I´ve got two doubts. First one is what is the main diference between patch test and ferrograpy, in terms of potenciality (strengths and weeknesses). And the other doubt is if PQ index can be complemented wiht FM (ferrogram maker), instead of RPD (rotary particle depositer). Thank you.

Patches can tell you what sort of "crap" you have in the oil and Ferrography, as far as I am concerned, will give you a better indication of what type of wear/ cutting you have going on in a component.

We use both DR & Analytical Ferrography along with patches. The biggest difference between DR Ferrography & patches is: DR Ferrography uses magnets to align the ferrous material so you can really focus on it. The majority of non-ferrous material has a tendency to get rinsed off the slide.

We make patches using several different patch sizes i.e .4 micron up to 11 microns depending on what we are looking for.