CYLINDER L.O AND ITS PROPERTIES

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The type of cylinder l.o. required will depend upon the cylinder conditions and the engine design e.g crosshead or trunk piston. However, the property requirements are basically the same but will vary in degree depending upon the fuel and operating conditions.

Normal properties required are;

a.     adequate viscosity at working temperature so that the oil spreads over the liner surface to provide a tough film which resists the scrapper action of the piston rings

b.    the oil must provide an effective seal between the rings and liner

c.     only a soft deposit must be formed when the oil burns

d.    alkalinity level (total base number or TBN) must match the acidity of the oil being burnt

e.     detergent and dispersant properties are required in order to hold deposits in suspension and thus keep surfaces clean

Additives

All oils for all purposes can be designed to give particular properties through the careful use of additives to the base mineral oil stock.

Common additives are;

·         Antioxidants-these are used in all oils to reduce the rate at which oxidation occurs and are especially useful were the lub oil cools the piston

·         Extreme pressure agents these are compounds of phosphorus, Sulphur or Chlorine which increase the strength of the oil film under conditions of high temperature or pressure.

·         Dispersants or detergents-found in trunk piston engine oils and cyl l.o. these keep surfaces clean by holding deposits in suspension.

·         Viscosity index imp rovers  these prevent excessive changes in viscosity with change in temperature

·         Other additives can be defined by name such as anti-wear, anti-corrosion, anti-bacteria, anti-foaming etc.

When running in, the cylinder lube oil injector pumps may be filled with a a straight mineral oil without anti-wear properties- typically the crankcase oil- once this small reserve of oil is exhausted  running in carries on with normal cylinder lube oil. The flow of oil is increased to carry away metallic particles.