Dear All,
I see wonderful questions and knowledgeable answers in this site specially related to lub oil problems.Please advise me on the following issues.

Generally we get the oil analysis results from the R&D oil lab., and we trend for any changes quarterly. But,what are the general alarm limits ( or, is there any specific alarm limits??) universally set for the following tests -
1. Viscocity (cst) @ 40deg.C and 100 deg.C of ISO 32, 46 and 68 grade oils.
2. We follow 2500 ppm as the alarm limit for the moisture contents in the synthetic oil (UCONAL 150) we use. But can this limit be adopted arbitrarily for any synthetic oils?
3. What's the cause of increase in TAN? And, how much is the limit? Is 0.92 found in Mobil DTE Light is high? If the TAN increase is due to oxidation, What should be the practical corrective action to be taken?
4.What are the best alarm levels to be initially set for metals Cr, Sn, Cu, and Al?

Hope you will help me with useful tips in this matter.
Thanks and regards, Sajeev

Sajeev

The alarm Limits are normally fixed based on the application point of view.

Moisture content is again application oriented for eg Hydraulic oils tolerate 500 ppm moisture.

TAN has to be plotted against hour used Based on increase over initial TAN and the point of intersection of the additive content level against hours would provide the alarm limit.

For metals again based on application
for high speed engine oils
Al - 40 ; Cu 40 ; Sn 40 ; Cr 40

It is also OEM specific.

Sirs,
How says Einstein many years ago - "There is all relatively In our world!"
In each individual case we must to consider all conditions. For example, you have circulation system with Mobil DTE Light. You sampling from reservoir and find the levels Al, Cu, Sn and so on as 20 ppm. Is this much or not? OEM says that it is not Alarm Limit. But if you have reservoir volume as 7,000 Liters you can think that you loss bearing already.
Sorry,

Sajeev,
There isn´t a single rule for all aplications. As Mr. Hughes recommend, Oil Analysis Basics is a good starting point.
From your request:
1. A good rule for viscosity is 20% over and 10% under are condenatories, therefore 10% over and 5% under could be your alarm point.
2. Every single oil (off course differents oil) have a unique water saturation point.
3. AN is a measure of oil acidity. An increase of oil acidity is a signal of aging (oxidation). Alarms? where did your new oil starts? whit a maximum of 2.0 I will sugest your first alarm at 50% of the way between new and 2.0. There are a lot of things involved in the oxidation process: high temperatures, additive depletion, water, contaminants, etc. You need to identify causes first, then corrective actions.
4. Once again, every equipment is unique. I like the Mikhail aproach. In example Franky gives you some OEM recomendations:
AL --- 40
Cu --- 40
Sn --- 40
Cr --- 40
However CAT numbers are different:
Al --- 4-15 (Diesel Engines)
1-10 (hyg¿draulics)
Cu --- 10-30 (Diesel Engines)
1-20 (hydraulics)
Every manufacturers have diferent values. And once again these are maximum vales, not alarms.

I know oil analysis is not an easy world, I hope this comments help you.