During the development of sewage pumps, their functionality and efficiency have continuously improved. Different impeller types have been developed to reduce clogging and associated maintenance and to increase the efficiency.

The energy requirement and the efficiency play an increasingly important role. The design of pump impellers with the aim of improving efficiency can have a negative influence of clogging susceptibility. So far there is no single test describing energy efficiency and wastewater pumping functionality. Operators require in addition to specifying a desired efficiency only the indication of plausible experience with respect to the impeller geometry: the impeller shape and the ball passage.

It is generally assumed that the clogging susceptibility can be derived from the impeller shape and the ball passage (or freely passable space for vortex impellers). Under this assumption, the vortex impeller should have the least susceptibility to clogging. With single and dual-channel impellers, accordingly, the largest possible ball passage points to a low susceptibility to clogging. Both, the hydraulically disadvantageous form of the vortex impeller and an enlargement of the freely passable space or ball passages beyond the hydraulic requirements leads to a significant reduction of the efficiency. Hence, it may be concluded that clog-free pumps are associated with low efficiency. This assumption, which is also taken up in the literature, requires a uniform test for the objective assessment of the clogging behavior of sewage pumps. 

At the *Chair of fluid system dynamics, TU Berlin* a test stand was developed to examine such assumptions to investigate the functionality and the clogging behavior of sewage pumps. Two different investigations are performed: the functional test the long-term functional performance test and.

In the functional test, a defined volume of water with different wipe loads is pumped once with the aid of the examined wastewater pump. The functional test corresponds to the first pumping process in the sewage system, where high amount of non-shredded wastewater components can be found, and can provide indications of initial blockages or blockage-prone impeller geometries.

In the long-term functional performance test, artificial wastewater, consisting of fresh water with different loads of textile cloths, is circulated for one hour with the examined wastewater pump. During the long-term functional performance test, all relevant parameters and power consumption are recorded. The recording of the measured values ​​enables the documentation of the efficiency curve as well as behavior during clogging. The long-term functional performance test represents the continuous operation of a sewage pump in a pumping station downstream from the first pumping station.

For evaluation the total weight of the wipes initially introduced is set in relation to the clogging weight of the wipes in the pump. This ratio represents a measure of the clogging susceptibility or functionality.

More than 40 different wastewater pumps were tested with this procedure. The results give the opportunity to show connections between the susceptibility to clogging and the shape of the impeller or ball passage of various sewage pumps. Based on investigations already carried out at the *Chair of fluid system dynamics, TU Berlin*, the following conclusions could be drawn from the measurements:

·         the impeller form (vortex, channel, etc.) does not allow any statement about the susceptibility to blockages,

·         the ball passage does not indicate the susceptibility to blockages.

From these observations it can be deduced:

·         a sewage pump with high efficiency may have a low tendency to clog at the same time.

Therefore it can be concluded, that the ball passage and the type of impeller are not appropriate means to characterize the functional performance of a sewage pump.


Ball Passage and Impeller Types Don\u2019t Characterize the Functional Performance of a Sewage Pump

Division / Sponsors: 
Heat Transfer Division (HTD), Fluids Engineering Division (FED)

Heat Transfer Summer Conference
Paper Proceedings: https://asmedigitalcollection.asme.org/HT/HT2020/volume/83709

18th International Conference on Nanochannels, Microchannels, and Minichannels
Paper Proceedings: https://asmedigitalcollection.asme.org/ICNMM/ICNMM2020/volume/83693

Fluids Engineering Division Summer Meeting
Paper Proceedings: https://asmedigitalcollection.asme.org/FEDSM/FEDSM2020/volume/83716

HT-ICNMM2020 - Virtual Conference, SHTC - Virtual Conference, FEDSM2020 - Virtual Conference

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