Yuhong Group Co., Ltd. designs and fabricates shell and tube heat exchangers, pressure vessels, and air-cooled heat exchangers at our manufacturing facility. Alongside complete equipment, we supply replacement tube bundles, U-tubes, heat exchanger tubes, finned tubes, and accessories including tubesheets, baffle plates, and heads. This page covers a shell and tube heat exchanger built with ASME SA240 Type 321 plate for the shell and ASME SA213 TP321 seamless tubes for the tube side, targeting continuous high-temperature duty in refining, petrochemical, and power generation service.
| Parameter | Value |
|---|---|
| Shell Material | ASME SA240 Type 321 (UNS S32100) |
| Tube Material | ASME SA213 TP321 (UNS S32100) |
| Design Temperature Range | -196 °C to 870 °C (continuous oxidation limit) |
| Tube OD Range | 6 mm to 127 mm (per SA213 scope) |
| Tube Wall Thickness | 0.5 mm to 50 mm (depending on diameter) |
| Min. Tensile Strength | 515 MPa (tube) |
| Min. Yield Strength | 205 MPa (tube) |
| Solution Annealing | 1040 °C minimum, rapid cooling |
Grade 321 appears under different designations across national and international systems:
| System | Designation |
|---|---|
| ASME & ASTM | TP321 / S32100 |
| GB | 06Cr18Ni11Ti / S32168 |
| EN / DIN | 1.4541 / X6CrNiTi18-10 |
| GOST | 12Х18Н10Т |
Type 321 is an 18Cr-10Ni austenitic stainless steel stabilized with titanium. The titanium addition (minimum 5× carbon content, maximum 0.70%) binds free carbon as TiC, preventing chromium carbide precipitation at grain boundaries during prolonged exposure in the 427–816 °C sensitization range. This mechanism directly addresses intergranular corrosion risk after welding or long-term high-temperature service.
In oxidizing environments, the material maintains scaling resistance to approximately 870 °C. Resistance to organic acids, sulfate/sulfide solutions, and moderate-temperature caustic environments is comparable to Type 304, with improved intergranular performance. Note that 321 remains susceptible to chloride-induced stress corrosion cracking above 60 °C, so chloride-containing cooling water should be assessed against actual operating conditions.
Tubes are supplied in the solution-annealed condition: heated to a minimum of 1040 °C followed by water quenching or rapid cooling to dissolve carbides and restore a fully austenitic structure. Tube-to-tubesheet joints are expanded and seal-welded; welding uses ER347 filler to compensate for titanium's poor arc transfer. Hydrostatic testing is conducted at 1.25–1.5× design pressure, and helium leak testing at tube-to-tubesheet joints is available. Post-weld heat treatment for corrosion resistance is generally not required for stabilized Grade 321.
Refinery hydrotreating and sulfur recovery unit heat exchangers
Power plant superheater and reheater tube sections
Petrochemical process heaters operating in the 500–800 °C range
Flue gas and steam heat recovery systems
Air-cooled heat exchanger tube bundles with finned TP321 tubes
Q: What is the difference between TP321 and TP321H?
TP321H has a higher carbon range (0.04–0.10%) and a specified grain size of ASTM 7 or coarser. TP321 (0.08% C max) is the standard grade for general heat exchanger service where grain size control is not critical.
Q: Does 321 require post-weld heat treatment?
For most heat exchanger service, no. Titanium stabilization provides adequate intergranular corrosion resistance in the as-welded condition. However, for service above 480 °C in polythionic acid environments, a stabilizing heat treatment at 850–900 °C should be evaluated.
Q: What is the maximum continuous service temperature?
Approximately 870 °C in oxidizing atmospheres. In sulfur-bearing flue gases, the practical limit drops to 600–750 °C depending on oxygen content and impurities.
Q: Can you supply replacement tube bundles for existing exchangers?
Yes. We manufacture replacement bundles using ASME SA213 TP321 tubes, ASME SA240 Type 321 tubesheets, and baffle plates to match original TEMA configurations.
