15th European Conference on Turbomachinery Fluid dynamics & Thermodynamics
Authors
Abstract
Wastewater pumps are facing ever-increasing challenges from solids. These solids cause a significant number of malfunctions, which can manifest itself in changed hydraulic performance, altered energy consumption, and system downtime due to clogging within the pump. A particular proportion of solids being responsible for disturbances in the wastewater system is represented by tear-resistant fibrous materials, e.g. wet wipes. The increased concentration of these wet wipes in the wastewater system and the resulting clogging provides the need to assess the functionality of wastewater pumps. At the new test rig for functional tests at the Technische Universität Berlin at the Chair of Fluid System Dynamics, more than 50 different wastewater pumps have been tested so far for their susceptibility to clogging. Previous assessments for pumps refer to the efficiency of the aggregates, for example in ISO 9906. However, since functionality does not correlate with efficiency, the test rig specifically examines functionality in different approaches. The two main test procedures that are used to evaluate functionality differ in their procedure and duration: the functional performance test involves the one-time pumping of a defined quantity of artificial wastewater, while the long-time functional performance test involves the continuous pumping of a defined quantity of artificial wastewater for 60 minutes. By means of these two test procedures, different aspects of the functionality of the wastewater pumps can be investigated. It has already been found by means of both test procedures that neither ball passage nor impeller type have a significant influence on the functionality of sewage pumps. To obtain more specific insights into the interaction between the impeller and wet wipes, an optical access is additionally installed on the test rig, with which targeted observations of the individual pumps can be carried out by means of an endoscope and a high-speed camera. This paper deals with the experience gained in measuring the functionality of wastewater pumps on this new test rig for functional tests by taking a holistic view of the pumps measured to date. The different experiences of the functional performance test, the long-time functional performance test and findings from optical examinations are discussed. The functionality of the aggregates is evaluated and compared with the aid of both test procedures. The behavior of the pumps is explained by means of a limit value for the degree of functional performance as well as the degree of long-time functional performance, and the composition of the individual partial results is discussed. Since the pumps tested so far vary in their performance class as well as in their suction- and pressure-side connection dimensions, the clogging behavior of these different pump sizes on the test rig is also analyzed within this paper. This is carried out to show that the clogging behavior of wastewater pumps can be evaluated on this test rig, irrespective of their performance class.
ETC2023-227
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