The damage of the shaft accounts for a large proportion of the damage of the parts of the single-use water ring vacuum pump. Damage to the pump shaft includes bending, cracking and breaking.
Pump shaft bending is mostly due to the sleeve stiffness is not enough, coupled with the impeller has a large imbalance, the operation of deformation. The bending direction and magnitude of the shaft can be measured by:
Put the shaft on the support, adjust the two support points (can be the hole in the center of the pump shaft, or the neck of the shaft) to the equal height, select several equidistance sections on the shaft, and measure the radial runout in four directions (that is, measure once per week when rotating 90°) with a micrometer in the rotation circle of the shaft, and record it. The bending values in the four directions can be obtained from this data, and the direction and size of the larger bending can be found by the graphical method, so that straightening can be carried out.
The cracked grave and broken parts of the pump shaft, often occur in the local stress concentration, such as the keyway edge, the diameter of mutation. The cause of damage is often due to vibration induced fatigue failure.
If the pump shaft fatigue crack (a precursor to breaking), should be promptly replaced. If due to objective factors cannot be replaced temporarily and need to continue to use, the temporary remedy is to carry out welding of cracks. When using the pump shaft after repair welding, always pay attention to the change of repair welding area, so as to avoid accidents.
In the use of single-use water-ring vacuum pump, the failure often occurs is the break of the pump shaft (especially the pump with large gas volume). The fracture surface is usually perpendicular to the axial line, very neat like a knife cutting, the whole section is mostly smooth and metallic luster, a small part of the rough. Obviously, this is the fracture characteristic caused by fatigue failure.
The main cause of fatigue damage is, due to the pump shaft in the process of operation, pump cavity gas on the pump shaft force, which is also called radial force.
In addition to the fundamental reason of radial force in water ring vacuum pump, the unreasonable structure is also an important reason that cannot be ignored. Mainly include:
At present, the water ring vacuum pump shaft and impeller are the first level of dynamic fit, and the keyway is not sealed with type 0 sealing ring, the liquid in the pump (especially when corrosive liquid is used as liquid ring in chemical industry) will enter the shaft hole through the fit gap and the keyway, corrosion shaft hole of shaft and impeller, greatly reducing the fatigue strength. The increase of fit gap after corrosion and wear (some wear into elliptic shaft hole) not only affects the performance, but also intensifies the vibration and promotes the fatigue fracture.
General water ring vacuum pump shaft without heat treatment, so low fatigue strength. In order to prevent fracture, the pump shaft at least to carry out conditioning treatment, where conditions are also nitriding treatment.
When designing, avoid too large cross section mutation. Use rounded corners instead of sharp corners in transitions. Surface finish should not be too low, especially in the shaft easily broken place to pay attention to. When processing, different shaft diameter transition at the circumference of the processing, to ensure quality, in strict accordance with the drawings required size and light pitch, pump shaft surface and transition execution can not have knife marks, scratches, bruises and other defects.
Pump shaft fatigue damage to the production of great harm, is the user is very concerned about the problem. The solution is: according to the size of radial force to check the fatigue strength of the pump shaft, the use of corrosive gas and liquid ring, to use the corresponding corrosion resistant materials, pump shaft must be conditioning treatment, processing must ensure the quality and so on. Above is the vacuum pump manufacturer not yao, for you to do the detailed introduction, hope to help you.
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