How burning of fuel oil with a high sodium content affects a diesel engine?
25 Mar '18, 08:12
In general, high sodium content fuel oil causes corrosion and grooving of exhaust valves.
Fuels leaves the refinery having sodium content well below 50mg/kg. If the sodium content increases, this is normally caused by the seawater contamination. A 1% seawater contamination corresponds potentially to a 100mg/kg increase. Vanadium is also present in the fuel oil, which in combination with oxygen forms V2O5 (vanadium pentoxide), which combines with sodium to form sodium/vanadium complexes. There are low melting temperatures of sodium/vanadium complexes of certain critical ratios. The most critical sodium/vanadium ratio is about 1:3. This will form a sodium/vanadium complex with a low melting point which will flow with the exhaust gases. It will get deposited as a hard and brittle layer on the cold surfaces such as exhaust valve spindles, turbocharger nozzles and turbine blades. This layer is highly corrosive and corrodes the metal. It is also brittle and breaks away exposing the metal for fresh attack especially when they get deposited on exhaust valve seats. The hard layer breaks and gives a cutting effect on the seat. Preventive measures can be taken such as keeping the temperature of the exhaust below the melting point of V2O5 and removal of sodium by proper purification and proper draining of the settling tanks. Therefore high sodium content in the fuel oil will result in corrosion and grooving of exhaust valves.
25 Mar '18, 08:16