Circular - The importance of lube-oil analysis

Although not always instantly accepted or recognised by some as a P&I issue, main engine breakdowns can, for example, lead to groundings, collisions, and dock damages, which in turn can result in General Average or third party claims, and in extreme cases may result in costly wreck removal claims.

Lube-oil analysis and monitoring is an effective tool in averting breakdowns by flagging up
potential problems before an actual breakdown occurs:

The latest analytical techniques in lubricant analysis can provide an invaluable tool for Owners in monitoring the health of a ship’s engine.

The following aspects of a lube oil sample may be analysed:

  • Viscosity - A measure of the resistance of a liquid to flow. Commonly referred to as the 'thickness of an oil'.
  • Closed Flash Point - Primarily a test for fuel dilution in engine oils. A decrease in flash point is generally an indication of fuel ingress which has contaminated the lubricant.
  • Insolubles - A test for the total solids contamination in a lubricant such as combustion soot, dirt, oxidation products and metal wear debris.
  • ase Number - 'Previously known as Total Base Number (TBN) is a measure of the reserve alkalinity of an engine oil and its ability to neutralise harmful acids.
  • Acid Number - Tests the acidity of the oil. 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.
  • Water - The percentage (by volume) of the total amount of water contamination.
  • PQ Index - Not an oil property but an indices that provides a quantitative assessment, for trending purposes, of the amount of ferrous wear debris in the sample.
  • Asphaltenes - Give an indication of heavy fuel derived components from raw fuel ingress and/or products of combustion from blow-by.
  • IR Oxidation - An Infrared method to assess the oxidation by the change in molecular structure that occurs during the oils ageing process.
  • Elemental analysis can identify high levels of metals in the oil sample, which can point to accelerated wear & tear in certain engine parts.  Some typical sources of various metals are listed below.

The elements reported depend on the machinery type and oil grade (and are reported in PPM - Parts Per Million).

  • Element           Typical source
  • Aluminium       Pistons, bearings, housings, fuel derivative
  • Antimony         Bearings
  • Calcium           Lubricant derivative
  • Chloride          Salt level of the water phase from sea water contamination
  • Chromium       Piston rings
  • Copper            Bearings, gears, oil coolers, pipe-work, piston-rod glands
  • Iron                   Cylinder liners, crankshafts, piston rings, gears
  • Lead                 Bearings
  • Magnesium     Casings, housings, lubricant derivative
  • Manganese    Cylinder liners
  • Molybdenum   Piston rings
  • Nickel               Bearings, valves, gears, fuel derivative
  • Potassium       Salt Water
  • Phosphorus    Lubricant derivative
  • Silicon              Dust, dirt, fuel derivative, lubricant derivative
  • Silver                Bearings
  • Sodium            Salt water, coolant derivative, fuel derivative
  • Tin                     Bearings
  • Vanadium        Fuel derivative
  • Zinc                   Lubricant derivative

In conclusion, we recommend that all Owners implement a regular system for analysing lube oil, reviewing and monitoring the results, and promptly acting on the findings.