Problem of excessive outlet pressure and low flow rate in centrifugal pumps
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The water circulation system includes a circulation pump, two heat exchangers, a filter, and various sensor elements. The parameters of the pump are shown in the figure. During operation, the pressure at the pump outlet before it enters the heat exchanger is 11 bar, and the flow rate at the location after passing through the heat exchanger is 0.42 m3/h. I’ve just taken on this project and am already on site. I think the head of this pump is too high, but I’m not entirely sure about it. I would appreciate it if everyone could help me understand the various effects that flow rate and pressure have in actual operation, such as those that occur when the head is set too high or due to other reasons.
The topic is too technical; I couldn’t quite understand it. There are a few questions below for your reference. First, how does the selected pump in the process know to determine that its head is too high? ”Flow rate and pressure under various conditions in actual operation. Pumps are installed in a process to meet the requirements of that process, thereby providing the necessary conditions. Without process conditions as a reference, how can one identify the issue of \"excessively high outlet pressure and low flow rate in centrifugal pumps\"? Please clarify, thank you! :)
I recommend that you take a look at the \"Industrial Pump Selection Manual.\" The value 23 indicates the number of impeller stages; it is most likely a piston pump. Generally, the pump is selected so that it operates near its optimal operating point. When selecting the head, the flow rate can be set slightly higher than what you require; if the head becomes too low later on, adjusting the valve can help achieve the desired level
Whether it’s due to the head or not, first calculate the parameters of the pump – whether the head, flow rate, etc., have been selected based on the appropriate operating conditions. Also, the most basic thing to check is whether the flow rate is correct Is it the flow meter that is inaccurate, or is the actual flow rate indeed 0.42 cubic meters? Does turning on the pump cause overheating? Determine whether it is overloaded and whether the valve is fully open? Determine whether there is pressure buildup at the pump outlet. Each one needs to be checked one by one; the pump performance curve cannot be used to identify specific issues with the equipment, as it is primarily utilized for equipment selection.
The determination of the pump head is related to both the inlet and outlet equipment as well as the piping system. Graphically, the rated head of the pump is approximately 143 m (about 14.3 bar). If the head selected by the designer has been calculated correctly, it indicates that the installation height of the heat exchanger is relatively high, around 20 m (assuming the pump suction pressure is at atmospheric level). https://bbs.hcbbs.com/thread-1764877-1-1.html If the pump’s head is selected to be too high, in actual operation, it is necessary to adjust it by closing the valves.
What is the inlet pressure of this pump? Is there a pressure gauge at the outlet to indicate the pressure while the pump is running?
The unit itself is used for heat dissipation on a vibration table, so the height difference isn’t significant and the distance isn’t great; however, there is a substantial difference between the pipes at the end and the main pipe. Due to the conditions on site, it’s not possible to determine the flow resistance and head loss at the end. In terms of operating conditions, the flow rate is indeed low; meanwhile, the outlet pressure of the pump reaches 11.2 bar, while the inlet pressure is not yet known. During discussions with users, it was learned that other manufacturers’ pumps of the same model are able to achieve the designed flow rate at that pressure. Since there isn’t enough information for an accurate assessment, I’m asking everyone: based on experience, what are the common reasons for this?
It’s actually 21; the previous entry was incorrect
It’s a Grundfos vertical pump. The system doesn’t have a large height difference, and the pipelines aren’t either dozens of meters long. Since this is a new project, there are no previous design documents or specifications available, so it’s difficult to figure out how to address this issue
The pump’s outlet pressure is 11.2 bar; there is no pressure gauge at the inlet. The flow resistance on the user side has not been specified. Based on the heat exchange performance of the unit, it is unlikely that the flow meter is inaccurate. The valves are fully open.