-side temperature at the fin location is within the safe operating limit for carbon steel (typically up to ~480°C / 900°F for prolonged service, though this depends on the specific gas composition and corrosion potential).
Core Application Philosophy
This tube is designed for high-efficiency, cost-optimized heat transfer in environments where:
1. Primary Application: Waste Heat Recovery Boilers & HRSGs
This is the most dominant application. These tubes are the "building blocks" for recovering energy from hot exhaust gases.
In Heat Recovery Steam Generators (HRSGs): They are used in the Evaporator and Economizer sections.
In Waste Heat Boilers (Chemical, Petrochemical, Refining): Used to capture heat from process furnace flue gases, reactor effluents, or incinerator exhaust.
2. Power Plant Boiler Sections
Economizers: Located at the boiler's back end, they preheat feedwater using relatively low-temperature flue gas (~250°C - 400°C). T11 handles the high-pressure feedwater, while CS fins efficiently extract heat from the non-corrosive flue gas.
Low-Temperature Superheaters: In some designs, the initial superheater stages where steam temperature is being raised, but metal temperatures are not extreme, can utilize T11 tubes with CS fins.
3. Process Heaters & Fired Heaters
In refineries and petrochemical plants, process heaters (fired heaters) often have a convection section.
4. Air Heaters
While often built with lower-grade tubes, certain steam-coil air heaters that use medium-pressure steam to heat combustion air can employ this tube type for durability and efficiency.
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ASME SA213 T11 Serrated Finned Tube with Carbon Steel Fins For HRSGs Application Images
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