Regarding the operation of centrifugal pumps: If the inlet and outlet are connected directly, will the pressure increase indefinitely?
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This post was last edited by ly90128 on 2016-5-31 at 13:33. There is a question I’ve been wanting to ask everyone: 1. If a centrifugal pump connects its inlet and outlet directly to each other, then the flow rate remains constant and the head is fixed – will the pressure at the pump’s outlet increase indefinitely? The reason for asking this question is that a colleague, while cleaning the closed-loop system, bypassed the tank that was originally located at the pump inlet; as a result, the inlet became directly connected to the outlet. Later, it seemed that the pump started to exhibit some abnormalities. 2. I would like to know what effects this approach will have on the pump Apart from the increase in temperature, will it have an impact on the mechanical seal? 3. Also, will the outlet pressure keep rising by doing this? The centrifugal pumps I’ve come across seem to have design requirements regarding the inlet pressure as well (x-xbara). What is the purpose of these regulations on inlet pressure? What impact will it have on the pump if the inlet pressure is increased by 10 times or 20 times compared to the design pressure? reward_7ree
The pressure won’t be high; don’t worry. In many cases, to ensure that the outlet pressure doesn’t become too high, a bypass is added to connect the inlet and outlet. The larger the bypass pipe, the lower the pump’s outlet pressure will be
"Bernoulli effect”. The relationship between the pressure of a fluid and its flow velocity, as well as the relationship between flow velocity and pressure: the greater the flow velocity of a fluid, the lower its pressure; the smaller the flow velocity, the higher the pressure. When you open the bypass, the flow rate at the pump outlet increases, while the pressure at the pump outlet decreases.
Thinking of what I usually do, I completely agree with the view from the first floor.
Uh, I thought of multi-stage pumps. What’s the principle behind them? Isn’t it either the inlet of the next stage pump or the outlet of the previous stage pump?
It should be known regarding centrifugal compressors that connecting the outlet to the inlet is done to prevent surge; surge occurs when the outlet pressure is too high or the flow rate is too low. Therefore, by connecting the outlet to the inlet, the outlet pressure does not increase but rather decreases. The same principle applies to centrifugal liquid pumps as well
Hehe, I didn’t say there was a bypass. . . When the bypass is opened, the pressure drops due to the increased flow rate; the head also decreases. I know that this happens. What I’m asking is: when the inlet and outlet of the pump are connected directly to each other, with no change in flow rate, does the pressure keep rising continuously? Thank you for your answer.
You are referring to the low-flow design similar to that of a centrifugal pump, which is used to prevent too low a flow rate. I did not mention low flow rates; what I meant was an inlet connected directly to the outlet, with no low-flow stage and no bypass. Thank you for your response
Yes, something like that, except a multi-stage pump does not connect the outlet of the next stage to the inlet of the previous stage. . . . What’s more important, I want to know what damage this does to the pump. . .
Electric energy is converted into heat energy, raising the temperature of the medium; in addition, the pump operates at a higher flow rate, causing the motor to experience excessive current.