Here is the back ground info: We decided to have our off site lab perform tests on all our oils used at our plant for baseline information. The reference samples we sent came straight out of our warehouse. The samples were drawn through a 1 micron filter into a certified clean container.

My question is: Do high viscosity / opaque oils give odd results on the Particle Count and metals? Some of our results show a particle count of 25/25/18 and an Fe of 50ppm. The oils are a cylinder oil W 680 and a machine gear oil AW 680. If the oil contains animal fats (lard) as with the cylinder oil W, will the fat show up as particles on the Particle Count?

Do we even need to use Particle Count results for gear box analysis, if the oil already indicates a high P.C. when it is new?

Pete,

Viscosity and opaqueness of oil is not an obstacle for laser particle counters. You would be surprised how often your in-service oil is found to be cleaner than the received new oil. However, particle count of in-service oil is important to test, because the generation of wear particles is a normal and inescapable occurrence with gears, and it is important to track it, especially the greater than 14-microns sizes (c) (ISO 4406/99 with ISO 11171 calibration).

I am not an oil formulator, but theoretically speaking, animal fats are supposed to be long-chain molecules in oil and not “chunks” of lard, and therefore, I would not expect them to interfere with the particle count.

Filtration through a 1-micron filter might be too risky for these high viscous oils, because of a danger for additives to be stripped out (antifoam and EP if it’s there). Of course, filtration is absolute necessity, but with no less than 3-micron in size (5-micron might be the best solution). Very valuable advice on Chevron oils you can get if you contact Chevron Research Lab in Richmond, CA (Dr. Mark Okazaki, (510) 242-5978 (I hope he’s not going to be mad at me for posting his name and phone # on the web without his consent).

Firstly find out what type of particle counter is used. A laser particle counter is effected by the colour (opaqueness) of the oil as it obtains a particle count by counting the shadows produced by the particles passing through the path og the laser. The fact that you have 50 ppm Fe shows that the high particle count is probably correct. Remember these Fe particles could be so small that they are not visible to the eye. Oils are usually cleaner in use (after filtration) than they are new. The fat should not show up as particles.