when you have rated diameter impeller very close the the minimum impeller diameter, the chance pump will suffer recirculation is higher. This is due to the gap or clearance between impeller vane tips and cutwater is wider. This recirculation will cause the unstable flow on impeller outlet...
Hydrodynamic thrust bearing must be lubricated by force feed system.If you want ring oil lubrication you must replace the pivot bearing with thrust ball bearings. Understand that most Pipeline application does not like force feed lubrication.
The replacement of pivot bearing with thrust ball...
You need to check 3 limitations of bearing selection per API 610 10th ed. Table 9; your MSND pump size is bigger than your DMX.
1. Thrust bearing speed.
2. Bearing life
3. Energy Density
