Lubricating Oil

Important oil parameters require to be monitored on regular basis is given bellow:

  • Viscosity @ 40 degree cSt

  • Viscosity @ 100 degree cSt

  • Total Acid Number (TAN)

  • Total Base Number (TBN)

  • Moisture Content

  • Particle Quantifier (NAS)

  • MCI

  • Analytical Ferrography Analysis

  • Allotting Machine Condition Index

Analytical Ferrography Analysis (Lubricant Oil / Grease)

Wear Debris Analysis (Ferrography) is a technique for analyzing the particles present in fluids that indicate mechanical wear. Ferrography provides Microscopic Examination and Analysis of Debris (particles) found in lubricating oils. These particles consist of metallic and non-metallic matter. The metallic particle is a wear condition that separates different size and shapes of metallic dust from components like all type of bearings, gears or coupling (if lubricated in path). Non-metallic particle consists of dirt, sand or corroded metallic particle. Analytical Ferrography is among the most powerful diagnostic tools in oil analysis in Tribology. When implemented correctly it provides tremendous information on machine under operation. Yet, it is frequently excluded from oil analysis programs because of its comparatively high price and a general misunderstanding of its value. Performance may be improved through proper filtration of oil. Clean oil lubrication is always more effective. Adopting approach of oil replacement is expensive. A rapid centrifuged and/ or magnetic separator cleaning system helps cost cutting and disposal of used oil, as well. Ferrography also helps improving filtration efficiency and frequency for oil cleaning systems.

Analytical Ferrography Analysis Identifies The Properties of :

  • Normal rubbing wear/Severe rubbing wear

  • Cutting wear / abrasives

  • Fatigue wear/Laminar wear

  • Fatigue spheres

  • Dark metallo-oxides

  • Red oxides (rust)

  • Corrosive wear

  • Ferrous metals-iron and iron alloys

  • Non-ferrous metals

  • Non-metallic particles

  • Friction polymers

  • Fibres Contaminants, such as dirt, coal dust, fly ash, fibres, etc.

95% of the Ferrography Analysis can be identified from this chart:


Viscosity is termed as the “Resistance against flow”. It is measured in Centistokes (cSt.@40O C)

Viscosity is the prime property of any lubricating oil which is responsible for creating a suitable thin oil film capable of sustaining the load of the rotating component, preventing both surfaces coming in contact.

Oil film thickness depends upon the types of lubricating mechanism.

  • Boundary film....h ~ o.oo5 μm

  • Hydro-dynamic film.... h =>0.25 μm

  • Elasto-hydrodynamic....h ~ o.o25 – 2.5 μm

  • In order to maintain the required oil film thickness, the viscosity must be adequate. Each ISO viscosity grade oil has got a specific permissible viscosity range. For example :- an oil of Viscosity Grade 320, should have a permissible range of 240 – 437 cSt.@40° C, with an average of 320 cSt. @ 40° C. This oil is considered to be unusable, if viscosity, during usage, becomes less than 240cSt. Or more than 437 cSt.@ 40° C.

During the course of lubrication process, oil viscosity may change either Increase or decrease due to certain reasons.

Reasons of Viscosity Increase

  • Addition of higher grade oil as make up.

  • Presence of sludge in oil.

  • Presence of oxides.

  • Additive depletion at higher temperatures.

  • Presence of moisture.

  • Misalignment/Unbalance/Overload. ( Thermal failure).

  • Air contamination/ Foaming.

  • Coolant contamination.

  • Base stock failure.

Reasons for Viscosity Decrease

  • Fuel / Refrigerant dilution

  • Make up with low grade oil.

  • Cracking ( Very high temperatures)

Water Content

1. Effects of water contamination in oil

  • It can cause rapid Failure of Oil Film Thickness.

  • It causes Corrosion.

  • It causes Oxidation.

  • It causes deterioration of oil by Hydrolizing Additives.

  • In storage tanks, it leads to Microbiological growth.

2. Potential Sources of Water Contamination

  • Oil Coolers, Steam heating Coils.

  • Condensation of atmospheric Humidity.

  • Blow by gases in Diesel Engines.

  • Breathers.

  • Coolant Jacket leaks.

3. Co-Existence

Water exists in oil in three states.

  • Dissolved State - Water remains in an invisible form. Oil may contain 0.02% –0.06% (200-600 ppm) in this state.

  • Emulsified state – Once water exceeds the saturation level, it remains in suspension state in the form of microscopic droplets.

  • Free state – Addition of more water will cause it to remain in free form.

4. Prevention Of Water Contamination

  • Prevention of water ingression source.

  • Water separation.

  • Water removal.

  • Oil condition monitoring.

5. Water Removal Techniques

  • Draining.

  • Providing Rest period in oil circulation.

  • Centrifuging.

  • Design of Tank Compartments and Baffles.

6. TAN and TBN values for lubricating

  • TAN (Total Acid Number) and TBN (Total Base Number) of a lubricant are measured to assess its Acidic or Alkaline Characteristics. These are measured in Labs through ASTM Standard (ASTM –D-974) procedure.

  • These are measured by Titration method by finding out the end points (Color Change)

  • TAN is measured for mainly Gear Oils / Bearing Oil /Compressor Oils and TBN is for Engine oils only. In an Engine, chances of fuel mixing with the lubricant are more.

  • As fuel has Sulphur and Sulphur causes Sulphuric Acid,Engine oils are more prone to become acidic. Hence these oils are kept always Alkaline and TBN is measured much the TBN value.

  • Base Metal Additives are added in Engine oils to help them to remain alkaline.

7. Why some Engine oils have high TBN?

  • High TBN is recommended to provide longer drain intervals.

  • They also contract the effects of higher Sulphur levels.

  • Base Metal Additives.

8. NAS (National Aerospace Standard)

  • NAS stands for 'National Aerospace Standard of America'. It is the standard for oil cleanliness which indicates the number of microscopic particles of different size say 2-5, 5-15, 15-25, 25-50, 50-100 and above 100 micron present in 100 ml oil sample.

  • It is inevitable that Hydraulic & Lubricating oil will be contaminated at different stages. This contamination is a nuisance as it seriously affects the performance of the equipment. Therefore, to have trouble free operation of the system, not only the level of contamination but sizes & number of particles must be tightly controlled and monitored. However, this method yields inaccurate results in the presence of water or air bubbles.

9. MCI (Machine Condition Index)

  • Machine Condition Index indicates condition of the dynamic component of the machine as well as its permissible value.

  • In assessing Machine Condition Index, it is essential to look at the machine’s current and past data through microscopic examination. The particles are readily identified and classified according to size, shape, and severity.

10. Apart from the above other oil parameter test we are providing at our laboratory are

Sulphated ash Colour Crackle Test Elemental Analysis Foaming Water Separately
WPC Emulsion Characteristics Corrosion Resistance Chlorine content Varnish Potential Particulate contamination
Nitration Specific Gravity & Density Insoluble in Pentane Oxidation RPVOT Conradson Carbon Residue
PQ Index Ruler Rust Prevention Characteristics Work Cone Penetration MPC Softening Point °C
Neutralization Number Sediment Brook Field Viscosity Drop Point Saponification Value Demulsibility
Density Total Halogens as Cl Water content by Distillation (Dean & Stark) Appearance Dissolve Gas Analysis (DGA) PH value
Air Release Property Break Down Voltage (BDV) Conductivity Flash Point Copper Strip Corrosion Calculated Cetane Index
FTIR Oxidation Base oil Viscosity Pour Point Type of Soap