Fuel Oil Properties / Bunker Oil Properties

Flash point - fire risk factor

It is the lowest temperature at which an oil will give off sufficient inflammable vapour to produce a flash when a small flame is brought to the surface of the oil. It may be measured as an open or closed flash point figure. The lower limit of 60°C for flash point of fuels used on board ships. Fuel oil in storage tanks must be kept at least 14°C lower than its flash point.

Viscosity -handling, preheating and centrifuging

This is a property of a liquid which is a measure of its internal resistance to flow. The viscosity of a liquid changes with temperature, decreasing as the temperature is increased. A low viscosity is required for fuels in order to obtain good atomization at the fuel valve.
Heating is therefore required when burning heavy fuel to reduce viscosity to approximately that of diesel oil. It is strongly recommended that the final control of fuel heating should be viscometric, rather than thermostatic.

Density

Density is an absolute relationship between mass and volume at a stated temperature, in contrast to specific gravity (or relative density), which is related to the density of water at the same or a different reference temperature. The unit is kg/m3 or gm/cm3 at 15°C.
ISO 8217 standard requires the density of Marine fuel oil at 15 °C to be 0.991 gm/cm3 or less.

Calorific Value

It is a measure of the amount of heat released during complete combustion of a unit mass of the fuel. It should be high, about 45000 kJ/kg, so as to reduce the quantity of oil stored and burned.

Asphalt Content

It should be low; otherwise the heaters will be clogged up when the oil is heated.

Sulphur Content

It should be low. When a fuel burns, any sulphur it contains is converted into sulphur oxides which condense in the water present to form acids that may cause corrosive wear.
This acid rapidly deteriorates combustion chamber, fuel pipings and especially heater tubes.

Water Content

It should be low. Any water in the oil will be boiled during the combustion process, thereby removing heat from the combustion chamber.

Ash and mechanical Impurities Content

They should be at a minimum as the ash contains small amount of iron particles it can cause damage to fuel injection pumps and injectors. Other impurities restrict flow through strainers, pipe lines and fuel injectors.

Cleaning and Treatment

The correct treatment of diesel engine fuel on board ship is vital to ensure trouble-free operation. It is essential that water and solid contaminants be removed from the fuel before it reaches the engine, and there are three principal ways of removing them.
(1) Centrifuging (Separated by Purifier alone and Series purification process that Clarifier place after purifier)
(2) Filtration
(3) Homogenising and ultra-sonic treatment (Break contaminants down into particles, that are small enough to pass through the injection system, without causing damage and then to be successfully burnt in the engine.

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Reference:

Marine Engineers' World (Facebook)

Bangladesh Marine Academy

Mariners Galaxy

Marine Insight