Multiple water pumps draw water from the same main pipe; what are the considerations regarding the diameter of the main pipe and the flow rate of the pumps?
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Since there is no space to install a reservoir, we have three 155t pumps that are intended to draw water from the same main pipe. We are concerned that the pumps located ahead may interfere with the water intake of the pumps behind them; therefore, we are considering enlarging the main pipe. The diameter of the pipe is being calculated based on a flow rate of 1.5 m/s, which is 1.5 times the total flow rate of all three pumps. However, we’re not sure if this diameter is large enough. Are there any specifications or experience requirements regarding the size of the main pipe?
A flow rate of 1.5 m/s for the inlet pipe is considered quite high; 1.5 times is actually too low as well. It’s necessary to calculate the net positive suction head. Also, if you’re worried about uneven distribution, a symmetrical arrangement will do
Thank you for your reply. Could you please specify what multiples are appropriate for the flow rate and volume? Additionally, due to limitations in the factory space, a symmetrical arrangement is not possible; it can only be installed on the same side as the pipes. Also, what does cavitation margin calculation mean? I’m new to this topic and don’t quite understand it yet.
Generally, a value below 1 m/s is chosen; the 1.5 times factor actually depends on the size of the individual feed pipe. If it’s large enough, 1.5 times is sufficient, but using 1.5 m/s as that 1.5 times factor is definitely not appropriate in your case. NPSH is a fundamental concept in pump calculation; it is covered in Baidu as well as in relevant books.
For three identical pumps, check their characteristic curves to determine the total flow rate when they are connected in parallel; such information is usually available in the selection software provided by manufacturers. Then calculate the net positive suction head, which is a more reliable approach