Composition and degradation of turbine oil sludge

Sludge is an inevitable by-product of turbine oil during the operation of lubricating turbines. However, there are few reports of the detailed analytical results of the sludge. In addition, no global specification exists to evaluate the sludge formation from turbine oils. Hence, it is critical to analyze the contents of the sludge. In this study, we investigate both fresh and in-service (contains sludge) turbine oil based on ASTM standards. In-service turbine oil was first washed by petroleum ether to obtain the sludge and then characterized by FTIR, SEM, TG and EDAX. We found that the main compositions of sludge were C, O and N, while metals were <4 mass %. The analytical results show that antioxidant, defoamer, antirust and demulsifier are possible origins for the formation of sludge, which would be beneficial to decrease the sludge for the formulation of turbine oil.