Fire-resistant turbine oil is widely used in thermal power plant. As the service time increases, its lubrication and electrical characteristic degrade. This work proposes a mini NMR (nuclear magnetic resonance) sensor for assessing the degradation of the turbine oils used in real time and in vivo. Two magnetic discs with poles opposed were separated in a distance to generate a relative homogeneous static magnetic field between them. A solenoid coil was placed between the magnets as the RF coil. The dimensions of the sensor are 30 mm×30 mm×36 mm and the mass is 107 g. The T1 and T2eff of the turbine oils from two different power plants were measured. The results demonstrated that an increase of the service time of turbine oils clearly results in a decrease of T1 and T2eff. This method of monitoring degradation of turbine oils could lead to the use of NMR to assess the degradation level of turbine oils in service.
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