STAINLESS STEEL SEAMLESS TUBE ASME SA213 TP347 HEAT EXCHANGER TUBE
A TP347 heat exchanger tube is a seamless austenitic stainless steel tube specifically designed for heat transfer equipment. It is a stabilized grade of 18/8 stainless steel (18% Chromium, 8% Nickel) that contains the element Niobium (Nb) or Columbium (Cb) .
Due to its excellent resistance to intergranular corrosion and high-temperature strength, it is widely used in:
- Shell and tube heat exchangers
- Condensers
- Boilers and superheaters
- Petrochemical refineries
- Power generation plants
The primary advantages of TP347 come from its Niobium (Cb) addition, which stabilizes the material against "sensitization."
1. Superior Resistance to Intergranular Corrosion
- The Problem: Standard stainless steels (like TP304) form "chromium carbide" at grain boundaries when welded or exposed to high heat (800-1500°F / 427-816°C). This creates a chromium-depleted zone that rusts/cracks easily.
- The TP347 Solution: Niobium has a higher affinity for Carbon than Chromium does. It binds with the Carbon first, preventing Chromium from forming carbides.
- Result: The tube retains its corrosion resistance without post-weld heat treatment. This is critical for heat exchangers where welding is required.
2. Excellent High-Temperature Strength
- Creep Resistance: TP347 maintains higher strength under long-term stress at high temperatures compared to TP304 or TP316L.
- Oxidation Resistance: It can withstand continuous service temperatures up to 1500°F (816°C) without scaling significantly.
- Structural Stability: It does not easily deform (creep) under pressure at high temperatures, making it ideal for superheaters and reformers.
3. Good Mechanical Properties
- Tensile Strength: Min. 515 MPa (75,000 psi)
- Yield Strength (0.2% offset): Min. 205 MPa (30,000 psi)
- Elongation: Min. 35%
- These properties ensure it can handle high-pressure fluids safely.
4. Weldability
- It is readily weldable by standard fusion and resistance welding methods.
- Because it is stabilized, the heat-affected zone (HAZ) of the weld remains corrosion-resistant without annealing.
You should select TP347 over standard grades (like 304 or 316) if your heat exchanger operates under any of these conditions:
1. High Temperatures: The operating temperature is above 400°C (750°F) .
2. Welded Construction: The tubes are welded to tubesheets, and you cannot perform a full annealing heat treatment afterward.
3. Corrosive Media: The fluid contains compounds that cause intergranular attack (e.g., hot organic acids, high-purity water, or specific refinery streams).
4. Long-term service: The tube will be under stress for decades at elevated temperatures (creep resistance).
ASTM A213 TP347 Stainless Steel Seamless Tube Chemical Composition
| TP347 |
Maximum |
Minimum |
| Ni |
13.00 |
9.00 |
| C |
00.08 |
00.04 |
| Mn |
2.00 |
– |
| P |
00.045 |
– |
| S |
00.030 |
– |
| Si |
1.00 |
– |
| Cr |
20.0 |
17.0 |
| Mo |
3 – 4 |
– |
| N |
– |
– |
| OTHER |
1.0 |
Nb=10(C+N) |
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