As a guidance please i need your help about oil limits TAN (ASTM D-974) for the following lubricants.
We are requesting TAN values of new oil to our lube supplier so we can begin monitoring these parameter.

SAE 10W used in hydraulic systems
(UTTO) SAE 10W30
Transmission oil SAE 80W-90/ 85W-140

Greetings

TAN values of new engine oil will be high, UTTO is an engine oil.
Also gear oil will be high depending on performance GL4 or GL5
TAN of new hydraulic oil 0.7 to 1, engine oil at least 2 to 3 times this
Unlikely that TAN will be a critical factor in these cases.
What are the applications?
TAN values of these products will fall in use as aditive is used and then at some stage will start to rise as oxidation takes place.Top ups will usually ensure that this process takes along time in hydraulic systems.

The application of these fluids are on harbour cranes, lifters, trucks. OEM recommends the use of these fluids. Gear oils are mainly GL-5 type while DEO engines are SAE 10W CF, SAE 10W30 (UTTO oil).

How much increase is acceptable in these used oils?. We'll be checking TAN in relation to viscosity, wear metals and also drain interval.

TAN values mentioned by Roger are high and I believe that you should reed the data sheets of the products ,the acceptable limit for fresh oil to which TAN value is critical (hydraulic /turbine /gear) is 0.2mgKOH /g As mentioned by ASTM ,for engine oil you can just test your fresh oil and take it as starting point and observe the increasing of TAN, increasing of 0.4 is taken as limits for most applcations but since organic acids vary widely in corrosion ,limits most be empirically established

Sorry to strongly disagree with Fageer.
Fageer seems to be talking about non additive oils and turbine oils which have typically new oils TAN ~0.01mg kOH per gm. Even then rejection limits seem low.
Additivated hydraulic oil and engine oil derived hydraulic oils have much higher TAN.
In these cases a TAN of say 0.7 (Tellus ZDDP type)will initially fall with use then rise due to oxidation. Absolute rejection TAN numbers are less important than the rate of increase in TAN. With top ups in hydraulic systems it is inferequent that oils are rejected on TAN value.

Iam sorry I was wrong 0.2 limit is for new turbine oils only for hydrauic it is higher than that we use Fuchs Renolin B and it is of 0.5 TAN value,thank you Roger for correction