Fine filtration (less than 3 micron) is becoming increasingly popular method of extending machinery life. Filtration companies have in recent years had a concerted effort to increase awareness of keeping oils clean and this has had a marked beneficial effect on overall cleanliness levels on these types of systems with the increased uptake. These systems sometimes going submicron in filtration size tend to be offline kidney filtration type systems rather than inline filtration because the pressure effects of filtering so finely.
One interesting point to consider is what effect this has on wear metals because normal wear metals are usually up to 15 microns and abnormal wear can be much larger. Therefore, surely wear metals are being removed by filtration too. This begs the question, is fine filtration meaning I could be missing early failure modes by oil analysis.
One major OEM in the construction sector once told me that they deliberately have a larger filter sizes specifically so wear metals can be detected and acted upon early on. This approach has be fairly sucessful for them, but it also means they have consistently higher particle counts as a result.
For some this is simply not acceptable as dirty oil leads to abrasive wear and reduced component life. They require fine filtration, but want the best of both worlds so they don’t miss any abnormal wear.
There are a few ways to address this, but sampling position becomes even more important and a return line before filter sample is far more beneficial than a main tank sample. The reason for this is the main tank will be under filtration and hence can give inconsistent wear trends. The return line will always be going through all the components without offline filtration after leaving the main tank and so wear will still be detectable.
The wear condemning limits will naturally need to be adjusted similarly to how you would do based on more regular oil changes as this is the effect the filtration is similar to. You may need to take a few samples to get a new baseline to trend before establishing new limits.
One thing you should also consider is when each filter insert is changed is to send that filter to the lab for a filter debris analysis. This is a great complement to your oil analysis programme in that all the debris collected by the filter can be analysed to determine what has been happening whilst the oil is being filtered. If you want a sure way to make sure you haven’t missed anything by the act of filtration, the combination of oil and filter analysis is perfect in these situations.
Remember if you are doing fine filtration make sure your oil analysis lab is aware of this so they can guide and advise you in the process.
So if you are doing oil analysis and have fine filtration too then consider adjusting your alarm limits and testing your filters too, so you don’t miss a potential early warning.
If you would like more advice on how to maximise your oil analysis programme when using fine filtration then click the chat icon at the bottom right of the screen to ask for help.