Varnish Testing by Color Evaluation - Membrane Patch Colorimetry ('MPC')

In this post, we shall discuss some of the harms caused by varnish due to oil oxidation product formation as well as Varnish Testing by Colour Evaluation - Membrane Patch Colorimetry.

KLEENTEK: Field Contamination Checker Unit

Microscope included as part of KLEENTEK: Contamination Checker Unit

This is also known as ASTM D7843 or MPC Varnish Potential Testing - one of the intended test that is used to measure the level of risk that varnish contaminantion poses to gas turbine performance.

Varnish Testing by Color Evaluation: Membrane Patch Colorimetry (MPC)

This technical advisory provides an overview of Membrane Patch Colorimetry (MPC), a powerful and widely accepted technique for evaluating and monitoring varnish formation in industrial oils. Understanding the severity of varnish precursors and deposits is crucial for proactive machinery maintenance and preventing costly failures.

Why Varnish is a Problem:

Oil varnish, a sub-micron particle or chemical byproduct of oil degradation, forms tenacious deposits on critical machinery components. These deposits can lead to:

• Restricted Oil Flow: Clogging filters, orifices, and heat exchangers, compromising lubrication and cooling.

• Abrasive Wear: Varnish components can act as abrasives, accelerating wear on valves, bearings, and gears.

• Compromised Tolerance: Deposits can interfere with the tight tolerances of precision components, such as servo valves and actuators.

• Reduced Heat Transfer: Varnish layers act as thermal insulation, impairing heat transfer and increasing operating temperatures.

  
  

Membrane Patch Colorimetry ('MPC') Explained:

MPC is a visual evaluation method designed to quantify the concentration and severity of varnish within an oil sample. It is a highly sensitive test that can detect varnish precursors before they form visible deposits and cause performance issues.

The core principle of MPC involves filtering an oil sample through a standardized micro-porous membrane. The contaminants present in the oil, including varnish precursors and degradation products, are captured on the membrane surface, creating a color patch. The color intensity and shade of this patch directly correlate with the degree of varnish contamination.

How the MPC Test is Performed:

Sample Collection: A representative oil sample is collected from the system, ideally at normal operating conditions.

Filtration: A specific volume of the oil sample is filtered through a precise membrane with a defined pore size (typically 0.45 or 0.8 micrometers).

Washing: The filtered patch is washed with a clean solvent to remove residual oil and any non-varnish contaminants.

Color Evaluation: The color of the patch is visually compared to a standardized color scale or evaluated using a spectrophotometer to assign a numerical value (often expressed as a "delta E" value). This value indicates the degree of deviation from the base membrane color and quantifies the varnish severity.

Interpreting MPC Results:

• Light Patch: Indicates minimal varnish contamination, suggesting that the oil is in good condition and varnish precursors are low.

• Moderate Patch: Indicates a moderate level of varnish contamination, suggesting the presence of varnish precursors and deposits. This may warrant increased monitoring and proactive measures.

• Dark Patch: Indicates severe varnish contamination, signifying high levels of varnish precursors and potential deposits. Immediate action is likely required to address the varnish problem and prevent component damage.

Related Product - KLEENTEK: Contamination Checker Kit

Benefits of MPC Testing:

• Early Detection: Identifies varnish precursors before they become a problem, enabling proactive maintenance.

• Sensitivity: More sensitive than traditional particulate analysis for varnish detection.

• Simplicity and Speed: Relatively quick and easy to perform, providing rapid results.

• Standardization: Utilizes standardized methods and color scales for consistent evaluation.

• Correlation with Field Observations: Strong correlation between MPC results and actual varnish-related problems in the field.

  
  

Integrating MPC into Your Maintenance Program:

• MPC testing should be an integral part of a comprehensive oil condition monitoring program for varnish-sensitive systems. Regular MPC analysis enables:

• Condition-Based Maintenance: Focus maintenance efforts on systems with elevated varnish levels.

• Process Improvement: Identify and address the root causes of varnish formation.

• Component Protection: Extend the life of critical machinery components by preventing varnish-related damage.

• Optimized Performance: Maintain optimal system efficiency and reliability by keeping oil systems clean.

Conclusion:

Membrane Patch Colorimetry (MPC) is a valuable and highly effective tool for detecting and monitoring varnish formation in industrial oils. By providing a quantifiable measure of varnish severity, MPC empowers maintenance professionals to implement proactive strategies for varnish control, safeguarding critical machinery and ensuring reliable, efficient operation. Regular MPC testing is a cornerstone of proactive oil condition monitoring and a critical component of any comprehensive maintenance program designed to extend equipment life and minimize costly downtime.

For more information, please contact one of your regional representative or local sales agent.

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