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peteMember

We are starting to make filter patches on equipment where we want to trend the non-ferrous debris in the oil. My question is: what size filter should we use? i.e. 4,5,11 micron. We do not make our patches using the Vampire pump method, we use 49mm filter patches in our patch maker.

A 4 micron filter has a tendency to fill up, on some occasions, that we can not make out the content of the debris. Should we go to an larger micron filter and cut back on the volume of the sample? We are more interested in the content and not the amount, our particle counts and ferrography results are within our limits most of the time (knock on wood).

10/21/053:22 AM

Original Post

Pete,
I use mostly 5 micron filters for my filter patches. I also have a problem with the filters loading up sometimes. My patchmaker is a part of my MiniLab and I sometmes replace the filter several times while drawing the sample through the filter and use successive patches for comparison. I even will put a clean patch in and rinse the vessel out through the patch after the sample is drawn through to catch the particles that may be left over. One feature my patch maker has is the ability to put two patches in seperated by a spacer, this allows me the option to seperate particles by size also by using a larger pore size on the upper patch. I haven't used that feature very often though

You can use a smaller oil sample and dilute more to get a patch that has less particle density so you can better see the individual particles. Analyzing filter patches is less about "how much" than about size and shape of the particles which give you clues to where they come from and how they are being generated.

10/21/058:32 AM

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