Most pump design incorprate a radial bearing and a thrust bearing. The radial bearing has to absorb the radial movement of the shaft (deflection, cavitation, vibration , pipe strain etc.) The thrust bearing is soften a double row bearing used to absorb axialmovement (thrust) of the sshaft
The curves on the above chart describe various size Duriron pumps, If you’re not familiar with pump notation, a 4 x 3 x 10 describes a pump with a 4 inch suction, a 3 inch discharge and the pump can carry an impeller as large as 10 inches in diameter.
The specific gravity (sg.) axis is referring to the specific gravity of the fluid you are pumping. Water has a sg. of one.The higher the specific gravity, the shorter the life of the radial bearing
You can see from this chart that a 3 x 2 x 10 Mark II, group II pump, pumping fresh water at room temperature has a design life of a little over 300 years.