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Oil analysis being a part of tribology is non-intrusive examination of identifying the lubricant health, lube contamination and equipment wear. Objectives of oil analysis is to make sure your lubricant is providing better lubrication to the equipment components, controlling contamination and identifying the predominant failures at an early stages.

A machine’s operating life is most often determined by the oil that lubricates its load-bearing surfaces. Good lubrication normally provides long life, even under harsh operating conditions, and poor lubrication results in short life, even under mild operating conditions. Industrial machines are generally supposed to have 40,000 hours (about 5 years) mean time between failure (MTBF). This can only happen if you have “good lubrication”. If you have “poor lubrication” or “no lubrication” you get a far shorter operating life.

There are 5 factors in maintaining good lubrication:

  • Clean oil
  • Dry oil
  • Oil with the right properties
  • Contamination Control
  • Wear debris monitoring

Maintaining a lubricant means ensuring that it has the correct viscosity and the necessary additives for the application. Steps must be taken to keep the lubricant clean and serviceable. Oil analysis is the most effective way to prolong the useful life of lubricants, while maintaining maximum protection of equipment.

Oil analysis tests reveal information that can be broken down into three categories:

  1. Lubricant condition: The assessment of the lubricant condition reveals whether the system fluid is healthy and fit for further service, or is ready for a change.
  2. Contaminants: Increased contaminants from the surrounding environment in the form of dirt, water and process contamination are the leading cause of machine degradation and failure. Increased contamination indicates that it is time to take action in order to save the oil and avoid unnecessary machine wear.
  3. Machine wear: An unhealthy machine generates wear particles at an exponential rate. The detection and analysis of these particles assist in making critical maintenance decisions. Machine failure due to worn out components can be avoided. It is important to remember that healthy and clean oil leads to the minimization of machine wear.

Lubricant condition is monitored with tests that quantify the physical properties of the oil to ensure that it is serviceable. Metals and debris associated with machine wear are measured to monitor equipment health. Some tests target specific contaminants that are commonly found in oils.  It is imperative to select the proper blend of tests to monitor the machine’s lubricant condition, wear debris and contaminants in order to meet the goals of successful oil analysis.

Test Parameters monitored by LubeXpert Labs.

Test  Test Description Purpose of Test
Machine Specific Analysis

 

Results from the following tests are reviewed by your Machine Condition Analyst and recommendations for your equipment are given with supporting data on each report. Both Lubricant Condition & Equipment Condition are analyzed based on specific characteristics of your equipment, previous component performance, and test data.
Direct Reading Ferrograph

 

The DR unit separates wear debris from the lubricant according to size.  A sample is pumped across a high-gradient magnetic field at a slow rate.  The ferrous particles are attracted to the magnetic field and deposited in two locations depending upon the amount of attraction.  There are two size ranges: Density Large (DL) and Density Small (DS).  The DL represents particles >5 mm and DS represents particles <5 mm.  The results are an optical density equivalent and not a particle count. The WPC, summation of DL and DS, provides a trendable quantity for monitoring the wear condition of a piece of equipment.  Fluctuations in the WPC suggest an abnormal condition in the component or possible contamination.
Analytical Ferrography

 

Particles are separated from the lubricant sample by magnets and gravity, allowing for the examination of the individual particles present in the sample. Debris is examined microscopically at magnifications between 100x and 1000x.  Particles’ size, shape, composition, and concentration can be determined. By identifying the size, shape, composition, and concentration of the abnormal wear particles, the wear mechanism and its possible origin can be determined.  Solid contaminants can also be identified.  Equipment and component metallurgical information aids the analyst in determining the root cause for the formation of these particles.
Elemental Analysis

ASTM D6595 

Elemental analysis is performed in accordance with atomic emission spectroscopy (AES).  A specific volume of lubricant is energized using an electrical arc.  The light frequencies and intensities are measured and reported in parts per million of various elements. Elemental analysis is useful for identifying contamination, confirming additive content, and indicating system wear.  The following elements are analyzed:  Fe, Cr, Al, Pb, Sn, Cu, Ag, Ni, Na, V, Cd, Ti, Mo, Ca, Ba, P, Zn, B, K, Mg, and Si..
Particle Count

ISO 4406

 

As particles in the oil flow pass a laser, the laser light is blocked allowing individual particles to be counted and sized.  The resulting data is a distribution of the concentration of particles in various size ranges. Since all contaminants in the oil are counted as particles, the particle count includes wear particles, soot, dirt, and other contaminates.  This test provides information on lubricant cleanliness.
Water by Karl Fischer

ASTM D6304

 

This test produces iodine when electricity is conducted across a mesh screen.  The electrical current needed to create iodine and remove existing water is measured and converted to parts per million (ppm). Quantification of water contamination – water in a lubricant not only promotes corrosion and oxidation, but also may form an emulsion having the appearance of a soft sludge.
Total Acid Number

ASTM D664

 

TAN is determined by titration of a known substance, such as KOH in order to determine an unknown quantity.  Weighed samples are titrated using an automatic titration system. TAN of a used lubricant is one measure of its degree of degradation by oxidation.
Total Base Number

ASTM D4739

 

TBN is determined by titration of a known substance, such as HCl, in order to determine an unknown quantity.  Weighed samples are titrated using an automatic titration system. TBN of a used lubricant is a measurement of its ability to neutralize the acid using basic buffers.
FT-IR

Infrared Analysis

 ASTM E2412

The infrared absorption spectrum of a lubricant furnishes a means of fingerprinting organic compounds and functional groups.  Test results are trended and quantitative and qualitative determinations can be made. Infrared analysis is often used for identifying additives and their concentrations, reaction products, and contamination by organic materials in used lubricants.  Oxidation (carboxylic acids and esters), nitrate esters, water, soot, and glycol can be quantified.
Crackle

 

Eye Dropper test of lubricant on a hot plate heated to 100° C to determine presence of water.  Detection can be made of water concentration > 800 ppm. This screening test is used by the analysts to check for water contamination and determination of whether more sensitive testing is required to determine more exact concentration.
Viscosity

Kinematic/Oil Bath

ASTM D445/446

 

ASTM test uses a constant temperature bath.  The efflux time is measured between two points.  The viscosity is computed by using a calibration constant and the efflux time.  Viscosity is reported in centistokes (cSt) at 40ºC or 100ºC. Viscosity is the single most important property of a lubricant.  A reduction usually indicates that the system has been contaminated with a solvent or refrigerant fluid.  A significant increase normally is traced to mixture with a high viscosity product, contamination, or oil oxidation.  Normal measurement range for 40ºC is +30% and -20% and for 100ºC is +20% and -10%.
Fuel Dilution of Diesel Lubricants

ASTM D3524

Gas Chromatograph

The sample is mixed with a specific amount of an internal standard.  One microliter of the mixture is injected into a 10 meter HP-1 WCOT capillary column, heated at a specified rate, detected via a Flame Ionizing Detector, and the results (in percentages/peak area) are displayed in a report generated from the computer software. Some fuel dilution of the engine oil may take place during normal operation.  However, excessive fuel dilution (> 5%) is of concern in terms of possible performance problems.  Immediate effects of high fuel dilution are decreased lubricant viscosity resulting in increased wear.

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