What is the Role of the Expeller of the Slurry Pump
In addition to the role of sealing, the expeller can also reduce the axial force. In the middle, the axial force is mainly composed of the differential pressure force of the liquid acting on the impeller and the gravity of the entire rotating part. These two forces The direction of action is the same, and the resultant force is formed by the addition of the two forces.
It can be seen that under the same performance parameters, the axial force of the submerged slurry pump is larger than that of the general horizontal pump, and the balance difficulty is more difficult than that of the vertical pump. Therefore, in the submersible sewage pump, the reason why the bearing is easily damaged is also closely related to the large axial force. If the expeller is installed, the direction of the pressure differential force acting on the auxiliary impeller is opposite to the resultant force of the above two forces, which can offset part of the axial force and prolong the bearing life. However, the use of the expeller sealing system also has a disadvantage, that is, a part of the energy is consumed on the expeller, generally about 3%, but as long as the design is reasonable, this part of the loss can be reduced to the limit.
In a general submerged slurry pump, the power always increases with the increase of the flow rate, that is to say, the power curve is a curve that increases with the increase of the flow rate, which will bring a problem to the use of the pump: When the pump is running at the design operating point, generally speaking, the power of the pump is less than the rated power of the motor, and the use of this pump is safe; but when the pump head is reduced, the flow rate will increase (from the performance curve of the pump, it can be seen that out), the power also increases. When the flow exceeds the design operating point flow and reaches a certain value, the input power of the pump may exceed the rated power of the motor, causing the motor to be overloaded and burned. When the motor is overloaded, either the protection system acts to stop the pump, or the protection system fails and the motor burns.
这在实践中经常遇到电梯of the pump is lower than the lift of the design operating point. The pump is used to reduce the head; another situation is that the working point of the pump during use is not well determined, in other words, the flow of the pump needs to be adjusted frequently; another situation is that the pump needs to be used frequently at different locations. These three situations may overload the pump and affect the reliability of the pump.
