Effects of Impurities in Fuel Oil

Q. Write brief notes on the adverse effects that a fuel containing high value of the following may cause: (a) Viscosity (b) Density (c) Sulphur (d) Corodson Carbon Residue (e) Asphaltene (f) Vanadium & Sodium (g) Ash (h) Water

(By Kamal Hossain, Chief Engineer)


High viscosity of fuel may cause the following effects being using high temperature heating
– Fouling of Oil heater
– Gassing of Fuel
– Thermal expansion to fuel pump and injector component leading to seizure or sticking
– Clogging of filter


High density of fuel oil means high contents of impurities . It may effect to
– Filter clogging
– High temperature require for sedimentation & purification
– Upsetting to purifiers
– Being fuel pump is volume-measuring device , produce more heat when combustion .


Natural ash are usually Silicon , Aluminium , Calcium , Iron , Nickle , Vanadium and Sodium . If high ash content may effect the following
– High density
– Defects in filtration and purification
– Deposits may effect as abrasive wear to piston rings , liner , fuel pump components , T.C turbine blades
– Dangerous effect of Vanadium and Sodium may shorter exhaust valve life.


More than 1 % of water content may cause
– Corrosion on fuel pump and injector component tend to seizure.
– Misfiring of engine and stop in extreme case
– Poor combustion , reduce out put and T.C surging
– Emulsification of fuel leading to sludge formation
– Fuel foaming in mixing column
– Promote microbial degradation
– Loss of energy content and quantity of fuel.


It may cause
– Instability of fuel
– Blockage of filters
– Upsetting of purifier operation


It is a hydrocarbon compound of solid combustible substances which are insoluble in fuel oil. Asphaltenes may cause

– Clogging of filters ,Fouling of heaters and upsetting purifier operation
– Corrosion of fuel pump’s component and seizure
– Sticking of nozzles and tend to trumpet formation
– Prolong combustion time and its flame close to liner wall and overheat , burn cyl. L.O
– Due to poor combustion , unburned products tend to abrasive wear of Piston Rings & Liners , seizure & broken piston rings.
– Fouling of scavenge port and exhaust system


– Produce combustion products containing SO2 & SO3 to cause cold corrosion wear of
Piston rings, Liners ,Turbocharger water cooled casing , Exhaust valve cage….. ect.
– High temperature corrosion to exhaust valve.
– Adhesion of black lacquer on the liner inner surface
– Form L.O acidity condition.


May cause hot corrosion during combustion . They are formed corrosive products as SODIUM VANADATE COMPOUND when combustion temperature 530 ‘C , stick to the metal and attack the protective coating of the surface , cause hot corrosion especially to Exhaust valve , Turbocharger turbine blades and nozzle ring.

Carbon residue Poor combustion with smoky exhaust and produce depositing product effect to ….
– Trumpet formation of nozzle
– Depositing Piston ring zone tend to seizure and broken
– Remove cylinder L.O film and act as abrasive to wear Piston rings and liners, – –
– Fouling of scavenge space and inlet / exhaust ports
– Depositing in Turbocharger and corrosion to nozzle ring and turbine blades
– Fouling at Economizer and uptake

Catalytic Fines.

These are very small size of 3 ~ 100 microns, hard and abrasive compound of Alumina and Silica.
Larger parts may increase wear in fuel pump and valve components
Smaller parts below 5 micron promote Piston rings & Liner wear.

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