The aging test “TOST
The TOST (Turbine Oil Stability Test) aging test is used to determine the aging behavior of steam turbine and hydraulic oils containing active ingredients.
Two samples mixed with 60 ml of distilled water are aged in parallel with the introduction of oxygen. A steel and a copper wire coil are suspended in the oil as catalysts. During the experiment, the neutralization number is determined at certain time intervals. Once a NZ of 2.0 mg KOH/g oil is reached, this is considered the final state of aging.
| Parameter | |
| Temperature range | 20 to 220°C; standard 95°C +/- 0.2°C |
| Flow media | Air, synth. Air, oxygen (standard 3 l/h +/- 0.5 l/h) |
| Catalysts | Steel/copper wire |
| Test duration | Depending on standard 1000 h (for high-performance oils up to 10,000 h) |
| Indicators | Kinematic viscosity, precipitation number, neutralization number |
| Oil quantity | 300 ml, 350 ml |
Standard tests
- DIN EN ISO 4263: Parts 1 to 3;
Part 1: Process for mineral oils;
Part 2: Procedure for HFC class pressure fluids;
Part 3: Anhydrous process for synthetic pressure fluids;
Part 4: Methods for industrial gear oils.