Verification and validation of the design procedure

This paper describes the validation and verification procedure of the rotor dynamic layout of a large steam turbine turbo set. Initially the standard independent procedures for designing the rotor system and the concrete foundation for a large steam turbine generator set are presented. A coupled rotor- foundation analyses is performed based on a finite element analyses of a concrete foundation. The derived transfer matrix is incorporated in the rotor dynamic analyses procedure. Based on this coupled rotor - foundation analyses the vibration characteristics of the turbo set are determined. In order to validate the foundation model, lateral shaker tests are performed on site on a concrete foundation without stationary components being installed. The comparison of measurement to calculation show good correlations especially with regard to the modes being most susceptible to vibration and the general level of dynamic stiffness. However, due to the high number of foundation modes and the complexity of boundary conditions differences between measurement and calculation become also visible. The comparison of coupled to uncoupled analyses results showed that the standard rotor dynamic analyses procedure neglecting the details of foundation design represent a valid and conservative approach in order to ensure an acceptable and smooth vibration characteristics of the turbo set. However, this conclusion is only valid if the dynamic stiffness of the foundation is sufficiently high.