Lubrication Tips for Reliability Professionals

June 21, 2001 Subscribers: 7,203

Q & A

Overcoming Particle Counter Interferences

“We are using an optical particle counter to determine fluid cleanliness. I recently read on your message boards that water can affect particles counts. Is there anything I can do to overcome this?”

With optical particle counters, which work either on the principal of light blockage or light scattering, free and emulsified water droplets can be counted as particles since they can interact with the light beam and cause scattering effects. In fact, as little as 0.5% water can change the reported fluid cleanliness by several ISO range codes.

To mitigate this problem, a simple procedure can be used which removes the free and emulsified water prior to performing an optical particle count. This procedure involves mixing the oil sample with a 3:1 mixture of toluene and isopropyl alcohol and shaking vigorously. This procedure works since free and emulsified water is soluble in the isopropyl alcohol. The isopropyl alcohol is soluble in toluene, which is itself soluble in the oil. All free and emulsified water thus becomes dissolved in the oil sample and no longer affects the particle count.

Today's Tip

• Oil quality is established by the refining processes and additives are most effective if the oil is well refined. Although the overall performance of an oil can be improved by introducing additives, a poor quality oil cannot be converted into a premium quality oil by introducing additives.
  

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Book Bits

"Low oil level is a serious cause of contamination in the hydraulic system. When the oil level is low, more air gets into the tank and this often leads to destructive cavitation in the pump and to condensation on the tank walls which generates sludge. Sludge decreases the lubricity of the oil, producing scoring and friction on surfaces with close tolerances."

For more information about the book "Fluid Power Maintenance Basics and Troubleshooting" go to:

http://www.noria.com/secure/product_detail.asp?catalogid=31

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