Hi Jimmy
The PQ is completed in bottle, it works by the ferrous content of the sample distorting the PQ magnetic field, PQ would trend ferrous wear particles > 20-30 µm.
PQ must be trended over several samples, the warning would be a steadily increasing PQ with every subsequent sample, most likely the first sample for the PQ trend should be new oil.
Direct Ferro is completed out of bottle with the lubricant processed through magnetic "filters" measuring all sizes and comparing the size range, a one off sample using Direct Ferro with abnormal results will be correct and should be checked out.
Are they relatable??
We would expect the large particle trend line from the DF would be similar to the trend line of PQ but there is no correlation for particle sizing with PQ,
Regards
Rob S
