1. Marine Fuel Oil

2. Combustion
The rapid chemical combination of oxygen with the combustible elements of a fuel resulting in the production of heat and light.

3. Fuel
A fuel may be defined as any combustible material which when burned gives off heat.
Fuel Oil
Coal
Wood

4. Crude Oil
Crude oil and the products derived from the raw material are considered petroleum products.
Crude oil is a mixture of a wide range of long chain hydrocarbon molecules.
A hydrocarbon molecule is essentially one or more hydrogen atoms linked with one or more carbon atoms.
Source: Tanker Operations 4th Edition by M. Huber

5. Crude Oil
The composition of crude oil varies widely depending on its geographic source.
Crude oil can be described as either “Heavy” or “Light” based on its specific gravity (S.G.).
The number of carbon atoms in the hydrocarbon molecule influences the specific gravity of a crude oil.
Source: Tanker Operations 4th Edition by M. Huber

6. Crude Oil
The greater the number of carbon atoms in the molecule, the heavier the molecule will be.
Crude oil vary from very sweet to sour in hydrogen sulfide content.
From heavy to light in weight
From yellow to black in color
Source: Tanker Operations 4th Edition by M. Huber

7. Crude Oil Crude oils generally fall into three classifications:
Asphalt based crudes contain little paraffin and are often high in sulfur, nitrogen and oxygen. These are used for making gasoline and asphalt.
Paraffin-based crudes are high in paraffin wax and can be refined into motor fuels, lube oils and kerosene.
Source: Tanker Operations 4th Edition by M. Huber

8. Crude Oil
Mixed-base crudes have some amounts of both paraffin wax and asphalt in them and can be refined into virtually all products, but of course in lesser amounts.
Source: Tanker Operations 4th Edition by M. Huber

9. Refining
The first step in the manufacture of petroleum products is he separation of crude oil into its main fractions using atmospheric distillation.
When the crude oil is heated the lightest and most volatile hydrocarbons boil off as followed by the heaviest and least volatile hydrocarbons.
The vapors are then cooled and condensed back into liquids
Source: A Practical Guide to Marine Fuel Oil Handling by Leigh-Jones

10. Refining
The atmospheric distillation process is carried out in a fractionating column which is divided into a series of chambers by perforated trays the condense vapors at each stage to allow the liquids to flow into storage tanks.
Source: A Practical Guide to Marine Fuel Oil Handling by Leigh-Jones

11. Refining
The residue from atmospheric distillation is sometimes referred to as “long residue”.
Further distillation is carried out at a reduced pressure and high temperature to recover more distillate product.
This distillation is known as “vacuum distillation”.
The residue from vacuum distillation is sometimes called “short residue”.
Source: A Practical Guide to Marine Fuel Oil Handling by Leigh-Jones

12. Refining
Residue or “feedstock” from the atmospheric or vacuum distillation units or a mixture of the two in most cases then undergoes further distillation thru a thermal cracking process
There are three types of thermal cracking visbreaking, a thermal gas oil unit and coking.
Source: A Practical Guide to Marine Fuel Oil Handling by Leigh-Jones

13. Refining
Visbreaking is a mild form of thermal cracking often used to reduce the viscosity of straight run residual fuels.
In most cases these fuels are highly viscous and if required for sale as heavy fuel oil must be blended with relatively high value distillate to meet the finished product specification.
Source: A Practical Guide to Marine Fuel Oil Handling by Leigh-Jones

14. Refining
Visbreaking reduces the quantity of distillate required to dilute or “cutter stock”.
A thermal gas unit is used to produce and recover maximum amount of gas oil.
In extreme cases the viscosity of the residue may be higher then that of the feed stock.
Source: A Practical Guide to Marine Fuel Oil Handling by Leigh-Jones

15. Refining
Coking is a relatively severe form of thermal cracking designed to convert straight run residues into more valuable products such as naphtha and diesel oil.
Gas oil and coke are also produced, therefore, coking does not feature in the manufacture of residual fuel oils.
Source: A Practical Guide to Marine Fuel Oil Handling by Leigh-Jones

16. Refining
Catalytic cracking is carried out in a large processing plant, employing a fluidized catalyst, usually a silica based material in direct contact with the feedstock.
A catalyst is a substance which aids and accelerates a chemical reaction, but which itself undergoes no permanent change in composition.
Source: A Practical Guide to Marine Fuel Oil Handling by Leigh-Jones

17. Refining
The very fine powdered fine catalyst flows like a fluid when kept in constant agitation and circulated by steam, air or vapor.
In the plant, as the preheated heavy gas oil feedstock enters the reactor, it is met by a stream of hot regenerated catalyst.
This vaporizes the feedstock, which in turn “fluidizes” the catalyst.
Source: A Practical Guide to Marine Fuel Oil Handling by Leigh-Jones

18. Refining
Cracking occurs in the reactor and the cracked oil vapors, composed of new, smaller molecules are separated into gases, high quality gasoline components, light gas oil used as heating oil and a heavy gas oil known as “cycle oil”.
Source: Marine Engineering by Harrington

19. Refining
Source: Modern Marine Engineers Manual Volume I, 3rd Edition by Hunt

20. Marine Fuel Oil Characteristics
Various grades of fuel are referred to by different names depending on the terminology of the supplier.
Gas oil is used in some smaller vessels and the auxiliary engines of larger vessels.
This grade of fuel is marketed under various names including bunker gas oil and marine gas oil.

21. Marine Fuel Oil Characteristics
Such fuel is a light distillate with a clear, bright appearance and is a clean fuel in that it does not contain any residual components.
In contrast diesel fuel may contain a small amount of residual fuel and be dark or black in color.
It is know by various names including light diesel and marine distillate.
Blended diesel oil does contain some residue and is frequently called marine diesel oil.

22. Marine Fuel Oil CharacteristicsBP
CHEVRON
ESSO
MOBIL
SHELL
TEXACO
Marine
Fuel Oil
(MFO)
Intermediate
Bunker Fuel
(IBF*)
Bunker
(BFO)
Motorship
Marine Fuel
Oil (MFO*)
Interfuel
(IF*)
(IF)
Fuel
Light Marine
(LMFO)
IF*
Marine Diesel Oil
(MDO)
Marine Diesel
Oil
Diesel Oil
Light
(LDO)
Diesel
Distillate
Diesel Fuel or Gas Oil
Gas Oil
(MGO)
(GO)
Marine Gas
Oil (MGO)
* Denotes a specific grade, usually shown by viscosity of the grade in cSt at 50 °F

23. Grade of Fuel Oil Min Max 38 (100) -18 (0) 0.05 0.15 0.8499 (35 min)
Flash Point
°C (°F)
Pour Point
Water and
Sediment %
Carbon
Residue
Ash
Weight
S.G.
60/60°F
Deg API
Sulfur
Grade of Fuel Oil
Min
Max
No. 1 Distillate oil intended for vaporizing burners
38 (100)
-18 (0)
0.05
0.15
0.8499
(35 min)
0.5 or
legal
No. 2 Distillate oil for general purpose heating
-6 (20)
0.35
No. 4 Preheating not usually required for handling
55 (130)
0.50
0.10
No. 5 (Light) Preheating may be required depending on climate
1.00
No.5 (Heavy) Preheating may be for burning and in cold climates be required for handling
No. 6 Preheating required for burning and handling 60
(140)
2.00

24. Kinematic Viscosity cSt
Saybolt Viscosity
Universal at 38°C Furol at 50 °C
Kinematic Viscosity cSt
At 38 °C (100 °F) At 50 °C (122 °F)
Grade of Fuel Oil
Min
Max
No. 1 Distillate oil intended for vaporizing burners
1.4
2.2
No. 2 Distillate oil for general purpose heating
(32.6)
(37.9)
2.0
3.6
No. 4 Preheating not usually required for handling
(45)
(125)
5.8
26.4
No. 5 (Light) Preheating may be required depending on climate
(>125)
(300) 65
No.5 (Heavy) Preheating may be for burning and in cold climates be required for handling
(>300)
(900)
(23)
(40)
>65
194
(42)
(81)
No. 6 Preheating required for burning and handling
(>900)
(9000)
(>45)
>92
638
50 °C
(122 °F)

25. Marine Fuel Oil Characteristics
Density
Viscosity
Flash Point
Fire Point
Pour Point
Carbon Residue
Ash

26. Marine Fuel Oil Characteristics
Water
Sulfur
Vanadium and Sodium
Aluminum and Silicon
Sediment and Stability
Compatibility
Specific Energy
Ignition Quality

27. Density
Density is the absolute relationship between mass and volume at a stated temperature.
The SI unit is kg/m3 and the standard temperature is 15 °C is used for the density calculation of petroleum and its products.
The density is required for quantity calculations and to select the optimum size of gravity disc for the centrifuge.

28. Density
The Specific Gravity (S.G.) of a substance is the ratio of the mass of a given volume to the mass of an equal volume of water at the same temperature.
The relative density of a substance is the ratio of the mass of a given volume at a temperature t1 to the mass of a given volume of pure water at temperature t2.

29. Density
In the United States and some other countries, the density of petroleum products is defined in terms of API gravity.
This is an arbitrary scale adopted by the American Petroleum Institute to express relative density of oils.
API gravity (degrees) = (141.5 / Relative 60 / 60° F) – 131.5

30. Viscosity
Dynamic viscosity is a property of the internal resistance of a fluid that opposes the motion of adjacent layers.
The unit of measure of this resistance in SI units is a Pascal.
Frequently the unit Poise is used where 1 Pascal =10 Poise.
Dynamic viscosity can also be referred to as absolute viscosity.

31. Viscosity
Marine fuel viscosity is usually expressed in kinematic viscosity which is measured in Stokes.
Kinematic viscosity is the quotient of the dynamic viscosity or absolute viscosity divided by density with both expressed at the same temperature.

32. Viscosity
Since one Stoke is a large unit, kinematic viscosity is usually measured in centistokes (cSt), one cSt = 1 mm2 / sec.
Viscosity can also be quoted in Saybolt, Engler or Redwood.
Typical maximum fuel viscosity for transfer is 800 – 1000 cSt.
For a boiler the atomization viscosity depends on the burner and can be in a range of 15 – 65 cSt.

33. Viscosity
For a diesel engine the injection viscosity can be in the range of 8 – 27 cSt with the range usually cSt.
Generally if the actual viscosity is greater than that ordered, the viscosity can be achieved by the fuel oil heaters but the performance of the centrifuge can fall below design conditions.

34. Flash Point
The Flash Point of a fuel oil is defined as the lowest temperature at which the oil gives off vapors in sufficient quantity to combust when mixed with air in the presence of a ignition source.
If the combustion source is removed combustion will stop.
The flash point of fuel oil generally should not be lower than 150 °F.

35. Fire Point
The Fire Point is defined as the lowest temperature at which a fuel oil gives off vapors in sufficient quantity to burn continuously when a flame is applied.
The Fire Point is generally 10 °F to 15 °F higher than the Flash Point.

36. Pour Point
The Pour Point is the lowest temperature at which a fuel oil will solidify.

37. Carbon Residue
The Carbon Residue of a fuel is the tendency of carbon deposits to form under high temperature conditions in an inert atmosphere.
It can be expressed as Ramsbottom Carbon Residue (RCR), Conradson Carbon Residue (CCR) or Micro Carbon Residue (MCR).

38. Carbon Residue
Carbon Residue is considered to be an indication of the combustibility and deposit forming tendency of a fuel.
The Carbon Residue of a fuel depends on the refining process employed in the fuels manufacture.

39. Ash
The Ash value is related to the inorganic material in the fuel oil.
The actual value depends on three factors, first the inorganic material naturally present in the crude oil, secondly the refining processes employed and finally subsequent contamination due to sand, dirt and rust scale.

40. Ash Ash levels in distillate fuels are negligible.
Residual fuels have more ash forming constituents as they are concentrated from the residue of crude oil.

41. Water
Usually the level of water in fuel is very low, typically 0.1 – 0.2 % by volume.
Water can be introduced from a number of sources including tank condensation, tank leakage, leaking heating coils and from the purifier if the wrong gravity disk is used.
Large water contamination can be removed by settling tanks and the remaining removed by centrifuge.

42. Sulfur
Sulfur is a naturally occurring element in crude oil, concentrated in the residual components in the crude oil distillation process.
The amount of sulfur in fuel oil depends mainly on the source of the crude oil and to a lesser extent on the refining process.
The sulfur amount usually varies between 2 – 4 %.

43. Sulfur
The level of sulfur in the fuel has a marginal effect on the Heating Value of the fuel.
During the combustion process in both a diesel engine and boiler the presence of sulfur in the fuel can cause corrosion .
In a diesel engine can cause corrosion on the cylinder liners. This can be offset with the use of a high alkaline lubricant.

44. Sulfur
In a boiler the sulfur can cause corrosive attack on the economizers.

45. Vanadium and Sodium
Vanadium is a metal present in all crude oils in a soluble form.
The levels found in residual fuels depends mainly on the crude oil source, with those from Venezuela and Mexico having the highest level.
The actual level is also related to the concentrating effect on the refinery process used in the production of residual fuel.

46. Vanadium and Sodium
Fuel generally contains a small amount of sodium typically below 50 mg/kg.
The presence of sea water increases this value by approximately 100 mg/kg for each percent of sea water.
If not removed in the fuel treatment process a high level of sodium will give rise to an increase to post combustion deposits in the turbocharger.

47. Vanadium and Sodium
High temperature corrosion and fouling can mainly be attributed to vanadium and sodium in the fuel.
During combustion these elements oxidise and form semiliquid and low melting salts which adhere to exhaust valves, turbochargers and boiler furnace walls.

48. Aluminum and Silicon
It is generally accepted that an indication of aluminum represents the potential presence of catalyst fines.
These fines are particles of spent catalyst the arises from the catalytic cracking process in the refinery.
The fines will vary in size and hardness and if not reduced by fuel treatment the abrasive nature of the fines will damage the fuel pumps, injectors, piston rings, liner and burner tips.

49. Sediment and Stability
Sediment is defined as insoluble residues that are not derived from the fuel such as sand, dirt and rust scale.
The stability of a residual fuel is defined as the ability of the fuel to remain in an unchanged condition, despite circumstances which tend to cause change, or the resistance of the oil to breakdown.

50. Compatibility
While a fuel is manufactured to be stable within itself (that is, not having a tendency to produce asphaltenic sludge), it does not necessarily follow that two stable fuels will be compatible when blended or mixed together.
Problems of incompatibility fuels are rare but when they happen the results are severe.

51. Compatibility
Typical problems of the are sludging, and blockage of the bunker and service tanks, piping, filters and centrifuge bowls.
In extreme circumstances the only remedy is to manually remove sludge buildup.

52. Heating Value
The Heating Value or Specific Energy of a fuel is usually expressed in BTU/lbm or MJ/kg depending on the fuel composition.
For marine fuels the main components carbon and hydrogen both release energy during the combustion process.
The sulfur content in the fuel also releases energy during combustion, but to a lesser extent then the carbon and hydrogen.

53. Heating Value
The density is mainly proportional to the ratio of carbon and hydrogen atoms in the fuel.
The Heating Value can be calculated from empirical equations.

54. Ignition Quality
The Ignition Quality of a fuel is a measure of the relative ease by which a fuel will ignite.
For distillate fuels this is measured by the Cetane Number, which is determined by testing the fuel in a special engine that has a variable compression ratio.
The higher the Cetane Number the easier it is for the fuel to ignite in the engine.

55. Ignition Quality
For residual fuel there are two acceptable empirical equations, both based on the density and viscosity of the fuel.
These are the Calculated Carbon Aromaticity Index (CCAI) and the Calculated Ignition Index (CII).
The CCAI gives numbers in the range 800 – 870, while the CII gives values in the same order as the Cetane Index.

56. Ignition Quality CCAI = d-81-141 log [log(VK + 0.85)]
d = density in 15 °C
VK = viscosity in 50 °C
In general CII values of less than 30 and CCAI values of greater than 870 are considered problematic.