Lets talk about the preparation of the oil sample, some labs use toluene and acetone and others don't.
The same for ISO patch, some use hexane and others don't, consequently we end up with very different results.
Are we interested in measuring/seeing all? e.g oxidation by-products, or are we simply interested in solid/insoluble contamination/wear ?
Frank

Most of the labs I have used all use hexane as a solvent. The hexane (regardless of what grade ie technical or analytical) is filtered through a 0.8 micron filter prior to use. I believe that acetone is sometimes used particularly when the sample has water. The key thing is that any solvent used should be put through the same cleaning process - it is possible that if the solvent used is not filtered which can cause a variation in the reading.

I have used 3 different labs for ISO via Patch testing from time to time, the most variation I have come across is by one ISO code for different operators.

The comparator labs use could possibly cause a variation in the reading - for example both PALL & Hydac have comparators out in the market - I have seen slight differences in the interpretation depending on which comparator is used.

Personally, I am interested in oxidation by products as well as insolubles and wear contamination as I believe all these help towards making a better judgement on the oil and machine condition.

Steel Pipe stainless steel pipe

quote:

Originally posted by macabf:
Lets talk about the preparation of the oil sample, some labs use toluene and acetone and others don't.
The same for ISO patch, some use hexane and others don't, consequently we end up with very different results.
Are we interested in measuring/seeing all? e.g oxidation by-products, or are we simply interested in solid/insoluble contamination/wear ?
Frank

Good question. I am not in the business of establishing procedures, but imo, the logic tells me that solvent used for rinsing or diluting the sample for patch test should not dissolve varnish particles that are “insoluble” in oil due to limited solubility characteristic of the oil. But if used solvent dissolves this varnish (insoluble in oil), then it should be noted that the result represents insoluble varnish (or particles in general) in a particular solvent that was used, and not the total varnish present in the oil (prior to the solvent treatment).