When to use Particle Counting Analysis
Particle counting is probably one of the best tests there is for maintaining system cleanliness. The point of contention lies with whether or not particle count is an appropriate test for all fluid types and systems. Whilst it is an excellent method for determining the number and size of particles being generated, particle counting won't tell you what the particles are. They could be metallic – both ferrous and non-ferrous – silica (dirt, dust), silt, filter fibres, bacteria colonies, varnish agglomerations, water, etc. Therefore, the decision to do particle count Oil testing should be based on the type of information you want to collect.
The unit types that benefit most from particle count testing are hydraulics, compressors, refrigeration compressors, turbines, automatic transmissions, natural gas engines, robotics, injection moulding machines and "filtered" bearing or gear systems.
Particle count is also a good test for diesel fuel, solvents, water-based hydraulic fluids and lubricants.It's also useful on new oils for the above units as it tells you how clean the oil is when introduced to the system. Many users aren't aware of the fact that new oil may actually have higher particle counts than the used oil from the machine. Oil can pick up dirt during the manufacturing process itself, where filtration is expensive and therefore an indication of the quality control applied during the process. Unwanted particles are also picked up during transport and distribution as new oils are transferred from container to container.
If a gear system is filtered, particle count data may be useful. But if the gearbox is not filtered, particle count data doesn't provide as much information as would other tests such as PQ/FW (Particle Quantifier / Ferrous Wear) or DR (Direct Read) Ferrography. Diesel engine oil is black and requires different techniques to the tried and trusted laser counting methods. FW/PQ, DR Ferrography and Wear Debris Analysis are probably wiser choices. (WDA is a vital tool in failure and warranty issues).