Overview of rotor faults in self suction centrifugal pumps and analysis and handling of common faults

(1) Overview of rotor faults in self suction centrifugal oil pumps

The rotor is a major component of self suction centrifugal oil pumps and is also a part that is prone to faults.

. Common rotor faults include: rotor imbalance, rotor eccentricity, rotor bending, rotor stator friction, and rotor misalignment

Firstly, it is a problem of rotor imbalance. In self suction centrifugal oil pump equipment, it is usually composed of a rotor with a rotating shaft and multiple discs. Due to the possibility of mass eccentricity in each disc, it can be inferred that two or more discs may convert the mass eccentricity of multiple particles into one or more vectors during the operation of a self suction centrifugal oil pump, resulting in rotor imbalance. The impact of rotor imbalance on the normal operation of self suction centrifugal oil pumps is low efficiency, high vibration, and high noise

Secondly, it is the issue of rotor eccentricity. The reason why the rotor undergoes eccentricity is because there is no concentric circle formed between the stator and rotor, which generates first-order frequency vibration during the rotation process. At the same time, due to fluid imbalance, vibration between the impeller and the blades is formed

Thirdly, there is a problem of rotor bending. Generally speaking, the bending failure of the rotor is caused by a change in the physical characteristics of the rotor due to long-term disuse. On the other hand, rotor bending can be divided into two situations: temporary bending and scattering. Temporary bending can be restored, possibly due to the excessive load on the self suction centrifugal oil pump, insufficient warm-up, and excessive speed; Bending cannot be restored, possibly due to design curves or prolonged exposure to cold and heat during parking

Fourthly, faults that occur due to rotor misalignment. The axis deviation between the rotors of the self suction centrifugal oil pump is caused by installation errors between the coupling, transmission of motion, and torque, or sudden changes in working conditions, or deformation and uneven settlement of the foundation after dry loading. Continuous operation with misaligned rotors can shorten the lifespan of self priming centrifugal oil pumps and increase the likelihood of scrapping

Fifth, there is a friction fault between the rotor and stator. Once the rotor rotates too heavily and rubs against the stator, it will cause system resonance, sudden increase in amplitude, and significant increase in noise. Friction can cause fatal damage to the rotor

(II) Common Fault Analysis and Handling of Self suction Centrifugal Oil Pump

There are various reasons for the failure of self suction centrifugal oil pump, including unreasonable selection and inherent equipment faults, installation, startup, and operation faults.

. For example, pump overpower caused by unreasonable selection; Severe pump cavitation and insufficient flow caused by design and manufacturing defects; Due to installation failure, the vibration and noise of the self suction centrifugal oil pump severely exceed the standard; Due to startup and operation failures of the self priming centrifugal oil pump, the pump cannot start normally, the water output gradually decreases, the packing heats up, and the bearings overheat. When the pump operates with abnormal sound or excessive vibration, the small unit composed of the motor should be stable and the sound should be normal. If there is noise or abnormal vibration in this small unit, it is often a precursor to pump failure, and it should be stopped immediately for inspection to eliminate hidden dangers. The possible causes of malfunctions may include: imbalanced rotation of the pump or motor rotor, misalignment between the pump and motor, aging of the impeller rubber ring, incorrect impeller balance, insufficient stiffness of the pump foundation, loose anchor bolts, excessive wear of bearings or seals, resulting in rotor eccentricity, gas in the pump, failure to vacuum, improper lubrication of bearings and packing, excessive wear, bearing wear or damage, excessive or insufficient lubricating oil (grease), excessive suction head, cavitation of the impeller, bubbles appearing in the low-pressure area when the liquid passes through the impeller, and bubbles collapsing in the high-pressure area, causing collision and vibration. At this time, the installation height of the pump should be reduced, foreign objects sucked in by the pump, blockage or damage to the impeller should be stopped. The vibration caused by cleaning foreign objects or replacing damaged impellers or resonance is mainly due to the natural frequency of the rotor being the same as the pump speed, resulting in resonance, etc. If the bearing is found to be hot during the operation of the pump, the cause can be investigated in the following items: the self suction centrifugal oil pump is not concentric with the electric motor, the coupling is poorly aligned, or the axial clearance is too small. The method is to check the alignment and adjust the axial clearance, insufficient lubricating oil or poor lubricating oil circulation, poor lubricating oil quality, impurities that cause bearing rust and wear, inflexible rotation, severe bearing wear, and poor scraping of the bearing. If the bearing clearance is too small, the bearing clearance should be readjusted or scraped. If the bearing assembly is poor, the bearing assembly should be checked according to requirements. Factors that do not meet the requirements, cooling, etc. If there is a water circuit break, the cooling water device should be checked and repaired immediately. If the pump shaft is bent, factors such as the pump shaft should be corrected