Tsentrifugaalpumpade liigse vibratsiooni põhjused ja lahendused

Foundation fastening
When a defect occurs, first check whether the anchor bolts of the prime mover and the centrifugal pump are securely fastened. If the foundation is unstable, it will inevitably cause the pump to vibrate. When other causes are ruled out but the problem still cannot be solved, it is also necessary to consider whether the strength of the anchor foundation is sufficient. Sometimes, due to design reasons, a relatively soft foundation can also cause vibration.

Centering adjustment
Misalignment is also a common cause of vibration. The center must be adjusted within the specified range in strict accordance with standards.

Bearing inspection
For pumps using sliding bearings, if vibration still cannot be eliminated after the above work, the contact condition of the bearing bushes should be checked. For normal bearing bushes, the lower bush should have uniform contact marks, mainly distributed in the middle and lower parts, and the contact area should be more than 75%. The upper bush should have a gap, generally 0.1 – 0.15% of the shaft diameter. The upper bush gland should have a tightness of 0.02 – 0.02mm on the upper bush. If the requirements cannot be met, generally, methods such as adding or removing gaskets at the bush mouth and scraping the bearing bushes are adopted to solve the problem. For pumps using rolling bearings, the tightness of the bearing gland on the outer ring of the bearing should be measured. Generally, an expansion gap of about 0.20mm should be reserved to prevent the bearing from being subjected to axial force when the rotor expands under heated conditions.

Adjustment of rotor center position
The pump rotor should be concentric with the stator. Otherwise, dynamic and static friction will occur during the operation of the pump, resulting in vibration. The adjustment of the pump rotor center position can generally be achieved by adjusting the radial position of the pump bearing. For the center adjustment of pumps supported by bearing bushes, the bearing bushes on both sides of the pump should be raised simultaneously to meet the requirements. Generally, the lifting amount is half of the seal ring gap, and the same applies to both sides. For horizontal split – case centrifugal pumps, if necessary, the upper cover of the pump can be opened to directly measure the gap at the seal ring. After adjusting to meet the requirements, drill holes between the bearing support and the pump body to configure pins, and then assemble again to achieve the purpose of precise adjustment.

Measurement and adjustment of shaft bending, runout and end play after rotor partial assembly
If no cause of vibration is found externally, the pump can only be disassembled. First, measure and correct the shaft bending. After confirming there is no problem, partially assemble the rotor, measure the overall runout and end play, and correct them if they exceed the standard.

Dynamic and static balance detection
After the pump is disassembled, to avoid vibration when starting the pump, each stage of the impeller should be subjected to a static balance test. If conditions permit, a dynamic balance test should also be conducted. Especially for large – scale multi – stage pumps, the dynamic balance test is particularly important.

Influence of external conditions on the pump
After eliminating all possible problems of the pump itself, if the vibration problem still cannot be solved, the influence of external conditions on the pump should also be considered. For example: resonance caused by the natural frequency of the pump foundation being similar to the vibration frequency, pump vibration caused by prime mover failure, and abnormal pump vibration caused by forced alignment in the connection between the pipeline and the pump. Generally, corresponding measures can be taken to solve the problem.