When the centrifugal pump is working, when the axial force on the impeller is greater than the balance force on the balance plate, the pump rotor will move in the suction direction, which reduces the axial clearance of the balance plate and increases the fluid resistance of the liquid. Reduce the amount of leakage. After the leakage is reduced, the pressure drop of the liquid flowing through the radial gap is reduced, thereby increasing the pressure in front of the balance plate, that is, increasing the balance force on the balance plate. As the balance plate moves to the left, the balance force gradually increases. When the balance plate moves to a certain position, the balance force is equal to the axial force and balance is reached.
Similarly, when the axial force is less than the balance force, the rotor will move to the right. After moving a certain distance, the axial force and the balance force will reach a new balance. Due to inertia, the moving rotor will not immediately stop at the new balance position, but continue to move to promote the destruction of the balance, resulting in a condition for the rotor to move in the opposite direction. (Pump housekeeper) When the pump is working, the rotor will never stop at a certain position, but will move axially at a certain balance position. When the working point of the pump changes, the rotor will automatically move to another balance The position moves axially. Because the balance plate has the feature of automatically balancing the axial force, it is widely used.
The key part of the thrust balance device is the working surface of the balance plate and the balance ring. If there is a skew or unevenness between the two working surfaces, a large amount of leakage will occur when the pump is running, and the balance chamber cannot maintain a balanced axial thrust. Due to the pressure, the role of balancing the axial force is lost.
The balance plate is installed on the pump shaft, which may form an eccentricity with the pump shaft, causing the rotor to vibrate during operation. This vibration will affect the normal operation of the bearing and the pump shaft. In severe cases, it may cause damage to the pump shaft and the bearing. This amount of eccentricity should be strictly controlled.
The verticality of the balance plate and the pump shaft is obtained by measuring the circular runout of the end face of the balance plate working surface. The eccentricity between the balance disk and the pump shaft is obtained by measuring the radial circular runout of the balance disk hub.
To measure the circular runout of the end face of the balance plate, the balance plate should be installed on the pump shaft, and the pump shaft should be supported by the two tops of the lathe to prevent the axial movement of the pump shaft, and then set the balance plate on the working surface side of the balance plate. The dial indicator makes the contact of the dial indicator vertically contact the working surface of the balance plate.
To measure the radial runout of the balance disc hub, a dial indicator should be set next to the hub so that the contacts of the dial indicator vertically contact the outer circular surface of the hub, as shown in Figure 2-62. Then, slowly rotate the balance plate one week, and the difference between the maximum reading and the minimum reading of the dial indicator in contact with the working surface of the balance plate is the circular runout of the end face of the balance plate; the maximum reading and the minimum reading of the dial indicator in contact with the hub The difference is the radial runout of the hub.
When measuring the runout of the impeller group, the balance plate can be installed on the pump shaft, and the end face circular runout of the balance plate and the radial circular runout of the hub can be measured at the same time. In this way, it is possible to save the work of re-installing the supports when measuring separately.
