Methodology for selection of optimum interference fit for enhancing performance of external gear pumps

Abstract

External gear pumps are the heart of mobile hydraulic equipment in the mining sectors where it requires precise control of work attachment functions, lubrication of transmissions and oil supply to steering control units. The external gear pumps encounter many tribological phenomena such as lubrication and wear of gear teeth, an inner profile of casing, wear plates, and press fitting of journal bearings. The major challenge involved during the design phase is the optimum selection of required interference dimensions between the shaft plain bushings and its housings such as bracket and covers. Though the analytical calculations provide some rough initial sizes, it is a time consuming and tedious process when it comes to different material combinations, non-uniform and unsymmetrical sections of brackets and housings. Also, it is difficult to include the effect of thermal variations and different surface finish conditions of mating surfaces in analytical calculations. Optimum interference dimensions are essential to avoid premature failure of the Pumps due to dislodging of the bushings. In the current study, the required initial interference fit dimensions are computed based on an analytical method for different materials combinations. Further, the effect of the surface finish of mating surfaces and thermal expansion of materials are studied using KISSsoft simulation. The validation of the same has been carried out using an experimental set up with different material and assembly conditions as a comparative study to find the optimum dimensions.