P Q INDEX

Sanjay,
The PQ Index is the particle quantification index. It is a measure of the magnetic quantity of the oil. The more magnetic particles, the higher the index. It has no real units as it is an index and the best way to look at it is to trend it. Also realise that there is not always a correlation of the PQ with the particle count as the PQ only detects "magnetic" particles, i.e. anything containing iron, cobalt or nickel, and the particle count detects all particles. It is good to use the PQ index as a "sreening" test to determine if further testing is needed to evaluate what the magnetic particles are etc. It is a very useful test in determining the general amount of wear in a component as most mechanical systems have at least one wearing part that is made up of a magnetic material but should not be used as a catch-all test as it can miss certain wear situations, i.e. non magnetic wear particles.

Yes as Michelle has stated the PQ should be trended from a new oil sample, PQ will change from lab to lab so always trend off the same lab,
usually thought to monitor Fe particles > 30 µm
We see PQ from 10 to 16,000 + for contaminated greases.

If PQ was doubling from test to test we would be checking the system to find why, Fe and particle count would be expexted to increase as well.

Often Fe and PQ do not increase @ the same rate as PQ measures > 30µm and Fe measures , 8 µm so the difference in increase rate will assist with size of wear debris being generated.

Sometime a grease sample will have a PQ of several thousand and when a Wear debris Analysis is completed no significant debris will be found so don't rely on PQ only.

Regards

Rob S

rttech.com.au