(PS9052) Splash Zone Protection of Hot Risers by Sheathing with CuNi Alloys

摘要

The performance of CuNi 90 10 (C70600) , CuNi 70 30 (C71500) and NiCu 70 30 (N04400, alloy 400) was investigated under conditions encountered in the splash and spray zone of hot risers with special consideration of the heat transfer at the wall causing salt crusts formation. Tubes of these alloys were heated internally to an inside temperature of 100 and 120 °C, respectively, and were exposed vertically for 1000 h i) half-submerged in ASTM seawater thermostated at 50°C and ii) to a spray of artificial ASTM seawater in a salt spray chamber kept at 50°C. Corrosion loss was quantified by topographic scanning. In the spray test all alloys experienced only general metal losses in the order of 2 to 4 μm regardless of the applied internal temperature. Very small needle-like pits were found only under the salt crusts. The pit depths were generally only 5 to 10 μm, the deepest pits amounted to 22 μm (NiCu70/30). Below the salt crusts on half submerged tube samples metal dissolution was widely uniform. At 100 °C internal tube temperature the wall loss was 10 to 40 μm (deepest local penetrations 30 to 45 μm). At 120°C internal tube temperature the general material loss ranged between 10 and 25 μm (local penetrations generally 15 to 40 μm, max 80 μm). In all cases no measurable corrosion attack was found below the waterline (<2μm). All alloys tested are applicable as sheating material for hot risers in the splash zone.