Excessive vibrations indicate something is incorrect inside the pump or in its adjacent pump system, which leads to lower pump efficiency and performance.
What is the primary source of this excessive vibration, and how can we address it? is the question that needs to be answered when the level of vibration is assessed to have reached an unfavorable level.
7 Causes of Vibrations
The noise detected is loud and it feels like the gravels are in constant interaction with the submersible pump’s interior. The cavitation occurs when cavities and low-density bubbles emerge in the fluid displaced at the pump’s vaccum side. A clogged sucking outlet or poor pipe construction can also lead to cavitation. The pump operates significantly to the left of the pump curve as a result of pressure bubbles produced by VFDs (Variable Frequency Drives). When low-pressure bubbles get close to the pump’s impeller end due to an imbalance in pressure, the pump breaks(starts vibrating). Breaking bubbles rise to the surface of the impeller, harming the housing and rotor.
How to tackle this problem?
- Proper inspection of the filtration and extractors for cleanliness helps to avoid cavitation.
- Referencing and monitoring the pump’s curve with a pressure sensor or flowmeter equipment.
- Reconsider the pump configuration, if the pump medium path is not suitable or correct.
Concerns with rotor imbalance typically arise as running velocity rises. On the other hand, no substantial vibrations were found during the investigation of these subject pumps at any specific maximum velocity. When charting the pump’s “all pass” vibrations at the apex of the submersible motor at various running speeds, this was a speed control application. As one would anticipate from an imbalance, the vibration does not appear to peak at any particular speeds, but there is a lot of scatter.
The same rotors experience significant axial vibration caused by bent shaft issues, with axial phase fluctuations close to 180°. Dominant instability occurs at 1X RPM if the bent is in the center of the shaft, and it rises to 2X RPM if the bent is close to the connection. More frequently, pumps with bent shafts develop at or at the connection. Using dial indications, bent shafts can be detected.
Pump Impeller Imbalance
Pumps sometimes show signs of misalignment, faulty bearing, and overheating, but the real problem appears to be the imbalanced impeller in the pump assembly.
The imbalance of the impeller in the pump leads to percussion and heat accumulation. The imbalance of the impeller will cause percussion and heat accumulation. The life of the pump bearings was significantly impacted by the impellers’ balance scale.
When the pump’s impeller is center-hung, force mismatch is more common than couple disparity. The largest vibrations at pump operating speed will likely be in either the horizontal or vertical direction, with a peak amplitude of 1X RPM.
Challenges faced because of pump impeller imbalance –
- Failure of the bearings
- High vibrations lead to an impact on the efficiency and operating life of the pump system.
- Mechanical sealing
- Seizing pump
You can observe a flow inversion at the impeller/discharge ends, and low flow leads to recirculation. Suction recirculation: By rerouting the flow in the impeller’s eye, we were able to create low-pressure bursts. The issue is caused by cavitation, which severely degrades impellers. Recirculation is the rerouting of movement at the pump’s outlet side. It is similar to suction recirculating, but the impeller’s force end sustains damage.
Misalignment of the Shaft
Pumps frequently vibrate, therefore it’s best to let a qualified repair specialist determine whether shaft misalignment or another factor is the reason for extreme vibration.
They can also let you know whether the issue is little enough not to affect the pump’s dependability and performance. From the outside, it can be difficult to identify and assess shaft imbalance.
The Misaligned Pumps will Show the Following Indications:
- The vibration that is excessively axial or radial
- Temperatures in the casing or around the bearings are extremely high.
- Temperatures of the output oil are extremely high.
- Oil leakage from the bearing seals in large quantities.
- Shafts that break or crack near the connecting hubs or inlet bearings.
Pump Flow Pulsation
This happens when a pump is operating close to its shut-off head. The pressure sensors on the pump’s outflow piping will change positions. If the pump uses a discharging swing check valve, the counterweight and valve arm will vary, indicating an irregular flow. One of the main causes of pulsation is a lack of proper nourishment. The pumped medium must remain in contact with the plunger’s surface as the plunger is extended and the pump is filled. If you don’t do this, the plunger will move forward and impact the fluid, causing undesirable pulsation.
Additional Read: Explore your submersible pump inside out
This blog covers 7 reasons that lead to vibrations and also helps with solutions to deal with it.
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