Selecting Wedge Wire Screens for Seawater and Desalination

Seawater is one of the most demanding environments for screening equipment. Chloride corrosion, marine biological fouling, and regulatory compliance all affect specification. Material selection is non-negotiable. Super Duplex 2507 (UNS S32750) is the minimum for open-ocean seawater. PREN must exceed 40. Standard 316L will pit and fail within 2-5 years in direct seawater contact. For less aggressive brackish water or pre-treated seawater, Duplex 2205 may suffice after water chemistry analysis. In RO (reverse osmosis) desalination plants, wedge wire serves as the critical first barrier protecting membranes from debris, marine organisms, and suspended solids. Typical slot apertures: 0.5-3 mm depending on the pre-treatment stage. Drum and T-type configurations are most common. Failure at this stage means membrane damage, which costs orders of magnitude more than the filtration element itself. In thermal desalination (MSF and MED plants), the equipment protects heat exchangers and flash chambers. Operating temperatures reach 110 C in MSF, which increases chloride corrosion rates. Material selection must account for both chloride concentration and temperature. Biofouling management is critical. Marine organisms colonize any submerged surface. Countermeasures include copper-nickel coatings, air-burst cleaning systems, and periodic manual cleaning. Aperture size must balance debris exclusion against fouling rate: narrower openings exclude more debris but foul faster. Regulatory compliance varies by jurisdiction. US EPA 316(b) requirements apply to cooling water intakes. Local agencies may specify maximum through-slot velocity, minimum surface area, and monitoring requirements.