ASTM A312 TP321H HFW Solid Finned Tube with 11-13Cr Fins For
Process Furnaces
ASTM A312 TP321H HFW Solid Finned Tube with 11-13Cr Fins is a
high-performance, composite tube designed for efficient heat
transfer in high-temperature and corrosive environments. It
consists of a core pipe made of a special stainless steel (TP321H)
with fins made of a heat-resistant chromium steel (11-13% Cr)
welded onto its outer surface. The "HFW" and "Solid" describe the
manufacturing process of the fins.
Here are some detailed Component Breakdowns:
1. Bare Tubes: ASTM A312 TP321H seamless tubes
(1)Chemical Composition (Weight %)
The composition is specified in ASTM A312/A312M standard. The
following table shows the requirements for TP321H.
| Element | Composition (%) | Notes |
| Carbon (C) | 0.04 - 0.10 | The key difference for the "H" grade. Higher carbon ensures
high-temperature strength. |
| Manganese (Mn) | 2.00 max | - |
| Phosphorus (P) | 0.045 max | - |
| Sulfur (S) | 0.030 max | - |
| Silicon (Si) | 0.75 max | - |
| Chromium (Cr) | 17.00 - 19.00 | Provides corrosion resistance and oxidation resistance. |
| Nickel (Ni) | 9.00 - 12.00 | Stabilizes the austenitic microstructure. |
| Titanium (Ti) | 5*(C+N) min - 0.70 max | The stabilizer. Prevents sensitization by tying up carbon. |
| Nitrogen (N) | 0.10 max | - |
Key Point on Stabilization: The minimum Titanium content is
calculated as 5 times the sum of the Carbon + Nitrogen content.
This ensures there is enough Titanium to fully stabilize the steel
and prevent chromium carbide formation at grain boundaries.
(2). Mechanical Properties
The mechanical properties are specified for the material in the
annealed condition.
| Property | Requirement | Notes |
| Tensile Strength, min | 515 MPa (75 ksi) | - |
| Yield Strength (0.2% Offset), min | 205 MPa (30 ksi) | - |
| Elongation in 2 in. (50 mm), min | 35% | Elongation requirement is reduced for thinner walls; see ASTM A312
for details. |
2. HFW Finned Tube Type-Solid Finned Tube
- Solid Fins: This means the fins are made from a solid strip of metal and are
integrally bonded to the base tube (in this case, via HFW). They
are not a separate piece mechanically attached (like embedded or
L-foot fins).
- Key Advantage: The solid, welded bond has very low thermal resistance, allowing
for highly efficient heat transfer from the tube to the fins and
into the surrounding medium (or vice-versa). It also makes the
assembly robust and resistant to fin loosening due to thermal
cycling.
3. Fins Material: 11-13Cr
11-13% Chromium (Cr) Steel: This is a classification for a family
of heat-resistant ferritic steels (like Grade 409 or 410S).
Why use this for fins?
- Oxidation Resistance: Chromium forms a protective oxide layer (Cr₂O₃) on the surface,
which prevents rapid scaling and degradation in high-temperature
environments (e.g., furnace flue gases).
- Cost-Effectiveness: While the base tube needs to withstand internal pressure and
corrosion from the process fluid, the fins primarily need to resist
the external atmosphere. Using a specialized heat-resistant steel
for the fins is often more economical than using the more expensive
TP321H for the entire finned surface, while still providing
excellent service life.
In essence, you specify and use an ASTM A312 TP321H HFW Solid
Finned Tube with 11-13Cr Fins when you need a reliable, efficient,
and long-lasting heat transfer solution in one of the most
demanding industrial settings. It is the material of choice for
critical heat recovery applications where failure is not an option
due to the extreme costs of downtime and replacement.
Core Application: High-Temperature, High-Pressure Heat Recovery
This finned tube is engineered for situations where standard carbon
steel or even basic stainless steel tubes would quickly fail. The
combination of the TP321H core tube and the 11-13Cr fins creates a
component that excels in:
- High-Temperature Service: Sustained operation at metal temperatures
typically above 1000°F (538°C), where creep strength (the gradual
deformation of material under constant stress) becomes a critical
design factor.
- Corrosive & Oxidizing Environments: Exposure to flue gases,
combustion products, and other aggressive atmospheres.
- High Internal Pressure: The core tube must contain a process fluid
(usually water, steam, or a process gas) at high pressure.
Specific Industries and Equipment
You will find this tube in the Convection Sections of the following
critical industrial units:
1. Heat Recovery Steam Generators (HRSGs)
What it does: Captures waste heat from the exhaust of a gas turbine
to produce steam for power generation or process use.
2. Chemical & Petrochemical Process Heaters/Furnaces
What it does: Heats process fluids (e.g., crude oil, hydrocarbons)
to very high temperatures for reactions like cracking or reforming.
3. Refinery Fired Heaters
What it does: Similar to process heaters, these are critical units
in oil refineries for distillation, hydrotreating, and coking
processes.
4. Waste Incineration & Biomass Boilers
What it does: Generates steam by burning waste or biomass. The flue
gases from these sources are often highly corrosive due to the
presence of chlorides, sulfurs, and other aggressive compounds.
5. Catalytic Cracking Units (FCCU)
What it does: A key unit in refineries that breaks down heavy gas
oils into gasoline and other lighter products. It involves intense
heat and catalyst circulation.
