The axial force of Roots reciprocating vacuum unit may have some problems when it is used, which will have a certain impact on our use. In order to eliminate this problem, we need to take certain measures to solve it. Let’s learn the correct method to eliminate the axial force of Roots reciprocating vacuum unit.
1. Reasons for axial force: because the pressure of suction inlet and outlet is not equal, and the fluid pressure on both sides of impeller is not completely symmetrical, the axial force is generated. If the influence of the sectional area of the shaft and the rotation of the impeller on the pressure distribution is not considered, the force acting on the impeller is the difference between the wheel disc and the wheel cover, which is converted into a formula for calculating the product of the difference between the outlet pressure and the inlet pressure and the area of the wheel cover. Because the outlet pressure is always greater than the inlet pressure, when the pump rotates, there must be an acting force along the shaft and pointing to the inlet on the rotor.
2. Problems caused by axial force: the unbalanced axial force will increase the working load of the thrust bearing of Roots reciprocating vacuum unit, which is unfavorable to the bearing. At the same time, the axial force makes the pump rotor move towards the suction inlet, causing vibration, which may cause friction of the impeller ring and damage the pump body.
3. The balance plate and impeller are generally installed symmetrically. Single stage pumps generally have balance holes on the impeller. Of course, the balance blade is installed on the impeller disk to balance the axial force.
4. Although we need to eliminate the axial force, if it is completely eliminated, it will also cause the instability of the rotor during rotation. Therefore, 30% of the bearings will be designed to offset it in the design. This is why the bearings at the non drive end of Roots reciprocating vacuum units are usually angular contact bearings, because they can withstand large axial forces.
Only when we know the axial force of Roots reciprocating vacuum unit from the beginning can we eliminate it better. I believe that we can easily solve the problem of axial force after understanding this knowledge.
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