The principle of the centrifugal pump is simply that when the impeller rotates at high speed, the liquid between the blades is rotated. Due to the centrifugal force, the liquid is thrown from the center of the impeller to the outer edge of the impeller. When the liquid enters the pump casing, due to the volute-shaped pump casing The flow path gradually expands, the liquid flow rate gradually decreases, and part of the kinetic energy is converted into static pressure energy, so the liquid flows out along the discharge port with a higher pressure, so it is called a centrifugal pump. In the case of improper handling, the centrifugal force generated by the impeller will cause the pump to vibrate and abnormal noise.
When the centrifugal pump is used, it is found that the pump vibration and noise are abnormal, and it should be stopped immediately for inspection.
1. Whether the pump foundation is reliable
When vibration occurs, first check whether the anchor bolts of the centrifugal pump are tight. If not tightened, it will cause centrifugal pump vibration. It is also necessary to consider whether the strength of the foundation is sufficient. Sometimes due to design reasons, the soft foundation can also cause vibration.
2. Align the coupling
Many centrifugal pumps are driven by couplings, and there are many types of couplings. The alignment of the conventional three-jaw coupling directly affects the normal operation and service life of the coupling, shaft, bearing, mechanical seal, etc.
3. Find a center
Irregularity of the center is also a common cause of vibration, and the center must be adjusted within the specified range strictly according to the standard.
4. Bearing inspection.
Is there any problem with the bearing installation or is it damaged?
5. Rotor center position adjustment.
The pump rotor should be concentric with the stator, otherwise friction and vibration will occur when the pump is running.
6. Dynamic and static balance detection.
After disassembling the centrifugal pump, in order to avoid vibration when the pump is turned on, the impeller should also be tested for static balance.
The influence of external conditions on the pump.
After all possible problems of the pump itself are eliminated, if the problem of vibration cannot be solved, the influence of external conditions on the pump must also be considered.
Installation process of horizontal centrifugal pump
It should meet the requirement of allowing the vacuum height of the pump to operate at the lowest suction level. The submersible pump's submerged depth at the lowest design water level shall meet the following requirements:
1. The tube well should be no less than 3m.
2. It should be no less than 1m in large wells and radiation wells.
3. The suction tank should be no less than 0.5m.
The distance between the suction port of the submersible pump and the bottom should be determined according to the siltation situation.
Rolling bearings have abnormal noise and high temperature during operation
1. The bearing has quality problems. Check the bearing to pay attention to the appearance of the bearing, whether the rolling element rotates flexibly, and the size gap of each part of the bearing.
2. Bearing running sleeve. When the temperature of the bearing box is high and there is abnormal noise, the amplitude is large and small, and the vibration period is indefinite. The disassembly inspection revealed that the outer surface of the bearing outer ring has wear marks and the gap is too large, indicating that the bearing and running sleeve can be glued and repaired. Welding and setting method repair. The running cover is serious and cannot be repaired by the above method and needs to be replaced.
3. The bearing is badly worn or damaged. The bearing runs loudly, and the temperature is high and the amplitude is large, so the bearing needs to be replaced.
4. The axial positioning of the bearing. When the pump is running, the temperature is high and the vibration is not large. It may be that the axial gap of the bearing is too large. After parking, tap the coupling back wheel with a tool to find that there is obvious axial movement. The gap needs to be adjusted again.
When the rolling bearing of the horizontal single-stage centrifugal pump is running, there is no abnormal noise, but the temperature is high
1. There is a problem with the cooling water. If the temperature of the cooling water is too high, it may be that the cooling water is not open or blocked, insufficient, or that the cooling water needs to be dredged or adjusted.
2. Too much or too little lubricating oil or poor oil quality. The temperature of the front and rear bearings is high at the same time, and the lubricant needs to be adjusted.
3. The bearing assembly clearance is small or the gland clearance is small. At this point, cranking is more laborious, indicating that the gap should be readjusted.
4. Vibration problem. The bearing temperature is high due to high vibration. First, the vibration problem must be solved to eliminate the vibration.
5. The center of the rotor is not concentric with the inner hole of the bearing box and the large cover (the bearing box or the large cover of the pump is deformed). If the above reasons have been checked and still cannot be solved, it can be considered that the bearing box or the large cover of the pump causes the different shafts before and after the bearing. The bearing load is increased, the wear is increased, and the temperature is too high. This situation can only be corrected on the lathe.
6. The centrifugal pump shaft is bent. The uneven stress on the bearing also leads to high bearing temperature. The processing method is to straighten the pump shaft.
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