Is it okay if the horizontal pipe at the inlet of the centrifugal pump is too far away?
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A horizontal centrifugal pump is used for the cooling tower of a project, with a flow rate of 300 cubic meters per hour, a head of 50 meters, and a required net positive suction head of 4 meters. There’s no space to install it; the water pump has to be placed in the pump house on the other side of the road, with the inlet horizontal pipe being over 30 meters long. The pump inlet is below the level of the cooling water tank, and the diameter of the inlet pipe is one size larger than that of the pump’s inlet – DN250. I’ve calculated that the friction loss along the pipeline is not significant, less than 1 meter. But will there be any problems at a distance of over 30 meters?
The resistance isn’t high; is sufficient conveying resistance enough? Are there higher requirements regarding installation sealing and the levelness of the pipes? The pipes chosen now are spiral welded pipes
The resistance isn’t high, so there should be no problems. Make sure that the pipes have a consistent slope when installed, and that no air accumulates inside them.
This requires calculating the pipe losses, and then the net positive suction head can be determined. If there’s no problem, then it’s fine. But with 300 m3 of water and a DN250 tank, the flow rate in the inlet pipe is also close to 2 m/s; personally, I think that’s quite high. It is advisable to keep the flow rate in the inlet pipe below 1 m/s.
I did the calculations; the flow rate is around 1.7 m/s, which is a bit high, but the resistance isn’t a major issue.
This post was last edited by Yunmu on 2019-3-17 22:29. Under normal circumstances, there’s no problem with this, but the impeller will wear out quickly. Additionally, the pump efficiency will decrease.
Not just a little bigger. With such a long inlet pipe, at least a DN350 pipe is required