By Jim Fitch
Machinery Lubrication Magazine
When the history of the condition monitoring field is written, there will likely be a chapter, or at least a few pages, on the odd paradox surrounding how infrequently use of used filter testing was employed (in the beginning). The assumption is that filter testing will eventually enjoy widespread use as misconceptions and ignorance of its benefits fade away. As I write today, the vast majority of people engaged in condition monitoring are oblivious to the wealth of information found in used filters.
The target application relates primarily to critical equipment, i.e., those that are expensive to repair or have high downtime costs. A well-engineered condition monitoring program should align the data being gathered with the failure modes we seek to detect. Granted, these are failure modes of highest risk to the machine, based probably on occurrence and consequences (business interruption, etc.).
Think of the logic behind this. Filters are intended to purify by removing solid contaminants that are harmful to the oil and the machine. If the filter is doing a good job, it is removing contaminants as fast as they are entering (ingression). This is known as mass balance. The number of particles coming into the oil system (particle ingression) equals the number being caught by the filter (particle removal); this achieves a stabilized and controlled oil cleanliness level. While particle removal is advantageous to the oil and the machine, it gets very low marks when the oil being cleaned is sampled for analysis.