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Marine Lubricating Oils Treatment

Lubricating oils are a product of the crude oil refining process. The various properties required of the oil are obtained as a result of blending and the introduction of additives. The physical and chemical properties of an oil are changed by additives which may act as oxidation inhibitors, wear reducers, dispersants, detergents, etc. The important lubricant properties will now be examined.

The Total Base Number (TEN) is an indication of the quantity of alkali, i.e. base, which is available in a lubricating oil to neutralise acids. The acidity of an oil must be monitored to avoid machinery damage and neutralisation number is used as the unit of measurement. The oxidation resistance of a lubricant can also be measured by neutralisation number. When excessively oxidised an oil must be discarded.

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The carbon-forming tendency of a lubricating oil must be known, particularly for oils exposed to heat. A carbon residue test is usually performed to obtain a percentage value.

The demulsibility of an oil refers to its ability to mix with water and then release the water in a centrifuge. This property is also related to the tendency to form sludge.

Corrosion inhibition relates to the oil's ability to protect a surface when water is present in the oil. This is important where oils can be contaminated by fresh or salt water leaks.

Viscosity is a resistance to flow. A highly viscous fuel will therefore require heating in order to make it flow. Viscosity index is also used, which is the rate of change of viscosity with temperature. Increasing the temperature of a lub oil will reduce its viscosity, and vice-versa. As a result of the varying properties of marine fuels, often within one tank, actual viscosity must be continuously measured and then corrected by temperature adjustment. A typical modern viscometer equipment shown below

Typical modern viscometer equipment

Fig: Typical modern viscometer equipment



The modern lubricant must be capable of performing numerous duties. This is achieved through blending and additives. It must prevent metal-to-metal contact and reduce friction and wear at moving parts. The oil must be stable and not break down or form carbon when exposed to high temperatures, such as where oil cooling is used. Any contaminants, such as acidic products of combustion, must be neutralised by alkaline additives; any carbon build up on surfaces must be washed away by detergent additives and held in suspension by a dispersant additive. The oil must also be able to absorb water and then release it during purification, but meanwhile still protect the metal parts from corrosion.

The various types of engine and other equipment will have oils developed to meet their particular duties.

Trunk piston engine lubricating oil must lubricate the cylinders as well as the crankcase: some contamination from the products of combustion will therefore occur, resulting in acidity and carbon deposits. The oil must, in addition to lubricating, neutralise the acids and absorb the deposits.

Turbine oil, while lubricating the moving parts, must also carry away considerable quantities of heat from the bearings. This calls for a stable oil which will not break down at high temperatures or form deposits. Where gearbox lubrication is also required certain extreme pressure (EP) additives will be needed to assist the lubricating film. Contact with water in the form of steam will be inevitable so good demulsifying properties will be essential.

Slow-speed diesel engines will have separate cylinder and crankcase lubrication systems. The cylinder oil will have to neutralise the acidic products of combustion and also have good detergent properties to keep the metal, surfaces clean. Crankcase oils are either detergent type, multi-purpose oils or rust and oxidation inhibited. Good demulsification and anti-corrosive properties are required together with oxidation resistance which is provided by the inhibited crankcase oil. The detergent or multi-purpose oil is particularly useful where oil cooling of pistons occurs or where contamination by combustion products is possible.

lubricating oils require treatment before passing to the engine. This will involve storage and heating to allow separation of water present, coarse and fine filtering to remove solid particles and also centrifuging.

The centrifugal separator is used to separate two liquids, for example oil and water, or a liquid and solids as in contaminated oil. Separation is speeded up by the use of a centrifuge and can be arranged as a continuous process. Where a centrifuge is arranged to separate two liquids, it is known as a 'purifier'. Where a centrifuge is arranged to separate impurities and small amounts of water from oil it is known as a 'clarifier'.

The separation of impurities and water from fuel oil is essential for good combustion. The removal of contaminating impurities from lubricating oil will reduce engine wear and possible breakdowns. The centrifuging of all but the most pure clean oils is therefore an absolute necessity.



Related Information:

  1. Lubrication Schedule and Orders
    2. The lubrication system of an engine provides a supply of lubricating oil to the various moving parts in the engine. Its main function is to enable the formation of a film of oil between the moving parts, which reduces friction and wear. The lubricating oil is also used as a cleaner and in some engines as a coolant.....

  2. Function of Lubricating oil filters
    3. Lubricating oil filters can be found both on the suction and discharge sides of the lubricating oil pump dependent on the installation and type of engine or engines. Their maintenance is absolutely critical to the life expectancy of the crankshaft and its bearings, which depends entirely on an uninterrupted supply of clean and correctly filtered oil.....

  3. Lubricating oil treatment
    4. lubricating oils require treatment before passing to the engine. This will involve storage and heating to allow separation of water present, coarse and fine filtering to remove solid particles and also centrifuging......

  4. Lubricating oil centrifuging
    5. Lubricating oil in its passage through a diesel engine will become contaminated by wear particles, combustion products and water. The centrifuge, arranged as a purifier, is used to continuously remove these impurities....

  5. Cylinder lubrication & maintaining sump level
    6. The sump level is to be according to manufacturers/shipbuilders instructions . The ‘Sump Quantity’ is always maintained at the same safe operating level and is given in litres. It is essential that the figures are mathematically steady and correct from month-to-month, taking into account consumption, losses and refills and reported .....



Sea water circulation of coolers for lubricating oil, piston cooling, jacket water, charge air, turbo-charger

Fuel oils treatment for marine use -The refining process for crude oil

Fuel oil separation process

Marine fuel oil treatment - use of filters and strainers

Control of marine exhaust emissions

Marine fuel oil Microbiological infestation

Mixing of heavy fuel oil and marine diesel oil using blenders

Lubricating oil centrifuging for marine use

Fuel oil centrifuging for marine use -Function of purifiers


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