New criteria to assess the remaining useful life of industrial turbine oils

Oxidative deterioration of mineral-based turbine oils has traditionally been measured by changes in an oil's physical properties such as viscosity or total acid number or by long standard oxidation tests taking up to 5000 hours to complete. Recently, the use of differential scanning calorimetry (DSC) has been applied to measure the oxidative stability of range of lubricants as it provides precise results, uses only microliter quantities of sample and is faster than the other commonly utilized oxidation tests. In this study, criteria was developed to assess the remaining useful life (RUL) of commercially available steam turbine oil using the technique of sealed capsule differential scanning calorimetry (SCDSC). The turbine oil was artificially oxidized and the results obtained with the SCDSC experiments were correlated with infrared spectroscopy analysis forming a safe/unsafe zone map which reflects the RUL of the oil at a given time. The zone map developed was then compared with results obtained from industrially oxidized turbine oils and a good correlation was achieved. It was found that this technique of assessment of a turbine oil's RUL provides reliable and accurate data and can be implemented in condition monitoring programs. It allows optimization of an oil's drainage period resulting in significant savings and reduced environmental impact.