Lube-Tech Figure 7: Varnish build up
PUBLISHED BY LUBE: THE EUROPEAN LUBRICANTS INDUSTRY MAGAZINE
No.122 page 6
As can be seen, the findings show that as the MPC value increases, the No. Particles >4 µm at 80°C decreases compared to 20°C. Some of this data was much more extreme, such as a change from 23/16/8 (20°C) to 13/11/7 (80°C) with an MPC value of 62; in cases such as this we can infer that most, if not all, of the colour of the membrane was due to oxidation products. Conversely, some of the results contradicted our main hypothesis, an example being a change from 14/12/9 (20°C) to 15/13/9 (80°C) with an MPC value of 44; in these instances, we can conclude that the colour of the filter was due to completely insoluble particulates or staining.
To summarise, varnish (oil oxidation products) is a serious threat to machinery condition and needs to be monitored appropriately. MPC is a reasonable measure of varnish potential within a system but further verification of MPC testing is important; this
can be achieved through Particle Counting at 80°C as well as 20°C. If a high MPC value accompanies a decrease in the Particle Count, we can confirm the presence of varnish.
The ending point here is that manipulating the temperature while particle counting provides us with another string to our analytical bow; the more testing that is available, the more knowledge we have and ultimately we have more control over our hydraulic and lubrication worlds.
LINK
www.fluidcarelab.hydac.com
LUBE MAGAZINE NO.151 JUNE 2019
27
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