IS LIQUID SANDPAPER LURKING IN YOUR MACHINE?

Certain subjects merit emphasis and should be frequently revisited. Contamination control is one such subject.

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Particles are like a virus, invisible to the naked eye but packing a powerful punch. The most destructive particles are typically less than ten microns in size (for comparison, a thousandth of an inch is roughly 25 microns).

The microscopic size of these destructive particles makes them hard to measure and count. Over time, they keep accumulating in the oil. Even in relatively high concentrations, their presence can remain hidden from view and undetectable to the touch. This explains why they are often referred to as "ghost riders".

Think of ultrafine sandpaper at 1000 grit. The size of abrasive particles that are bound to the paper range from 6.8 - 9.3 microns in diameter. Lubricants with high populations of suspended particles of that size range effectively form a medium with the potential to exact considerable harm to the machine.

Compared to larger particles, small silt-size particles easily evade even the finest filters, and larger particles are often quickly crushed into many smaller particles (comminution). As shafts rotate or slide against opposing surfaces (bearings, seals, gears, pistons, cams), microscopic excavations occur (dents, gouges, scratch marks), producing even more particles. Over time, the concentration of these small particles forms a medium that is functionally equivalent to liquid sandpaper.

Think of a belt sander. Even fitted with fine 1000-grit paper, it can polish away vast amounts of metal in short order. Now imagine a heavily loaded shaft rotating at high speed against a journal bearing lubricated with contaminated oil. It's the same thing, and the shaft and bearing get polished. This is called three-body abrasion.

The Causes of Liquid Sandpaper