Overcurrent when shielded pumps are used in parallel
Thread Content
The head and flow rate of the two shielded pumps are the same. When used in parallel, the current drawn by the Xinhu pump exceeds its rated value by about 90A, while the current of the Jiamusi pump remains within normal levels at around 56A； When any one of them is started alone, the flow rate, head, current, etc., all meet the performance curve of the pump. It is a closed-loop system; check valves are installed at the outlets of both pumps. The pumps start operating when the circuit pressure exceeds 3 MPa. Different sequencing of starting the two pumps has also been tried – for example, starting the Jiamusi pump first and then the Xinhu pump – and in this case the current consumption of the Jiamusi pump decreased while that of the Xinhu pump increased. Reversing the order of starting the pumps did not affect the performance. The medium used is deionized water. The Xinhu pump has just been overhauled by the manufacturer, and the two pumps worked properly when used together previously. During operation, the indicators on the bearing monitors of both pumps were within the normal range, and there were no abnormal noises coming from the pumps. Based on these assessments, the pumps themselves may be normal; since there are no inlet or outlet valves for each pump in the inlet and outlet pipelines, it is suspected that the issue might be related to the process pipelines (for example, problems such as uneven flow at the inlet in a closed loop). I hope experts can help clarify this matter.
As a supplementary note, the total flow rate when both devices are in use is 40 cubic meters per hour
It is estimated to be closely related to the design of the import pipeline.
“Since there are no individual inlet and outlet valves in the inlet and outlet pipelines, \"was it designed to be used in parallel from the start, rather than with one valve in use and another as a backup?\"
Let’s take a look at the performance curves of the two pumps – one is steep while the other is gentle
No, because it’s not the kind of continuous production seen in factories; instead, two units are used in parallel when starting up.
Okay, thank you. I’ll check it. The first time it was used in parallel, everything worked fine, but this time it doesn’t work.
The 5th floor answer is correct – it’s likely that the curves of the two pumps are different. If you adjust the outlet valve to an approximate opening, one pump will work more while the other works less or not at all. The pump that works more will experience overcurrent, while the other will have lower current levels. If these two pumps must be used in parallel, first, a valve is required at the outlet of each pump to control the flow rate; moreover, the piping design must provide space for parallel operation. Second, it is necessary to determine the balance point for parallel operation of the two pumps based on experience – it’s possible that one pump can operate at a flow rate of 30 cubic units while the other can only operate at 10 cubic units, and this is related to the relevant curves