Summary:

A nuclear power the company purchased several new service water VS6 pumps for their power plant.  As for all new nuclear installations, it needed to be shown that these pumps could withstand  static and dynamics loadings without structural failure.  The pump manufacturer requested Pythagoras Engineering (PE) to perform a three-dimensional finite element analysis to evaluate the response of the pumps to the vibrational loads. 

Scope:

The aim of this analysis is to find the natural frequencies of the VS6 pump assembly.

Methodology:

To compute the natural frequencies, a detailed finite element analysis was conducted with the model including the discharge head, column shaft, motor casing, lines-haft, enclosure tube, baseplate, impellers, motor, and pedestal foundation.  Higher-order elements are used for meshing the component. First, the natural frequencies were investigated and compared to frequencies of pump speed and multiples of running speeds including 1x pump speed, 2x pump speed, and vane passing frequency. First bending mode is observed to be closure to the vane passing frequency. Design modifications were made to increase the first natural frequency of the assembly.