Lube-Tech Figure 2: ESD at filter
Once a risk of ESD occurrence has been identified, what can be done to remove this? Because the charge build up is a result of a huge number of interactions at the filter element, this is the target area for change. It has already been explained that simply making the filter conductive is not a solution, therefore it is essential that the interaction process is stopped at the source; by preventing the electron transfer in the first place, the charge does not build up and the risk of sparking is mitigated. This technology is not available from every filter supplier, so it is best to enquire about the ESD prevention process built into filters prior to acquisition.
Why is varnish a problem and why does it need to be measured?
The build up of sludge in a system can be damaging in many ways, the first key issue being malfunctioning valves. Sludge can prevent the normal functioning of valves, causing sticking of spools, the end result of which can be serious, especially if the valves in question are required for a safety function. Another problem is the blocking of filters; typical inline pressure filters are developed to filter out solid particulates of various shapes and sizes. Many use depth filtration, where multiple layers are used to filter out a complex range and large quantity of contaminants. This level of technology can result in a
24 LUBE MAGAZINE NO.151 JUNE 2019
PUBLISHED BY LUBE: THE EUROPEAN LUBRICANTS INDUSTRY MAGAZINE
No.122 page 3
more expensive filter, but it is still cost-effective when performing its intended duties. However, instead of using the full range of filtration media embedded, varnish will stick to the exterior of the filter; this causes premature blocking and increased costs due to higher frequency of element changes.
More critical issues caused by varnish includes the reduction in lubrication gaps; the incompressible nature of oil is the reason it is used for these high pressure and power applications. Lubrication gaps are the pockets of lubricant that prevent direct metal-to- metal contact in the system, therefore preventing wear and extending the lifetime of components. If oxidation products begin to deposit in these areas, the amount of lubrication is reduced and the level of wear can drastically increase.
Figure 3: Example of contaminants in a filter
Lastly, but just as important, is the obstruction of heat transfer. Due to the nature of varnish, it’s solubility in the oil is dependent on the operating temperature. At higher temperatures the sludge can remain dissolved, but at lower temperatures it can become free. Because of this, varnish will typically deposit on
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48
