Axial Balance in Centrifugal Pumps - Back Labyrinth

Redesign and correct sizing of hydraulic machines, like centrifugal pumps, must take account of hydraulic thrusts. This is useful to minimize the components wear and properly size of bearings and extending the bearings durability. These are minimal conditions for pumps optimal working. The article analyzes two methods of balancing the axial forces - first with front and back labyrinths and wear rings of impeller, the second using dorsal vanes. The article presents the calculation procedure of axial forces customized for these two balancing methods. Calculations are exemplified for a multistage pump with 2-7 stages. Variations of axial forces are analyzed with the number of stages of multistage pumps, with labyrinth positioning or dorsal vanes diameter, width vanes diameter and clearance between vanes and casing and with the suction pressure of the pump. It also indicates the axial thrust reversal and most convenient rotor geometry.