Ferrography can be considered a two-part process. Direct read ferrography (trending tool/instrument that yields wear particle concentration) and analytical ferrography (microscopic analysis/evaluation/judgement).
I am curious if you are considering performing these tests at your site or adding these tests to your test slate for samples going to an offsite lab. Or, perhaps you are just curious. The financial costs to obtain the ferrography equipment, supplies, and necessary training can be a large committment, depending on your situation.
I would add that there are other tests available that might be more meaningful or run in conjunction with DR ferrography that would benefit machine evaluation. As always, all tests have limitations.
My opinion, DR ferrography is great for gearboxes and like components. I might offer some other ideas if you are primarily looking at systems such as turbines and the like where you would not "expect" much ferrous debris.
Contact me via email, if interested.
sjmitchell@aep.com
BTW: I'm an analyst at a power generation facility, not a salesman.