Sudden increase in shaft vibration of centrifugal compressor
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In one of our plants, the shaft vibration sensors located on the inlet side of the high-pressure cylinder of the centrifugal ammonia refrigeration compressor are arranged at 45 degrees to each other. After replacing the dry gas seal, the shaft vibration on one side increased continuously, rising from 38 um to 85 um, while the vibration level on the other side remained essentially unchanged. After shutting down the machine and replacing the vibration sensors on both sides, the same high vibration level was observed on the first side. After a few days of operation, the vibration level on that side decreased significantly; subsequently, the vibration level on the other side began to rise, eventually reaching 80 um. Reducing the rotational speed by 500 revolutions helped to lower the vibration levels, with those on the upper part dropping to 80 um and those on the lower part dropping to 78 um, though they continued to rise slowly. We plan to maintain production at a rotational speed of 100 revolutions for the next few days. Could you help determine what the problem might be? The sensor probes and amplifiers have been replaced, and we have tried using different wires connected to other measurement points, with no issues detected in those cases.
As you said, instrument issues have been ruled out. One side is larger than the other; it is presumed that there may be issues such as friction between moving parts and excessive clearance in the bearing shells. Specifically, it requires detailed data analysis.
As you said, instrument issues have been ruled out. One side is larger than the other; it is presumed that there may be issues such as friction between moving parts and excessive clearance in the bearing shells. Specifically, it requires detailed data analysis.
Thank you, but the other side also gradually rose to 80um later on
Is there a spectrum? Which frequency is mainly increasing, causing the rise from 38um to 80um? Have there been any changes in the temperature of the bearings and dry gas seals?
There are two vibration values, one for y and one for x; these indicate issues with your assembly clearance or dynamic balance
There are installation issues; when reinstalling, it is essential to take accurate measurements, and no measurement point should be missed. It is best to use the data provided in the installation instructions given by the equipment manufacturer.
The speed of a centrifugal compressor is determined by its flow rate and pressure In other words, the vibration was normal before replacing the dry gas seal. Regarding the vibration that occurs after the replacement, it is recommended to wait until the problem is completely resolved before driving.
Is there any area where there is friction or scraping?
It is possible that the dry gas seal was not installed properly, and there may be a leak. A leak could lead to problems, so it is recommended to check the dry gas seal again.
Agree with the opinions from floors 5 and 6! I also think it’s a installation issue; it was caused by an improper measurement of the gap for the vibration probe when installing the shaft bearings after replacing the dry gas seal. The same problems occur when the probes in the X and Y directions are installed in reverse order, which indicates that there are no issues with the measuring elements or the wiring; the problem lies in the gap at the measurement site. When the vibration on the other side also increases, this can be understood as a result of the gap at the point where the vibration level was originally high gradually being worn flat, which in turn causes a change in the axis trajectory; examining the axis trajectory diagram should help identify this issue. The above are purely my personal opinions; please refrain from criticizing if you don’t agree!