Lubricant Degradation and Corrosion Mechanisms in Turbine Actuator Oil Systems

초록

Hydraulic actuators in gas turbine (GT) inlet guide vane (IGV) systems are crucial for the stable operation of combined heat and power (CHP) plants. This study systematically investigates the internal damage and corrosion behavior of a GT IGV hydraulic actuator recovered after long-term service in a district heating CHP plant. The manifold block, cylinder tube, and piston were disassembled and analyzed to assess the effects of lubricant degradation and water contamination. Visual and cross-sectional examinations revealed localized corrosion pits, oxide accumulation, and uneven material thinning on lubricant-contacting surfaces, with maximum pit depths measuring 0.18 mm in the manifold block, 0.13 mm in the cylinder tube, and 0.07 mm in the piston. The chromium plating, approximately 18 mu m thick, effectively suppressed degradation of the cylinder tube; however, localized coating damage led to interfacial corrosion and accelerated substrate degradation. Lubricant analysis showed fluctuations in water content, particle contamination, and PQ index, indicating a lubricant environment susceptible to hydrolysis, additive depletion, and tribocorrosion. These findings demonstrate that monitoring lubricant properties alone is insufficient to accurately represent the evolution of internal damage and provide direct experimental evidence linking lubricant degradation and water contamination to the internal corrosion of hydraulic actuators.

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