Fan vibration
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The fan vibration triggers a cascade shutdown; vibration measurements on site show no issues. Seeking advice? Thank you
This post was last edited by liaifeng on 2020-9-19 at 20:55. 1. There is a discrepancy between on-site vibration measurements and the actual values. 2. The sensor that triggers the interlock mechanism is faulty; the measured values are not accurate. 3. Sudden changes in the fan’s operating conditions can cause temporary increases in vibration levels, leading to the activation of the interlock mechanism. The possible causes of this interlock activation should be checked one by one
It is best to have trend lines as a reference. If it is a trend line for the time of the vibration process, it might be true. If there is a sudden rise and no trend can be seen over time, then it’s likely a problem with the instrument. As for the vibration issues of fans, the most common cause is an imbalance in rotational dynamic balance resulting from the detachment of scale deposits on the impeller; this is provided for reference.
Is the vibration installation proper? It’s possible that water has gotten in
1. For fans that are already in operation, if the installation was not proper, is it still necessary to wait for them to shut down due to interlock mechanisms? 2. For fans that are already in operation, under normal circumstances, how can water suddenly get inside them?
The vibration DCS shows a trend that is in line with time, over a total of 40 seconds, but the actual measurements show no issues
Could it be a false alarm from the instrument? It is recommended that they check the instrument
I think I know why. The range of on-site vibration sensors is usually 0-20 mm/s; please check the corresponding range at your control room – these two ranges need to be identical
First, determine which one is the actual value; based on what you’ve described, there must be one that is a false signal
Can you measure the vibration on-site to show that the fan has started running again? For speeds exceeding 10,000 rpm, we should rely on the PLC readings; the machine should be started only after checking the tightness of the bolts securing the bearing caps in the gearbox, if conditions permit. I can’t fix it myself; after checking the vibration trend, activate the interlock and try again. Under normal operating conditions with interlocks in place, German compressors ensure that there are no issues with the oil system; even if there are vibration problems, the system can still shut down properly through the interlocks, without causing damage to the equipment