I will disagree.
UOAs can be a reasonably accurate tool to judge wear. It's been shown as such in many SAE studies using various different methodologies ranging from filter studies to OCI studies.
UOAs are not perfect; that's true. But they are a very low expense relative to the information they impart.
They cannot see wear particles above 5um, but what they do see (below 5um) can be inferred as a relative wear rate.
UOAs are a direct view of lube status (FP, vis, etc). But these are only predictors; they are not an assurance that anything WILL happen.
UOAs are an indirect view of wear (wear metals). These are results; they are a story of what has actually happen.
Most people don't know how to properly use a UOA. UOAs are tools; there are proper and improper uses for the tool. You have to understand both the benefits and limitations of the tool. Most folks around here use UOAs at toys, not tools. UOAs can provide lots of good information, but that information is only useful to someone who actually understands what it will, and will not, tell you.
What I agree with is that you should never base a major decision on a sole UOA and nothing more. Don't decide to rip an engine apart based on one UOA. Don't decide to run an OCI way longer based on just one UOA; you need to know the historical basis of the equipment and also the trends of the species.
Respectfully, I must countermand your disagreement. What I said (in context to what I was addressing) is correct regardless, but I am not sure I understand what you are disagreeing on as your commentary seems to mirror my own except on the judgement of wear part. That’s a significant part of a machine’s life cycle and all the asset metrics so can’t just be set aside. (Particularly as the cost of the machine and associated costs go up)
I was (inactive) a Professional Member of SAE and am intimately familiar with their studies and findings. (and many of the inherent weaknesses). That stamp of approval doesn’t carry significant weight with me beyond the perfunctory professional just due.
Factually there is no direct relationship to any UOA finding anywhere by anyone where readings directly identify and correlate to a specific mechanical component in any legitimately qualifiable way. (which was the crux my statement is based on). That’s a stand-alone irrefutable fact.
As a direct result of that fact as stated, there is no way to judge any wear of any component of any machine by particle counts on a UOA. (even the tables of origin are generic, generalized and non-descript)
I personally have done/managed/certified thousands of machines globally from design (sometimes) to commissioning to end of life rebuild with full compliment of OA, VA, Therm, Technical Inspections and have yet to see a single machine where any degree of wear could be measured or identified on any P-F curve anywhere. At best a vague reference to a bearing or gear based on alloys but then try to find that wearing spot.
I additionally have never seen one that measured wear on the P-F curve once we went to continuous monitoring with a known failure.
I am reasonably confident neither you nor SAE as an org nor anyone else has either, but I invite anyone to produce one. I would love to see it.
I concede that in certain cases a particular item might be specifically identified by a unique alloy mixture but that’s rare and even then not enough data in a particle count or wear analysis to solely base any mechanical decision on.
OA’s are good to identify contamination events, event ranges, operational changes and to a degree patterns of overall degradation of a given machine but that’s about the equinox of the technology in its current state. Anything beyond that is better served by UT, VA, Therm etc.
I agree without reservation on people misunderstanding the power and role of the OA (I make a living off it)
Unfortunately, I also know of “aggressive salespeople” who push OA claims to extremes in terms of what it can and can’t do. (deal with that too)
Sorry but I had to push back on that part of your disagreement- too much evidence to the contrary.
