Inadmissible displacement of the rotor shaft of high-pressure boiler feed pumps reduce the reliability of the pumps, the displacements may consist of a steady and an unsteady component. The steady component is called "deflection", whereas the unsteady component is commonly referred to as "vibration".The displacements of the rotor shaft largely depend on the rotor gaps, for example the gaps between impeller and pump casing, between balancing device and casing as well as the clearances of the journal bearings. Besides the dynamics of the rotor, these gaps also affect the efficiency and warm-starting capability of the pump. From the points of view of efficiency and dynamics, these rotor gaps should be small, whereas the demand for a warm-starting capability that is only controlled by the gap implies that the gaps in the hydraulic section have to be large. So far, rotor displacements have only been measured in the areas of the bearings. In the present study, the measurements of the displacement of the middle section of the rotor (between the bearings) will be compared with those of the bearing areas.
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