Desalination Plant Stainless: 2507 vs. 254 SMO vs. AL-6XN

 

 

Why super duplex 2507 for high-pressure pumps?
2507's 550 MPa yield strength handles 80+ bar pressures. PREN >42 prevents chloride pitting in 45,000 ppm saline. Half the cost of nickel alloys with equivalent corrosion resistance.

 

Where does 254 SMO outperform 2507?
254 SMO (6% Mo) excels in bleach-dosed streams resisting hypochlorite degradation. Lower magnetic permeability allows MRI inspection of welds. Maintains corrosion resistance up to 40°C seawater.

 

When is AL-6XN essential?
For acid-cleaned membranes exposed to pH<2. Higher nickel (24%) prevents stress corrosion cracking. Necessary for sulfuric acid dosing systems and CIP return lines.

 

Minimum wall thickness for RO piping?
Schedule 10S (1.24mm) for 6" lines at 70 bar. Erosion-corrosion limits flow velocity to 3 m/s. External insulation must be chloride-free to prevent SCC under lagging.

 

Critical welding procedures?
Gas tungsten arc welding with 2594 filler metal for 2507. Interpass temperature <100°C. Post-weld solution annealing at 1120°C for critical joints. Ferrite content 35-55% verified by Fischer MP30.