Thread Content
This post was last edited by Aggregated Cat_IEB8P on 2020-6-29 09:45. 1. Motor-related faults – Rotor imbalance fault: The main cause of this fault is an offset in the center of gravity of the rotor components. A rotor consists of a shaft along with several rotating discs, and it is very easy for the center of gravity of these discs to shift during operation, which in turn causes the rotor’s center of gravity to shift as well, ultimately leading to rotor imbalance. Eccentric rotor faults: Typically, they manifest as either misalignment of the stator or misalignment of the rotor, and both of these conditions can cause frequency vibrations. Therefore, after such faults occur, they usually manifest primarily as a condition of rotor excitation force, which is closely related to the load, but not related to the rotational speed. 2. Abnormal noises and vibrations: The main factors that cause centrifugal pumps to produce abnormal noises and vibrations are the following two. In terms of hydraulic performance, one possible issue is that the centrifugal pump draws in debris into its internal structure, causing the impeller to become clogged or damaged; in such cases, it is necessary to stop the machine immediately and carry out rapid cleaning ； Subsequently, the flow rate of the centrifugal pump experiences significant fluctuations, which leads to pressure changes and, as a result, abnormal noises and vibrations. Finally, an excessive suction lift leads to quite severe cavitation at the inlet of the impeller; in other words, the water flowing over the impeller forms bubbles in the low-pressure areas, and these bubbles are destroyed in the high-pressure areas. This results in certain impacts, which are quite severe, and vibrations will show abnormal patterns as a consequence. If such a situation occurs, the installation height of the centrifugal pump should be reduced. In terms of mechanical issues, the first one is an abnormal rotation of the rotor in the centrifugal pump or motor, that is, a condition of imbalance ； Subsequently, the anchor bolts of the centrifugal pump became loose, which led to abnormal vibration ； Another issue is the misalignment between the centrifugal pump and the motor; the solution is to correct this alignment ； Finally, since the impeller has not been balanced, corrective actions are also required. 3. Mechanical seal failures Mechanical seal failures can be primarily divided into two types: failure of the stationary and rotating rings, and failure of the elastic elements. The factors leading to the failure of the stationary and rotating rings are directly related to the high temperature of the medium inside the centrifugal pump, which affects the sealing rings. If an eccentric rotor fault occurs, it is necessary to adjust the load appropriately before conducting relevant tests to identify the cause of the fault. The embedded structure became loose or even detached, thereby leading to the failure of the stationary and rotating rings. To address this fault, the hard alloy surfacing method should be employed. The pump warms up quickly, which greatly increases the likelihood of leakage; this phenomenon is particularly likely to occur when the pump vibrates or fluctuates. After such failures occur, it is very likely that the graphite rings inside the stationary and rotating rings will break or even fall off, ultimately leading to the failure of these rings. After long-period operation of the centrifugal pump, the maintenance staff failed to carry out maintenance tasks according to the scheduled maintenance schedule; as a result, the compression ratio of the elastic components exceeded normal levels. This easily led to damage to the stationary ring of the friction pair, and in severe cases, it caused failure of both the stationary and moving rings. Failure modes of elastic elements: The failures of elastic elements are usually fracture or loss of elasticity. Generally, the cause of failure is severe vibration generated by the centrifugal pump during operation, or a vacuum condition that occurs. If the above situation occurs, the probability of component failure will **increase**. In addition, fracture failures may also be caused by improper heat treatment methods or weak welding, in which case it is necessary to replace the faulty elastic element immediately. For the failure to fire, the primary cause is the presence of certain scale within the cracks in the components; it is also possible that improper handling during heat treatment leads to this failure to fire. Therefore, such faults can be addressed by cleaning methods, with softened water typically being used as the cleaning agent.