Physical/Chemical Analysis
The parameters that are typically evaluated include viscosity, total base number (a measure of the oil's ability to neutralize acids), and the concentration of some metal ions (e.g., calcium, magnesium, phosphorus, sodium, and zinc) which are components of many additives. Once the samples are analyzed, various factors concerning the history of the equipment must be considered to determine when the oil requires changing. For example, metal levels in engine oils can vary depending on such factors as:

• Engine metallurgy
• Oil/lubricant consumption and replacement
• Types of engine lubricants and additives Filtration efficiency
• Dispersion characteristics of the oil�s additive package (which help hold metals in suspension)
  

These and other factors must be considered when evaluating whether an oil is acceptable for continued use. Rapid changes in contaminant metal concentrations, or rapid fluctuations of other oil properties are more important than strict adherence to published ranges of criteria, in determining whether an oil fails. Rapid changes in oil properties may indicate faulty equipment, severe operating conditions, or insufficient maintenance activities.

Determining whether an additive package is depleted is difficult largely because additive packages vary from one manufacturer to another. In addition, most available analytical tools do not directly measure the concentration of the additive package. This process is particularly difficult when oils from different manufactures are mixed together. Using a single brand of oil will minimize this difficulty. Instrumentation for analyzing engine oil should be calibrated to the specific type and manufacturer of oil being used. Differences in oil additives between manufacturers can affect the accuracy of the tests.

Ferrographic Analysis
Ferrographic analysis is a predictive method for determining equipment condition long before signs of wear are detected. Ferrography detects particles of ferrous, non-ferrous, and nonmetallic materials that are generated at the contact surfaces of moving parts. These particles are analyzed, and changes from previous results indicate a developing mechanical problem. If sufficient information concerning the equipment's metallurgy is available, analysts may be able to determine which gear, bearing, or other part is wearing. The size, number, composition, and type of particles will indicate the severity of the wear.

Dielectric Constant
A third form of analysis is a field test unit that measures the dielectric constant of lubricating oil, which indicates oxidation of the lubricant molecules. Dielectric constant is monitored as a function of time. Once the deterioration exceeds recommended limits, the oil should be changed. The test equipment can identify any of three potential problems:

1. moderate dielectric increase indicates contamination due to fuel soot, sludge, dirt, oxidation, or acid build-up (this condition is monitored over time until a predetermined point is reached, at which time the oil should be changed);
2. severe dielectric increase indicates water, antifreeze, or metal particles (immediate action is required to avoid potentially serious equipment damage); and
3. moderate dielectric decrease indicates gasoline or diesel fuel dilution, a condition indicative of a potentially serious problem requiring immediate attention. Note that moderate dielectric decreases are sometimes difficult to detect.

Particle Counters
A fourth form of analysis is the particle counter, which measures the number and size of particles present in oils and hydraulic fluids. Use of an electronic particle counter offers a viable alternative to the patch test, which has traditionally been conducted with CFC-113 or methyl chloroform (both Class 1, ozone depleting substances). This equipment requires no hazardous solvents. Test results are accurate and non-subjective. Use of this technology is approved for Navy activities as specified in the NA 01-1A-17 Aviation Hydraulics Manual.

The compliance benefits listed here are only meant to be used as a general guideline and are not meant to be strictly interpreted. Actual compliance benefits will vary depending on the factors involved, e.g. the amount of workload involved.

• Reduces the frequency of oil changes.
• Decreases consumption and purchase of virgin oil.
• Reduces the generation of waste oil.
• Provides valuable diagnostic information.
  
  
  

• Higher level of knowledge is required to perform the diagnostic tests or take representative samples.
• Data must be collected over time and analyzed to determine trends.
• Results are subject to interpretation.
• Oil analyzers must be calibrated to the type and manufacturer of the oil being used.
  
  
  

Assumptions:

• Dielectric constant sensor cost: $700
• Program involves monitoring 125 vehicles with average 6.5 quarts oil each
• Regular oil changes conducted at six month intervals
• Analysis program increases oil change interval to eight months
• Labor: 45 minutes per oil change, 15 minutes per test.
• Average of three tests conducted per vehicle per year
• Labor rate: $30/hr
• New oil purchase cost: $4.42/gal. or $1.11/quart
• New oil filters purchase cost: $6.00/each
• Oil Disposal: oils are recycled at no cost to the facility
• Filter Disposal: Estimated at $100 per drum, 100 filters per drum
• Filter Disposal cost: Estimated at $1.00 each
  

Annual Operating Cost Comparison for Lubricant Analysis Program and Scheduled Oil Changes

Economic Analysis Summary

Annual Savings for Lubricant Analysis Program: -$515
Capital Cost for Diversion Equipment/Process: $700
Payback Period for Investment in Equipment/Process: N/A

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