Influence of hydrostatic pump operation period on performance of a thrust bearing of a 125 MW pump-turbine

A special instrumented pad was installed at hydrodynamic thrust bearing of 125 MW pump turbine in one of Polish power plants. “Spring mattress” type thrust bearings of these machines are quite heavily loaded and have caused many problems so far. It was intended to assess bearing present state more thoroughly than with the use of standard monitoring system and to assist in bearing research and development attempts. Instrumentation of the pad comprises 16 thermocouples for measurements of temperature distribution in the pad and 3 proximity probes to evaluate the pad position and film thickness. The pump-turbine with an instrumented bearing was tested at various operating conditions including steady state and transient conditions. One of the examples of the research carried out with the use of the described instrumentation was the research into the influence of hydrostatic jacking pump operation period on bearing performance in transient states which is presented in the paper. The results showed that current practice of pump operation is far from optimum, and that bearing reliability could be improved by changing the current start-up and coasting procedures. The results also showed that pad position during operation is not satisfactory and also some improvement could probably be achieved by rearranging the support of the bearing pad.