Influence of Faults on the Efficiency of Centrifugal Pumps

Pumps are among the largest energy consumers in industry and in the household sector. Across the EU, pumps consume 22% of electric motor energy. It has been shown in the literature that a defective motor can not only lead to higher breakdown times, but also to a decrease in motor efficiency. In an application such as a centrifugal pump, further types of faults can appear, such as dry-running, hydraulic blockage, clogging, or cavitation. According to the state of the art, it is not known how much these individual faults influence the efficiency of a pump unit. To address this problem, two types of centrifugal pumps, a dry-runner and a wet-rotor pump, were measured in a pump test bench. The dry-runner pump was driven by a mains-fed induction motor with a power of 1.1 kW. For the wet-rotor pump, a frequency converter-fed permanent magnet motor with a power of 800 W was used. The test bench was equipped with flow and pressure sensors and control valves. The electric power was measured by high-precision power analyzers. In order to evaluate the data, a standardized procedure was used that not only considers the efficiency at one single load point but also the efficiency of part load points and different operating times. The answers provided in this chapter will help plant operators, in particular, to better plan the maintenance of their centrifugal pumps. By comparing different faults for different types of centrifugal pumps, this experiment represents another step in the research to evaluate the energy efficiency of faulty pumps.