Oil Analysis

Testing for Water Contamination

• Testing for water in oil can be done through a variety of methods with the most common and simple being the "crackle" test.
• A crackle test is a test where a couple of drops of oil is put on a hot plate and heated to about 300 F (150 °C).
• If water is present, audible crackling will be heard as the water heats up, bubbles form and grow and finally pop.
• Another method is the FTIR (discussed earlier) where the presence of water will be indicated in a particular wavelength.
• In order to quantify the water in the oil, the Karl Fischer test is often used. This test will provide a ppm or percentage water value. Measures all water - free, emulsified and dissolved.

Solid Contaminants

• Solid (particle) contaminants can be quite destructive
• Destructiveness:
• Quantity
• Size
• Hardness
• Sharpness of edges
• Weight

• Examples include:
• Wear metals (depends on system components)
• Soot (combustion by-product)
• Rust
• Dirt / Dust
• Fibers
• Silt (class of very small particles (~ 1 micron) and can be composed of many different materials

Introduction To Ferrography

• Also known as Wear Debris Analysis
• A powerful tool in analyzing the health of machinery.
• Wear particles suspended in the oil are separated by magnetic or filtration methods
• Examine this debris under optical microscope (100x is standard)
• Analyst can gain much information on the health of the machinery from which the sample was taken
• Relatively simple technique
• periodically quantify amount of wear taking place over time
• identify location and mechanism of such wear

Example

• Large Ferrous Abrasive Wear
• 100× Magnification

Wear Debris Particle Recognition

• Appearance of wear debris is related to conditions under which they were formed
• This facilitates the identification of wear mechanisms.
• Only a limited number of ways in which surface wear can occur.
• Each mechanism generates particles of a specific appearance.

• Damage due to wear can occur by any of the following specific wear mechanisms:
• Abrasion
• Gouging
• Adhesion
• Cavitation
• Erosion
• Micro fatigue
• Fretting
• Corrosion