I refer to the overhung impeller pump. They normally have two bearings supporting the shaft, (and an oil box between the bearings). Why is that? why not only one bearing? what would happen if they are manufactured with one bearing only?
You could do that but you would have to rely on the bearings of the driver to help support the load. You would also have to be sure one of the two bearings could take an axial thrust load. As you may know there are vertical inline pumps that do just that.
This is a rough guess by an electrician. There is a lot of radial pressure on the shaft of a rotary pump. Were pumps to have only one bearing, the bearing would have a lot more pressure on one side of the race than on the other. This would cause the bearing to fail. With two bearings, set some inches apart, the radial pressure on the races would be small.
There are two bearings on the pump shaft to prevent lateral movement of the pump shaft during rotation. If a bearing is mounted at only one end of the shaft, the other end of the shaft will be free to wobble, which would be destructive to the pump. Some pumps may also feature a thrust bearing to prevent axial movement of the pump shaft.
A pump bearing system consists of bearings to carry radial loads and at least one bearing to carry axial or thrust loads. If one fails other bearing to carry on the work.
