The shielded pump vibrates severely; the TRG gauge is in the yellow zone – seeking advice on this issue
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Dalian Empire single-stage shielded pump, equipped with circulating water cooling tubes, for transporting C7 crude toluene. The pump vibrates heavily, and the TRG monitor is in the yellow zone; the pump was stopped for inspection, and the bearing sleeves, thrust discs, etc., are all in good condition with no signs of wear. Hello Haiyou, where does this problem lie? ? ? Thank you!
It seems there might be a problem with the rotor’s dynamic balance
You should first analyze when this pump started showing this issue How long has the pump been in use? When was the last maintenance? Have the process conditions changed? Has there been any change in the outlet pressure of the pump? What was the vibration level in the previous pump inspection records? Is the pump prone to cavitation? Now that it’s disassembled, what is the axial play of the pump rotor? Is it above the standard? What is the radial clearance? What is the runout of the rotor shaft? Is there any foreign object inside the impeller? Causes rotor imbalance? These aspects can be ruled out one by one. Generally, shielded pumps have very low levels of vibration and noise; since the vibration has increased, it is definitely abnormal and requires careful analysis, both in terms of the process and the pump itself.
In shielded pumps, the source of vibration is most often the pump’s mechanical components themselves, with graphite bearings being the most common issue. In such cases, the problem can be caused by damage or wear that leads to an increased gap; naturally, wear of the shaft sleeves can also result in an increased gap, although shaft sleeves are not as prone to damage as bearings.
The expert mentioned earlier that there could be a problem with the rotor. I believe that although the probability is low, it cannot be ruled out. Our factory has been using shielded pumps for over a decade, and in that time shaft bending has also occurred. As for the cause of this phenomenon, there was no definite answer at the time
If it is cavitation, the possible causes include a high temperature of the medium, an excessively low liquid level in the tank before the pump, or a blocked vent pipe in that tank, which results in a certain degree of negative pressure in the space above the tank. But I believe that if it is cavitation, the vibration and noise of the pump should originate mainly from the pump head, that is, the impeller area; this is probably the biggest difference compared to mechanical causes
Here, we also use shielding pumps from Dalian Empire for xylene and pure benzene. What is the temperature of the crude benzene at your location? Consider cooling the pump head and feed pipes
The common fault in our unit is a bent shaft, as the pump was not filled properly.
If the TRG gauge moves into the yellow zone, it must be due to a problem with the shaft displacement, which needs to be addressed; as a result, the corresponding vibration will be eliminated. The bearing sleeve thrust disc is used to position the shaft (rotor); for vibrations in other parts, it’s necessary to check components such as the impeller and inducer. If there are no issues with the mechanical parts, then the system itself needs to be examined, such as for signs of cavitation or the opening degree of the valves at the operating point. Additionally, the company requires that their personnel be on site 24/7 to discuss the situation, as this will help to resolve any mechanical problems immediately!