Overcurrent in the shielded pump, help!
Thread Content
There is a shielded pump on site, with a flow rate of 5 cubic meters per hour, a head of 75 meters, and a power consumption of 11 kW. The operators on site reported that when the outlet valve of the pump was fully open, the pump overheated and tripped due to overcurrent; however, when the outlet valve was closed, the flow rate met the design requirements and the pump operated normally. I’m not quite sure why overcurrent occurred when the valve was fully open – could it be due to an incorrect pump selection or a problem with the piping layout? How can we theoretically explain the cause of this problem? Thank you all for your guidance
It should be caused by an excessive axial clearance
Fully opening the pump outlet may cause overload, leading to the motor tripping due to excessive current. Pay attention to the outlet pressure and flow rate of the pump; generally, they should not exceed the rated values.
This post was last edited by A Le on 2015-6-24 08:26. When selecting a pump for design purposes, there is no requirement that the current consumption must not exceed a certain level when the outlet valve is fully open. Selection is done to ensure compliance with the rated parameters; in actual use, the rated flow rate, head, and current values must be taken as the basis, and it is not appropriate to determine whether the selection is suitable based on whether the current exceeds a certain level when the valve is fully open. Usually, after the process engineering team in the design institute specifies the design flow rate and head, the selection is made based on the maximum (rated) flow rate and head required by the process. If the outlet valve is fully open and the flow rate and head reach the pump’s rated parameters, yet these still do not meet the process requirements, then it is likely a problem with the pump selection or with the process calculations.
Thank you for your reply. I have one more question: you mentioned that when selecting a pump design, there is no requirement to ensure that the current does not exceed limits when the outlet valve is fully open. If the pump operates for an extended period with the outlet valve at 1/2 open, it will inevitably lead to a loss in pump efficiency. Is this a common phenomenon during the design phase? Generally, is there a rough range of requirements during the design phase, specifying that the opening degree of the pump outlet valve must not be less than a certain value? Avoid power loss.
First, understand the working principle of the pump; then, by referring to the manual, you will be able to operate it. The most common method for adjusting the flow rate in centrifugal pumps is to adjust the valve at the pump’s outlet, which is generally not opened fully. Why did you open the outlet valve all the way? Is the flow rate and pump outlet pressure insufficient?
I’ve learned it! ! ! ! ! ! ! ! ! !
Regarding the issue of \"excessive pump current when the valve is fully open,\" I would like to ask whether this is considered normal in terms of process design From a design perspective, what is the reason for this issue? How can we avoid this problem from occurring?
You can carry up to 200 pounds of weight. If you were asked to carry 200 pounds every day, could you handle it? If you were asked to carry 100 pounds every day, would you feel comfortable?
Check whether there are any changes in the piping; an overload in the current at the outlet valve indicates a flow rate overload, which may be caused by too low head pressure leading to excessive flow
The outlet valve should generally be opened to an adequate level; there is no need to open it fully.