What is MPC Oil Testing and What Does it Indicate?
The Membrane Patch Colorimetry (MPC) test measures the color bodies of insoluble contaminants in lubricants. It uses solvent extraction to capture varnish and oxide insolubles from a fluid sample on a micron filter membrane (patch). Varnish tends to color the patch and by measuring the hue and intensity of the colored material deposited on the patch, the color can be correlated to the amount of oxidation byproducts in the oil.
MPC is commonly called Varnish Potential, because it is measuring the byproducts that potentially lead to varnish within the system. There are some nuances to interpretation, though. A high MPC result does not definitively confirm that there are deposits in the system. Rather, several different scenarios need to be considered:
- A constantly increasing MPC suggests the creation of insolubles, but:
- The value may be increasing largely because the fluid is retaining all the insolubles as they are being created.
- Or it can be presumed that, since the insolubles are forming at an increasing rate, some of them are depositing.
- A static MPC value, or a value that has seemingly leveled off, might mean:
- The rate of formation of new insolubles equals the rate of deposition.
- The fluid is no longer forming insolubles—although this is unlikely.
- The rate of formation of new insolubles equals the rate of removal via a filtration system.
- A decrease or sudden drop in MPC value might mean:
- The mitigation technology is getting ahead of the rate of formation of new insolubles and the fluid is becoming cleaner.
- The insolubles have now deposited within the system and will no longer show up in the fluid because they are on the metal parts.
The overall evaluation is most accurate when a trend can be observed and established through MPC and other tests. Trend analysis tends to head off lubrication related machinery issues before downtime occurs.
With more than 30 years of experience in the oil analysis industry, TestOil focuses exclusively on assisting industrial facilities with reducing maintenance costs and avoiding unexpected downtime through oil analysis program implementation. As industry experts in diagnosing oil-related issues in equipment such as turbines, hydraulics, gearboxes, pumps, compressors and diesel generators, TestOil provides customers with a guarantee of same-day turnaround on all routine testing. With in-house, certified training professionals, TestOil offers lubrication and oil analysis training, private onsite training, certification training and exams, and educational webinars. For more information on partnering with TestOil on oil analysis programs or training opportunities visit www.testoil.com.