sixth semester

Cold corrosion is when 1 SULPHUR acid forms on the liner walls in an engine cylinder and corrodes the liner surface. This 2 NORMAL corrosion then creates 3 EXCESS wear of the liner material. This has become an issue 4 RECENT in new engines which are now designed to comply with the Tier II NOx regulations and Energy Efficiency Design Index (EEDI) guidelines. To meet the new regulations, engine cylinders must operate under increased pressures and reduced 5 .OPERATE temperatures. This creates conditions below the dew point that allows water to 6 CONDENSATE on the cylinder liner walls. This then combines with sulphur from the combustion process to form sulphuric acid, which leads to cylinder liner wear or cold corrosion. How serious is cold corrosion for my engine? Cold corrosion is at its most serious in the 7 LATE engine designs. It also impacts earlier engine designs modified for part-load or low-load operation (known as ‘slow steaming’, where vessels may operate as low as 10% load). These 8 MODIFY may include; turbocharger cut-out, 9 VARY turbo charger nozzle rings fitted, exhaust gas by-pass valve fitted, and engine tuning changes. Some modified engines become mildly 10 CORRODE whereas others may be more seriously affected.