Elemental analysis is performed using ICP (Inductively Coupled Plasma) or in some cases XRF (X-Ray Fluorescence) spectroscopy. These machines provide us with the elemental composition of the oil in mg/kg (parts per million). Each oil type has a unique signature of elements from the oil additives which are present in the new oil.
During use the oil accumulates microscopic particles of wear metals which are detected as elements. These wear metals should accumulate at a slow, steady rate. Rapid changes in the rate of wear can be an early indication of a fault developing or of abnormal conditions that are decreasing the life expectancy of the component.
There are also many contaminants that can enter an oil compartment and cause damage, and elemental analysis can detect these before significant harm is done. For example - salt water contamination would cause as an increase in Chlorine, Sodium and Magnesium and some lesser elements. Dirt and dust show as silicon from the silicon dioxide (silica) and typically associated with aluminium from aluminium oxide, depending on the type of dirt/sand.
The PQ (Particle Quantifier) is machine that uses electromagnet coils to provide an index number representing the total ferromagnetic content of the sample bottle. This machine is very useful for detecting larger pieces of iron or steel that can settle to the bottom of a sample bottle and could be missed by ICP. PQ is particularly useful for large unfiltered gear compartments such as Final Drives that can experience dramatic iron wear when there is significant water and dirt contamination or when in failure mode. This test is so useful that we run this on most samples, including coolants, fuels and grease.
Fourier Transform Infra-Red spectroscopy measures the absorption of infra-red light over a selected wavelength band. Specific chemical compounds absorb energy at their own unique wavelengths and the FTIR software is programmed to detect some known contaminants such as Water, Soot, Nitration, Oxidation, Sulfation.
FTIR oil analysis techniques were first developed for military purposes where equipment in the field where access to a laboratory was restricted. It is not a total oil analysis solution but it is very useful for screening samples for further tests.
Viscosity is arguably the most important physical property of a fluid. Viscosity is a measure of the resistance to flow or the internal friction of a fluid. It provides an indication of the ability of that fluid to flow to where it needs to be - or the ability of that fluid to stay where it needs to be.
Viscosity of a fluid changes with temperature. Most fluids increase in viscosity when cooled or decrease in viscosity when heated. This is why the viscosity of a fluid is stated at specific temperatures such as 40°C or 100°C. This is also why engine oils are sold in summer or Winter grades or multi-grades that include a Winter and summer grade (e.g. SAE 10W-40).
If the viscosity of a fluid is too high (for example, cold start up) it may not be able to be pumped to the components that need it and sudden failure can result. Or if the viscosity is too low (e.g. extreme heat or an incorrect light grade) then the fluid may not be able to maintain pressure and metal-to-metal contact can occur, causing sudden failure.
Some contaminants can increase the viscosity of a fluid (e.g. soot, water, glycol, particulate matter or oxidation of the oil itself). Other contaminants such as fuel, solvent or light hydraulic fluids can cause the viscosity to decrease. Multigrade oils typically use VI Improver additives that can break down in use.
Laser Particle Counting
Particle counting is important for some applications that require fine filtration. It is not relevant to engine oils which are too dark for laser particle counting. It is also not so relevant for unfiltered compartments. When it is possible and relevant, laser particle counting provides a way to measure the effectiveness of the filters in a system. Especially in hydraulic systems that use high speed and high pressure fluids, reducing the particle count can greatly reduce the wear rate of components.