In the paper presented are course and results of investigations of the influence of slide bearing bush and shaft mutual skewness on the dynamic properties of the 200 MW 13K215 turboset. The defect was simulated by means of numerical model of the turboset. Simulation was performed for each bearing individually in both, horizontal and vertical planes. Maximum values of the skewness angle were calculated for each bearing at both planes. The influence of the defect on dynamic properties of turboset was presented. Basing on the results of the simulation multiple defect-symptom diagnostic relations were built. Diagnostic relations were used as learning and testing data sets for a knowledge base of an expert system based on the inverse diagnostic model. This expert system is implemented at the unit 7 at the Kozienice Power Station as a first domestic diagnostic system.