Expeller not only with sealing effect, but also can serve to reduce the axial force. The axial force in the slurry pump is mainly caused by the liquid pressure acting on the impeller and the rotating part of the composition of gravity.
So it is easy to know, in the same identical performance parameters, slurry pump axial force is stronger than the common horizontal slurry pumps and harder than vertical slurry pumps in balance. Therefore, submersible sewage pump is easy to damage the bearing also has a great relationship with axial force.
And if you install expeller, the expeller fluid pressure acting on the sub-direction opposite to these two forces above, which can offset part of the axial force, also played a role in extending bearing life.
But the use of expeller sealing system also has a drawback, it is in the sub-part of the energy to be consumed on the impeller, usually around 3%, but with reasonable design, this part of the loss can be reduced to a minimum.
In general slurry pump system, the power always increases according the flow, that is, the power curve is increased with the flow rising curve. Then there maybe cause a problem: When working at designed point operation, the slurry pump power is lower than the motor rated power, which is safe; but when the pump head is reduced, the flow will increase (Got from the slurry pump performance curve), slurry pump power also increases. When the flow exceeds the design operating point and reaches a certain value, the slurry pump input power may exceed the rated power of the motor, then cause motor overload and burnout. Motor overload protection system is running or stop the pump; otherwise it will burn the motor protection system.
Slurry pump head lower than the design point lift usage in practice is often encountered. When selecting the pump, slurry pump head election was too high, and the actual use of the pump is lower; another situation is that operating point is not very good, in other words, the slurry pump flow requires frequent adjustment; also the case that the pump need to frequently change locations. These three cases all may get the slurry pump overload and affect the reliability of the slurry pump.