How to Select Materials for Shell-and-Tube Heat Exchangers in Specific Working Environments

How to Select Materials for Shell-and-Tube Heat Exchangers in Specific Working Environments

‌I. Core Considerations‌

1. ‌Medium Characteristics‌

   • ‌Corrosivity‌:
     • For media containing chloride ions (e.g., seawater, brine), prioritize ‌titanium alloys (Gr.1/Gr.2)‌ or ‌super austenitic stainless steel (254 SMO)‌ due to their superior resistance to pitting and crevice corrosion.
     • For highly acidic media (e.g., sulfuric acid, hydrochloric acid), use ‌Hastelloy C-276‌ or ‌tantalum‌ to avoid rapid material degradation.
   • ‌Particulate Content‌: For media with solid particles, select ‌duplex stainless steel (2205)‌ or ‌nickel-based alloys‌ for enhanced wear and erosion resistance.

2. ‌Temperature and Pressure Conditions‌

   • ‌High Temperature (>300°C)‌:
     • Use ‌nickel-based alloys (Inconel)‌ or ‌duplex stainless steel (2507)‌ for shells and tube sheets to prevent high-temperature oxidation and creep deformation.
   • ‌High Pressure (>600 bar)‌: Opt for ‌forged steel‌ or ‌high-strength stainless steel‌, and validate structural integrity via Finite Element Analysis (FEA).

3. ‌Cost-effectiveness and Maintainability‌

   • For non-corrosive media (e.g., freshwater, air), use ‌carbon steel‌ or ‌304 stainless steel‌ to reduce costs.
   • In applications requiring frequent cleaning or maintenance, avoid welded tube sheets and instead use ‌detachable designs‌ with ‌316L stainless steel‌ or ‌titanium alloys‌.

‌II. Key Component Material Recommendations‌

‌III. Material Solutions for Typical Environments‌

1. ‌Marine Engineering (Seawater Cooling)‌

   • ‌Tube Sheet & Tubes‌: Titanium alloy (Gr.2)
   • ‌Shell‌: 316L stainless steel (molybdenum-enhanced)
   • ‌Sealing‌: Titanium spiral-wound gaskets

2. ‌Chemical Strong Acid Systems (Sulfuric/Hydrochloric Acid)‌

   • ‌Tubes & Shell‌: Hastelloy C-276 or tantalum
   • ‌Tube Sheet‌: Duplex stainless steel (2507) with nickel-based weld filler

3. ‌Oil & Gas Sour Environments‌

   • ‌System Material‌: Duplex stainless steel (2205)
   • ‌Tube Sheet Connections‌: Laser welding + stress relief treatment

‌IV. Material Validation Process‌

1. ‌Material Pre-screening‌: Narrow options based on corrosivity, temperature/pressure (refer to ASTM standards).
2. ‌Lab Testing‌:
   • Electrochemical corrosion tests (e.g., polarization curve analysis).
   • Stress corrosion testing under simulated high-temperature/pressure conditions.
3. ‌Cost Analysis‌: Compare lifecycle costs (initial + maintenance).

‌Note‌: For extreme conditions (e.g., supercritical CO₂), collaborate with manufacturers to develop custom materials and optimize designs via multi-physics simulations (CFD + FEA).

‌Supplementary Notes on Heat Exchanger Tube Materials‌

• ‌Stainless Steel‌:

  • ‌Austenitic (304/316L)‌:
    • ‌304‌: Low-cost for non-chloride media (e.g., freshwater).
    • ‌316L‌: Molybdenum-enhanced for chloride resistance (e.g., seawater, weak acids).
  • ‌Duplex (2205/2507)‌: High strength and stress corrosion resistance for H₂S/salt environments.
  • ‌Super Austenitic (254 SMO)‌: High pitting resistance for concentrated chlorides.

• ‌Titanium & Alloys‌:

  • ‌Pure Ti (Gr.1/Gr.2)‌: Ideal for seawater, HCl, and high-temperature oxidation (≤300°C).
  • ‌Ti-Pd Alloy (Gr.7)‌: Enhanced crevice corrosion resistance for acidic chloride solutions.

• ‌Other Materials‌:

  • ‌Nickel Alloys (Hastelloy C-276)‌: For sulfuric/phosphoric acids and oxidizing media.
  • ‌Tantalum‌: Extreme acid resistance (e.g., concentrated H₂SO₄), but costly.

‌Critical Reminder‌: Validate material choices with corrosion testing and ensure compliance with industry standards (e.g., ASME, NACE).