Perhaps the sample was given a passing grade (note the double entendre), if a certain amount of debris was found but not more than that amount. No oil is perfect. Metal parts are going to lose bits of metal over time, no matter what. The best oils will greatly diminish the destructive effects of friction, heat, pressure, and colliding metal parts, but no oil completely eliminates those effects.
You are correct here Frostedman. That is how a proper sample is taken. There must be less than a certain amount of debris in the sample. Also a certain moisture content as well. However...the question arises ...is the sample representative of what is floating around in the system itself...not just in the sample.
When you have sharp metal debris in the test bag taken...but not in the sample jar going to the laboratory..or gritty debris in the test bag but not in the sample...do you have an actual representation of conditions in the system itself. That is the proper goal..not just the sample only per se.
The purpose of all this work is to prove the System itself clean
Not just the oil sample per se.
This is the difference in appearances and substance...legal and lawful..
Legal...only the appearance of law...the form only of law..
Lawful....what the law is intended to accomplish. What the law is intended to do in a structure of people.
What we have here is the appearance/form of being a clean system.
The system itself has filters throughout it to help keep debris down. Filters which are occasionally changed on schedules. But it is best to start out with a System itself... cleaned to a high degree of confidence.
What happens if you do not have a clean system with which to start operating..you will be changing out these strainers often...between schedules...and you do not want a catastrophic failure...while operating....under operations. For this could be disastrous.
On another note about oil itself......oil samples are taken from the 55 gallon barrels as they come from the factory before this oil is used in a system..and I have know oil to fail the sampling. Astonishing but true. The oil did not meet the standard for particles/make up as well as water content....from the factory.
I notice some companies are willing to sample your automobile oil today...for it's content. Very interesting.