During the normal operation of the pressure unit in our plant’s intensification system, no adjustments were made to the process; however, on May 7, the vibration level at monitoring point 4 of the compressor suddenly increased
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During the normal operation of the pressure unit in our plant, no adjustments were made to the process. On May 7th, the vibration level at measurement point 4 of the compressor suddenly increased by about 12 μm; currently, there is no further increase and the vibration level remains stable. From a spectral analysis perspective, the dominant frequency is the first harmonic, with no other frequency components present, and no back-rotation occurs. However, there are changes in the axis trajectory before and after the vibration fluctuations. It is initially suspected that a component of the rotor may have fallen off. Could the experts out there help analyze what exactly is the cause?
Since the image has not been able to be opened, if the frequency remains primarily at double that value after the change, it is likely that something has fallen off the rotor. It is important to consider whether there might be some material attached to the rotor, as well as the rotor coupling.
From the vibration trend, it can be seen that the vibration increases for a while before decreasing again; it seems that there is friction caused by certain components. The primary cause of the first harmonic vibration is rotor imbalance. However, in the case of rotor imbalance, the phases of all four probes should change simultaneously, but in this case only the phases of three probes changed, with one remaining unchanged. Additionally, the trajectory of the rotor’s axis was normal before vibration occurred, but it became oval-shaped after vibration started. If it were due to rotor imbalance, it would be an elliptical shape with little difference between the long and short axes. Based on the above analysis of various factors, first, check whether the stiffness of the bearing is intact and whether the bearing clearance is within a reasonable range ； Secondly, adjust the speed of the compressor and observe whether the vibration changes with the speed; if it does change, it may be a fault caused by rotor imbalance.
Overall, it seems that the vibration surge was caused by the detachment of dirt attached to the rotor blades, after which the system stabilized at a new equilibrium state. Further observation is recommended; if no significant fluctuations occur, the system can continue to operate.
We also think it is caused by something falling or sticking to it. Currently, the vibration is particularly sensitive to changes in speed; once the speed stabilizes, the vibration level remains stable