Abstract
Slurry pumps are extensively used in the construction industry while positive displacement screw pumps are used in most mobile concrete pump applications. The aggregate size is known to significantly affect pump performance in terms of clogging. Large aggregates tend to be trapped against the stator-rotor interface, blocking the continuous and smooth operation of the screw pump. In order to avoid the development of excessive stress values able to damage the rotor-stator mechanism of the pump, the typical de-clogging mechanism deployed by most positive displacement screw slurry pumps includes reversing the rotation of the pump driving motor thus allowing the aggregates to be carried away with the mixture, so that the pump can soon resume its operation. This procedure causes frequent start-stops of the pump resulting in dis-continuation of the pumped mixture lasting a few seconds, that while being of little importance in most construction applications, can be of significance in applications requiring higher levels of accuracy and continuous mixture flow. In the context of this work, a novel concept of positive displacement screw slurry pump is presented, including a continuous de-clogging mechanism, without the need to reverse the rotation of the driving motor. This de-clogging operation is achieved through the modification of the geometry of both the rotor and stator introducing a conical form along the axial direction. This configuration of the rotor-stator, allows for small displacements along the axial direction, which in turn increases the size of the cavities facilitating the de-clogging of the pump. Variable pitch is also introduced to both the rotor and stator in order to ensure constant mass flow of the mixture throughout the length of the screw pump covering for the velocity increase as a result of the conical geometry. The axial movement of the rotor in relation to the fixed stator, is achieved through the elastic support of the rotor in the axial direction, that allows for small axial displacements, when stresses induced from trapped aggregates exceed the stiffness of the support. The proposed concept comprises a passive real-time de-clogging mechanism that greatly reduces pump idle time compared to the conventional mechanism described earlier, providing smoother operation and stable mass flow of the mixture.
Highlights
Progressive cavity pumps (PCPs) are extensively used in a variety of applications including water and waste handling, deliquification of gas wells [1], oil production as well as the construction industry, given their ability to efficiently handle viscous liquids and solid materials while having relatively low surface profile compared to other positive displacement pumps used in similar applications
Due to their extensive use in gas and oil applications, progressive cavity pumps are thoroughly investigated in such applications, describing their function using analytical methods as performed by Nguyen et al [2] and Zhou et al [3] who performed three-dimensional analysis on progressive cavity pumps used in the gas and oil industry using semi-analytical models and Finite Element Analysis (FEA)
The lack of scientific works related to this topic is justified by the fact that construction industry PCPs are considered to have finite lives turning the attention of the manufacturers towards fast and easy disassembly and spare part sales [8]
Summary
Progressive cavity pumps (PCPs) are extensively used in a variety of applications including water and waste handling, deliquification of gas wells [1], oil production (in shallow oil wells) as well as the construction industry, given their ability to efficiently handle viscous liquids and solid materials (usually granular solids or mixtures of liquids and solids) while having relatively low surface profile compared to other positive displacement pumps used in similar applications. A common practice used worldwide as a de-clogging mechanism includes driving motor rotation reversal – as soon as high torque requirements are developed – so that the trapped aggregates can be carried away with the mixture allowing the pump to resume its operation This procedure (rotation reversal and restoration) is a frequent phenomenon in most construction applications and can last for up to a few seconds, leading to intermittent pump operation including slurry mass flow discontinuation and unstable operation. The redesign of the coupling mechanism serves two distinct functions, namely providing the rotor with the required pretension that prevents axial movement during normal operation (i.e. as a result of the pressure difference between the inlet and the outlet of the PCP) and secondly allowing the axial movement and in consequence the de-clogging operation when extreme axial loads are developed as a result of trapped aggregates
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
