# Fault Investigation of Circulation Pumps to Detect Impeller Clogging
## 4 Conclusions  
In this paper a concept for the investigation of faults in circulation pumps is presented and applied to the case of clogging of impeller channels. With the help of the test bench, the data supplied by the pump as well as the differential pressure of the pump can be recorded with the help of a data acquisition system. The measuring devices for recording the motor currents are suitable for collecting the data needed for the later application of the fault diagnosis algorithms. The test bench has been designed for life cycle tests. That this is possible with the test bench is part of future work. As a fault, a clogged impeller was investigated. In order to have a reference, the healthy pump was measured at the same power consumption as in the respective fault cases. First, the influence of the fault on efficiency is considered. It is found that the efficiency of the pump is reduced by 9 to 15% compared to the healthy version at the same power consumption. Based on the literature research on pump fault detection [13; 14; 15; 16; 17; 18; 19; 20; 21; 22], the hypothesis can be made that the amplitudes at the frequencies \(f_{r,pump}\) \begin{table}
\begin{tabular}{l c c c c c c c} \hline \hline  & **1 Clogged** & **2 Clogged** & **3 Clogged** & **4 Clogged** & **5 Clogged** & **6 Clogged** & **7 Clogged** \\  & **Channel** & **Channels** & **Channels** & **Channels** & **Channels** & **Channels** & **Channels** \\ \hline \hline \multicolumn{8}{c}{n = 2500 rpm} \\ \hline \(f_{r,pump}\) = 125.0 Hz & +17.0 dB & +36.81 dB & +47.1 dB & +35.0 dB & +18.2 dB & +18.3 dB & +18.6 dB \\ \(f_{r,pump}\) = 208.4 Hz & +18.7 dB & +29.0 dB & +48.7 dB & +35.1 dB & +15.2 dB & +20.8 dB & +5.8 dB \\ \hline \multicolumn{8}{c}{n = 1800 rpm} \\ \hline \(f_{r,pump}\) = 90.0 Hz & +8.1 dB & +30.5 dB & +39.2 dB & +42.2 dB & +24.0 dB & +7.1 dB & +16.9 dB \\ \(f_{r,pump}\) = 150.0 Hz & +14.0 dB & +29.1 dB & +46.9 dB & +36.6 dB & +18.4 dB & \(-26.1\) dB & +8.9 dB \\ \hline \multicolumn{8}{c}{n = 1000 rpm} \\ \hline \(f_{r,pump}\) = 50.3 Hz & \(-\)20.8 dB & \(-\)1.3 dB & +7.0 dB & \(-\)27.9 dB & \(-\)17.5 dB & +18.4 dB & +7.8 dB \\ \(f_{r,pump}\) = 83.8 Hz & +5.1 dB & +9.0 dB & +12.9 dB & +6.2 dB & +0.5 dB & +20.6 dB & +4.0 dB \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Increase of amplitudes in case of an impeller clogging for different speeds and numbers of clogged channels. and \(f_{BPF}\) are influenced by the fault of the clogged impeller. The results show that the frequency \(f_{r,pump}\) is mainly influenced when used as a circulation pump. The fault frequency \(f_{BPF}\) is not affected. It can be seen that when three and four of seven channels are clogged, the greatest increase in amplitude occurs at the fault frequency \(f_{r,pump}\). The findings are especially true for higher speeds, in this case 1800 rpm and 2500 rpm. At a speed of 1000 rpm the results are not distinct. Furthermore, it is found that the sidebands are increased by the fifth harmonic due to the fault. The results show that the implementation of online fault detection algorithms can have an added value for the pump operator. This is supported by the fact that efficiency decreases and the hydraulic power decrease. It is shown that at the frequencies \(f_{r,pump}\) different amplitudes can occur with the healthy variant, depending on the load. This must be taken into account when implementing fault thresholds. One possibility would be the storing of load-dependent thresholds in the electronics of the pump. Conceptualization, J.A.A.-D., S.U., V.B. and T.S. ; methodology, software, validation, formal analysis, V.B. ; investigation, V.B. and T.S. ; resources, S.U. ; data curation, V.B. ; writing--original draft preparation, V.B. ; writing--review and editing, J.A.A.-D., S.U., T.S. ; visualization, V.B. and T.S. ; supervision and project administration, S.U. and J.A.A.-D.; funding acquisition, S.U. All authors have read and agreed to the published version of the manuscript.