PQ Index

When wear occurs in equipment, the particles resulting from the wear process can be of several types, namely:

Normal Wear - small wear particles due to typical welding/breaking cycle as outlined in earlier discussions.

Significant wear - medium sized particles causing gouging of metal and resulting in larger than normal particles being generated. These in turn become the cause of even larger particle generation.

Severe Wear - large particle occurrence which may reflect presence of metal particles due to fatigue fracture or pitting of the metal components. This production of large metal chips can in turn induce enough wear to cause further disintegration and rapid onset of failure.

Since most of the metal fragments referred to in the above wear scenarios are iron in nature, the effect of the particles on a magnetic field can be used to detect the type of wear. Small fragments would, as expected, have the least effect on a magnetic field, while the large chips of iron would be expected to have a large effect. The instrument used in the laboratory for determination of Particle Quality (PQ), measures the effect of the wear particles on a magnetic field. When calibrated on known standards, an index or relationship number can be produced and from this the criteria for satisfactory, significant and severe wear can be determined and reported as the PQ Index.

Dispersancy

Dispersant additives are incorporated in engine oil formulations to ensure that minimal accumulation of contaminants that result in sludging will occur.  Sludging is the combination of mainly moisture and soot or wear debris from the engine. It can adversely affect the engine operation through filter plugging, deposition on moving surfaces and by thickening of the oil to an extent that incorrect lubricant supply will result.

RULER measurement of Anti-Oxidant Content

Oils, with the exception of normally formulated EP Gear Oils, in general have one or more Anti-oxidants (AO) included into their formulation. AO’s are sacrificial additives in that they are the first to be consumed in their function of protecting the equipment that is lubricated and more specifically the oil itself. It stands to reason therefore that monitoring the AO level in an oil (or grease) can provide data that permits accurate determination of how much life the oil still has. This saves money to maintainers by using the oil until it can no longer satisfactorily protect the lubricant (usually when the RULER AO value is less than 30% of the new value) which from past experience may be significantly longer than the recommended service change-out. If the AO levels are being severely depleted in a shorter time frame than expected, then proactive maintenance to rectify a potential problem can also be reflected in saving by the reduction of unscheduled down-time.

Glycol by gas chromatography method