ASME VIII-1 U-Tube Heat Exchanger Clad UNS N06600 for Chlor-Alkali Process NACE MR0175
The ASME VIII-1 U-Tube Heat Exchanger is designed specifically for the Chlor-Alkali Process, featuring a UNS N06600 (Inconel 600) alloy lining that complies with NACE MR0175 certification for Sulfide Stress Cracking (SSC) resistance. It is suitable for extreme conditions involving high chloride ions, high-temperature alkaline, and sulfur-containing media, such as in the production of vinyl chloride and caustic soda evaporators. Its double-pass U-tube design enhances turbulence, reduces fouling, and improves heat transfer efficiency by over 40%.
Base Material and Lining Material Parameters
| Component | Material Standard | Key Features | Applicable Conditions |
| Shell / Tube Sheet | SA-516 Gr. 70 | Carbon steel substrate, with compressive strength ≥ 485 MPa | Design pressure ≤ 10 MPa |
| Lining / Heat Exchange Tube | UNS N06600 (Clad) | Ni ≥ 72%, Cr 14-17%, Fe 6-10%; resistant to chloride ion corrosion (≤0.05 mm/year), withstands dry chlorine gas at 510°C | Temperature range: -196°C to 1093°C |
Advantages of UNS N06600 Alloy
- Corrosion Resistance: Corrosion rate in 80°C concentrated NaOH solution < 0.01 mm/year; withstands 50% boiling hydrochloric acid.
- Mechanical Properties: High-temperature creep resistance (strength ≥ 240 MPa at 700°C), elongation ≥ 30%.
- Process Compatibility: Supports TIG welding (filler ERNiCr-3) and hot extrusion forming; lining thickness ≥ 3 mm.
Cladding Process and Documentation Requirements
Key Cladding Steps
- Welding Material Selection: Use ERNiCr-3 wire (AWS A5.14), matching the N06600 alloy composition to prevent carbon migration.
- Process Specifications:
- Preheat temperature: 90-120°C (carbon steel substrate)
- Interpass temperature: ≤ 150°C
- Post-weld heat treatment: 980°C solution annealing + water quench (to eliminate residual stress).
Required Quality Documentation
- Welding Procedure Qualification (WPS/PQR): Compliant with ASME Section IX, covering all positional welding parameters.
- Non-Destructive Testing Report:
- Lining PT (Penetrant Testing) 100% coverage, no cracks or porosity.
- Tube-to-tube sheet weld RT (Radiographic Testing) per ASME Sec. V standards.
- Corrosion Testing Report:
- Neutral salt spray test (ASTM B117) ≥ 1000 hours without delamination.
- Accelerated corrosion test in chlor-alkali medium (40% NaOH + 5% NaCl, 90°C).
- NACE MR0175 Certification: Verification of hydrogen sulfide stress cracking performance (H₂S partial pressure ≥ 0.3 kPa).
Technical Advantages and Design Innovations
-
High-Efficiency Heat Transfer Structure:
- U-tube double-pass design increases turbulence by 60%, reducing biological fouling compared to single-pass designs.
- Optimized corrugated tubes (wall thickness 0.8 mm), heat transfer coefficient 8% higher than copper tubes.
-
Adaptability to Extreme Conditions:
- Thermal shock resistance: No leakage under a sudden temperature change of 200°C (simulating chlor-alkali process start-stop cycles).
- Seismic design: Passes ASME Sec. III NF-level certification (nuclear power plant application standards).
-
Lifespan and Maintenance Costs:
- Design lifespan ≥ 20 years (average lifespan of copper tube heat exchangers is 10 years).
- Removable tube bundle design reduces maintenance time by 50%.
Industry Applications and Certification Endorsements
- Core Applications: Vinyl chloride reactor condensation, caustic soda evaporation concentration, sulfur-containing wastewater treatment.
- Typical Clients:
- China Chlor-Alkali Chemical Group (30 units in service, failure rate < 0.5 times/year).
- Middle East petrochemical base (seawater cooling + high-sulfur crude oil conditions).
- Full Chain Certifications:
- ASME VIII-1 2025 (Pressure Vessel)
- NACE MR0175/ISO 15156-3 (Sulfide Corrosion Resistance)
- PED 2014/68/EU (EU Pressure Equipment Directive).
