Water pump in series
The series connection of pumps means that the outlet of one pump transmits fluid to the inlet of another pump. Taking the simplest two centrifugal pumps of the same model and performance in series as an example: the series performance curve is equivalent to the single pump performance curve. The working point B of the pump is large, but it is not twice that of a single pump. This is because the increase of the lift of the centrifugal pump is greater than the increase of the pipeline resistance after the centrifugal pump is connected in series. The increase of the resistance increases the resistance, which inhibits the increase of the total lift. When the pumps are running in series, attention must be paid to whether the latter pump can withstand the boost. Before starting, the outlet valve of each pump should be closed, and then the pump and valve should be turned on in sequence to supply water to the outside.
Parallel connection of pumps
Parallel connection of pumps means that two or more pumps deliver fluid to the same pressure pipeline, and the purpose is to increase the flow when the pressure head is the same. Still taking the simplest parallel connection of two single-stage centrifugal pumps of the same model and performance as an example, the parallel performance curve is equivalent to the superposition of the flow of the single pump performance curve under the condition of equal head, and the flow and head of the parallel operating point A are superimposed. Both are larger than the single-pump operating point B, but considering the pipe resistance factor, it is also less than twice that of the single-pump.
If the purpose is purely to increase the flow rate, then whether to use parallel or series connection should depend on the flatness of the pipeline characteristic curve. The flatter the pipeline characteristic curve, the closer the flow rate after parallel connection is to twice that of single pump operation, which is better than The flow in series is greater, which is more conducive to operation.
Pumps in series: two pumps of the same model or with little difference in flow rate are connected end to end, that is, the outlet pipe of the first is connected to the inlet pipe of the second, so that the water can obtain the energy of the two pumps and increase the lift, and the flow rate remains constant. Change, in order to reduce the pressure on the casing of the second water pump, the two water pumps can be installed on two different elevations. When the pumps are used in series, attention must be paid: the pumps running in series should preferably be of the same model and the same diameter. If pumps with different flow rates are connected in series, the pump with large flow should be placed in the first stage to supply water to the pump with small flow, otherwise, the pump with large flow will generate gas energy. When two pumps with different lifts run in series, the pump with low lift should be placed in the first stage, and the pump with high lift should be placed in the second stage.
The purpose of parallel connection of pumps is to increase the flow, but what is the purpose of series connection?
If the heads of the parallel pumps are the same, the flow rate is the sum of the flow rates of the two centrifugal pumps.
Three centrifugal pumps with the same Yang Cheng are connected in parallel, and the principle of flow superposition under equal lift can be used. The flow is equal to the sum of the flow of the three centrifugal pumps, and the lift remains unchanged.
Three centrifugal pumps with different Yang Cheng are connected in parallel, and the principle of flow superposition under the same head cannot be used, which may cause the low head pump to be unable to pump water, and the parallel flow is much less than the sum of the three centrifugal pumps.
For two centrifugal pumps of the same model (with the same characteristic curve), the parallel flow can be increased by more than 90%.a
