Vacuum pump shaft vulnerability causes and remedies!
Jun 20, 2018

Most of the reasons for the water shaft vacuum pump shaft bending is due to the lack of stiffness of the sleeve, in addition to the impeller has a large imbalance, caused by deformation during operation. The bending direction and size of the shaft can be measured by the following method: Place the shaft flat on the support, and adjust the two bearing points (which can be the center hole of the pump shaft, or the shaft neck position) to the same height, and select on the shaft. Several equidistant sections, in the rotation of the shaft with a dial indicator to measure the tilt in four directions (that is measured once every 90 ° rotation) on the radial jump, make a record. Based on this data, the bending values in four directions can be obtained. The direction and size of the maximum bending can be found graphically so that straightening can be performed. The cracked graves and fractured parts of the water ring vacuum pump shaft often occur at places where local stress is concentrated, such as at the edge of a keyway or at a sudden change in diameter. Causes of damage are often due to vibrations that promote fatigue.

If the water ring vacuum pump shaft has fatigue cracks (those that are about to break off), it should be replaced in time. If it is necessary to continue using it temporarily because of objective factors, the temporary remedy is to repair the crack. When using the repaired pump shaft, always pay attention to changes in the repair area to avoid accidents. The main cause of fatigue failure is that due to the action of the gas in the pump chamber on the pump shaft during the operation of the pump shaft, this force is also called radial force. The fatigue failure of the pump shaft, in addition to the root cause of the radial force in the water ring vacuum pump, is not an important reason why the structure is irrational.

At present, the water ring vacuum pump shaft and the impeller are in a first-stage dynamic match, and the 0-ring seal is not used at the keyway. The liquid in the pump (especially when a corrosive liquid is used as a liquid ring in the chemical industry) passes through the clearance and The keyway enters the shaft hole and corrodes the shaft and the shaft hole of the impeller, which greatly reduces the fatigue strength. The increase in the clearance after corrosion and wear (some of which are milled into oval shaft holes) not only affects the performance, but also exacerbates the vibration and promotes fatigue fracture. The general water ring vacuum pump shaft has not been heat-treated, so its fatigue strength is low. In order to prevent fracture, the pump shaft must be at least tempered and treated, and where necessary, nitriding treatment is also required. When designing, avoid cross-sectional sudden changes. The corners are applied at the transition without the use of sharp corners.

The surface finish should not be too low, especially when the shaft is easily broken. During processing, the circumferential processing at the transitions of different shaft diameters must be performed in a quality and strictly in accordance with the dimensions and apertures required by the drawings. There must be no defects such as knife marks, scratches, and bumps on the surface and transition of the pump shaft. The fatigue damage of the pump shaft is very harmful to the production and it is a matter of great concern to the user. The solution is: check the fatigue strength of the pump shaft according to the radial force. When using corrosive gas and liquid ring, use the corresponding corrosion-resistant material. The water ring vacuum pump shaft must be quenched and tempered. , processing must ensure quality and so on.

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