I´d like to know if is there any correlation between ferrography and particle counting and between ferrography and spectroscopy?

Hi Duarte.
Ferrography is a state-of-the-art predictive maintenance technique based on wear debris (particles) analysis. Therefore if you don't have any "wear debris" (particles) then there is nothing to carry out a ferrographic analysis on.

Likewise Spectroscopy is the study of matter and its properties by investigating light, sound, or particles that are emitted, absorbed or scattered by the matter under investigation. Spectroscopy is often used in physical and analytical chemistry for the identification of substances through the "spectrum" emitted from them or absorbed in them.
Again without particles there is nothing to perform a spectographic analysis on.

Ferrography and Spectroscopy are therefore two different methods of analysing what the wear debris (particles) found in an oil sample are made of (where they are coming from).

Hope this helps.

cheddarcaveman@yahoo.co.uk

Duarte,

To expand on Cheddar-Caveman's post, particle counting only identifies particles by size. My particular lab shows particle count (particles /ml) for particles >4,>6,>14,>38, and >70 micrometers and then list the ISO code. Ferrography uses a magnetic field to characterize ferric versus non-ferric materials and can be used to identify particles (not just wear particles) by material and if wear particles, by the general mechanism that caused the wear.
It is normal to perform emission spectroscopy on used oil samples. Part of the sample is burned and the light given off is put through a difraction grating element to isolate the individual elemental components. The intensity of each line in the spectrum is analogous to the amount of that specific material in the sample and are reported as parts per million by weight. Thus you can look at machine wear, contamination and lubricant chemical properties.

I think that elemental spectrometry is a reasonably common test with used oil, particle counting a little less common and ferrography more used to investigate a problem. All three tests are complementary but I do not know of a valid way to correlate particle count to spectrometry to ferrography.

Ken Culverson

Duarte,
To expand further on Dai Wei's comments.
Emission spectroscopy is heavily biased toward smaller particle size. It can see elements from devolved solid to a maximum particle size of ~8 micron. But a particle as small as 4 or 5 micron may not be fully burned and you would only get a partial reading of that element. With Ferrography you can see particles from ~1 micron to well over 150 micron (note: if you see a lot of these SELL immediatly
If you find yourself becoming overwhelmed on the number of samples you need to preform Ferrography on it would be a good idea to filter your samples on a particle counter. So a clean sample (depends on the equipment, environment, and machine condition), wouldn't get ferrography but a dirty one would.
Hope this helps, and good luck!