TAN limits

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.

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.