Sudden fluctuations in current and pressure occur in the two-stage centrifugal pump
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This post was last edited by Lantian on 2017-5-26 at 16:52: Current and pressure fluctuations, decreasing outlet flow; increasing the outlet valve size does not reduce the flow rate； The current increases when the outlet valve is closed; as the flow rate is gradually increased, the current also rises, but after one or two minutes the flow rate starts to drop again, resulting in fluctuations ； Keep the current and pressure of the machine seal flushing water stable ； After the seal flushing water was adjusted to normal, fluctuations occurred again ； It is judged that vaporization has occurred in the pump; the liquid level and pressure in the inlet tank are normal, as well as the heating system at the inlet. The pump has been operating stably up to now. I would appreciate some guidance from those with more experience.
A centrifugal pump? And I guess the machine seal flushing is self-flushing, right? It leads from the pump outlet to flush the mechanical seal. Based on the phenomenon, the analysis is as follows: 1. When the outlet valve is opened wider, the current decreases; when the outlet valve is closed more, the current increases again. After holding the pressure for a while, opening the valve wider increases the current, which can be maintained for a short period before dropping again. Analysis: When the outlet valve is opened fully under normal conditions, the flow rate should increase, and the current should also increase. A decrease in current indicates that the flow rate has also decreased; there can only be one reason for this: insufficient feed at the inlet, which leads to evacuation. After holding the pressure for a while, the situation improves, indicating that the flow rate at the inlet is better after applying pressure, but it becomes poor again after a short time. I think this fits the situation of a clogged inlet filter. 2. The flushing water for the start-up seal has improved. It seems that the seal flushing water is entering the pump, which is equivalent to the pump operating in reverse flow. Thus, the amount at the inlet is ensured. Turn off the rinse water and continue to evacuate. Based on the above analysis, it’s time to clean the filter at the entrance of the homeowner’s house.
Check if the inlet T-filter is clogged. The vast majority is this problem.
It’s possible that the filter is clogged, resulting in insufficient water supply. The pilot drain valve at the front of the pump can be opened before starting the pump to check the water inlet condition. You can also touch the pump head with your hand to check whether the outlet pipeline is hot. Is there any leakage at the pipe fittings?
It’s possible that the filter or the bottom valve is clogged, preventing the inlet flow from reaching the pump’s designed flow rate.
Please provide the pump model, as well as its rated flow rate and head What were the outlet pressures before and after the flow rate decreased due to the opening of the outlet valve? It's necessary to have these parameters in order to make a judgment. If the liquid level in the inlet tank is not below the pump inlet and the outlet pressure is lower than the head, cavitation may be the cause.
The problem has been resolved; in the previous system, crystalline substances entered the pump body, causing blockages in the impeller channels. This led to poor performance, disruption of the dynamic balance, and significant vibration. After cleaning the impeller, it is now working properly!
The described evacuation phenomenon is quite standard