Seawater Cooling System Consulting

The first design decision in any seawater-cooled plant is once-through versus recirculated. Once-through systems avoid the concentration of salts and heat that recirculating towers create, but commit the plant to large intake/outfall infrastructure, intake screening against marine organisms, and a permanent thermal-discharge obligation. Recirculated seawater towers concentrate chloride, magnesium, and sulphate as cycles rise, which changes the corrosion and scaling calculus entirely versus a freshwater tower — carbonate scaling is usually less of a limiting factor than calcium sulphate and magnesium hydroxide scaling at elevated pH and temperature. Either configuration lives or dies on metallurgy selection: titanium tubing is the default for the most aggressive seawater duties because it is essentially immune to chloride pitting and crevice corrosion; 90/10 and 70/30 copper-nickel alloys remain common for condenser tubing where biofouling resistance from copper's toxicity to marine organisms is valued, but they are vulnerable to sulphide attack and ammonia-driven corrosion; super-duplex stainless steels offer a cost-effective compromise for piping and heat exchangers if chloride stress- corrosion-cracking thresholds and welding procedures are properly controlled.

Biofouling and microbiologically influenced corrosion (MIC) are the dominant operating risks. Warm seawater loops — particularly in the Gulf, where intake temperatures can reach 35°C or higher in summer — support fast biofilm growth, sulphate-reducing bacteria under deposits, and macrofouling organisms (mussels, barnacles, oysters) that colonise intake screens, box culverts, and low-flow zones inside condensers and heat exchangers. Left unmanaged, macrofouling restricts flow area, raises pressure drop, and can shed material that fully blocks tube bundles. The standard control is continuous or intermittent chlorination via electrolytic hypochlorite generation or bulk sodium hypochlorite dosing, held to a target free- or total-residual oxidant level at the condenser inlet — high enough to suppress biofilm and larval settlement, low enough to limit chlorine-driven corrosion of copper alloys and to manage any regulated discharge limit on residual oxidant at the outfall.

Scaling in warm seawater behaves differently from freshwater scaling: as temperature rises through a condenser or heat exchanger, calcium carbonate and magnesium hydroxide solubility falls, favouring deposition on the hottest surfaces — exactly where heat-transfer loss matters most. We evaluate antiscalant dosing, recirculation cycles, and blowdown strategy against real seawater ion chemistry rather than generic cooling-water models, and assess whether observed heat-transfer degradation is scale, biofilm, or macrofouling debris — each demands a different fix.