The key properties of marine lubricants and their functions

The ability to elucidate used oil analysis results is significant for taking decisions on planning maintenance activities. It is essential for marine engineers to understand the characteristics of the lubricating oil used onboard.

With expertise in marine lubricants trade and supply, I will explain in this article the properties of lubricating oil on ships and substantial of oil analysis.

VISCOSITY

One of the most important properties of the marine lubricants is a measure of internal resistance to flow at a specific temperature and lubricants should have the right viscosity for certain machinery to perform its functions properly. Commonly referred to as the ‘thickness of an oil’.

The viscosity of oil drops down when its temperature raises and vice versa. The ISO viscosity grade (ISO VG) refers to the oil kinematic viscosity at 40 degrees C and must fall only between 10 percent of the ISO grade, as an example the ISO VG 32 has limits between min 28.8 and max 35.2.

VISCOSITY INDEX

It measures fluid’s change in viscosity relative to temperature changes. The lower the viscosity index, the more the viscosity is affected by changes in temperature. Stable viscosity over temperature changes requires a high viscosity index.

FLASH POINT

This is the lowest temperature at which the  marine lubricant will generate sufficient vapour to produce a flash when exposed to ignition. While testing the oil for analysis, a decrease in flash point is generally an indication of fuel ingress which has contaminated the lubricants.

POUR POINT

Pour point of an oil is the temperature below which the oil loses its flow characteristics. It indicates the capability of oil to flow at the maximum low temperature.

TOTAL BASE NUMBER (TBN)

TBN is the number of milligrams of potassium hydroxide per gram of oil sample (mg KOH/g). It is a property that measures the reserve alkaline additives to neutralize acids that formed during engine operation and determines how effectively the acids formed during the combustion process can be controlled.

TOTAL ACID NUMBER (TAN)

TAN is the measurement of acidity that is determined by the amount of potassium hydroxide in milligrams that is needed to neutralise the acids in one gram of oil.

While testing the oil for analysis, certain oils have an inherent acidity level related to their additive chemistry. Increasing acidity may be indicative of the presence of organic acids derived from oil oxidation. It indicates the potential of oil to cause corrosion.

SAE

The Society of Automotive Engineers is responsible for the classification of SAE numbers. SAE indicates its viscosity based on classification involving two temperatures.

PARTICLE ELEMENTS

While testing the oil for analysis, elements reported will depend on the machinery type and the oil grade. If wear particles are found in the oil, this indicates a component problem.

– Aluminum: Bearings, pistons, housing and fuel derivative
– Copper: Bearings, oil coolers, gears and piston-rod glands
– Iron: Crankshafts, cylinder liners, piston rings and gears
– Calcium: Lubricants derivative
– Magnesium: Housing, casing and lubricants derivative
– Chromium: Piston rings
– Manganese: Cylinder liners
– Nickel: Valves, gears, bearings and fuel derivative
– Molybdenum: Piston rings
– Potassium: Salt water
– Phosphorus: Lubricants derivative
– Sodium: Salt water, coolant derivative and fuel derivative
– Tin: Bearings
– Lead: Bearings
– Zinc: Lubricants derivative
– Silicon: Dirt, dust, fuel derivative and lubricants derivative
– Silver: Bearings
– Vanadium: Fuel derivative

Draining out the enough amount of oil from the line before taking the sample is important to avoid sampling contamination. The oil sample must be filled in a special oil testing container and should be closed immediately after taking the sample of oil. All correct records must be mentioned.

About Ennero

Ennero is one of the leading suppliers of marine lubricants in UAE and provides an extensive range of marine lubricants, oils, greases and specialty products to maritime customers globally. We also provide oil testing and analysis services for our customers to ensure that their machinery is safe and working optimally. Our team of experienced professionals have the expertise to help you get the best out of your machinery. If you are looking for a reliable and professional supplier of marine lubricants in UAE, then contact us today. We look forward to hearing from you.

The writer is the technical sales manager at Ennero.