Oil Analysis And Testing
Whats it all about?…
FTIR stands for Fourier Transform Infrared Spectroscopy. It is often simply referred to as an ‘Infrared test’. Infrared testing allows us to get a picture of an oil’s health and also whether any contaminants are present such as fuel or coolant.
An infrared spectrometer works by passing an infrared beam through a fixed thickness of oil, usually 100µm (0.1mm).
Firstly, a sample of new oil is tested to establish a baseline reading.
Then, a sample of the used oil is tested. Oil contaminants and additive molecules will absorb some of the infrared radiation, but only at certain frequencies. Soot and other particles will absorb the radiation at all frequencies.
After Oil testing, the frequency spectrum of the used oil is compared to that of the ‘new’ reference oil tested beforehand. From that we can then see how the oil condition has changed from its virgin state to its current state and make recommendations as necessary.
Above, A typical Infrared Spectrum
It is very important that we receive a sample of virgin oil to get the most out of this test – the accuracy improves considerably if the correct reference oil is used. Accurate measurements of fuel dilution and glycol content are highly dependent on the correct reference oil. With this test, we gain an appreciation for the oil condition by determining the values for Oxidation, Sulphation, Nitration and Soot.
OCLS Maintain a FTIR machine (Thermo Scientific Nicolet iS10 FTIR Spectrometer), it’s main role is to monitor engine “oil condition”, but is used for many other forms of analysis, including calculating the FAME/”Biodiesel” content in diesel fuels.
Oil Contaminants & Particles
Oxidation – Sudden or catastrophic – this is caused when a small number of particles invade a critical space and create a torque reaction large enough to cause a seizure or fracture, which is irreversible.
Sulphation – Is usually a result of abnormal blow-by in diesel crankcase engines. It can also occur due to the use of high-sulphur fuels. A high sulphation value indicates the presence of sulphur oxides and sulphuric acids. Engine over-cooling and also short journeys can result in an increase in sulphation. Sulphation correlates inversely with the TBN. See TAN & TBN section.
Nitration – Is similar to oxidation but concerns the reaction of Nitrogen from the air with oil rather than Oxygen. The nitration process is linked to high running temperatures and can form such organic compounds as nitrate esters. High nitration can lead to the formation of grease-like sludge deposits and varnishing.
Soot – Is produced as a result of the incomplete combustion of fuel. It is made up of black, impure particles of carbon. High soot can occur due to an incorrect fuel-air ratio in the combustion chamber of an engine. Faulty injectors can also lead to high soot. High soot can cause sticking rings, piston damage and bore polishing.
The Nicolet iS10 FT-IR Spectrometer, used by OCLS for FTIR Analysis.