Lube-Tech
oil. This is achieved through the use of a light source emitting a beam through the oil, which is detected by a photo diode opposite. As a particle breaks the beam, this gets registered. This is repeated thousands, or millions, of times to provide a particle count.
Figure 5: Oil in water
PUBLISHED BY LUBE: THE EUROPEAN LUBRICANTS INDUSTRY MAGAZINE
No.122 page 5
Particle counters are typically operated at the system temperature, or at room temperature in laboratory conditions, but what if we could manipulate this temperature and observe any differences in results as a measure of oxidation products?
This was the premise of our research in the HYDAC Fluid Care Laboratory. Our initial hypothesis being that fresh oil samples will have low MPC values and negligible differences between the particle count at 20°C and 80°C. In samples with high MPC values, they will also display a decrease in the particle counts at the two temperatures, such as 22/20/15 at 20°C and then 19/18/15 at 80°C. This would indicate that the deposits dissolve back into the oil at higher temperatures. Alternatively, it is expected that there will be some instances where the high MPC value is not reflected in the particle counts. This would indicate that the colour is not due to “varnish”, but perhaps due to typical solid contaminants or staining of some kind.
These counters can be calibrated to a variety of standards, but for this research task, we are looking at ISO 4406:2017 (Hydraulic Fluid Power – Fluids – Method for coding the level of contamination by solid particles); this standard categorises particles by size and quantity, resulting in a three digit classification system. This is one of the defining standards in the industry and it is available online, but essentially it allows for the easy comparison of contamination levels – the higher the value, the greater quantity of particles at that size range. For example, an ISO 4406 code of 17/14/11 could translate to:
• 17 – 101,232 particles >4µm per 100ml of fluid • 14 – 13,333 particles >6µm per 100ml of fluid • 11 – 1,564 particles >14µm per 100ml of fluid
Whereas a higher code of 21/18/15 could translate to:
• 21 – 1,324,412 particles >4µm per 100ml of fluid • 18 – 172,113 particles >6µm per 100ml of fluid • 15 – 31,321 particles >14µm per 100ml of fluid
Figure 6: Results of MPC vs Difference between particle count 26 LUBE MAGAZINE NO.151 JUNE 2019
The study involved 100 real oil samples from a variety of industrial applications, including Power Generation, Pulp and Paper, Oil Manufacturers, Injection Moulding. Each of these samples was subjected to MPC and Particle Count (20°C & 80°C) testing. Results were plotted as “MPC” against “% Difference Between the No. Particles >4µm at 20°C and at 80°C”.
The findings of this research can be seen in the following chart:
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