Varnish Potential by MPC Testing

Identifying Varnish and Sludge Potential in Oil

MPC (Membrane Patch Colorimetry) tracks the amount of insolubes present in the lubricating oil. In this way catastrophic failures can be avoided.

MPC is the only ASTM method (certified ASTM D7843 test: Standard Test Method for Measurement of Lubricant Generated Insoluble Color Bodies in In-Service Turbine Oils using Membrane Patch Colorimetry) to determine Varnish Potential. By separating oil degradation products their color is measured. It is an important part of turbine and compressor lubricant management. In this type of industry the oil may be in use for many years before it is completely changed. If not properly monitored risk is there of harmful sludge and varnish.

With MPC, a direct correlation is made between the color and intensity of the insoluble contaminants and oil degradation. The test is designed to identify soft contaminants directly associated with oil degradation. This test is considered to be highly sensitive and reliable for detecting subtle changes in insoluble levels

A varnish potential analysis (VPA) combines multiple testing technologies to measure a lubricating oil’s propensity to create varnish deposits. Following tests are combined:

  • Membrane Patch Colorimetry (MPC): A highly sensitive test and reliable for detecting subtle changes in insoluble levels.
  • Remaining Useful Life Evaluation Routine (RULER®): The RULER test uses linear sweep voltammetry to measure hindered phenolic and aromatic amine antioxidant content.
  • Karl Fischer Method: Increased water concentrations indicate coolant leaks, process leaks around the seals and possible condensation.
  • IR Spectroscopy: FTIR covers the monitoring of base stock degradation, oxidation and additive depletion in machine lubricants, hydraulic fluids and other fluid types.
  • Ultra Centrifuge Test: an excellent indicator of varnish potential.
  • Acid Number: A rapidly rising acid number indicates antioxidant depletion.
  • Particle Count: Particulate contamination is tested using two methods, optical (soft/varnish particles) and pore blockage (hard particles).

It provides a high level of confidence when extended oil drains on critical equipment are established. It is up to the operator to conduct the tests routinely, by exception or utilized in conjunction with a regular testing package.

Standard: ASTM D7843


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