Selection issues for cooling water pumps
Thread Content
Hello everyone. The water from the cooling tower collects in a tank, and the cooling water pump draws water from this tank. The liquid level is about 1 meter lower than the inlet pipe of the pump. My questions are: 1. Given that the NPSH required for the pump remains roughly the same, is there any difference in the water suction performance between vertical pipeline pumps and horizontal end-suction pumps (some pipelines are also suitable for horizontal pumps), considering that the suction height is only about 1 meter? 2. Currently, there is a section where 2 units are in operation with 1 as a backup; both the inlet and outlet pipes, as well as the main pipes leading to the equipment to be cooled, have a diameter of DN200. The flow rate is between 340 and 380 (with the frequency of the variable frequency drive around 45 Hz), and a flow rate of 340 is also sufficient for operation. Should we choose to replace 2 pumps, with a flow rate of 200 per pump and DN150 for the pump inlet and outlet, or should we replace 1 pump, with a flow rate of 400 per pump and DN200 for the pump inlet and outlet? We think that replacing just one pump would result in lower costs, but since the pump inlet and outlet connections as well as the water pipes are all DN200, could this lead to insufficient water intake and thus affect the actual flow rate? Choose 2 water pumps, with a pump diameter of DN150 and an inlet diameter of DN200 – does this better meet the water suction requirements? Which option would be better for ensuring sufficient traffic handling, switching to 1 unit or 2 units, or does it make no difference?
1. When the liquid level is about 1 meter lower than the inlet pipeline of the cooling water pump, there is not much difference in suction performance between vertical pipe pumps and horizontal end-suction pumps. If cavitation margin needs to be considered, a pump model with a good cavitation margin can be selected. 2. If a flow rate of 340–380 is required, it is possible to replace them with 2 new pumps, each with a flow rate of 200, and the inlet and outlet sizes of these pumps should be DN150. If a pump with a flow rate of 400 per unit is selected, although the pump’s inlet and outlet are DN200, it may not be able to draw in enough water, which will affect the actual flow rate. Therefore, choosing 2 water pumps better meets the water suction requirements and can ensure a more stable flow rate. .
I don’t have any experience to answer questions for now; I’ll come and learn from everyone’s experience.