Radial force on the impeller of mining multistage pump
In calculating the shaft and bearing, the radial forces acting on the mine multistage pump impeller must be considered, since the pump will not always operate at the design flow and will even operate at zero flow during starting and stopping.
Sometimes, radial forces can cause large deflections in the shaft and even damage the seal ring, interstage sleeve and bushing. At the same time, for a rotating shaft, the radial force is an alternating load, which causes the shaft to be damaged by fatigue. Therefore, it is necessary to eliminate the radial force and reduce the effect of the radial force on the shaft.
The vortex chamber is divided into two symmetrical portions, which constitute a double vortex chamber or a double vortex chamber as commonly referred to. In the double vortex chamber, although the pressure distribution is not uniform in each vortex chamber, since the two vortex chambers are symmetrical to each other, the radial forces acting on the impeller are balanced with each other. In the volute multistage pump, a double vortex chamber as shown in Figs. 7 to 36) is sometimes used, so that the radial forces acting on the impeller can be balanced with each other.
In the volute multi-stage pump, the arrangement of two adjacent vortex chambers rotated by 180 degrees can reduce the effect of the radial force on the shaft, as shown in Fig. 7~4. This method, although not able to eliminate the radial force on a single impeller, has only one force couple effect on the shaft. Since the arm of the couple (the distance between adjacent impellers) is not large, the bending moment of the force on the shaft is very small.
For the vane-type pump, since the number of vane blades of the multi-stage pump is relatively large, the radial forces generated by the respective vanes are balanced with each other, and the influence on the shaft is small, and is generally not considered.
