Journal bearings
                                                        Roller bearings

• Condition of the oil wetted components of the machine and their wear rates;

• Condition of the lubricant and whether it can continue to be used or has to be replaced or reconditioned;

• Level of contamination and what the contamination is.

                                               Paper Chromatography
                                               Centrifuge
                                               Spectrographic Metals analysis
                                               Viscosity
                                               Neutralization Number (TAN and/or TBN)
                                               Fourier Transform Infrared Analysis (FTIR)
                                               Flash Point
                                               Karl Fischer Water Titration
                                               Particle Count/Distribution
                                               Direct Read Ferrography
                                               Wear Particle Analysis
                                               Others as required

• Probably the first test that should be done to every sample that is processed in a lab.

• Good qualitative test for the presence of water, fuel, coolant, excessive solids, and the oil’s dispersency

• This test also forces the technician to visually inspect the sample for large particulates and odd coloration, as well as note any odd odors.

• Quantifies water >.1% and sediment > 0.06%

• Test is usually not done unless blotter or other test indicates need.

• Usually performed on rotating disk emission spectrometer or inductively coupled plasma spectrometer. Both use atomic emission principle.

• Instruments can analyze for 20 – 25 metals simultaneously. Results are usually reported in parts per million (ppm)

Rotating Disk Atomic Emission Spectrometer

• Instrument is quick, accurate, and inexpensive to operate

• Particle size limitation is about 10 µ, depending on metal and level of surface oxidation on particle surface.

• Accurate to about 1 or 2 ppm

• No dilution of sample is required

• Results include wear, additive, and contaminant metals

Inductively Coupled Plasma Spectrometer

• Instrument is very accurate,

• Particle size limitation is 1-3 µ

• Sample dilution is required

• More expensive to operate as argon and nitrogen gases are required.

Typical spectrographic metals reported

• Key property of a lubricant

• Many things affect an oil viscosity

• Product or fuel dilution

• Polymerization caused by degradation

• Water and glycol

• Dirt and wear metals

• Usually run at standard temperatures: 40°c for most oils and 100°c for engine oils. Results are reported in centiSstokes (cSt) for these temperatures. Test can also be run at 100°f and 210°f respectively and reported in Saybolt Universal Seconds (SUS)

• Tests are accurate and easily trended

• Inexpensive to run

Total Acid Number (TAN)

• Titration of the acids that build up in lubricant due to degradation and contamination.

• Reported as mg KOH/gm sample, or simply how many milligrams of potassium hydroxide did it take to neutralize the total amount of acid in one gram of sample.

• Test can be varied to report strong and weak acids.

• Test can be run with a color indicator or potentiometrically (using a pH sensor)

Total base number (TBN)

• Titration of the alkaline, caustic, or basic constituents in the oil due to corrosion inhibitor additives or contaminants

• Reported as mg HCl/gm sample, or how much hydrochloric acid did it take to neutralize the basic constituents in one gram of sample.

• Test is usually run potentiometrically, but can be run with color indicator.

• TBN titrations are appropriate for engine oil analysis

Both tests report on the condition of the oil

• Measures a number of different chemical bonds by absorbing infrared light. Different chemical bonds will react at different wavelengths

Water Glycol Oxidation products

Fuel Nitration Sulfur-oxygen

• Instrument passes an infrared light through or reflected off of a sample in a sweeping range of wavelengths from 600 to 4000 nanometers. A detector measures the amount of absorption at each preset increment, usually 2 nanometers

• Unless a calibration curve is developed for each lubricant and each constituent, FTIR analysis is more qualitative than quantitative. Constituents such as soot, fuel, oxidation, nitration are often reported in indexes, rather than parts per million for example

• Instrument can be used in % transmission or absorbence mode.

• Quantitative titration for measurement of water

• Measures free, dissolved, and emulsified water

• Accurate down to 10 ppm

• Most often performed with automatic titrators

• Only acceptable method for measuring quantities below 500 ppm

• Subject to some interference:
  Free alkali
  Some sulfur compounds
  Some nitrous compounds

• Can be used for trending purposes when strong interference is present.

• With sample pre-treatment, can measure moisture in solids and semi-solids

• Can measure moisture in gases

• Reagents are hazardous and expensive

• Reported in particles in various size ranges per cc of sample.

• The count can be put into an NAS 1638 or ISO 4406 classification

• Laser light scattering

A laser light is shined through a flowing stream of lubricant. The reflected, refracted, and transmitted lights resulting from particles passing through the laser light are measured versus time. The number and size of the particle can then be calculated.

• Flow curve degradation

A known quantity of sample is flowed through a calibrated screen. The flow curve degradation due to particles building up on the screen is measured versus time. The number and size of particles can then be calculated

• Microscopic count

A portion of sample diluted to 100 ml is poured evenly over a 0.45µ gridded filter patch. Particles on a representative number of grids are visually counted and sized.

• ISO classification is reported in three ranges.

Ex: 17/13/10 where 17 is the range number of particles > 2µ, 13 is the range number of particles > 5µ, and 10 is the range number of particles > 15µ.

 

ISO 4406 range number classification (particles/100 ml)

NAS 1638 range number classification (particles/100 ml)

• The sample is classified as the highest class reported in any size range.

• Reported in unit-less empirical values as direct read small (DRS) and direct read large (DRL)

• DRS includes ferro magnetic particles generally less than 5µ

• DRL includes ferro magnetic particles from 0.1µ to over 300µ.

• Both DRS & DRL will include non-ferro magnetic particles of all sizes.

• Sample is flowed through a glass tube at a slight incline over a permanent magnet. Two light detectors placed in series along the front end of the tube will detect the amount of transmitted light before and after the sample has flowed through.

• Because the instrument is ‘zeroed’ with the portion of sample that first reaches the detectors, oil color does not interfere.

• Not hindered by particle size like the emission spectrometer.

• A ferrographic slide is prepared

• Microscopic examination and classification of particulates present in the sample. Analyst will identify contaminants, wear particles, and rate them as normal, moderate, excessive, etc. The analyst will also make a wear judgement as to the condition of the equipment in question.

• Requires an experienced analyst

• The analyst can identify the morphology of the wear particles and identify the wear mode.

• Most organic contaminants can be identified

• Metallic particles can be identified by magnetic alignment and heat treating the slide