Different Methods of Lub oil Analysis

       This test uses a spectrometer to measure the level of specific chemical present in an oil. There are two types:- a) Arc emission spectrometer and b)ICP (Inductively coupled plasma) spectrometer.
Principle--- An oil sample is mixed first with a solvent and then with argon gas to form a fine mist.This mist is introduced into a plasma flame. Elemental metals present in the sample will emit energy in the form of light when introduced to plasma. Each element  emits light at known wavelengths. By measuring the intensity of light emitted at these known wavelengths the calibrated instrument can determine the concentration in PPM for the metallic elements present in the sample.

      It is a versatile tool used to detect common contaminants, lub degradation byproducts and additives within lube oil. When exposed to infra red radiations molecules absorb radiations at very specific wavelength. Knowing this you can pass infra red radiation through a sample and use a detector on the other side of the sample to identify the molecules found in the sample.
       The first component in the system is the source. The source will emit infra red energy and send it through an aperture to control the amount being presented to the sample.Next the beam enters the interferometer where it is encoded using a series of stationary and movable mirrors. This encoding is a way to produce a signal that consists of all the important infra red frequencies simultaneously.
  The beam then enters the sample and certain frequencies of the energy are absorbed. The energy that escapes the sample is sent to detector where it is measured. This measured signal is then sent to a computer where Fourier transformation takes place. At this point the results are plotted on a screen and a sample analysis can be made by a technician.

     This method focuses on particle counting and related standards. Perhaps the most widely developed method today for determining fluid cleanliness is to use an automatic optical particle counter. The instruments use either a white light source or more commonly today, a Laser.
   In a white light instrument, particle pass through the capillary detection zone and create a shadow on the photocell detector.The drop in voltage produced by the photocell is directly proportional to the size of the shadow and hence the size of the particle passing through.
   In a Laser beam instrument, due to near parallel nature of the laser beam, light scattering from the unimpeded laser beam is minimal because it is focused into a beam stop - until a particle passes through the instrument. As the laser strikes the particle, light scatters and hits the photocell. Just like the white light instrument, the change in voltage across the photocell is directly related to the size of particle. It is considered more accurate and sensitive than white light instrument.

     The Acid number and base number of in service oil are considered key indicator of oil quality and are used monitor the accumulation of acid and depletion of base additive package. A significant rise in acid number or decrease in base number may reflect a deterioration in oil quality either due to chemical reaction, oxidation, incorrect oils, additive depletion and contamination. 


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