In Shell and Tube Heat Exchangers (STHE), the tube material is selected based on corrosion resistance, thermal conductivity, mechanical strength, and cost. Below are the most commonly used tube materials, along with their key properties and applications:
1. Carbon Steel (CS) Tubes
- Grades: ASTM A179, A192, A210
- Properties:
- Low cost, good thermal conductivity
- Moderate corrosion resistance (prone to rust in water/oxygen)
- Applications:
- Steam condensers, oil cooling, non-corrosive fluids
- High-pressure/temperature services (boilers, power plants)
2. Stainless Steel (SS) Tubes
- Grades:
- SS 304 – General-purpose corrosion resistance
- SS 316/316L – Better chloride resistance (Mo addition)
- SS 321 – Stabilized with Ti for high-temperature use
- Properties:
- Excellent corrosion resistance (acids, alkalis)
- Moderate thermal conductivity, weldable
- Applications:
- Chemical processing, food & beverage, marine
- Refineries, petrochemical plants
3. Copper & Copper Alloys
- Types:
- Admiralty Brass (Cu-Zn-Sn) – Good for freshwater
- Cupronickel (90/10, 70/30 Cu-Ni) – Seawater resistance
- Aluminum Brass (Cu-Zn-Al) – Better erosion resistance
- Properties:
- High thermal conductivity
- Biofouling resistance (marine applications)
- Applications:
- Power plant condensers, ship cooling systems
- HVAC, desalination
4. Titanium Tubes
- Grades: Gr. 1, Gr. 2, Gr. 7 (Pd-alloyed for HCl resistance)
- Properties:
- Outstanding corrosion resistance (seawater, chlorides, acids)
- Lightweight but expensive
- Applications:
- Offshore platforms, desalination plants
- Chemical industries (HCl, sulfuric acid)
5. Nickel Alloys
- Types:
- Inconel 625 – High strength, oxidation resistance
- Hastelloy C276 – Resistant to pitting/chlorides
- Monel 400 – Resists hydrofluoric acid (HF)
- Properties:
- Extreme corrosion/heat resistance
- Expensive but long-lasting in harsh environments
- Applications:
- Sulfuric/Nitric acid plants
- Nuclear, aerospace, and offshore
6. Duplex & Super Duplex Stainless Steel
- Grades:
- 2205 (Duplex) – Mixed austenitic/ferritic structure
- 2507 (Super Duplex) – Higher corrosion resistance
- Properties:
- Stronger than SS 316, chloride-resistant
- Good for high-pressure services
- Applications:
- Oil & gas (seawater cooling)
- Pulp & paper industry
7. Aluminum Tubes
- Grades: 1100, 3003
- Properties:
- Lightweight, good thermal conductivity
- Poor corrosion resistance in alkaline/chloride environments
- Applications:
- Low-temperature refrigeration
- Air-cooled heat exchangers
8. Non-Metallic Tubes (Special Cases)
- Teflon (PTFE), Graphite, Ceramic
- Applications:
- Highly corrosive acids (e.g., hydrofluoric)
- Pharmaceutical industries
Selection Criteria Summary
| Material | Best For | Avoid |
| Carbon Steel | Steam, oil, non-corrosive fluids | Oxygenated water, acids |
| SS 316 | General chemicals, chlorides | Hydrochloric acid |
| Cupronickel | Seawater cooling | Ammonia environments |
| Titanium | Seawater, chlorides, acids | Fluoride solutions |
| Nickel Alloys | Extreme corrosion (HF, H₂SO₄) | High-cost if not required |