Application of Sealed Capsule Differential Scanning Calorimetry, Part I: Predicting the Remaining Useful Life of Industry Used Turbine Oils

To ensure successful operation of a turbine lubrication system, particular attention needs to be paid to monitoring chemical changes occurring in the turbine oil, particularly changes in oxidation stability. Traditionally, long standard oxidation tests such as the ASTM D 2272 Rotating Bomb Oxidation Test (RBOT) in conjunction with TAN values have been used to monitor the oxidation stability reserve of turbine oils. Recently, however differential scanning calorimetry (DSC) has been applied to measure the oxidation stability of a range of industrial lubricants as it uses only microliter quantities of sample, provides precise results and is faster than the other commonly used oxidation tests.In this study, a sealed capsule DSC technique (SCDSC) was applied to determine the remaining useful life (RUL) of industry used steam turbine oils. The RUL was found by comparing the SCDSC result of the industry used oil sample to a previously generated "safe /unsafe" zone map based on data obtained from laboratory oxidized oil samples. It was found that this zone map exhibited good correlation with results obtained from 23 used turbine oil samples. It was also found that the SCDSC technique correlates well with results obtained from RBOT and TAN rests and as such SCDSC may be a suitable technique to be implemented in an oil condition monitoring program. The effects of water and metal contamination, both particulate and soluble, on SCDSC results were investigated and are also discussed in this paper.